JP2019039813A - Electromagnetic wave measuring device - Google Patents

Abstract

To provide an electromagnetic wave measuring device which has a wide dynamic range and can detect an electromagnetic wave with high sensitivity.SOLUTION: The electromagnetic wave measuring device comprises: a first photoconductive element having a first substrate, a first photoconductive layer formed on the first substrate and having a region irradiated with pulse light, and a first electrode pair formed on the first photoconductive layer and separate from each other in the irradiated region; and a second photoconductive element having a second substrate, a second photoconductive layer formed on the second substrate and having a top face smaller than the top face of the first photoconductive layer, and having a region irradiated with pulse light, and a second electrode pair formed on the second photoconductive layer and separate from each other in the irradiated region.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a photoconductive element that generates an electromagnetic wave for measurement and an electromagnetic wave measuring apparatus including the photoconductive element that detects the electromagnetic wave.

  Conventionally, a target object is irradiated with a terahertz wave that is an electromagnetic wave in a frequency band (for example, 0.1 to 10 THz) between radio waves and infrared light, and a reflected wave or a transmitted wave from the target object is subjected to time domain spectroscopy. A technique for measuring (analyzing) by means of is known. Such an analysis system includes a photoconductive element that generates a terahertz wave and a photoconductive element that detects a reflected wave or a transmitted wave from an object of the terahertz wave generated by the generating element.

  For example, a photoconductive element that generates or detects electromagnetic waves such as terahertz waves includes a semiconductor layer having photoconductivity and an electrode connected to the semiconductor layer. For example, Patent Document 1 discloses a photoconductive element having a plurality of semiconductor layers grown on a substrate and a terahertz time domain spectroscopic device using the photoconductive element.

JP-A-2014-197669

  For example, when measuring electromagnetic waves, it is preferable that the photoconductive element as the electromagnetic wave generating element generates high output electromagnetic waves, and the photoconductive element as the detection element detects the electromagnetic waves with high sensitivity and high accuracy. . Specifically, for example, it is preferable that the amplitude of the electromagnetic wave (signal) generated from the generating element is large, and that there is little noise in the electric signal representing the electromagnetic wave detected by the detecting element.

  For example, when analyzing an object using terahertz time domain spectroscopy, the amplitude of the time waveform of the terahertz wave obtained from the detection element is large, and the S / N ratio of the spectrum of the terahertz wave obtained from the time waveform It is preferable that the dynamic range is large.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an electromagnetic wave measuring apparatus having a large dynamic range and capable of detecting electromagnetic waves with high sensitivity.

  According to the first aspect of the present invention, there is provided a first substrate, a first photoconductive layer formed on the first substrate and having an irradiation region of pulsed light, and the first photoconductive layer formed on the first photoconductive layer. A first photoconductive element having a first electrode pair spaced apart from each other on the irradiation region; a second substrate; and an upper surface formed on the second substrate and having a smaller upper surface than the upper surface of the first photoconductive layer. And a second photoconductive element having a second photoconductive layer formed on the second photoconductive layer and having a second electrode pair formed on the second photoconductive layer and spaced apart from each other on the irradiated region. It is characterized by having.

  The invention according to claim 5 is formed on the first substrate, the first photoconductive layer formed on the first substrate and having the irradiated region of the pulsed light, and the first photoconductive layer. And a first photoconductive element having a first electrode pair spaced from each other on the irradiated region, a second substrate, and an upper surface formed on the second substrate and smaller than the upper surface of the first photoconductive layer And a second photoconductive layer having a region irradiated with pulsed light and a second electrode pair formed on the second substrate and sandwiching the second photoconductive layer in the irradiated region And a photoconductive element.

1 is a perspective view of an electromagnetic wave measurement device according to Embodiment 1. FIG. 3 is a top view of an electromagnetic wave generating element and an electromagnetic wave detecting element in the electromagnetic wave measuring apparatus according to Embodiment 1. FIG. 1 is a schematic circuit diagram of an electromagnetic wave measurement system according to Example 1. FIG. It is a figure which shows the dynamic range of the signal obtained by the electromagnetic wave measurement system which concerns on Example 1. FIG. 6 is a perspective view of an electromagnetic wave detection element in an electromagnetic wave measurement device according to Modification 1 of Embodiment 1. FIG. 6 is a cross-sectional view of an electromagnetic wave detection element in an electromagnetic wave measurement device according to Modification 1 of Embodiment 1. FIG. 6 is a top view of an electromagnetic wave generating element in an electromagnetic wave measuring apparatus according to Modification 2 of Embodiment 1. FIG. 6 is a top view of an electromagnetic wave generating element in an electromagnetic wave measurement device according to Modification 3 of Embodiment 1. FIG. 6 is a perspective view of an electromagnetic wave measuring apparatus according to Embodiment 2. FIG. 6 is a top view of an electromagnetic wave generating element and an electromagnetic wave detecting element in an electromagnetic wave measuring apparatus according to Example 2. FIG.

  Examples of the present invention will be described in detail below.

  FIG. 1 is a perspective view of an electromagnetic wave measuring apparatus (hereinafter, simply referred to as a measuring apparatus) 10 according to the first embodiment. The measuring device 10 receives the pulsed light P1 and generates the electromagnetic wave W1, and detects the electromagnetic wave W2 upon receiving the pulsed light P2 and the electromagnetic wave generating element 20 (hereinafter sometimes referred to as a generating element) 20. An electromagnetic wave detecting element (second photoconductive element, hereinafter may be referred to as a detecting element) 30.

  In the present embodiment, the generating element 20 receives a laser beam pulsed to have a femtosecond pulse width as the pulsed light P1, and emits a terahertz wave as the electromagnetic wave W1. The detection element 30 receives the same laser beam as the pulsed light P1 as the pulsed light P2, and detects a terahertz wave as the electromagnetic wave W2.

  In the present embodiment, the detection element 30 detects the electromagnetic wave W1 reflected or transmitted by the sample S as the electromagnetic wave W2. That is, the measuring device 10 is an analyzer that generates a terahertz wave and analyzes the sample S using the terahertz wave.

  FIG. 2 is a schematic top view of the generation element 20 and the detection element 30. The generation element 20 and the detection element 30 will be described with reference to FIGS. 1 and 2. First, the generating element 20 will be described.

  As shown in FIG. 1, the generation element 20 includes a substrate (first substrate) 21 and a photoconductive layer (first photoconductive layer) 22 made of a photoconductive material formed on the substrate 21. In this embodiment, the substrate 21 is a semiconductor substrate, and the photoconductive layer 22 is a photoconductive semiconductor layer formed on the semiconductor substrate. For example, the photoconductive layer 22 can be formed by using the substrate 21 as a growth substrate and epitaxially growing the photoconductive layer 22 on the substrate 21 by a known crystal growth method.

  In the present embodiment, as shown in FIG. 2, the photoconductive layer 22 has a rectangular upper surface 22S. In the present embodiment, the substrate 21 has a rectangular upper surface shape. The photoconductive layer 22 is formed on the entire top surface of the substrate 21.

  The substrate 21 is made of, for example, single crystal GaAs, InP, Si, or the like. The photoconductive layer 22 is made of, for example, GaAs, AlGaAs, InGaP, AlAs, InP, InAlAs, InGaAs, GaAsSb, InGaAsP, InAs, or InSb, and has a structure in which a plurality of semiconductor layers are stacked.

  The generation element 20 has a pair of drive electrodes (a first electrode pair, hereinafter may be referred to as a drive electrode pair) 23 formed on the photoconductive layer 22. The drive electrode pair 23 is formed on the upper surface 22S of the photoconductive layer 22, and the first and second electrode films 23A and 23B are spaced apart from each other with a predetermined distance (first distance) G1. Consists of. The first and second electrode films 23A and 23B are made of a transparent conductive film such as ITO or IZO, or a metal film such as Au or AuSn. In this embodiment, the drive electrode pair 23 is connected to a power source PS such as a voltage source.

  As shown in FIG. 2, the first and second electrode films 23A and 23B have first and second facing portions 23A1 and 23B1 facing each other. The first electrode film 23A has a first connection portion 23A2 connected to the first facing portion 23A1. The second electrode film 23B has a second connection portion 23B2 connected to the second facing portion 23B1. In this embodiment, the drive electrode pair 23 has a configuration in which the first and second facing portions 23A1 and 23B1 face each other with a predetermined distance G1.

  The drive electrode pair 23 can be formed, for example, by forming a photoconductive layer 22 and then forming a patterned transparent conductive film or metal film on the photoconductive layer 22. As the film forming means, for example, various lithography and etching techniques can be used.

  The photoconductive layer 22 is a region between the first and second electrode films 23A and 23B on the upper surface 22S of the photoconductive layer 22, and has an irradiated region 22G to which the pulsed light P1 is irradiated. When the pulsed light (pump light) P1 is irradiated to the irradiated region 22G of the photoconductive layer 22 in a state where a voltage is applied by the drive electrode pair 23, the generating element 20 has photoexcited carriers (ie, Photocurrent) occurs. The photoconductive layer 22 emits an electromagnetic wave W1 having a wavelength (frequency) corresponding to the pulse width of the pulsed light P1.

  In the present embodiment, the irradiated region 22G of the photoconductive layer 22 is irradiated with a laser beam having a femtosecond pulse width as the pulsed light P1. In the present embodiment, the generating element 20 is a terahertz wave generating element that receives a femtosecond pulse laser by the photoconductive layer 22 and emits a terahertz wave.

  In other words, the generating element 20 is formed on the substrate 21, the substrate 21 and the photoconductive layer 22 having the irradiated region 22G of the pulsed light P1, and the photoconductive layer 22 provided on the irradiated region 22G. And a pair of drive electrodes 23 spaced apart from each other. The drive electrode pairs 23 are separated from each other by a predetermined distance (first distance) G1 on the irradiated region 22G. The generating element 20 generates the electromagnetic wave W1 by irradiating the irradiated region 22G with the pulsed light P1.

  Next, the detection element 30 will be described. As shown in FIG. 1, the detection element 30 includes a substrate (second substrate) 31 and a photoconductive layer (second photoconductive layer) 32 made of a photoconductive material formed on the substrate 31. The photoconductive layer 32 of the detection element 30 has an irradiated region 32G to which the pulsed light P2 is irradiated on the upper surface 32S of the photoconductive layer 32.

  The detection element 30 has a pair of detection electrodes (second electrode pair, hereinafter may be referred to as a detection electrode pair) 33 formed on the photoconductive layer 32 and spaced apart from each other on the irradiated region 32G. . In this embodiment, a measuring instrument ME such as an ammeter is connected to the detection electrode pair 33 of the detection element 30.

  The detection electrode pairs 33 are separated from each other by a predetermined distance (second distance) G2 on the irradiated region 32G. In the present embodiment, the detection electrode pair 33 includes first and second facing portions 33A1 and 33B1 facing each other with a predetermined distance G2.

  Specifically, the detection electrode pair 33 includes first and second electrode films 33A and 33B. The first and second electrode films 33A and 33B include first and second facing portions 33A1 and 33B1 that face each other with a predetermined distance (second distance) G2. The first electrode film 33A has a first connection portion 33A2 connected to the first facing portion 33A1. The second electrode film 33B includes a second connection portion 33B2 connected to the second facing portion 33B1.

  The upper surface 32S of the photoconductive layer 32 in the detection element 30 is smaller than the upper surface 22S of the photoconductive layer 22 in the generating element 20. Specifically, in this embodiment, the substrate 31 of the detection element 30 has the same shape as the substrate 21 of the generation element 20 and has the same top surface size. Further, the photoconductive layer 22 of the generating element 20 is formed on the entire substrate 21.

  On the other hand, as shown in FIG. 2, in this embodiment, the photoconductive layer 32 of the detection element 30 is formed in a partial region on the substrate 31. Therefore, most of the upper surface 32S of the photoconductive layer 32 is covered with the detection electrode pair 33 (first and second electrode films 33A and 33B) except for the light irradiation region 32G. Further, the upper surface of the substrate 31 of the detection element 30 is partially exposed.

  Each of the substrate 31, the photoconductive layer 32, and the detection electrode pair 33 is made of the same material as the substrate 21, the photoconductive layer 22, and the drive electrode pair 23 of the generating element 20. For example, the substrate 31 is made of a semiconductor substrate, and the photoconductive layer 32 is made of a plurality of semiconductor layers grown on the semiconductor substrate. The detection electrode pair 33 is made of a transparent conductive film or a metal film.

  In the detection element 30, when the electromagnetic wave W <b> 2 enters the photoconductive layer 32 in a state where the irradiated region 32 </ b> G of the photoconductive layer 32 is irradiated with the pulsed light (probe light) P <b> 2, photoexcited carriers ( That is, the photocurrent fluctuates. This photoexcited carrier appears as a current (detection signal) in the detection electrode pair 33. That is, the detection element 30 detects the electromagnetic wave W2 by irradiating the irradiated region 32G with the pulsed light P2.

  In this embodiment, the irradiated region 32G of the photoconductive layer 32 is irradiated with laser light having a femtosecond pulse width as the pulsed light P2. In the present embodiment, the detection element 30 is a terahertz wave detection element that receives a femtosecond pulse laser by the photoconductive layer 32 and detects a terahertz wave.

  FIG. 3 is a circuit diagram schematically showing a configuration of a measurement system 60 using the terahertz time domain spectroscopy including the measurement apparatus 10. The measurement system 60 will be described with reference to FIG. Hereinafter, the electromagnetic wave W1 emitted from the generating element 20 will be described as a terahertz wave, and the electromagnetic wave W2 incident on the detection element 30 will be described as a terahertz wave.

  The measurement system 60 places the sample (measurement object) S in the path through which the terahertz wave W1 generated by the generation element 20 propagates, and transmits the sample S (or reflected by the sample S or the like). And the time waveform of the terahertz wave W2 without the sample S are Fourier transformed to obtain information on the amplitude and phase of the terahertz wave W2. The measurement system 60 can measure detailed physical properties such as the complex refractive index and complex dielectric constant of the sample S, for example.

  The measurement system 60 includes a laser irradiation device 61 that generates femtosecond pulsed laser light as the pulsed light P1 and P2, a beam splitter 62 that separates the pulsed light P1 and P2 from the laser irradiation device 61, the generation element 20 and the detection. Including a device 30, a delay circuit 63 that delays the pulsed light P2 incident on the detection device 30, a power source PS that applies a voltage to the generation device 20, a measuring device ME that measures a detection signal from the detection device 30, and the same And a signal processing circuit 68.

  The measurement system 60 has a general configuration as a measurement system using time domain spectroscopy. For example, the measurement system 60 is bonded to the generating element 20 and the first optical system 64 such as a hemispherical lens that efficiently extracts the terahertz wave W1 and the hemispherical lens that is bonded to the detecting element 30 and efficiently captures the terahertz wave W2. The second optical system 65 is included.

  First, laser light including pulsed light P1 and P2 emitted from the laser irradiation device 61 is divided into pump light (pulsed light P1) and probe light (pulsed light P2) by the beam splitter 62.

  The pulsed light P1 is condensed by the condensing lens CL1 and enters the irradiated region 22G of the generating element 20. The generating element 20 generates a terahertz wave W <b> 1 by applying a voltage to the drive electrode pair 23. The terahertz wave W <b> 1 passes through the first optical system 64, is collected by the third optical system 66, and is applied to the sample S. The terahertz wave W <b> 2 that has passed through the sample S is collected by the fourth optical system 67 and is incident on the detection element 30 via the second optical system 65.

  On the other hand, the pulsed light P2 is given a time delay by a delay circuit 63 having a plurality of reflecting mirrors M, is condensed by a condenser lens CL2, and enters the irradiated region 32G of the detection element 30. The signal detected by the detection element 30 is measured by the measuring instrument ME and input to the signal processing circuit 68.

  The signal processing device 68 stores the time waveform of the terahertz wave W2 that has passed through the sample S and the time waveform of the terahertz wave W2 in the absence of the sample S as time-series data, respectively, and performs Fourier transform processing on this in the frequency space. Convert. In this way, the measurement system 60 obtains a spectrum of intensity amplitude and phase of the terahertz wave W2 from the sample S.

FIG. 4 is a diagram showing the dynamic range of the spectrum of the terahertz wave W2 obtained from the measurement system 60. As shown in FIG. In order to obtain the results of Figure 4, the generating element 20 having two photoconductive layer 22 made of an In ₅₃ Ga ₄₇ not containing As and impurity an In ₅₃ Ga ₄₇ As impure each of these Comparative Example 1 And 2, a generator element having a photoconductive layer from which the photoconductive layer 22 was partially removed was prepared. In addition, a measurement system was configured using a general detection element for each of these four generation elements, and terahertz waves were measured. The four results on the left side of FIG. 4 were obtained.

Further, in order to obtain the result of FIG. 4, the detection element 30 having the photoconductive layer 32 made of In ₅₃ Ga ₄₇ As doped with Be and the photoconductive layer 32 as the comparative example 3 were formed on the entire surface of the substrate 31. A detection element was prepared. In addition, a measurement system was configured using a general generation element for these two detection elements, and terahertz waves were measured. Then, two results on the right side of FIG. 4 were obtained.

As shown in FIG. 4, when the generating element 20 is made of In ₅₃ Ga ₄₇ As containing impurities, the dynamic range is improved by 2.4 dB compared to the generating element of Comparative Example 1. Similarly, when the generating element 20 is made of In ₅₃ Ga ₄₇ As containing no impurities, the dynamic range is improved by 1.3 dB as compared with the generating element of Comparative Example 2. When the detection element 30 is made of In ₅₃ Ga ₄₇ As doped with Be, the dynamic range is improved by 2.7 dB compared to the detection element of Comparative Example 3.

  Therefore, it can be seen that when the generating element 20 according to this example (that is, the photoconductive layer 22 formed on the entire surface) is used, a detection signal having a large dynamic range can be obtained. On the other hand, it can be seen that a detection signal with a large dynamic range can be obtained when the detection element 30 according to the present embodiment (that is, the photoconductive layer 32 partially removed) is used.

  This increase in the dynamic range is because the generation element 20 has a large photoconductive layer 22 to increase the amount of carriers excited (generated) by the pulsed light P1, and a high-power terahertz wave W1 is generated. It is understood that it is caused by this. Further, in the detection element 30, it is understood that the irradiation region 32G of the pulsed light P2 that is the detection region of the terahertz wave W2 in the photoconductive layer 32 is left and the other regions are partially removed.

  In addition, if the photoconductive layer 32 is widely formed in the detection element 30, excited carriers may be generated by irradiation with the pulsed light P2 other than the irradiated region 32G. Generation of excited carriers in a region other than the irradiated region 32G may lead to noise. Therefore, by making the area (volume) of the photoconductive layer 32 relatively small, generation of noise is suppressed, and detection sensitivity and detection accuracy are improved.

  The separation distance G2 of the detection electrode pair 33 in the detection element 30 is preferably smaller than the separation distance G1 of the drive electrode pair 23 in the generation element 20. That is, the drive electrode pair 23 is separated from the irradiated region 22G of the photoconductive layer 22 by a distance G1, and the detection electrode pair 33 is separated from the irradiated region 32G of the photoconductive layer 32 by a distance G2 smaller than the distance G1. It is preferable.

  In the generation element 20, the carrier generation region is increased by separating the drive electrode pair 23 relatively large, and the output of the electromagnetic wave W1 is improved. Moreover, in the detection element 30, generation | occurrence | production of the unnecessary carrier which can interfere with a detection precision is suppressed by making the separation distance of the detection electrode pair 33 small. Therefore, noise in the detection signal is suppressed.

  In the present embodiment, the generating element 20 has the photoconductive layer 22 on the entire surface of the substrate 21, and the detecting element 30 is a photoconductive layer from which a portion exposed from the detection electrode pair 33 other than the irradiated region 32G is removed. The case of having 32 has been described. In the present embodiment, the generation element 20 and the detection element 30 have been described as having the substrates 21 and 31 having the same size and the same shape.

  However, the configuration of the photoconductive layers 22 and 32 is not limited to this. It is sufficient that the area of the upper surface 32S of the photoconductive layer 32 of the detection element 30 is smaller than the area of the upper surface 22S of the photoconductive layer 22 of the generating element 20.

  The configuration of the drive electrode pair 23 and the detection electrode pair 33 described above is only an example. For example, in the present embodiment, the case where the drive electrode pair 23 and the detection electrode pair 33 form a dipole antenna has been described. However, the drive electrode pair 23 and the detection electrode pair 33 may be configured and arranged to form an arbitrary antenna such as a bow-tie antenna, a stripline antenna, or a spiral antenna.

  As described above, the measurement apparatus 10 includes the generation element 20 having the photoconductive layer 22 and the drive electrode pair 23, and the detection element 30 having the photoconductive layer 32 and the detection electrode pair 33. Also, the photoconductive layer 32 of the detection element 30 has an upper surface 32S that is smaller than the upper surface 22S of the photoconductive layer 22 of the generating element 20. As a result, it is possible to provide the measuring apparatus 10 having the high-output generation element 20 and the high-sensitivity detection element 30.

  FIG. 5 is a perspective view of the detection element 30A in the measurement apparatus 10A according to the first modification of the first embodiment. FIG. 6 is a cross-sectional view of the detection element 30A, and is a cross-sectional view taken along the line VV of FIG. The detection element 30A of the measurement apparatus 10A will be described with reference to FIGS. The detection element 30A has the same configuration as that of the detection element 30 of the measurement apparatus 10 except for the configuration of the photoconductive layer 32A.

  In the detection element 30A, the photoconductive layer 32A has a protruding portion 32P protruding from the upper surface 32S in the irradiated region 32G. In this modification, the region (space) between the first and second facing portions 33A1 and 33B1 in the first and second electrode films 33A and 33B is filled with the protruding portion 32P of the photoconductive layer 32A. . In the present modification, the photoconductive layer 32A is configured such that the upper surface of the detection electrode pair 33 and the upper surface of the protruding portion 32P in the photoconductive layer 32A are in the same plane.

  In the present modification, the upper surface of the protrusion 32P functions as an irradiation region 32G of the pulsed light P2. The protrusion 32P is in physical and electrical contact with the first and second electrode films 33A and 33B (first and second opposing portions 33A1 and 33B1). Accordingly, when the projecting portion 32P is irradiated with the pulsed light P2, excited carriers are intensively generated in the projecting portion 32P, and a current (detection signal) corresponding to the excited carrier in the projecting portion 32P is detected by the detection electrode pair. It appears in 33.

  Therefore, the detection operation in the region of the photoconductive layer 32A other than the protrusion 32P, that is, the generation of noise is suppressed. Therefore, the detection sensitivity and detection accuracy of the detection element 30A are improved.

  FIG. 7 is a schematic top view of the generating element 20A in the measurement apparatus 10B according to the second modification of the first embodiment. FIG. 8 is a schematic top view of the generating element 20B in the measuring apparatus 10C according to the third modification of the first embodiment. The generation elements 20A and 20B have the same configuration as that of the generation element 20 of the measurement apparatus 10 except for the configuration of the photoconductive layers 22A and 22B, respectively.

  First, in the photoconductive layer 22A, the upper surface 22S1 has a rectangular shape. In the photoconductive layer 22B, the upper surface 22S2 has a circular shape. The photoconductive layers 22A and 22B can be formed by forming a photoconductive material in layers on the entire surface of the substrate 21 and then removing a part thereof.

  It is not necessary to provide a photoconductive layer on the entire top surface of the substrate 21 as in these modifications. The generation elements 20 </ b> A and 20 </ b> B need only have an area larger than at least the upper surface 32 </ b> S of the photoconductive layer 32 of the detection element 30. As a result, a high-power electromagnetic wave W <b> 1 can be generated with respect to the detection element 30.

  In this embodiment, the case where the generating element 20 is a photoconductive element for generating electromagnetic waves and the detecting element 30 is a photoconductive element for detecting electromagnetic waves has been described. However, the configuration of the photoconductive element may be reversed depending on the application, for example, when giving priority to the waveform of the generated electromagnetic wave and detecting weak electromagnetic waves with high sensitivity. That is, the photoconductive element 20 of the large photoconductive layer 22 may be used as the detection element, and the photoconductive element 30 of the small photoconductive layer 32 may be used as the generating element. In this case, the power source PS may be connected to the electrode pair 33 of the photoconductive element 30, and the measuring instrument ME may be connected to the electrode pair 23 of the photoconductive element 20.

  As described above, in this embodiment, the measuring device 10 includes the first photoconductive layer 22 that is formed on the first substrate 21 and the irradiated region 22G of the pulsed light P1 that is formed on the first substrate 21. And a first photoconductive element 20 having a first electrode pair 23 formed on the first photoconductive layer 22 and spaced apart from each other on the irradiated region 22G.

  The measuring device 10 is formed on the second substrate 31 and the second substrate 22, has an upper surface 32S smaller than the upper surface 22S of the first photoconductive layer 22, and is irradiated with the pulsed light P2 32G. The second photoconductive layer 32 and the second photoconductive element 30 having the second electrode pair 33 provided on the second photoconductive layer 32 and spaced apart from each other on the irradiated region 32G. Therefore, it is possible to provide the electromagnetic wave measuring apparatus 10 having a large dynamic range and capable of detecting electromagnetic waves with high sensitivity.

  FIG. 9 is a perspective view of the measuring apparatus 40 according to the second embodiment. The measuring device 40 may be referred to as a generating element (first photoconductive element) 20 similar to the measuring apparatus 10 and an electromagnetic wave detecting element (second photoconductive element, hereinafter simply referred to as a detecting element) that detects the electromagnetic wave W2. ) 50. FIG. 10 is a schematic top view of the generation element 20 and the detection element 50.

  The measurement device 40 has the same configuration as the measurement device 10 except for the configuration of the detection element 50. The detection element 50 is formed on the substrate (first substrate) 51, the photoconductive layer (second photoconductive layer) 52 formed on the substrate 51 and irradiated with the pulsed light P2, the substrate 51, and And a pair of detection electrodes (second electrode pair, hereinafter may be referred to as detection electrode pairs) 53 that are spaced apart from each other with the photoconductive layer 52 interposed therebetween.

  In this embodiment, a part of the upper surface region (partial upper surface region) 51G of the substrate 51 functions as a region for forming the photoconductive layer 52, and the photoconductive layer 52 is formed on the partial upper surface region 51G of the substrate 51. Yes. The detection electrode pair 53 is formed on the substrate 51 and sandwiches the photoconductive layer 52 on the partial upper surface region 51G. The detection electrode pair 53 is in contact with the side surface of the photoconductive layer 52.

  In the present embodiment, the detection electrode pair 53 is separated from each other by a predetermined distance G2 through the photoconductive layer 52, and the first and second electrode films 53A, whose side surfaces are in contact with the side surfaces of the photoconductive layer 52, and 53B. The first and second electrode films 53A and 53B are made of the same material as the first and second electrode films 33A and 33B in the detection electrode pair 33 of the detection element 30.

  The first and second electrode films 53A and 53B are opposed to each other with the photoconductive layer 52 interposed therebetween, and have first and second facing portions 53A1 and 53B1. In the present embodiment, the first and second facing portions 53A1 and 53B1 are in contact with the photoconductive layer 52. The first electrode film 53A includes a first connection portion 53A2 connected to the first facing portion 53A1. Further, the second electrode film 53B has a second connection portion 53B2 connected to the second facing portion 53B1.

  In the present embodiment, the photoconductive layer 52 is formed only on the partial upper surface region 51G on the substrate 51. On the other hand, in this embodiment, the photoconductive layer 22 of the generating element 20 is formed on the entire substrate 21. Also in this embodiment, the photoconductive layer 52 of the detection element 50 has an upper surface 52S that is smaller than the upper surface 22S of the photoconductive layer 22 of the generating element 20.

  In the present embodiment, the entire upper surface 52S of the photoconductive layer 52 is formed as an irradiated region 52G of the pulsed light P2. The entire photoconductive layer 52 functions as a detection region for the electromagnetic wave W2. Thus, for example, by generating the electromagnetic wave W <b> 1 having a sufficient output by the generating element 20, the photoconductive layer 52 can be provided only between the detection electrode pair 53. In the present embodiment, the presence of noise in the signal of the detected electromagnetic wave W2 is greatly suppressed. Therefore, the detection sensitivity and detection accuracy of the electromagnetic wave W2 in the detection element 50 are greatly improved.

  In the present embodiment, the case where the generating element 20 has the photoconductive layer 22 on the entire upper surface of the substrate 21 has been described. However, also in this embodiment, the photoconductive layer 22 of the generating element 20 may not be provided on the entire upper surface of the substrate 21 as long as it has a larger upper surface 22S than the photoconductive layer 52 of the detection element 50. Good. For example, the measuring device 40 may include the generating element 20A in the measuring device 10B or the generating element 20B in the measuring device 10C instead of the generating element 20.

  Further, the photoconductive layer 52 of the detection element 50 may be formed on a region other than the partial upper surface region 51G as long as it has a smaller upper surface 52S than the photoconductive layer 22 of the generating device 20. That is, the photoconductive layer 52 is not limited to the case where the entire upper surface 52S functions as the irradiated region 52G of the pulsed light P2. The photoconductive layer 52 only has to have an upper surface 52S smaller than the upper surface 22S of the photoconductive layer 22 and an irradiated region 52G of the pulsed light P2.

  As described above, in this embodiment, the measurement device 40 includes the first photoconductive layer 22 formed on the first substrate 21, the first substrate 21, and the irradiated region 22G of the pulsed light P1. On the first photoconductive element 20 having the first electrode pair 23 formed on the first photoconductive layer 22 and spaced apart from each other on the irradiated region 22G, the second substrate 51, and the second substrate 51 Formed on the second photoconductive layer 52 and the second substrate 51 having an upper surface 52S smaller than the upper surface 22S of the first photoconductive layer 22 and having an irradiated region of the pulsed light P2. A second photoconductive element 50 having a second electrode pair 53 sandwiching the second photoconductive layer 52 in the irradiated region 51G. Therefore, it is possible to provide the electromagnetic wave measuring device 40 that has a large dynamic range and can detect electromagnetic waves with high sensitivity.

10, 10A, 10B, 10C, 40 Electromagnetic wave measuring device 20, 20A, 20B Electromagnetic wave generating element 22, 22A, 22B Photoconductive layer 30, 30A, 50 Electromagnetic wave detecting element 32, 32A, 52 Photoconductive layer

Claims (6)

A first substrate, a first photoconductive layer formed on the first substrate and having an irradiated region of pulsed light, and formed on the first photoconductive layer and spaced apart from each other on the irradiated region A first photoconductive element having a first electrode pair that
A second substrate, a second photoconductive layer formed on the second substrate and having an upper surface smaller than the upper surface of the first photoconductive layer and having an irradiation region of pulsed light, and the second And a second photoconductive element having a second electrode pair formed on the photoconductive layer and spaced apart from each other on the irradiated region. The first photoconductive layer is formed over the first substrate;
The electromagnetic wave measurement apparatus according to claim 1, wherein the second photoconductive layer is formed only in a partial region on the second substrate.   3. The electromagnetic wave measurement apparatus according to claim 1, wherein the second photoconductive layer has a protruding portion that protrudes from the upper surface and contacts each of the second electrode pairs on the irradiated region. . The first electrode pairs are separated from each other by a first distance on the irradiated region of the first photoconductive layer;
The second electrode pair is separated from each other by a second distance smaller than the first distance on the irradiated region of the second photoconductive layer. Electromagnetic wave measuring apparatus as described in any one. A first substrate, a first photoconductive layer formed on the first substrate and having an irradiated region of pulsed light, and formed on the first photoconductive layer and spaced apart from each other on the irradiated region A first photoconductive element having a first electrode pair that
A second substrate, a second photoconductive layer formed on the second substrate and having an upper surface smaller than the upper surface of the first photoconductive layer and having an irradiation region of pulsed light, and the second And a second photoconductive element having a second electrode pair formed on the substrate and sandwiching the second photoconductive layer in the irradiated region. The first photoconductive layer is formed over the first substrate;
The electromagnetic wave measuring apparatus according to claim 5, wherein the second photoconductive layer has the entire upper surface formed as the irradiated region.

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