JP2009139395A - Wavelength conversion laser beam source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wavelength conversion laser beam source which is formed by optically bonding a laser beam generating part including a tapered optical amplifier or a tapered laser element to a planar waveguide type wavelength conversion element by using a single lens, and is stable and easy in optical axis adjustment. <P>SOLUTION: The wavelength conversion laser beam source includes: the laser beam generating parts (1, 2, 3) generating a fundamental wave of a laser beam; the planar waveguide type wavelength conversion element (4) converting the fundamental wave into harmonics and having a periodically poled structure part (4a) in at least a part of a core; and the lens (5) which optically bonds the laser beam generating parts (1, 2, 3) to the wavelength conversion element (4) and whose first surface (5a) opposed to the laser beam generating part is a convex in a direction vertical to the planar waveguide surface with respect to the emitted laser beam and is a convex in a direction parallel thereto and whose second surface (5b) opposed to the wavelength conversion element is a convex in the direction vertical thereto and a concave in the direction parallel thereto. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength-converted laser light source that converts the wavelength of laser light output from a tapered laser element or a tapered optical amplifier using a nonlinear optical crystal.

  In recent years, there has been a demand for a high-power visible light laser, for example, in a laser printer device or a laser display device. As a kind of such laser light source, a nonlinear optical crystal having a fundamentally polarized laser beam output from a tapered laser element or a tapered optical amplifier and having a periodically poled structure in a single mode optical waveguide or a multimode optical waveguide. A wavelength-converted laser light source that converts the wavelength of the fundamental wave into a second harmonic having a half wavelength (double frequency) is known (see, for example, Patent Document 1).

US Pat. No. 5,321,718

  The conventional wavelength conversion laser light source disclosed in Patent Document 1 includes an optical coupling between a tapered optical amplifier having a large astigmatic difference and a wavelength conversion element having a single mode waveguide using two lens systems. Therefore, there are a problem that the adjustment of the optical system is complicated and a problem that a large wavelength converted light cannot be obtained because the cross-sectional area of the single mode waveguide is small.

  In addition, the conventional wavelength conversion laser light source disclosed in Patent Document 1 includes a tapered optical amplifier having a large astigmatic difference and a wavelength conversion element having a multimode waveguide using two lens systems. Since they are coupled, there is a problem that the adjustment of the optical system is complicated and a problem that the wavelength conversion efficiency is lowered although a large wavelength converted light can be obtained because the cross-sectional area of the multimode waveguide is too wide.

  Further, the conventional wavelength conversion laser light source disclosed in Patent Document 1 varies in coupling efficiency with a single mode waveguide or a multimode waveguide depending on the temperature and current dependency of the astigmatic difference of the tapered optical amplifier. There was a problem of doing it.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wavelength conversion laser light source capable of obtaining a large output, high efficiency, and stable output with a simple structure.

  The present invention relates to a laser light generating unit that generates a fundamental wave of laser light, a planar waveguide type wavelength conversion element that has a periodically poled structure part at least in part of a core that converts the fundamental wave into a harmonic, and Convex surface in a direction perpendicular to the planar waveguide surface and parallel to the laser light emitted from the first surface facing the laser light generation portion, which optically couples the laser light generation portion and the wavelength conversion element And a lens whose second surface facing the wavelength conversion element is convex in the perpendicular direction and concave in the parallel direction.

  In the present invention, a laser beam generator that outputs a fundamental wave of high output including a taper type laser element or a taper type optical amplifier, and a planar waveguide type wavelength conversion element that converts the wavelength of the fundamental wave into a harmonic, The optical axis can be adjusted easily because it is optically coupled with a single lens that provides high coupling efficiency.

  Also, the waveguide mode of the tapered laser element or the tapered optical amplifier is the waveguide mode of the planar waveguide type wavelength conversion element, and the Gaussian propagation mode of the tapered laser element or the tapered optical amplifier is the planar waveguide type. Since this is arranged so as to be optically coupled to the Gaussian propagation mode of the wavelength conversion element, the refractive index variation induced by heat or carrier density due to the operating current or temperature change of the tapered laser element or tapered optical amplifier is viewed from the output side. Even if the horizontal beam waist position changes, there is a special effect that the change in wavelength conversion efficiency can be reduced.

Embodiment 1 FIG.
The wavelength conversion laser light source according to the first embodiment of the present invention includes a semiconductor laser element, an optical fiber incorporating a Bragg diffraction grating, a tapered optical amplifier, a lens constituting an anamorphic optical system, and a planar waveguide type. And a wavelength conversion element.

  1 is a perspective plan view of a wavelength conversion laser light source according to Embodiment 1 of the present invention, FIG. 2 is a perspective side view of the wavelength conversion laser light source of FIG. 1 viewed from the x-axis direction, and FIG. 3 is a taper of FIG. FIG. 4 is a perspective view showing an example of the structure of the planar waveguide type wavelength conversion element 4 of FIG. 1, and FIG. FIG. 5 is a diagram illustrating an example of propagation characteristics of a Gaussian beam in the waveguide of the planar waveguide type wavelength conversion element 4 of FIG. As shown in FIG. 1, the wavelength conversion laser light source according to this embodiment includes, for example, a semiconductor laser diode 1, an optical fiber 2, a taper type optical amplifier such as a taper type laser amplifier 3 and a planar waveguide type. The wavelength conversion element 4 and the lens 5 are arranged in order. The semiconductor laser diode 1, the optical fiber 2, and the taper type laser amplifier 3 constitute a laser light generator. Also, the z axis (different from the Z axis in FIG. 4) is the laser beam emission direction, the x axis and the y axis are orthogonal to each other in a plane orthogonal to the z axis, and the y axis is the main surface of each element. A perpendicular direction (or a direction perpendicular to the planar waveguide surface of the planar waveguide type wavelength conversion element 4) is shown.

  Next, a detailed configuration and operation will be described. The semiconductor laser diode 1 is a Fabry-Perot resonator type laser diode having an optical waveguide 1a. The semiconductor laser diode 1 has a maximum gain in a wavelength of 1064 nm and has a back end surface (laser light in the z-axis direction) to increase light extraction efficiency. A high-reflection film having a reflectivity of 90% on the rear surface in the emission direction), and a low reflectivity of 0.5% on the front end surface (the front surface in the emission direction of the laser beam in the z-axis direction: or the output end surface). A reflective film is provided, and the semiconductor laser diode 1 alone oscillates in a multi-longitudinal mode.

  In the semiconductor laser diode 1, the optical waveguide 1a includes a single quantum well active layer, a light guide layer, and a cladding layer in the thickness direction (y-axis direction in the figure), and oscillates in a single transverse mode. On the other hand, the optical waveguide 1a needs to have a relatively low current density and light density in order to improve reliability in the plane direction (x-axis direction), and a wide ridge type optical waveguide is adopted. Therefore, since the confinement as an optical waveguide is loose, excitation is performed in the fundamental mode, that is, the single transverse mode when the injection current value is small, but higher order due to the spatial hole burning effect when the injection current value increases and the light density increases. The mode is easy to be excited, and the width is set to about 4 to 6 μm so that the fundamental mode is maintained until the light output to be used. The polarization extinction ratio is approximately 27 dB above the laser oscillation current threshold.

  Next, a polarization-preserving optical fiber 2 having a mode field diameter of 6.6 μm is employed, and the Bragg diffraction grating 2b is disposed by irradiating the core portion 2e with ultraviolet rays through a phase mask. Since the polarization-maintaining optical fiber 2 prevents the coupling of both modes by changing the propagation speeds of the HE11 even mode and the HE11 odd mode, which are propagation modes, linearly polarized light is converted into a polarization-maintaining optical fiber. If it is coincident with the slow axis or the fast axis of 2, the linearly polarized wave is maintained. On the other hand, since the equivalent refractive index of the optical waveguide 2a is slightly different between the first axis and the slow axis, the reflection peak wavelength of the Bragg diffraction grating 2b is shifted between the first axis and the slow axis, but here the electric field direction is set so as to be strong against bending loss. Although it is aligned with the slow axis, the polarization extinction ratio is about 23 dB at the output end although it deteriorates due to the stress when the optical fiber 2 is fixed.

  The outgoing beam of the semiconductor laser diode 1 has a large aspect ratio (the ellipticity of the beam) since the optical waveguide 1a is flat, and is polarized in order to optically couple with the fiber 2 including the circular optical waveguide 2a with low loss. The aspect ratio is corrected by making the incident end face (back end face) of the storage-type optical fiber 2 into a biconical lens processed surface 2c processed by a biconical lens.

  Since the gain band of the semiconductor laser diode 1 has a single quantum well structure, the wavelength dependence is relatively gentle. If the reflection peak wavelength of the Bragg diffraction grating 2b is set in this gain band, the gain band is near the reflection peak wavelength. The gain is maximized and the oscillation wavelength of the semiconductor laser diode 1 is controlled. The longitudinal mode by this composite resonator is a single mode, multiple mode based on the relationship between the phase relationship due to the optical length of the semiconductor laser diode 1 and the Bragg diffraction grating 2b and the amount of light returning from the Bragg diffraction grating 2b to the semiconductor laser diode 1. It can oscillate in various states such as mode and coherent collapse mode.

  Here, the back end face reflectance and the front end face reflectance of the semiconductor laser diode 1 are 90% and 0.5%, the resonator length is 1.8 mm, and the Bragg diffraction grating 2b is reflected so as to oscillate in a coherent collapse mode. The coherent collapse mode is stabilized by arranging the Bragg diffraction grating 2b and the semiconductor laser diode element 1 at a distance of 50 cm or more with a rate of 5%, a reflection bandwidth of 0.5 nm, and a coupling efficiency of 80%. Thus, a spectrum half width of 0.25 nm is obtained. If the Bragg diffraction grating 2b has a reflectance of 30% and is disposed close to the semiconductor laser diode 1, it is possible to oscillate in a single longitudinal mode.

  Next, as shown in FIG. 3, the taper type laser amplifier 3 has an active layer including a planar single quantum well active layer 3a, and has a taper type gain with a current confinement structure 3b whose resistance is increased by proton injection. Region 3c (showing half of 3c in FIG. 1) is formed. The tapered gain region 3c has an incident side width of 10 μm, an output side width of 324 μm, a spread half angle of 3 degrees, a chip length of 3 mm, and a refractive index of about 3.5. Further, in order to prevent the filament phenomenon, an antireflection film (not shown) having a reflectance of 0.01% or less is applied to both end faces of the chip. Since the core 2e of the polarization plane preserving optical fiber 2 has a circular cross section in the direction perpendicular to the z-axis, the exit end face is formed as a biconical lens processed surface 2d, and the thickness direction (y (Axis direction) is mode-matched with the waveguide mode spot diameter of 0.6 μm of the optical waveguide composed of the single quantum well active layer 3a, the light guide layer 3d, and the cladding layer 3e, and in the plane direction (x-axis direction) Was incident at a spot diameter of about 1.65 μm, propagated in the active layer of the tapered laser amplifier 3 in a Gaussian beam mode, and optically amplified.

  The specific curvature radii of the biconical lens 2d in the vertical direction (y-axis direction in the figure) and in the horizontal direction (x-axis direction in the figure) were 4 μm and 11 μm, respectively. Accordingly, the outgoing beam of the taper type laser amplifier 3 is diffracted and spreads from the exit of the optical waveguide in the vertical direction, and diffracted and spreads from the exit of the optical fiber 2 in the horizontal direction. It has a disparity and almost three aspects. The light output of the sample was 5.5 W at room temperature and a current of 9 A, and the beam quality was about 1.5. The ratio of diffraction limited light in the total light output was about 85%. By the way, the taper type laser amplifier 3 has a great drawback that when the operating current and the element temperature are changed, the position of the light emitting point in the horizontal direction seen from the output side is apparently changed due to the refractive index change induced by heat generation or carrier density. . This phenomenon is somewhat improved if the heat conduction of the heat sink or submount for fixing the element is increased.

Next, as shown in FIG. 4, the wavelength conversion element 4 includes a comb-shaped electrode and a lithium niobate (LiNbO ₃ ) substrate 4c to which 5 mol% of Y-cut or X-cut magnesium oxide having an off angle θ of 5 degrees is added. A periodically poled structure 4a having a width W of 150 μm is formed by attaching a counter electrode and applying a high electric field, a core having a thickness t of 3 μm by polishing, and a clad in which silicon dioxide is vapor-deposited on both sides (not shown because it is thin) ) And the optical waveguide 4b is made and attached to the lithium niobate substrate 4c. After cutting it into length L (for example, 7 mm) and optically polishing the end face, silicon dioxide and tantalum pentoxide, or silicon dioxide and titanium dioxide having passbands for the fundamental and second harmonic wavelengths. An antireflection film made of a multilayer film is applied. The cross section of the periodically poled structure portion 4a is a parallelogram, and the width W where the entire thickness direction is inverted is 116 μm.

  FIG. 5 is a diagram showing the beam propagation characteristics of the fundamental wave and the second harmonic of the periodic polarization reversal structure 4a (illustrated with the beam waist position as the origin), and the broken line is a periodic polarization reversal of length 7 mm and width 116 μm. The structure portion 4a, the solid line shows the fundamental wave of the Gaussian beam in which the beam waist coincides with the center of the wavelength conversion element 4 with a spot diameter of 44 μm by the electric field intensity 1 / e, and the alternate long and short dash line follows the calculation formula of Boyd Kleinman The wavelength-converted second harmonic is indicated by the electric field intensity 1 / e. As can be seen from FIG. 5, it is understood that both the fundamental wave and the second harmonic wave pass through a range of 116 μm by passing a substantially collimated Gaussian beam. Since this high refractive index difference waveguide is essentially a multimode waveguide, it is necessary to make the fundamental waveguide mode and the Gaussian beam of the incident light coincide well to prevent the generation of higher order modes. For this purpose, the optimum spot diameter of the Gaussian beam incident on the waveguide is approximately 1.1 μm.

  In order to prevent the coupling efficiency and wavelength conversion efficiency of the wavelength conversion element 4 with the optical waveguide 4b from being affected by the thermal lens effect and the carrier lens effect, which are disadvantages of the taper type laser amplifier 3, the taper type laser amplifier 3 is used. These waveguide modes and the waveguide mode of the wavelength conversion element 4 may be coupled so that the Gaussian propagation mode of the tapered laser amplifier 3 is coupled to the Gaussian propagation mode of the wavelength conversion element 4. That is, even if the position of the light emitting point viewed from the output side of the taper type laser amplifier 3 fluctuates due to a change in refractive index induced by heat or carrier density, the waveguide mode in the vertical direction of the taper type laser amplifier 3 does not change. Therefore, the coupling efficiency with the wavelength conversion element 4 is stable. On the other hand, although the astigmatic difference appears to change in the horizontal direction of the tapered laser amplifier 3, the waveguide of the wavelength conversion element 4 is also in the Gaussian propagation mode. Although the beam waist position changes significantly, the change in light density is small and the change in wavelength conversion efficiency is small due to the substantially collimated light beam. Further, the waveguide mode of the tapered laser amplifier 3 is stable, and can be stably optically coupled with the waveguide mode of the wavelength conversion element 4.

  Next, the lens 5 that is a feature of the present invention will be described in detail. The lens first surface 5a of the lens 5 facing the tapered laser amplifier 3 is convex in the direction perpendicular to the planar waveguide surface (y-axis direction) and parallel to the direction of the emitted laser light (y-axis direction). The second lens surface 5b that is convex and faces the wavelength conversion element 4 is convex in the perpendicular direction and concave in the parallel direction. Since the light beam 6 having a spot diameter of 1.65 μm is emitted from the object point 6a in the horizontal direction of the tapered laser amplifier 3, the lens first surface 5a of the lens 5 is made convex to be refracted at a low light beam position to be converged light, The wavelength conversion efficiency is maximized when the lens second surface 5b is concave, the light beam 6 is substantially collimated light beam 6b, and the beam waist position is at the center of the wavelength conversion element 4. In addition, if wavefront aberration due to lens aberration is added, the wavelength conversion efficiency decreases. Therefore, it is desirable to reduce the wavefront aberration by making the both surfaces aspherical, and the distance between the lens surfaces is relatively large so that the light flux is gently Convergence suppresses the occurrence of aberrations. Next, light having a spot diameter of 0.6 μm is emitted in the vertical direction from the object point 6c to the exit of the optical waveguide of the tapered laser amplifier 3, and the refractive power is dispersed by the lens first surface 5a and the lens second surface 5b. If the aberration is suppressed and converged, and the entrance of the optical waveguide of the wavelength conversion element 4 is coupled as the image point 6d with a spot diameter of 1.1 μm, the fundamental mode is excited in the vertical direction of the wavelength conversion element 4. Since a lens aperture larger than that of diffraction theory is required, an aspheric shape is desirable on both surfaces in order to reduce spherical aberration.

  The wavelength conversion laser light source according to the present invention has a simple structure because the optical coupling between the tapered laser amplifier 3 and the wavelength conversion element 4 is performed by a single lens 5, and the optical axis is adjusted. Will be easier. Furthermore, even if the horizontal light emitting point of the taper type laser amplifier 3 fluctuates due to the thermal lens effect or the like, there is an effect that the coupling efficiency and the wavelength conversion efficiency do not change so much.

Embodiment 2. FIG.
6 is a perspective plan view of a wavelength conversion laser light source according to Embodiment 2 of the present invention, and FIG. 7 is a perspective side view of the wavelength conversion laser light source of FIG. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. The wavelength conversion laser light source according to the second embodiment includes a tapered laser amplifier 3 having a low reflection film deposited on the front end face 3f (outgoing end face) of the element, a reflectivity of approximately 99.7%, and a reflection spectrum width of 0.2 nm. The Bragg diffraction grating 2b is provided with the optical fiber 2 processed and formed in the core portion 2e. The taper type laser amplifier 3 and the Bragg diffraction grating 2b of the optical fiber 2 form an unstable resonance type laser resonator. Configure and oscillate. Since the oscillation wavelength is determined by the Bragg diffraction grating 2b, the oscillation wavelength is stable even when the external environment such as temperature changes, and it exhibits an excellent effect as a fundamental wave light source of the wavelength conversion laser light source by the wavelength conversion element 4. . The back end face 2f of the optical fiber 2 is processed obliquely so that the laser operation is not destabilized by constituting the composite resonator, and the biconical lens processing is performed on the front end face of the optical fiber 2 as in the above embodiment. An antireflection film is deposited on the tip lens 2 g and the back end surface 3 g of the tapered laser amplifier 3. The optical fiber 2 and the taper type laser amplifier 3 constitute a laser light generator.

  By configuring as described above, for example, the semiconductor laser diode required in the first embodiment is not required, the structure is simplified, and the cost can be reduced.

Embodiment 3 FIG.
8 is a see-through plan view of a wavelength conversion laser light source according to Embodiment 3 of the present invention, and FIG. 9 is a see-through side view of the wavelength conversion laser light source shown in FIG. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. The wavelength-converted laser light source according to the third embodiment is provided with a tapered laser element 30 in which a Bragg diffraction grating 3h is integrated in an element of a tapered laser amplifier as a laser light generating unit. It operates as a Distributed Bragg Reflector) laser diode. There is an advantage that the structure is simplified. Since the oscillation wavelength is likely to change depending on the operating current and temperature, it may be devised such as mounting on a Peltier element and controlling the temperature.

  By configuring as described above, a simple structure can be obtained.

  Note that a monolithic integrated master oscillator power amplifier structure in which another Bragg diffraction grating is provided in the channel waveguide portion and the front end surface of the tapered laser amplifier 3 is an antireflection film (for example, a distributed Bragg reflection laser element (illustrated) A taper type laser amplifier 3 monolithically integrated as a laser beam generator is provided), and the same effect is obtained.

Embodiment 4 FIG.
10 is a see-through plan view of a wavelength conversion laser light source according to Embodiment 4 of the present invention, and FIG. 11 is a see-through side view of the wavelength conversion laser light source shown in FIG. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. In the wavelength conversion laser light source according to the fourth embodiment, a volume type Bragg diffraction grating element 7 is disposed close to the back end surface 3g of the tapered laser amplifier 3 having a low reflection film on the front end surface 3f. It operates as a high output DBR (Distributed Bragg Reflector) laser diode (the taper type laser amplifier 3 and the Bragg diffraction grating element 7 constitute an unstable resonance type laser oscillator). Since it is a volume type Bragg diffraction grating element 7, there is an advantage that the change in characteristics is small even when the axis is shifted, and the oscillation wavelength is hardly changed by the operating current and temperature. However, it may be devised such that the temperature is controlled by mounting on a Peltier element or the like so that the distance between the back end face 3g of the tapered laser amplifier 3 and the Bragg diffraction grating element 7 does not change. The Bragg diffraction grating element 7 and the taper type laser amplifier 3 constitute a laser beam generation unit.

  By configuring as described above, a simple structure can be obtained.

Embodiment 5 FIG.
12 is a perspective plan view of a lens of a wavelength conversion laser light source according to Embodiment 5 of the present invention, and FIG. 13 is a perspective side view of the lens of FIG. 12 as viewed from the x-axis direction of the figure. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. In the lens 5 for the wavelength conversion laser light source of the fifth embodiment that can be used in each of the above-described embodiments, the lens 5 is optically necessary so that the angle of the lens 5 does not become steep (the whole has a low curvature). The unnecessary portion 5c is used, for example, to have a shape in which a surface parallel to a laser beam emission direction (z-axis) and a surface perpendicular to each other are connected by a gentle curved surface or a tapered surface. That is, generally, corners that are unnecessary portions are made gently curved or tapered to eliminate the corners. That is, the optically unused surface of the lens 5 has a shape that smoothly connects the used surfaces. Thereby, the strength of the lens 5 is improved.

Embodiment 6 FIG.
14 is a perspective plan view of a lens of a wavelength conversion laser light source according to Embodiment 6 of the present invention, and FIG. 15 is a perspective side view of the lens of FIG. 14 viewed from the x-axis direction of the figure. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. In the lens 5 for the wavelength conversion laser light source according to the sixth embodiment that can be used in each of the above-described embodiments, the unnecessary portion 5c that is not optically required is formed into a simple shape. That is, the optically unused surface has a shape that connects the used surfaces with a plurality of planes. As a result, the processing area of the aspheric mold can be reduced.

  In each embodiment, the lens 5 can be formed such that at least one surface is formed of an aspherical surface that is not an axis object. The lens 5 can be formed to constitute an anamorphic optical system. Further, the lens 5 can be formed so as to have a finite system in the vertical direction and an infinite system in the horizontal direction.

1 is a perspective plan view of a wavelength conversion laser light source according to Embodiment 1 of the present invention. FIG. It is the see-through | perspective side view which looked at the wavelength conversion laser light source of FIG. 1 from the x-axis direction of the figure. FIG. 2 is a cross-sectional view showing an example of a cross-sectional structure cut along the center in the x-axis direction of the tapered laser amplifier of FIG. 1. It is a perspective view which shows an example of the structure of the planar waveguide type wavelength conversion element of FIG. It is a figure which shows an example of the propagation characteristic of the Gaussian beam in the waveguide of the planar waveguide type wavelength conversion element of FIG. It is a perspective top view of the wavelength conversion laser light source by Embodiment 2 of this invention. It is the see-through | perspective side view which looked at the wavelength conversion laser light source of FIG. 6 from the x-axis direction of the figure. It is a see-through | perspective plan view of the wavelength conversion laser light source by Embodiment 3 of this invention. It is the see-through | perspective side view which looked at the wavelength conversion laser light source of FIG. 8 from the x-axis direction of the figure. It is a perspective top view of the wavelength conversion laser light source by Embodiment 4 of this invention. It is the see-through | perspective side view which looked at the wavelength conversion laser light source of FIG. 10 from the x-axis direction of the figure. It is a perspective top view of the lens of the wavelength conversion laser light source by Embodiment 5 of this invention. It is the see-through | perspective side view which looked at the lens of FIG. 12 from the x-axis direction of the figure. It is a perspective top view of the lens of the wavelength conversion laser light source by Embodiment 6 of this invention. It is the see-through | perspective side view which looked at the lens of FIG. 14 from the x-axis direction of the figure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Semiconductor laser diode (semiconductor laser element), 1a Optical waveguide, 2 Optical fiber (Polarization plane preservation type optical fiber), 2a Optical waveguide, 2b Bragg diffraction grating, 2c Biconical lens processing surface, 2d Biconical lens processing surface, 2e core portion, 2f back end surface, 2g tip lens, 3 taper type laser amplifier (tapered optical amplifier), 3a single quantum well active layer (active layer), 3b current confinement structure, 3c gain region, 3d light guide layer, 3e cladding layer, 3f front end face, 3g back end face, 3h Bragg diffraction grating, 4 wavelength conversion element (planar waveguide type wavelength conversion element), 4a periodic polarization inversion structure, 4b optical waveguide, 4c lithium niobate substrate, 5 Lens, 5a Lens 1st surface, 5b Lens 2nd surface, 5c Unnecessary part, 6 rays, 6a Object point, 6b Collimated rays, 6 c Object point, 6d image point, 7 Bragg grating element, 30 taper type laser element.

Claims (12)

A laser beam generator for generating a fundamental wave of the laser beam;
A planar waveguide type wavelength conversion element having a periodically poled structure part in at least a part of the core for converting the fundamental wave into a harmonic; and
Convex surface in a direction perpendicular to the planar waveguide surface and parallel to the laser light emitted from the first surface facing the laser light generation portion, which optically couples the laser light generation portion and the wavelength conversion element And a second surface facing the wavelength conversion element is convex in the perpendicular direction and concave in the parallel direction;
A wavelength conversion laser light source characterized by comprising:   A laser beam generator having a semiconductor laser element having an antireflection film on the front end surface on the laser beam emission side, an optical fiber having a Bragg diffraction grating in the core, and a taper type optical amplifier having antireflection films on both end surfaces The wavelength conversion laser light source according to claim 1, wherein the wavelength conversion laser light sources are arranged in order in a laser beam emission direction.   The laser beam generator has an optical fiber with a highly reflective Bragg diffraction grating in the core, and a tapered optical amplifier with a low-reflection film on the front end surface on the laser beam emission side. The wavelength-converted laser light source according to claim 1, wherein an unstable resonance type laser oscillator is configured by the tapered optical amplifier and the Bragg diffraction grating of the optical fiber.   4. The wavelength conversion laser light source according to claim 2, wherein the optical fiber is a polarization plane preserving type.   2. The wavelength-converted laser light source according to claim 1, wherein the laser light generation unit is composed of a tapered laser element in which a Bragg diffraction grating is integrated in a tapered optical amplifier.   2. The wavelength-converted laser light source according to claim 1, wherein the laser light generation unit comprises a tapered optical amplifier in which distributed Bragg reflection laser elements are monolithically integrated.   The laser beam generator comprises a volume type Bragg diffraction grating element and a taper type optical amplifier having a low reflection film on the front end surface on the laser beam emission side, arranged in order in the laser beam emission direction. 2. The wavelength conversion laser light source according to claim 1, wherein an optical amplifier and the Bragg diffraction grating element constitute an unstable resonance type laser oscillator.   The wavelength conversion laser light source according to any one of claims 1 to 7, wherein the lens has a shape in which an optically unused surface smoothly connects between used surfaces.   8. The wavelength-converted laser light source according to claim 1, wherein the lens has a shape in which an optically unused surface connects the used surfaces with a plurality of planes. 9.   10. The wavelength-converted laser light source according to claim 1, wherein at least one surface of the lens is formed of an aspheric surface that is not an axis target. 11.   The wavelength conversion laser light source according to any one of claims 1 to 9, wherein the lens constitutes an anamorphic optical system.   The wavelength conversion laser light source according to any one of claims 1 to 11, wherein the lenses are arranged in a finite system in the vertical direction and an infinite system in the horizontal direction.

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