JP2000214082A - Measuring apparatus for nonlinear optical response of medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which a nonlinear optical effect generated in a substance can be measured directly. SOLUTION: Optical pulses from an ultrashort-pulse light source 11 are branched by an optical branching device 12 so as to be guided to a medium 4 to be measured, as exciting pulses and probe pulses having a prescribed linearly polarized state by an excitation optical system 2 and a probe optical system 3. An interaction region which is generated in the medium 4 when the exciting pulses are incident and in which a refractive index is changed due to a nonlinear optical effect, is irradiated with the probe pulses. The component, out of the component which is passed through the medium 4, of the probe pulses which are passed through the interaction region and whose polarization state is changed, is detected by a camera 53 via an analyzer 51 in a light detection part 5. As a result, the nonlinear optical response of the medium 4 can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a nonlinear optical response of a medium, which can measure a nonlinear optical effect generated in a substance by incidence of light such as a light pulse.

[0002]

2. Description of the Related Art With the development of laser technology such as high-intensity ultrashort pulse lasers, the nonlinear optical effect of substances such as the optical Kerr effect caused by laser light having a higher intensity than ordinary light. And various phenomena caused by it. That is, the non-linear susceptibility of a substance to the second or higher order term of the electric field is 1
Since the value is smaller than the following term, only a linear response is measured in ordinary light. However, for light having sufficiently large intensity (electric field) such as laser light, such a 2 The effect of the non-linear term of the second or higher order appears.

A phenomenon caused by such a nonlinear optical effect is, for example, a self-focusing effect of light generated by irradiating a substance with a high intensity light pulse.
ct) and self-constraining effects (self-t
rapping effect) is known.

[0004]

In recent years, the use of the above-mentioned phenomena for controlling laser light has been promoted, and application to more advanced light control is expected in the future. In order to realize such advanced optical control applications, the response to the occurrence of nonlinear optical effects in various materials, such as the generation conditions and time changes (hereinafter referred to as nonlinear optical response), is measured. In addition, it is essential to determine a nonlinear constant such as a nonlinear susceptibility.

On the other hand, the above-mentioned phenomena may cause a problem when using an ultrashort pulse laser or the like. For example, a light pulse having a self-focusing effect or a self-binding effect causes a problem that an optical element or an optical material such as a lens is broken and a defect is generated. Also, when trying to focus an optical pulse on a gas or liquid, a laser plasma is created,
There is a problem that light cannot be collected effectively due to the scattering or the like. In order to avoid this problem, the optical system needs to be evacuated, but in this case, the necessity of evacuating restricts the device configuration and the use conditions of the light pulse.

In order to solve these problems, it is highly necessary to measure the nonlinear optical response of a substance. For this purpose, it is important to establish a technique for directly measuring the state of occurrence of the nonlinear optical effect in each part of the substance and its time change.

The present invention has been made in view of the above problems, and provides a medium nonlinear optical response measuring apparatus capable of directly measuring a nonlinear optical response due to a nonlinear optical effect generated in a medium. The purpose is to:

[0008]

In order to achieve the above object, a device for measuring nonlinear optical response of a medium according to the present invention comprises a medium for measuring a nonlinear optical effect generated in a medium to be measured by an optical pulse. A non-linear optical response measurement device, comprising: a light pulse supplied by a pulse light source;
A light source unit that generates and outputs a first light beam and a second light beam whose output timings are synchronized, forms an excitation pulse based on the first light beam, and enters the excitation pulse into the medium to be measured A probe pulse is formed based on the excitation optical system and the second light flux, and a probe is formed in a predetermined region of the medium to be measured including an interaction region in which the nonlinear optical effect is induced by the excitation pulse being incident on the medium to be measured. A probe optical system for irradiating a pulse, and a light detection unit for detecting a probe pulse that has passed through a predetermined region of the medium to be measured, wherein the excitation optical system is an excitation pulse polarization for setting the excitation pulse to a predetermined polarization state. Means, and an incident optical system for causing the excitation pulse to be incident on the medium to be measured under predetermined incident conditions, wherein the probe optical system has a probe path for bringing the probe pulse into a predetermined polarization state. It has a scan polarizing means, the light detecting unit, among the probe pulse which has passed through the predetermined region of the measured medium,
An analyzer that transmits only a predetermined polarization component, an optical detector that detects and measures a probe pulse that has passed through the analyzer, and a probe that transmits a predetermined region of the medium to be measured and transmits the probe pulse through the analyzer. Imaging means for forming an image on the detection means;
It is characterized by having.

In the above-described apparatus for measuring nonlinear optical response of a medium, a pulse light source such as a high-intensity femtosecond laser which is an ultrashort pulse light source is used, and two light beams output from the pulse light source are in respective predetermined polarization states. An excitation pulse and a probe pulse are generated, and they are incident on and irradiated on the medium to be measured. At this time, in the spatial region where the excitation pulse is distributed in the medium to be measured due to the excitation pulse, the excitation pulse light and the medium to be measured interact with each other to generate a nonlinear optical effect and to change the refractive index (interaction). A working area) is formed. The state of the interaction region is measured by selecting a component having a changed polarization state among the probe pulses that have passed through the medium to be measured by the analyzing means and detecting the component by the light detecting means. With this, for the nonlinear optical response in a specific region in the medium to be measured,
It is possible to directly measure the generation state / condition of the nonlinear optical effect such as the intensity of the incident light or its correlation with the spatial distribution, and it is also possible to measure the time change thereof and determine the nonlinear constant. Particularly, by using a pulse light source such as an ultrashort pulse light source, measurement of a nonlinear optical response with high time resolution is realized.

The light source section includes, for example, a single pulse light source for outputting a light pulse, and light branching means for splitting the light pulse to generate a first light beam and a second light beam. Can be configured. In this case, by using the same pulse light source, the two light beams are synchronized, and the configuration of the light source unit can be simplified.

Alternatively, the light source unit includes an excitation pulse light source that outputs a light pulse that becomes a first light beam, a probe pulse light source that outputs a light pulse that becomes a second light beam, a first light beam and a second light beam. And timing control means for synchronizing the output timings. In this case, the two light beams are synchronized by the timing control means. This timing control means can be composed of, for example, a trigger circuit and a delay circuit. In the case of such a configuration, for example, the pulse width and the wavelength of the excitation pulse and the probe pulse can be set to be different.

Further, one of the excitation optical system and the probe optical system has a variable optical delay means for setting and changing an optical path length difference between the excitation optical system and the probe optical system.

Further, the incident optical system is characterized by having a movable optical system whose position in the direction of the optical path is movable.

An interaction area generated by changing the irradiation timing of the probe pulse with respect to the injection of the excitation pulse or the spatial distribution shape of the excitation pulse during the irradiation of the probe pulse by using a variable optical delay means or a movable optical system. It is possible to perform measurement while changing the state such as the position and range in the medium to be measured.

Further, the excitation pulse polarization means and the probe pulse polarization means are configured so that at least one of them includes a wave plate or a polarizer, and the polarization states of the excitation pulse and the probe pulse are respectively set to predetermined linearly polarized light. The axis of irradiation of the medium to be measured with the pulse is in a plane perpendicular to the axis of linearly polarized light of the excitation pulse, including the axis of incidence of the excitation pulse to the medium to be measured, and the axis of linearly polarized light of the probe pulse is The analyzer is set as an inclination of 45 degrees with respect to the plane, and the analyzer detects only a polarization component orthogonal to the linearly polarized light of the probe pulse irradiated on the medium to be measured among the probe pulses that have passed through a predetermined region of the medium to be measured. Is transmitted.

Further, the irradiation angle of the probe pulse irradiation axis with respect to the excitation pulse incidence axis is 90 degrees.

As described above, by setting the polarization state of each pulse, the analyzing means, and the like, an efficient measuring apparatus can be constructed.

Further, the irradiation angle of the irradiation axis of the probe pulse with respect to the incident axis of the excitation pulse is set to an angle larger than 0 degree and smaller than 90 degrees, and the probe optical system matches the wave front of the probe pulse with the wave front of the excitation pulse. By having a wavefront converting means for irradiating the medium to be measured, it is possible to perform a measurement that does not impair the time resolution and that increases the interaction length between the excitation pulse and the probe pulse. .

The excitation optical system, the probe optical system, and a part or all of the light detection unit are integrally held, and are configured to be rotatable about the excitation pulse incident axis as a rotation axis. Excitation optics for the measurement medium,
By further comprising an optical system holding mechanism capable of changing the installation angle of the probe optical system and the light detection unit, by measuring the interaction area from different angles, for example, Using the same image reconstruction method as that for X-ray CT, it becomes possible to obtain three-dimensional information and the like on the nonlinear optical effect generated in the interaction region.

Further, the light detecting section further has a light image converting means for converting a two-dimensional light image of the probe pulse which has passed through a predetermined area of the medium to be measured into a one-dimensional light image, and the light detecting means has a primary light. It is characterized by comprising a source photodetector.

A two-dimensional light image is focused and converted into a one-dimensional light image by a light image conversion means using a cylindrical lens or the like, and detected as a one-dimensional image by a one-dimensional photodetector. By measuring the change, it is possible to efficiently measure the movement and the time change of the interaction region accompanying the movement of the light track.

Further, the light detecting section includes a light image converting means for converting a two-dimensional light image of the probe pulse having passed through a predetermined area of the medium to be measured into a one-dimensional light image, a light image converting means and a light detecting means. And a probe optical system having a pulse stretcher for chirping a probe pulse.

A pulse stretcher is installed in the probe optical system to chirp the probe pulse, that is, to spread the time waveform by the wavelength so that each wavelength component corresponds to the time information. On the other hand, in the light detecting section, a cylindrical lens or the like is used. The one-dimensional light image from the light image conversion means is separated by the light separating means, and the two-dimensional light image generated by the light separation is measured by the light detecting means. This makes it possible to obtain a measurement image in which the spectral wavelength axis corresponds to the time axis.

Further, at least one of the excitation optical system and the probe optical system may have a wavelength conversion means for changing the wavelength of the excitation pulse or the probe pulse. Alternatively, the excitation optical system may include a waveform conversion unit that changes a time waveform such as an individual waveform of an excitation pulse or a configuration of a pulse train. The provision of the wavelength or waveform conversion means makes it possible to measure the nonlinear optical response to the light pulse in various states and its change.

Further, by having the image processing means for processing the image data from the light detecting means, it is possible to perform image processing such as deriving an autocorrelation waveform from the image data and necessary calculations in real time. Becomes
Measurement can be made more efficient.

Further, a pulse laser is used as a pulse light source of the light source section, a laser medium of the pulse laser is used as a medium to be measured, an optical pulse in a resonator of the pulse laser is used as an excitation pulse, and an optical pulse output from the pulse laser is used. The method is characterized in that a probe pulse is formed, and feedback to a laser controller of the pulse laser is performed based on information of the measured laser medium to optimize and stabilize the operation of the pulse laser. In this method, a device for measuring nonlinear optical response of a medium is used for measuring a nonlinear optical response in a pulse laser which is another device.

Such an apparatus can be applied to observation or control of thermodynamics.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a device for measuring nonlinear optical response of a medium according to the present invention will be described below in detail with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also,
The dimensional ratios in the drawings do not always match those described.

FIG. 1 is a block diagram showing a first embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.
The device for measuring nonlinear optical response of a medium according to the present embodiment includes:
It comprises a light source unit 1, an excitation optical system 2, a probe optical system 3, and a light detection unit 5.

The light source unit 1 includes an ultrashort pulse light source 11 for generating and emitting an optical pulse, and an optical splitter 12. The first optical pulse emitted from the ultrashort pulse light source 11 is guided to the excitation optical system 2 by the optical splitter 12.
And a second light beam guided to the probe optical system 3.

The first light beam and the second light beam output from the light source unit 1 are converted into an excitation pulse and a probe pulse, respectively, and guided to the medium 4 to be measured, which is a substance to be measured. The excitation optical system 2 forms an excitation pulse based on the first light beam from the light source unit 1 and enters the medium to be measured 4 from a predetermined incident axis. The excitation optical system 2 is
A variable optical delay unit 21 for setting / changing a delay time difference between the probe optical system 3 and the probe optical system 3, an excitation pulse polarization unit 22 including a wave plate 23 and a polarizer 24 for converting an excitation pulse into a predetermined polarization state, And an input optical system 25 for inputting the excitation pulse to the medium to be measured 4 under a predetermined input condition.

On the other hand, the probe optical system 3 forms a probe pulse based on the second light beam from the light source unit 1 and irradiates the medium 4 to be measured from a predetermined irradiation axis. The probe optical system 3 includes a probe pulse polarizing means 32 including a wave plate 33 and a polarizer 34 for turning a probe pulse into a predetermined polarization state.

In the above configuration, the excitation pulse is focused and incident on the medium to be measured 4 via the excitation optical system 2, for example. At this time, the condensed excitation pulse forms a high-intensity and high-density luminous flux in a predetermined region in the medium 4 to be measured, and in a spatial region where the light of such an excitation pulse is distributed,
A change in the refractive index in the measured medium 4 is induced by a nonlinear optical effect such as the optical Kerr effect. A region where such an interaction between the excitation pulse and the medium under measurement 4 produces a nonlinear optical effect is referred to as an interaction region here.

Here, the medium to be measured 4 including the interaction region
Is irradiated with a probe pulse through the probe optical system 3 through the probe optical system 3, only the probe pulse component that has passed through the interaction region is subjected to other regions of the measured medium 4 due to the anisotropy of the refractive index in the interaction region. The polarization state of the passed probe pulse component changes. By detecting the changed light component using the light detection unit 5, the image of the interaction area is measured, and the state of the nonlinear optical effect generated in the interaction area from the intensity distribution of the image data (non-linear state) Position and light intensity dependence of optical response)
In addition, the time change of the nonlinear optical effect (time dependency of the nonlinear optical response) can be measured from the time change of the image data, and the nonlinear constant can be determined from the information.

The light detection unit 5 includes an analyzer 51 that transmits only a predetermined polarization component of the probe pulse that has passed through a predetermined area of the medium 4 to be measured, and an imager that forms an image of the probe pulse component that has passed through the analyzer 51. It is configured to include an image lens 52 and a camera 53 that is a light detecting unit for measuring a light image of the formed probe pulse. by this,
The probe pulse component passing through the interaction area is analyzed by an analyzer 5
1, the probe pulse component is measured and imaged by the camera 53, and the nonlinear optical response in the measured medium 4 is measured.

In the above embodiment, the polarizing means 22 and 32 are composed of the wave plates 23 and 33 and the polarizers 24 and 34, respectively.
2 and 32 show an example of the configuration, and other configurations depending on the polarization state of the light beam input to the excitation optical system 2 and the probe optical system 3 and the polarization state of the excitation pulse and the probe pulse to be set. For example, a configuration including only a wave plate can be used.

As the incident optical system in the excitation optical system 2, an incident optical system 25 for converging an excitation pulse and making it incident on the medium to be measured 4 is used. An optical system that does not perform focusing may be used as the incident optical system, depending on the measurement conditions such as the type.

FIG. 2 shows an example of the apparatus for measuring nonlinear optical response of a medium according to the embodiment shown in FIG. 1 together with a specific configuration.

In this embodiment, the wavelength is 800 nm, the pulse width is 100 fs, and the energy per pulse is 7 mJ.
The titanium sapphire laser is used as the ultrashort pulse light source 11, and the light pulse from the pulse light source 11 is firstly split by an optical splitter 12 composed of, for example, a half mirror.
Are divided into a light beam l ₁ and a second light beam l ₂ . Here, this optical pulse is horizontal to the paper surface in FIG. 2, that is, a plane (hereinafter, referred to as a measurement plane) including the axis of incidence of the excitation pulse to be measured and the irradiation axis of the probe pulse, which will be described later. It has linear polarization in the direction. If necessary, a wave plate or the like may be provided between the pulse light source 11 and the optical splitter 12. In this case, for example, a prism type polarizing beam splitter can be used as the optical splitter 12.

The first light beam l ₁ is guided to the excitation pulse l _e and has been measured medium 4 by the excitation optical system, whereas,
The second light flux l ₂ is converted into a probe pulse l _p by the probe optical system and guided to the medium 4 to be measured.

The timing of the incident-irradiation of the excitation pulse l _e and probe pulse l measured with _p medium 4 includes a variable optical delay unit 21 in the excitation optical system, adjusted and set by the optical path portion 30 in the probe optics Or be changed.

The optical path portion 30 of the probe optical system is set and fixed when the apparatus is constructed, has a function as an optical delay unit with a fixed delay time, and has a difference in optical path length with respect to the excitation optical system. It is used for adjusting and setting the initial condition of the delay time difference. On the other hand, the variable optical delay unit 21 of the excitation optical system is configured to have a movable right-angle mirror 21a, and the optical path length is changed by moving the movable right-angle mirror 21a so that the optical path length difference with respect to the probe optical system is changed. And the delay time difference caused by the change can be changed and set.

[0043] Each of the polarization state of the excitation pulse l _e and probe pulse l _p is the wavelength plate 23 and the polarizer 24 is an excitation pulse polarizing means in the excitation optical system, the wavelength is a probe pulse polarizing means in the probe optics Board 33
And the polarizer 34.

The wavelength plate 23 of the excitation pulse polarizing means is a half-wave plate in this embodiment,
First beam l ₁ that has passed through the is converted by 1/2 wavelength plate 23 is the direction of the linearly polarized light to have a linearly polarized light perpendicular to the measurement plane is rotated 90 degrees, further linearly polarized light perpendicular Pass through the polarizer 24 that transmits only the component having Thus, the excitation pulse l _e is obtained with a linearly polarized light perpendicular to the measurement plane. The polarizer 24 is for more surely selecting a component having vertical linearly polarized light, and may be configured not to be provided.

On the other hand, the wavelength plate 3 of the probe pulse polarization means
Reference numeral 3 denotes a １ ／ wavelength plate, which is the second wavelength plate passing through the optical path portion 30.
The light beam l ₂ of its linearly polarized light by the / 4 wavelength plate 33 is converted into circularly polarized light, passes through the polarizer 34 that transmits only a component having a more linear polarization inclined by 45 degrees with respect to the measurement plane. Thus, the probe pulse l _p having a linear polarization inclined by 45 degrees with respect to the measurement plane is obtained. Here, the 波長 wavelength plate 33 is used as a 波長 wavelength plate,
Generate a probe pulse with linear polarization tilted by 5 degrees,
This may be used.

The excitation pulse l _e obtained as described above
And probe pulse l _p are respectively incident and irradiated to the measured medium 4 by predetermined incident axis and the irradiation axis.

The excitation pulse l _e from the excitation optical system passes through the focusing lens 25a is a plano-convex lens of focal length 50 mm, is incident while being focused on the measurement medium 4 by predetermined incident axis. At this time in the measured medium 4, by the interaction between the excitation pulse l _e and the measured medium 4, the interaction region resulting nonlinear optical effect such as an optical Kerr effect is generated. This is interaction region changes the refractive index of a measured medium 4, resulting in anisotropy in a plane perpendicular especially to the irradiation axis of the probe pulse l _p in its refractive index.

[0048] For a given area of the measured medium 4 comprising the interaction region, the probe pulse l _p of the probe optical system is irradiated as irradiation axis an axis perpendicular to the axis of incidence of the excitation pulse l _e You. Of this probe pulse l _p ,
Is a component which has transmitted through the DUT medium 4 permeation probe pulse l _p 'is detected by the light detection unit.

Transmission probe pulse 1_p’Is the objective lens
The light enters the analyzer 51 via 54. This analyzer 51
Is the transmission probe pulse l_pOf the medium to be measured 4
Irradiated probe pulse l_pOrthogonal to linearly polarized light
Is configured to transmit only the linearly polarized light component
You. Therefore, due to the nonlinear optical effect of the measured medium 4
A transmission probe that has passed through a region where no refractive index anisotropy has occurred.
Pulse l_p′ Component does not pass through the analyzer 51 and
After passing through the action area, the anisotropy of the refractive index in the interaction area
Therefore, the transmitted probe pulse whose polarization state has changed
l_pOnly the components of the 'pass through the analyzer 51. That is,
Transmitted probe pulse l passed through analyzer 51 _p’Component
Image is induced by refractive index change due to nonlinear optical effect
Corresponding to the image of the interaction region.

The light image formed by the component of the transmitted probe pulse l _p ′ that has passed through the analyzer 51 is converted by the imaging lens 52 into C light.
An image is formed and imaged on the CD camera 53, whereby the nonlinear optical response in the measured medium 4 is measured. In this embodiment, the objective lens 54 has a magnification of 10 times, and the measurement is performed with the focal point of the camera lens of the CCD camera 53 set to infinity. Also, CCD
The camera 53 has a width of 640.times.480 pixels and can obtain 16-bit intensity information. In order to reduce the influence of scanning lines, the CCD camera 53 is tilted 90 degrees with respect to the measurement plane. vertical structure was established to coincide with the direction of propagation of in the measured medium 4 of the excitation pulse l _e (incident direction). Under these conditions, the distance on the measurement surface corresponding to the pixel interval of the CCD camera 53 is 4.8 μm.

Further, in the measuring apparatus shown in FIG.
Excitation pulse l _e but is concentrated into a very small area in the measured medium 4, in this case, the measured medium 4 along with this
May cause breakdown, laser plasma may be generated, and plasma emission may occur. Such plasma emission is white light having broadband spectral components. To eliminate the influence of this light emission, we have established an interference filter 55 having a wavelength 800nm to remove spectral components different from the probe pulse l _p between the analyzer 51 and the imaging lens 52.

[0052] On the other hand, the probe pulse l _p same spectral component and, prior to the measurement of the nonlinear optical response, performs the measurements were the same as the conditions of the measurement and other conditions without irradiating the probe pulse l _p, this by subtracting the image data of the measurement result from the image data of the measurement result at the time nonlinear optical response measurements, perform selective measurement and imaging of the light image of the interaction region by transmitting a probe pulse l _p '. However, it can also be measured by the conditions the excitation pulse l _e is not accompanied by plasma emission, in which case, need not be performed in the subtraction processing of image data as described above.

[0053] Further, the energy per pulse of the excitation pulse l _e is the loss or the like in the optical elements were 3.5mJ immediately before the focusing lens 25a. Incidentally, by the nonlinear optical response measuring apparatus of the medium according to the embodiment shown in FIG. 2, although actually measured the nonlinear optical response, as will be described later, in this measurement, decrease the excitation pulse l _e by addition ND filter Light was measured at 2.3 mJ per pulse. In this measurement, air at normal temperature and 1 atm was used as the medium 4 to be measured. However, the measurement was performed by installing the entire measuring device in an air atmosphere, and a portion of the air in a predetermined region was used as the medium 4 to be measured.

The effects of the apparatus for measuring nonlinear optical response of a medium according to the present invention will be described below together with the results of measurements performed under the apparatus configuration and measurement conditions according to the above-described embodiment. In the nonlinear optical response measuring apparatus of the present medium, an ultrashort pulse laser capable of outputting ultrashort pulse light is used as a pulse light source 11 as a light source, and the light beam of the ultrashort pulse is split by an optical splitter 12 to generate an excitation pulse l. _e and forming the probe pulse l _p. By using an ultrashort pulse having a time width of a very short light pulse, it is possible to measure a nonlinear optical response with high time resolution. Further, by using by branching the ultrashort pulse, synchronization of the excitation pulse l _e and timing of the incident-irradiation of the probe pulse l _p measured medium 4 can be realized.

In particular, by using an optical pulse having a sufficiently short time width such as the pulse width of the ultrashort pulse of 100 fs in the above-described embodiment, the generation of the nonlinear optical effect in the measured medium 4 at a specific time is achieved. For the first time, it is possible to directly measure an image of the interaction region almost corresponding to the state as a two-dimensional image. According to actual measurement results, 66.
Data of 48 nonlinear optical responses are continuously acquired at a delay time interval of 7 fs, and detailed information on the nonlinear optical response in the interaction region, such as the spatial distribution structure of the nonlinear optical effect caused by the light pulse and its time change, is obtained. The measurement has been successful.

[0056] Further, in the above embodiment, the excitation optical system 2 includes a variable optical delay device 21, thereby changing the mutual timing of the incident-irradiation of the excitation pulse l _e and probe pulse l _p Can be. At this time, the change of the timing becomes the change in the position of the incident direction of the excitation pulse l _e when the probe pulse l _p is irradiated, therefore, by changing the timing of the mutual continuously measured medium the moving-time change in the interaction region corresponding to the movement of the excitation pulse l _e in the 4, can be measured as a continuous image with high time resolution.

FIG. 3A schematically shows the movement of the interaction area in the measured medium 4 measured in this manner. The horizontal axis represents the excitation pulse l _e and the delay time is the change in the mutual timing of the incident-irradiation of a probe pulse l _p. On the other hand, the vertical axis represents the propagation distance of the excitation pulse l _e (moving distance of the interaction region). Here in FIG. 3 (a), of the two-dimensional image obtained by the CCD camera 53, by adding the image data in the direction perpendicular to the axis of incidence of the excitation pulse l _e, the axis of incidence of the excitation pulse l _e direction,
That 1-dimensional image of the propagation direction of the excitation pulse l _e (hereinafter, referred to as operation image) it converts the image data displayed in the vertical direction in the drawing for each delay time, the one-dimensional image The sequence of the data shows the movement of the interaction area (indicated by the shaded area).

From FIG. 3 (a), it can be seen that the movement / time change of the interaction region is clearly measured with high time resolution by the medium nonlinear optical response measuring apparatus according to the present invention. The tilt of the image of this movement of the interaction area is
This corresponds to the speed of light in the medium 4 to be measured. Also, the lateral intensity profile near the center becomes an autocorrelation waveform, from which information about the range of the interaction region can be obtained.

It should be noted that the intensity of the transmission probe pulse is almost proportional to the square of the intensity of the excitation pulse in the measurement results using the air as the medium 4 to be measured.
It was found that the nonlinear optical effect was caused by the optical Kerr effect in the inside. At this time, the image data of the obtained measurement image corresponds to the square distribution of the intensity of the excitation pulse.
Therefore, for example, by taking the square root of the intensity of the image data of each pixel or by performing an operation such as arcsin ² to obtain a measurement image, it is possible to obtain a measurement image in which the spatial distribution of the intensity of the light pulse is reflected. it can.

[0060] Further, the specific measurement point in the 4 measured medium, by measuring the time variation of the intensity of the transmitted probe pulse l _p 'after passing through the excitation pulse l _e, the measured medium 4 by nonlinear optical effect The relaxation time of the resulting birefringence can be measured. When performing such measurements by the measurement points in the vicinity of the position where the excitation pulse l _e is most focused in the measured medium 4,
By shortening the time that the probe pulse l _p passes through the measurement point, it is possible to improve the time resolution of the measurement. Further, as the focusing lens 25a in FIG. 2, for example by using a focal length plano-convex lens and long focal point of the lens of 200 mm, to be more favorable measurement conditions to avoid rapid changes of the focusing state of the excitation pulse l _e it can. Such a measurement can be performed by a single light pulse, and can be measured in a short measurement time.

[0061] Such conditions, to measure the time variation of the intensity of the transmitted probe pulse l _p '. The axis (distance) in the propagation direction of the calculated image near the measurement point is
FIG. 3B is a diagram in which (horizontal axis) is converted into (distance) / (light velocity in the medium to be measured) on the time axis, and the added image data (intensity) is normalized and created on the vertical axis. At this time, if the light velocity in the medium to be measured is unknown, FIG.
It can be obtained from the diagram in FIG.

Here, the measurement was performed using CS ₂ (liquid at normal temperature) as the medium 4 to be measured. In this graph, after the non-linear optical effect is caused by the incidence of the excitation pulse l _e, time and time change of the nonlinear optical effect will be relaxed is shown with, thereby, the relaxation time of the birefringence due to the nonlinear optical effect Can be determined.

The variable optical delay device 21, which is a means for changing the mutual timing described above, is installed in the probe optical system 3 instead of the excitation optical system 2, or is installed in both optical systems 2, 3. It is good. When only the nonlinear optical response is measured at a specific timing and there is no need to measure the time change, a configuration without a timing adjusting means such as a variable optical delay device may be adopted.

[0064] When the measurement was carried out using a variable optical delay device as described above, when changing the delay time, the propagation direction of the excitation pulse l _e during the measurement position (in the interaction area generated As the position changes, the spatial distribution of the light pulse (the shape of the generated interaction region) changes due to the change in the focusing state. On the other hand, in the measurement of the spatial distribution change of the interaction region, for example, in the embodiment shown in FIG. 2, the delay time is fixed without using the variable optical delay device 21, and the focusing lens 25a which is the incident optical system is moved along the optical axis. by the movable optical system of the movable structure in a direction, similar to the case where by changing the focusing state of the excitation pulse l _e of the same measurement point 4 to be measured medium, using a variable optical delay device 21 Measurements can be made.

In the case of using the movable focusing lens 25a as described above, the measurement can always be performed under the same timing conditions, and the measurement point does not move.
There is no limitation on the measurement range due to the imaging range of the camera 53, and it is possible to measure the nonlinear optical response over a wider range of the focused state. Moreover, spatial beam pattern is always the same next to the probe pulse l _p, the accuracy of the resulting image is improved.

[0066] Further, in the embodiment shown in FIG. 2, the irradiation axis of the probe pulse l _p has been set with a radiation angle perpendicular to the axis of incidence of the excitation pulse l _e, the irradiation angle Need not necessarily be 90 degrees. For example, the irradiation angle and an angle smaller than than 90 degrees than 0 degrees, irradiation is performed with a wavefront of the probe pulse l _p is matched with the wave front of the excitation pulse l _e by the wavefront converting means constituted by using a diffraction grating With this, without impairing the time resolution,
And it is possible to take longer interaction length of the excitation pulse l _e and probe pulse l _p.

For the medium 4 to be measured, the present measuring apparatus can be applied to various substances such as gas, liquid and solid. The response speed of the nonlinear optical effect of a gas or a liquid is generally higher than that of a solid.

As an installation method when the medium to be measured is a gas or a liquid, for example, in the case of air or the like, a configuration in which the entire apparatus is installed in the air to be the medium to be measured as described above can be adopted. However, various methods other than such an installation method are conceivable. For example, a predetermined region excitation pulse l _e and probe pulse l _p is incident-irradiation, the enclosure is placed to a region including a part of the other device, by the measurement medium and the interior of the enclosure There is a way to meet. For example, FIG.
A region 40a or 40b indicated by a dotted line is possible, and a region other than this can be set.

In this case, the material for forming at least the portion of the enclosure where the light pulse is incident, irradiated, or emitted is as follows: (1) sufficient transmittance for the wavelength of the incident light pulse; (2) sufficiently transmitting a polarization component perpendicular to the measurement plane of the excitation pulse;
(3) not disturb the polarization state of the probe pulse;
It is preferable to use one that satisfies (4) no dispersion that greatly changes the pulse width of the incident light, and (5) sufficient resistance to the light energy of the incident light. It should be noted that the medium to be measured also needs to be sufficiently considered when selecting the medium or analyzing the data with respect to the various conditions described above.

The enclosure in this case is shown in FIG.
As shown in the example of 0, a part other than the part where the light pulse is incident / irradiated or emitted is painted black or the like in order to reduce the influence of the background light (hatched part in FIG. 4).
Is desirable. The part where the light pulse is incident, irradiated, or emitted is formed in a window shape made of, for example, quartz glass having an antireflection film on both surfaces.

FIG. 4 shows an enclosure 40 which is used when the enclosure includes all the photodetectors inside, as in an area 40b shown in FIG. 2, and an entrance window 41a formed in the excitation pulse incidence surface 41 is provided. It is shown. An irradiation window (not shown) is similarly formed on the probe pulse irradiation surface 43. When a part of the light detection unit is installed outside the enclosure 40 as in a region 40a shown in FIG. 2, it is necessary to further provide an emission window on the probe pulse emission surface 44. If necessary, the excitation pulse emission surface 42 may have an emission window. In addition, when the medium to be measured during observation is a problem, such as when the area where the enclosure is installed is small, it is preferable to connect a pump or the like to circulate the medium to be measured.

If the medium to be measured is a gas, the portion where the light pulse is incident / irradiated or emitted may be an opening instead of a window. In this case, it is necessary to continuously supply the gas, which is the medium to be measured, released from the opening from the cylinder to the inside of the enclosure via a hose or the like.

When a harmless gas is used as the medium to be measured, the output port of the hose connected to the cylinder or the like is set at a predetermined position near the area of the medium to be measured without using an enclosure.
It is also possible to supply gas by injecting it into the area and use it as a medium to be measured. In this case, although the purity of the gas is slightly inferior, there are advantages that the operation is easy and the apparatus is simplified, and that problems such as absorption and reflection of light by the window material do not occur.

Further, there is a method in which a cell filled with a gas or a liquid serving as a medium to be measured is provided in a region of the medium to be measured to be a medium to be measured. This method is particularly suitable for a liquid or a gas that is difficult to handle such as a toxic gas. In addition, the amount of the medium to be measured can be reduced. In this case, it is desirable to use a container for constituting the cell that also satisfies the above-mentioned preferable conditions for the material of the enclosure.

At this time, corresponding to the fact that the polarization direction of the incident light is determined, as shown in FIG. 5 as a cell 45, (a) a top view and (b) a side view, an excitation pulse incidence surface 46 is shown. Alternatively, the excitation pulse emission surface 47 is connected to its normal (FIG. 5).
By indicated by a dotted line in (b)) is formed so that the Brewster angle theta _b with respect to the optical axis, it is possible to increase the transmittance to suppress the reflection for the excitation pulses incident surface 46, also On the other hand, the excitation pulse emission surface 47 can suppress the light reflected on the emission end surface of the cell and returned to the medium to be measured, thereby improving the accuracy of the time resolution. This is particularly effective when using a liquid in which the generation of bubbles in the medium to be measured poses a problem, since reflected light can be prevented from being scattered by the bubbles.

[0076] Incidentally, when using the Brewster angle as described above with respect to the incident and emitting surfaces of the excitation pulse l _e, especially when the liquid to be measured medium, the air and the refractive index is largely different, the excitation pulse l _It is necessary to set the optical path in consideration of the change in the traveling direction of _e .

[0077] Also, the irradiation-emitting surface of the probe pulse l _p, it is desirable that the antireflection film is applied. Furthermore, to the extent that does not influence the polarization state of the probe pulse l _p, as shown the example by respective top view in FIG. 6 (a) and (b), the probe pulse irradiation surface for the purpose of suppressing the reflection of light 48, the probe pulse emission surface 49 is formed obliquely in the horizontal direction or the like, and the cell is trapezoidal (for example, the shape of FIG. 6A) or parallelogram (for example, the shape of FIG. 6B) when viewed from above. May be used. In this case, similarly, the optical path is set in consideration of the change in the traveling direction of the light pulse.

When the cell is used as described above, two cocks are preferably provided at an upper portion or the like so that a gas or a liquid to be measured can be appropriately exchanged or circulated. In addition, as a method for increasing the purity of the medium to be measured, particularly when the medium to be measured is a gas, a method of first evacuating the cell from one cock, closing the cock, and then filling the gas with the other cock is used. be able to. The shape of the cell is not limited to the above, and various shapes and configurations can be used according to various conditions such as the energy of the light pulse, the polarization state, and the optical path.

Conventionally, as a device for measuring such a nonlinear optical effect, for example, Opt. Commun., Vol.
pp. 433-437 (1984). This device measures the third-order nonlinear susceptibility by interferometric measurement of probe pulse light. The measurement content is limited, and a nonlinear constant is obtained only by calculation because interference is used. Therefore, it is not possible to measure the nonlinear optical response directly with such a device as in the present measuring device.

FIG. 7 is a block diagram showing a second embodiment of the medium nonlinear optical response measuring apparatus according to the present invention.
The device for measuring nonlinear optical response of a medium according to the present embodiment includes:
The light source unit 1, the excitation optical system 2, and the probe optical system 3 are the same as in the first embodiment. On the other hand, with respect to the light detection unit 5, a cylindrical lens 56 which is a light image conversion means for converting a two-dimensional light image of the transmitted probe pulse into a one-dimensional light image is provided downstream of the analyzer 51 and the imaging lens 52.
A one-dimensional photodetector 57 for detecting a one-dimensional light image generated by the cylindrical lens 56 is provided. In particular, the cylindrical lens 56 is connected to the one-dimensional photodetector 5 in a direction perpendicular to the axis of excitation pulse incidence.
By focusing the transmission probe pulse on 7 so as to form a one-dimensional optical image, an image of the movement of the interaction area as shown in FIG. Becomes possible.

FIG. 8 is a block diagram showing a third embodiment of the medium nonlinear optical response measuring apparatus according to the present invention.
The device for measuring nonlinear optical response of a medium according to the present embodiment includes:
The light source unit 1 and the excitation optical system 2 are the same as in the first embodiment. On the other hand, as in the second embodiment, a cylindrical lens 56 is used as a light image conversion unit in the light detection unit 5, and a spectroscope 58 is provided at a stage subsequent to the cylindrical lens 56, and the light is generated by the cylindrical lens 56. The obtained one-dimensional light image is incident on the entrance slit of the spectroscope 58 to be separated, and the output image position of the spectroscope 58 is made coincident with the light receiving surface of the camera 53, and the two-dimensional output image from the spectroscope 58 is obtained. Is observed by the camera 53.

At this time, a pulse stretcher 37 is installed in the probe optical system 3 as shown in FIG. 8, and the probe pulse that has passed through the pulse stretcher 37 is chirped to widen the pulse width (see FIG. The wavelength component distribution with respect to the time axis at each point on the road is shown). By expanding the time waveform in this manner, each wavelength component of the probe pulse can be associated with time information. As the pulse stretcher 37, for example, an optical fiber, a pair of diffraction gratings, a pair of prisms, a waveform conversion unit described later, or the like can be used.

FIG. 9 shows an example of a measurement image obtained by using such a configuration. The horizontal axis is the wavelength, which is converted and corresponded to the time axis as described above. Therefore, a diagram equivalent to FIG. 3 shown in FIG. 9 can be observed by one measurement. In order to improve the measurement accuracy, it is preferable to obtain the spectrum of the probe pulse in advance and apply a filter to the obtained measurement image.

FIG. 10 is a block diagram showing a fourth embodiment of the apparatus for measuring nonlinear optical response of a medium according to the present invention. The nonlinear optical response measuring device for a medium according to the present embodiment has the same configuration as that of the first embodiment, but further includes a control unit 6 for controlling each unit of the device, performing calculations on image data, and the like. I have. This control unit 6
The image processing device 61, the control device 62, and the display device 6
3.

The image processing device 61 is connected to the CCD camera 53, and the image processing device 61 sorts, analyzes, performs necessary calculations, and the like, the measurement images captured by the CCD camera 53. For example, the subtraction of the image data at the time of irradiation and non-irradiation of the probe pulse and the generation of the diagram shown in FIG.
The image data can be obtained by acquiring the image data by the camera 53 and then performing an analysis. By connecting the CCD camera 53 to the image processing device 61 as shown in FIG. It is possible to perform processing. Further, it is also possible to perform arithmetic processing by a predetermined function, for example, by performing an arithmetic operation of a square root on the image data of each pixel.

The image processing device 61 is further connected to a control device 62 for controlling the entire device. The control device 62 obtains image data and the like via the image processing device 61 and displays the obtained data on the display device 63. Further, the control device 62 is connected to the variable optical delay device 21 and can control the delay time in correlation with the measurement. Further, if necessary, a configuration may be adopted in which the light source is further connected to the pulse light source 11 or the like.

FIG. 11 is a block diagram showing a fifth embodiment of the apparatus for measuring nonlinear optical response of a medium according to the present invention. In the medium nonlinear optical response measuring apparatus according to the present embodiment, each part is integrally held by a T-shaped optical system holding mechanism 7. This optical system holding mechanism 7
Is a cylindrical excitation optical system holding unit 71 that is installed with the incident axis of the excitation pulse as the central axis and holds the excitation optical system, and a part of the probe optical system that is installed with the irradiation axis of the probe pulse as the central axis and It has a cylindrical probe optical system holding section 72 for holding the light detecting section.

In the present embodiment, the quarter-wave plate 13 is provided between the pulse light source 11 and the optical splitter 12, and the first light flux and the second light flux split by the optical splitter 12 are It has circularly polarized light. On the other hand, the excitation pulse polarization means and the probe pulse polarization means are respectively constituted only by the polarizers 24 and 34, and select the linear polarization state of the excitation pulse and the probe pulse.

The excitation optical system holding unit 71 is divided into a plurality of cylindrical parts, and the optical delay unit 21, the polarizer 24, and the incident optical system 25 are fixed between the cylindrical units. As described above, the excitation optical system holding unit 71 is divided and formed, and each optical element is installed in a portion therebetween, thereby facilitating the exchange of each optical element and not obstructing the optical path of the optical delay unit 21. It can be. In addition, each part of the divided excitation optical system holding unit 71 is connected by a connecting unit 73 to be integrated.

At the center of the probe optical system holding unit 72,
The medium 4 to be measured is arranged, and an opening 72a is provided in a predetermined portion facing the medium 4 to be measured. The excitation optical system holding section 71 is connected to the opening 72a, and the medium 4 to be measured is An excitation pulse is incident on the substrate. Opening 72
An opening 72b is also provided on the surface facing a. The polarizer 34 of the probe optical system is held above the probe optical system holding unit 72.

In this embodiment, an optical fiber 35 is used in the optical path of the probe optical system, and a variable optical delay unit 31 for the optical fiber is provided in the optical path. Further, in order to enter and exit the optical fiber 35,
Condensing lenses 36a, 36c and collimating lens 36
b and 36d are arranged.

When an optical fiber is used as described above, the pulse width of the probe pulse is increased due to the dispersion of the optical fiber, and the time resolution of the nonlinear optical response measurement is deteriorated. For this reason, it is desirable to use a dispersion-shifted fiber, a grating fiber, a diffraction grating pair, a prism pair, or the like to correct the spread of the pulse width, and to configure the medium to be measured 4 to be an optical pulse having a short pulse width.

Under the probe optical system holding section 72, each element of the light detecting section, that is, the objective lens 54, the analyzer 51,
An imaging lens 52 and a CCD camera 53 are held.

Here, the optical system holding mechanism 7 is fixed and fixed.
It is configured to be rotatable around the incident axis of the excitation pulse as a central axis together with the held optical elements and the like of each optical system.
With such a configuration, it is possible to measure the nonlinear optical response in the interaction region in the measured medium 4 from different angles. Therefore, for example, using the same image reconstruction method as that of X-ray CT, it is possible to obtain three-dimensional information and the like on the nonlinear optical response at a specific delay time.

FIG. 12 is a block diagram showing a sixth embodiment of the apparatus for measuring nonlinear optical response of a medium according to the present invention. In the apparatus for measuring nonlinear optical response of a medium according to the present embodiment, the laser medium 4a of the pulse light source 11, which is an ultrashort pulse laser used as a light source, is used as the medium to be measured. At this time, the excitation pulse is an optical pulse existing in the laser resonator of the pulse light source 11, and the probe pulse is a pulse light source 11 split by the optical splitter 12.
Output laser pulse is used.

In such a configuration, information on the state of occurrence of the nonlinear optical effect occurring in the laser medium 4a is obtained from the measurement image obtained by the camera 53, and the information is transmitted to the laser controller 14 via the laser controller 14. By using the feedback, the pulse laser can be used for optimization and stabilization. Further, data for improving the laser device itself can be obtained. Such a measurement can be performed using the dispersion compensation prism as the medium to be measured. The present embodiment for a laser is an example of the use of the apparatus for measuring nonlinear optical response of a medium according to the present invention, and the same application can be applied to various apparatuses other than a laser. In consideration of the polarization state of light in the laser medium 4a, it is desirable that the two prisms in the figure be arranged perpendicular to the plane of the drawing.

FIG. 13 is a block diagram showing a seventh embodiment of a medium nonlinear optical response measuring apparatus according to the present invention. In this embodiment, a single pulse light source is not used for the light source unit 1 but an excitation pulse is used. Excitation pulse light source 11a and probe pulse light source 1
1b.

The timing of the probe pulse with respect to the excitation pulse is controlled by the timing control circuit 15 in addition to the variable optical delay unit 21. Timing control circuit 1
5 has a trigger circuit 16 and a delay circuit 17, which can synchronize both pulses and set / change the delay time difference. In this case, both the excitation optical system 2 and the probe optical system 3 may have no variable optical delay device. When two light sources are used in this way, the pulse width and wavelength of the excitation pulse and the probe pulse can be different. In particular, by selecting the probe pulse light source 11b so as to further shorten the pulse width of the probe pulse with respect to the excitation pulse, it is possible to perform measurement with higher time resolution.

The apparatus for measuring nonlinear optical response of a medium according to the present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, a wavelength conversion means for changing the wavelength of the excitation pulse or the probe pulse may be provided on the optical path of the excitation optical system or the probe optical system. By using the wavelength conversion means in the excitation optical system, it is possible to measure the nonlinear optical response and its change when light of different wavelengths enters the medium to be measured. Also,
By using wavelength conversion means in the probe optical system,
The excitation pulse and the probe pulse have different wavelengths.For example, when laser plasma emission occurs in the medium to be measured, the wavelength of the probe pulse is set to a wavelength that is not easily absorbed or scattered by the plasma, and the efficiency of the measurement is improved. Can be improved. Examples of such a wavelength conversion unit include an optical parametric amplifier, a sum / difference frequency generator, and an SHG crystal.

Further, a waveform conversion means for changing the waveform of the excitation pulse or the like may be provided on the optical path of the excitation optical system to measure the nonlinear optical response due to the light pulse having various time waveforms. The waveform conversion means is disclosed, for example, in Japanese Patent Application Laid-Open No. 10-206234, and includes a pulse train generator, a waveform generator, and the like. Among them, the pulse train generator converts an optical pulse into a pulse train and the like, and for example, an etalon or the like can be used. The waveform generator changes the state of the waveform or the like of an optical pulse, and for example, a spatial light modulator can be used.

The measurement of the nonlinear optical effect using the apparatus for measuring nonlinear optical response of a medium according to the present invention can be used, for example, as shown in FIG. In this case, a predetermined portion of the device to be measured for which the non-linear optical response is to be measured is the medium to be measured.

Furthermore, it is possible to measure the speed of light in a medium, etc., thereby measuring the refractive index of the medium, and measuring the plasma density, plasma temperature, and the dielectric constant of plasma when laser plasma is generated. It is possible to Such measurement can be applied to measurement and control of dynamic thermodynamics, for example, measurement of non-equilibrium high energy state, laser ablation of semiconductor, laser ablation of liquid crystal, measurement of laser track used for laser processing, etc. . Further, as shown in FIG. 14, the reaction product generated in the reaction process A of a chemical plant, a semiconductor manufacturing plant, or the like is used as a medium to be measured, and the measurement B of the nonlinear optical response is performed. Is fed back via a control unit C of a plant or the like, and is used for optimization and stabilization of a reaction process, and various applications are possible.

[0103]

As described above in detail, the apparatus for measuring nonlinear optical response of a medium according to the present invention has the following effects. That is, by using two synchronized light pulses output from an ultrashort pulse laser or the like into a predetermined polarization state, and using them as an excitation pulse for inducing a nonlinear optical effect in the medium to be measured and a probe pulse as a measurement probe, Measurement of nonlinear optical response with high time resolution can be performed.

As a measuring method, a change in the refractive index of a region (interaction region) in which a nonlinear optical effect is generated by excitation pulse light in the medium to be measured, which is a substance to be measured, Detection is performed using the change in the polarization state of the probe pulse. As a result, the nonlinear optical response of a substance, such as the state of occurrence of the nonlinear optical effect and time change, is directly detected and detected by a photodetector such as a CCD camera.
It becomes possible to measure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.

FIG. 2 is a configuration diagram showing an example of a device for measuring nonlinear optical response of a medium according to the embodiment shown in FIG. 1;

3A and 3B are diagrams showing (a) a movement of an interaction region and (b) a time change of a nonlinear optical effect measured by the medium nonlinear optical response measuring device shown in FIG. 2;

FIG. 4 is a perspective view showing an example of an enclosure used for a medium to be measured.

5A is a top view and FIG. 5B is a side view showing an example of a cell used for a medium to be measured.

FIG. 6 is a top view showing another example of the cell used for the medium to be measured.

FIG. 7 is a block diagram showing a second embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.

FIG. 8 is a block diagram showing a third embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.

9 is a diagram showing an optical image measured by the device for measuring nonlinear optical response of a medium shown in FIG. 8;

FIG. 10 is a block diagram showing a fourth embodiment of the medium nonlinear optical response measuring apparatus according to the present invention.

FIG. 11 is a block diagram showing a fifth embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.

FIG. 12 is a block diagram showing a sixth embodiment of the device for measuring nonlinear optical response of a medium according to the present invention.

FIG. 13 is a block diagram showing a seventh embodiment of a medium nonlinear optical response measuring apparatus according to the present invention.

FIG. 14 is a diagram showing an example of a use form of the medium nonlinear optical response measuring device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source part, 11 ... Ultra short pulse light source, 11a ... Excitation pulse light source, 11b ... Probe pulse light source, 12 ... Optical splitter, 13 ... Wave plate, 14 ... Laser control device, 15 ... Timing control circuit, 16 ... Trigger Circuit, 17 delay circuit, 2 excitation optical system, 21 variable optical delay device, 21a movable rectangular mirror, 22 excitation pulse polarizing means, 23 wavelength plate, 24 polarizer, 25 incident optical system, 25a ... focusing lens, 3 ... probe optical system, 30 ... optical path portion, 31 ... variable optical delay device, 32 ... probe pulse polarizing means, 33 ... wavelength plate, 34 ... polarizer, 35 ... optical fiber, 36a, 3
6c: condenser lens, 36b, 36d: collimating lens, 37: pulse stretcher, 4: medium to be measured, 4
a: laser medium, 40: enclosure, 45: cell, 5: photodetector, 51: analyzer, 52: imaging lens, 53: camera, 54: objective lens, 55: interference filter, 56 ...
Cylindrical lens, 57 ... one-dimensional photodetector, 58 ...
Spectroscope, 6 control unit, 61 image processing device, 62 control device, 63 display device, 7 optical system holding mechanism, 71 excitation light system holding unit, 72 probe optical system holding unit, 72
a, 72b ... opening, 73 ... connecting part.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Hosoda 1126-1, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Inside (72) Inventor Hiroshi Tsuchiya 1126, Nonomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture 1 F-term within the company (reference) 2G059 AA02 BB01 BB04 BB08 DD13 EE04 EE12 FF01 FF04 GG01 GG08 GG09 HH09 JJ03 JJ05 JJ11 JJ13 JJ17 JJ19 JJ20 JJ22 JJ30 KK04 LL03 MM01 MM02 MM10 BB02 AB16 BC33 BB04 BC22 DA02 DA20

Claims (16)

[Claims] An apparatus for measuring a nonlinear optical response of a medium for measuring a nonlinear optical effect generated in a medium to be measured by an optical pulse, wherein respective output timings are synchronized from an optical pulse supplied by a pulse light source. A light source unit that generates and outputs the first light beam and the second light beam, and an excitation optical system that forms an excitation pulse based on the first light beam and that enters the excitation pulse into the medium to be measured. Forming a probe pulse based on the second light flux, and forming a probe pulse on the predetermined area of the measured medium including an interaction area in which the nonlinear optical effect is induced by the excitation pulse being incident on the measured medium. A probe optical system that irradiates a probe pulse, and a light detection unit that detects the probe pulse that has passed through a predetermined region of the medium to be measured. Excitation pulse polarization means for setting the excitation pulse to a predetermined polarization state, and an incident optical system for causing the excitation pulse to enter the medium to be measured under predetermined incident conditions, wherein the probe optical system includes the probe A probe pulse polarization unit for setting a pulse to a predetermined polarization state, wherein the light detection unit transmits only a predetermined polarization component of the probe pulse that has passed through a predetermined region of the medium to be measured. Means, a light detecting means for detecting and measuring the probe pulse transmitted through the light detecting means, and a probe pulse passing through a predetermined area of the medium to be measured and transmitting the light detecting means to the light detecting means. Imaging means for imaging;
An apparatus for measuring nonlinear optical response of a medium, comprising: 2. The light source unit includes: a single pulse light source that outputs an optical pulse; and an optical branching unit that splits the optical pulse to generate the first light beam and the second light beam. 2. The apparatus for measuring nonlinear optical response of a medium according to claim 1, further comprising: 3. The light source unit includes: an excitation pulse light source that outputs an optical pulse that becomes the first light beam; a probe pulse light source that outputs an optical pulse that becomes the second light beam; 2. The apparatus according to claim 1, further comprising: timing control means for synchronizing the output timing of the second light flux. 4. The apparatus according to claim 1, wherein one of the excitation optical system and the probe optical system has a variable optical delay unit for setting and changing an optical path length difference between the excitation optical system and the probe optical system. The apparatus for measuring nonlinear optical response of a medium according to claim 1. 5. The medium according to claim 1, wherein the incident optical system has a movable optical system whose position in an optical path direction is movable. Nonlinear optical response measurement device. 6. The excitation pulse polarization means and the probe pulse polarization means are configured so that at least one of them includes a wave plate or a polarizer, and the polarization states of the excitation pulse and the probe pulse become predetermined linearly polarized light, respectively. The irradiation axis of the probe pulse to the medium to be measured is set in a plane perpendicular to the axis of linearly polarized light of the excitation pulse, including the axis of incidence of the excitation pulse to the medium to be measured, The axis of the linearly polarized light of the probe pulse is set as an inclination of 45 degrees with respect to the plane, and the analyzing unit is configured to detect the medium to be measured among the probe pulses that have passed through a predetermined region of the medium to be measured. The nonlinear optics of a medium according to any one of claims 1 to 5, wherein only a polarization component orthogonal to a linear polarization of the probe pulse to be irradiated is transmitted. Answer measurement device. 7. The nonlinear optic medium according to claim 1, wherein an irradiation angle of the irradiation axis of the probe pulse with respect to the incident axis of the excitation pulse is 90 degrees. Response measuring device. 8. An irradiation angle of the irradiation axis of the probe pulse with respect to the incident axis of the excitation pulse is set to an angle larger than 0 degree and smaller than 90 degrees, and the probe optical system changes a wavefront of the probe pulse. 8. The apparatus according to claim 1, further comprising a wavefront converting unit configured to irradiate the medium to be measured with the wavefront of the excitation pulse in accordance with the wavefront of the excitation pulse. 9. 9. A system in which a part or all of the excitation optical system, the probe optical system, and the light detection unit are integrally held, and can be rotationally driven with the incident axis of the excitation pulse as a rotation axis. 9. An optical system holding mechanism configured to change an installation angle of the excitation optical system, the probe optical system, and the light detection unit with respect to the medium to be measured. A device for measuring nonlinear optical response of a medium according to any one of the preceding claims. 10. The light detection unit further includes a light image conversion unit that converts a two-dimensional light image of the probe pulse that has passed through a predetermined region of the medium to be measured into a one-dimensional light image. 10. The apparatus for measuring nonlinear optical response of a medium according to claim 1, wherein the detection means includes a one-dimensional photodetector. 11. A light image conversion means for converting a two-dimensional light image of the probe pulse having passed through a predetermined area of the medium to be measured into a one-dimensional light image, and the light image conversion means And a spectroscopic means provided between the light detecting means, and the probe optical system has a pulse stretcher for chirping the probe pulse. An apparatus for measuring nonlinear optical response of a medium as described in the above. 12. The apparatus according to claim 1, wherein at least one of the excitation optical system and the probe optical system has a wavelength conversion unit for changing a wavelength of the excitation pulse or the probe pulse. A non-linear optical response measuring device for a medium according to the above item. 13. The pumping optical system according to claim 1, wherein the pumping optical system has a waveform converting unit that changes a time waveform such as an individual waveform of the pumping pulse or a pulse train configuration.
13. The apparatus for measuring nonlinear optical response of a medium according to any one of claims 12 to 12. 14. The apparatus for measuring nonlinear optical response of a medium according to claim 1, further comprising image processing means for processing image data from said light detection means. 15. A pulse laser as a pulse light source of the light source unit, a laser medium of the pulse laser as the medium to be measured, an optical pulse in a resonator of the pulse laser as the excitation pulse, Forming the probe pulse from the output light pulse, feedback to the laser controller of the pulse laser based on the measured information of the laser medium, optimization of the operation of the pulse laser, stabilization. The apparatus according to claim 1, wherein the measurement is performed. 16. The apparatus according to claim 1, wherein the apparatus is applied to observation or control of thermodynamics.