JP2016096333A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high optical output semiconductor laser device in which a light beam has superposed wavelengths even when a reflective wavelength dispersion element is used.SOLUTION: The semiconductor laser device includes: a plurality of semiconductor laser elements 1a, 1b, 1c emitting light beams 11a, 11b, 11c of mutually different wavelengths; a reflective wavelength dispersion element 6 for reflecting the light beams emitted from each of light emission points 2a, 2b, 2c with wavelength dependent diffraction angles; a partial reflection mirror 7, constituting an external resonator along with an end face of the semiconductor laser element, for partially reflecting a light beam 12 diffracted at the reflective wavelength dispersion element; a beam coupling element 4 for superposing at the reflective wavelength dispersion element a light beam emitted from each of the light emission points; and a beam divergence angle correction element 5, disposed so as to make the light beam incident on the reflective wavelength dispersion element and the light beams diffracted at the reflective wavelength dispersion element to pass, for correcting divergence angles of the light beams so that light beams incident on the partial reflection mirror becomes parallel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor laser device that superimposes light beams having different wavelengths.

  In a conventional semiconductor laser device (for example, Patent Document 1), a lens is arranged immediately after each light emitting point of the semiconductor laser bar, thereby condensing the beam from each light emitting point on the wavelength dispersive element and in the vicinity of the wavelength dispersive element. Parallelizing each beam by arranging lenses, superimposing the beam from each light emitting point by the wavelength dispersion of the wavelength dispersion element, and forming a partial transmission mirror on the superimposed beam to form an external resonator Thus, the brightness of the beam output from the apparatus is improved.

US Patent Application Publication No. 2013/0215517

  In such a wavelength-coupled external cavity semiconductor laser device, when a reflective wavelength dispersion element is used, the separation angle between the light beam incident on the wavelength dispersion element and the light beam diffracted and reflected from the wavelength dispersion element Therefore, there is a problem that the beam collimating element cannot be disposed in the vicinity of the wavelength dispersion element.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser device that focuses a beam from each light emitting point on the wavelength dispersive element by disposing a beam coupling element immediately after each light emitting point of the semiconductor laser bar. It is to provide a small and highly efficient semiconductor laser device that can realize wavelength superimposition of a light beam even when using a laser beam.

In order to achieve the above object, a semiconductor laser device according to the present invention includes:
A semiconductor laser device having a plurality of light emitting points that emit light beams having different wavelengths;
A reflective wavelength dispersion element that reflects the light beam emitted from each light emitting point at a wavelength-dependent diffraction angle;
An external resonator together with the end face of the semiconductor laser element, and a partially reflecting mirror that partially reflects the light beam diffracted by the reflective wavelength dispersion element;
A beam combining element disposed on the emission side of the semiconductor laser element for superimposing a light beam emitted from each light emitting point on the reflective wavelength dispersion element;
The light beam incident on the reflection type wavelength dispersive element and the light beam diffracted by the reflection type wavelength dispersive element are arranged to pass, and the light beam diverges so that the light beam incident on the partial reflection mirror is parallel. A beam divergence angle correcting element for correcting the angle.

  According to the present invention, it is possible to reduce the size of the external resonator by configuring the light beam incident on the reflection type wavelength dispersion element and the light beam diffracted by the reflection type wavelength dispersion element to pass through the beam divergence angle correction element. Figured. Further, since a reflection type wavelength dispersion element that can have higher diffraction efficiency than a transmission type wavelength dispersion element can be used, the oscillation efficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the semiconductor laser apparatus by Embodiment 1 of this invention, Fig.1 (a) is a side view, FIG.1 (b) is a top view. FIGS. 2A and 2B are configuration diagrams illustrating a semiconductor laser device according to a second embodiment of the present invention, in which FIG. 2A is a side view and FIG. 2B is a plan view. FIGS. 3A and 3B are configuration diagrams illustrating a semiconductor laser device according to a third embodiment of the present invention, in which FIG. 3A is a cross-sectional view, and FIG. FIGS. 4A and 4B are configuration diagrams showing a semiconductor laser device according to a fourth embodiment of the present invention, in which FIG. 4A is a cross-sectional view and FIG. 4B is a plan view.

Embodiment 1 FIG.
1A and 1B are configuration diagrams showing a semiconductor laser device according to a first embodiment of the present invention. FIG. 1A is a side view and FIG. 1B is a plan view. The semiconductor laser device includes a plurality of semiconductor laser elements 1a, 1b, 1c, a beam collimating optical system 3, a beam combining element 4, a beam divergence angle correcting element 5, a reflective wavelength dispersion element 6, and a partial reflection mirror. 7 and the like, and using the wavelength dispersion effect of the reflection type wavelength dispersion element 6, light beams 11a, 11b, 1b, 2c emitted from the light emitting points 2a, 2b, 2c of the semiconductor laser elements 1a, 1b, 1c and having different wavelengths 11c is configured to be superposed on one light beam 12. Here, a case where three semiconductor laser elements are used is illustrated, but the present invention can be similarly applied to two or four or more semiconductor laser elements.

  Hereinafter, for easy understanding, the arrangement direction of the semiconductor laser elements 1a to 1c is defined as the X direction, the traveling direction of the light beam 11b is defined as the Z direction, and the X direction and the direction perpendicular to the Z direction are defined as the Y direction.

  The semiconductor laser elements 1a to 1c generate light by recombination of electrons and holes by energizing the semiconductor crystal. The semiconductor crystal has two opposing end faces. A general semiconductor laser element is configured as an internal resonator type using these two end faces as a resonator mirror. On the other hand, the semiconductor laser devices 1a to 1c according to the present embodiment are configured as an external resonator type in which the rear end face is used as a first resonator mirror and the external partial reflection mirror 7 is used as a second resonator mirror. The In this case, it is preferable that the rear end face is provided with a highly reflective coating and the front end face is provided with a non-reflective coating. Such an external resonator satisfies the laser resonance condition in the X direction and the Y direction.

  The semiconductor laser elements 1a to 1c may be configured as individual elements (a so-called single emitter semiconductor laser) in which one chip has one light emitting point (emitter), or one chip emits two or more lights. You may comprise as an integrated element (what is called a semiconductor laser bar) which has a point.

  The light beams 11a to 11c radiated from the light emitting points 2a to 2c propagate along the optical axis shown in FIG. 1, but their beam widths and divergence angles are independent in the X direction and the Y direction. The divergence angle of light generated from a general semiconductor laser element is anisotropic, and diverges rapidly in the Y direction and diverges slowly in the X direction. The beam product parameter (BPP: product of beam radius and beam divergence angle) indicating the quality of the light beam is generally the diffraction limit in the Y direction, but is generally about 10 times the diffraction limit in the X direction. It is.

  The beam collimating optical system 3 has a function of collimating the light beams 11a to 11c emitted from the light emitting points 2a to 2c of the semiconductor laser elements 1a to 1c. For example, a cylindrical lens, a spherical lens, and an aspheric lens , A mirror having a curvature, or a combination thereof. As described above, the divergence angle of the light beam emitted from the semiconductor laser element is anisotropic, that is, the X-direction divergence angle is different from the Y-direction divergence angle. Therefore, the beam collimating optical system 3 combines the plurality of lenses or the curvature mirror so that the X direction power and the Y direction power are such that the X direction divergence angle and the Y direction divergence angle of the light beam become substantially zero. It is preferable to configure different optical systems. Further, the beam collimating optical system 3 may include a beam rotating optical system (for example, a cylindrical lens array (see FIG. 2 of Japanese Patent Laid-Open No. 2000-137139), a reflector array (see International Publication No. 98/08128), etc.). Good. The light beam having anisotropy emitted from the light emitting point rotates about 90 degrees in a plane perpendicular to the optical axis by passing through such a beam rotating optical system.

  The beam combining element 4 is arranged on the emission side of the semiconductor laser elements 1a to 1c, preferably in the vicinity of the light emitting points 2a to 2c, and spatially transmits the light beam emitted from each light emitting point on the reflective wavelength dispersion element 6. For example, a cylindrical lens, a spherical lens, an aspherical lens, a mirror having a curvature, or a combination thereof, preferably having a refractive power only in the X direction and having a Y direction power of zero. Includes a cylindrical lens.

  By setting the focal length of the beam combining element 4 in the X direction as fa and the reflective wavelength dispersive element 6 at a distance of approximately fa from the light emitting point 2, the light beams 11a to 11c emitted from the light emitting points 2a to 2c are reflected. It is spatially superimposed on the type wavelength dispersion element 6. At this time, since the distance between the light emitting points 2 a to 2 c and the beam combining element 4 is sufficiently shorter than the focal length fa, the divergence angle of the light beam emitted from the light emitting point is hardly influenced by the beam combining element 4.

  As described above, the light beams 11a to 11c are collimated when they pass through the beam collimating optical system 3, but the distance from the beam collimating optical system 3 to the reflective wavelength dispersion element 6 is the beam collimating optics. Since it is sufficiently longer than the Rayleigh length of the light beam after being emitted from the system 3, and the divergence angle of the light beam is hardly influenced by the beam combining element 4, the light beams 11a to 11c are propagated while diverging again. become.

  The beam divergence angle correction element 5 has a function of correcting the divergence angle of the light beam so that the light beam 12 incident on the partial reflection mirror 7 becomes parallel. For example, a cylindrical lens, a spherical lens, an aspheric lens, a curvature Including a cylindrical lens having a refractive power only in the X direction and having zero power in the Y direction.

  By setting the beam divergence angle correction element 5 at a distance fb from the light emitting points 2a to 2c, where the X-direction focal length of the beam divergence angle correction element 5 is fb, the divergence angles of the light beams 11a to 11c are corrected. The light beam is collimated. Here, in order to prevent the light beams 11 a to 11 c superimposed on one point on the reflection type wavelength dispersion element 6 using the beam combining element 4 from shifting, the beam divergence angle correction element 5 is in the vicinity of the reflection type wavelength dispersion element 6. It is preferable that fa and fb have the same length as much as possible. Further, in order to completely overlap the plurality of beams 11a to 11c on the reflective wavelength dispersion element 6, it is preferable that the position of the beam combining element 4 is slightly shifted.

  The reflective wavelength dispersion element 6 has a function of reflecting the light beams 11a to 11c having different wavelengths at a wavelength-dependent diffraction angle, and has, for example, an uneven lattice pattern periodically arranged at a pitch less than the wavelength. It is composed of a reflective diffraction grating. Since the plurality of light beams 11a to 11c superimposed on the reflective wavelength dispersion element 6 are diffracted at different angles according to the respective wavelengths, the incident angles are shifted in advance corresponding to the difference between these diffraction angles. Can be superimposed on a single light beam 12.

  Here, with respect to the ZX plane, the arrangement angle Θ of the reflective wavelength dispersion element 6 is such that any one of the incident angles α of the plurality of light beams 11a to 11c with respect to the reflective wavelength dispersion element 6 and the superimposed light beam 12 It is preferable to set so that the diffraction angle β is substantially equal. Such an arrangement in which the incident angle α and the diffraction angle β are substantially equal is generally called a Littrow arrangement, and the diffraction efficiency of the reflective wavelength dispersion element 6 is the highest.

  If the reflective wavelength dispersion element 6 is completely Littrow arrangement, it becomes difficult to separate the light beams 11a to 11c from the superimposed light beam 12. Therefore, it is preferable that the reflection type wavelength dispersion element 6 is slightly inclined with respect to the YZ plane so that the light beam 12 is inclined with respect to the ZX plane, whereby the light beams 11a to 11c and the light beam 12 are separated. Is possible. It has been found by experiments by the present inventors that the diffraction efficiency decreases when the tilt angle Ψ of the reflective wavelength dispersion element 6 becomes too large. As a result, the tilt angle Ψ is preferably 5 ° or less. . The tilt direction of the reflection type wavelength dispersion element 6 may be tilted in the YZ plane as shown in FIG. 1B and / or tilted in the XY plane. It can be set to be inclined with respect to the ZX plane.

  As the reflective wavelength dispersion element 6, a reflective diffraction grating is used. In the transmissive diffraction grating, when diffracted light is transmitted, a reflection loss occurs on the back surface where the grating pattern is not formed. On the other hand, in the reflection type diffraction grating, since such back surface reflection loss does not occur, higher diffraction efficiency can be obtained compared to the transmission type. In particular, when a reflective diffraction grating having a dielectric multilayer film on which a grating pattern is formed is used, the number density of grooves is about 1850 lines / mm for a broadband beam with a wavelength of 960 nm to 1000 nm. Theoretically, a diffraction efficiency of 95% or more can be obtained even with the above diffraction grating.

  The light beam 12 diffracted and superimposed by the reflection type wavelength dispersion element 6 at the diffraction angle β is incident again on the beam divergence angle correction element 5 disposed in the vicinity of the reflection type wavelength dispersion element 6. The beam divergence angle correction element 5 has an X-direction focal length fb, and the light beam 12 is collimated when entering the beam divergence angle correction element 5. Therefore, the light beam 12 that has passed through the beam divergence angle correction element 5 is condensed from the beam divergence angle correction element 5 so as to be a beam waist at a distance fb.

  At this time, by arranging the partial reflection mirror 7 in the vicinity of the beam waist of the light beam 12, the light beam 12 incident on the partial reflection mirror 7 becomes substantially parallel. As a result, a stable optical resonator is obtained between the rear end faces of the semiconductor laser elements 1a to 1c and the partial reflection mirror 7. A part of the light beam 12 passes through the partial reflection mirror 7 and is extracted as a laser output 21, while the remaining part of the light beam 12 is reflected by the partial reflection mirror 7 and passes through the reflective wavelength dispersion element 6. Propagating in the reverse direction toward the light emitting points 2a to 2c of the semiconductor laser elements 1a to 1c contributes to the laser oscillation operation. In order to realize a stable optical resonator, the position of the partial reflection mirror 7 is preferably in the range of 0.6 × fb to 1.4 × fb from the beam divergence angle correction element 5, and further, 0.8 × fb to 1 The range of 2 × fb is more preferable.

  In a state where this external resonator is established, one optical axis through which the superimposed light beam 12 propagates is formed between the partial reflection mirror 7 and the reflection type wavelength dispersion element 6, while the reflection is performed. Three optical axes through which the light beams 11a to 11c propagate individually are formed between the mold wavelength dispersion element 6 and the light emitting points 2a to 2c. Therefore, the laser oscillation wavelengths at the respective light emitting points 2a to 2c are uniquely determined so that these optical axes are established. That is, when the external resonator is established, the oscillation wavelengths λa, λb, and λc at the light emitting points 2a, 2b, and 2c are changed so that the light beams 11a to 11c are superimposed on each other in FIG. They are uniquely determined so as to be different from each other (λa ≠ λb ≠ λc ≠ λa).

  In this way, the three light beams 11a to 11c are superposed from the light emitting points 2a to 2c to form one light beam 12, which is taken out from the partial reflection mirror 7 as the laser output 21, thereby increasing the luminance about three times. Is possible. Note that the luminance can be further improved by increasing the number of semiconductor laser elements and light emitting points.

  In the present embodiment, the beam divergence angle correcting element 5 is disposed in the vicinity of the reflective chromatic dispersion element 6, and the light beam passes through the beam divergence angle correcting element 5 before and after the reflection of the reflective chromatic dispersion element 6. Explained. However, the beam divergence angle correction element 5 is installed not at the vicinity of the reflective wavelength dispersion element 6 but at a position where the light beam 12 is sufficiently separated from the light beams 11a to 11c, that is, only the light beam 12 passes. However, in this case, the focal length of the beam divergence angle correcting element 5 becomes very long. According to the results of experiments conducted by the present inventors, it has been found that the longer the focal length of the beam divergence angle correction element 5, the more the resonator loss increases and the laser output 21 decreases.

  Further, if a large separation angle between the light beams 11a to 11c and the superimposed light beam 12 is secured, it is possible to arrange the beam divergence angle correcting element 5 in the vicinity of the reflective wavelength dispersion element 6, In that case, the Littrow arrangement is lost, the diffraction efficiency is lowered, and the laser output 21 is lowered.

  As described above, in the present embodiment, the plurality of beams 11a to 11c emitted from the plurality of light emitting points 2a to 2c are reflected on the reflective wavelength dispersion element 6 by using the beam combining element 4 disposed in the vicinity of the light emitting point. In the semiconductor laser device that superimposes on one point and converts it to one light beam 12, it is possible to configure an external resonator with the beam divergence angle correcting element 5 arranged in the vicinity of the reflective wavelength dispersion element 6. Become. Therefore, the focal length of the beam divergence angle correcting element 5 can be shortened, and the resonator loss can be reduced. Further, by using the reflection type wavelength dispersion element 6 that can expect higher diffraction efficiency than the transmission type wavelength dispersion element, the laser output 21 is greatly increased, and the oscillation efficiency is improved. Furthermore, since the beam coupling element 4 can be disposed in the vicinity of the light emitting point, the device can be miniaturized.

Embodiment 2. FIG.
2A and 2B are configuration diagrams showing a semiconductor laser device according to a second embodiment of the present invention. FIG. 2A is a side view and FIG. 2B is a plan view. 2, the same reference numerals as those in FIG. 1 denote the same or similar parts. In the first embodiment, the X-direction focal length of the beam divergence angle correcting element 5 is made to correspond to the distance fb from the light emitting point to the beam divergence angle correcting element. However, in this embodiment, the beam divergence angle correcting element 31 The X-direction focal length fc is set to about twice or more the distance fb (fc ≧ 2 × fb), and the superimposed light beam 12 is parallel when passing through the beam divergence angle correction element 31. ing.

  Here, the X-direction focal length fc of the beam divergence angle correction element 31 will be considered. In the present embodiment, the light beams 11a to 11c having a specific divergence angle pass through the beam divergence angle correction element 31, and then are diffracted by the reflective wavelength dispersion element 6, so that the superimposed light beam 12 is re-beamed. When passing through the divergence angle correction element 31, the light beam 12 is collimated. That is, the light beam is collimated by passing the light beam having a specific divergence angle through the beam divergence angle correction element 31 twice.

  In order to obtain the X-direction focal length fc of the beam divergence angle correction element 31, the combined focal length Fall (two divergence angle corrections) when the two beam divergence angle correction elements 31 are arranged at a distance of 2L. What is necessary is to consider a focal length combining elements). The combined focal length Fall can be obtained by the following equation (1).

  The distance S from the beam divergence angle correction element 31 to the combined focal point obtained by the equation (1) can be obtained by the equation (2).

  In order to establish an external resonator, since it is preferable that S> fb, fc is obtained by the following equation (3).

  Next, Formula (3) will be specifically examined. As an example, substituting fb = 550 mm and L = 50 mm into Equation (3) results in fc> 1152.268 mm. Therefore, a beam divergence angle correction element 31 having a focal length fc that satisfies the above-described results may be used.

  As described above, in the present embodiment, the beam divergence angle correction element 31 is set to have a focal length fc of the beam divergence angle correction element 31 that is approximately twice or more the distance fb from the light emitting point to the beam divergence angle correction element. The superposed light beam 12 after passing through can be collimated. Therefore, the position of the partial reflection mirror 7 behind the beam divergence angle correction element 31 can be arbitrarily set. As a result, the degree of freedom and arrangement latitude of the device configuration are remarkably increased, and the design and assembly can be simplified. Further, since the beam diameter of the light beam 12 on the partial reflection mirror 7 is increased, the power density is reduced and the reliability of the apparatus is enhanced.

Embodiment 3 FIG.
3 is a block diagram showing a semiconductor laser device according to a third embodiment of the present invention. FIG. 3A is a side view and FIG. 3B is a plan view. 3, the same reference numerals as those in FIG. 1 denote the same or similar parts.

  In order to explain the effect of the third embodiment, first, the restriction on the installation location of the partial reflection mirror 7 in the first embodiment which is a comparison target will be described again.

  In the first embodiment, the beam divergence angle correction element 5 is used to collimate the beams 11a, 11b, and 11c incident on the reflective wavelength dispersion element 6 in the X direction. The superimposed light beam 12 diffracted by the reflection type wavelength dispersion element 6 and incident again on the beam divergence angle correction element 5 is condensed in the X direction, but a partial reflection mirror 7 is provided in the vicinity of the beam waist. doing. Since the position of the beam waist is away from the beam divergence angle correction element 5 by the focal length fb of the beam divergence angle correction element 5, as is apparent from FIG. It will be installed in the vicinity.

  Around the semiconductor laser elements 1a to 1c, a beam collimating optical system 3 and a beam coupling element 4 are installed. Further, the semiconductor laser element 1 is provided with wiring (not shown) for supplying power. In order to install these components, it may be difficult to install the partial reflection mirror 7 and its angle adjustment mechanism. Therefore, if the inclination angle Ψ of the reflective wavelength dispersion element 6 is increased in order to ensure a sufficient installation space, the diffraction efficiency of the reflective wavelength dispersion element 6 tends to decrease, and the laser output obtained tends to decrease.

  As a countermeasure, in the third embodiment, an X-direction relay lens 41 is installed between the reflective wavelength dispersion element 6 and the partial reflection mirror 7. The X-direction relay lens 41 has refractive power only in the X direction, the focal length in the X direction is fd, and the refractive power in the Y direction is zero. The X-direction relay lens 41 is installed at a position where the distance between the reflective wavelength dispersion element 6 and the X-direction relay lens 41 is approximately fb + fd + L. The partial reflection mirror 7 is installed in the vicinity of a position where the distance from the X-direction relay lens 41 is fd. Therefore, the distance between the reflective wavelength dispersion element 6 and the partial reflection mirror 7 is approximately fb + 2 × fd + L. When the distance between the elements is satisfied, a beam waist in the X direction is formed on the partial reflection mirror 7 and stable oscillation is possible. Since the distance between the partial reflection mirror 7 and the semiconductor laser element 1 is approximately 2 × fd, the tilt angle Ψ of the reflective wavelength dispersion element 6 can be set by appropriately setting fd, that is, the focal length of the X-direction relay lens 41. Regardless, it is possible to secure a sufficient space for installing the partial reflection mirror 7 and its adjustment mechanism.

  As described above, according to the present embodiment, it is possible to obtain high diffraction efficiency while keeping the tilt angle Ψ of the reflective wavelength dispersion element 6 small. As a result, there is a remarkable effect that both high laser output and ease of adjustment and assembly can be achieved.

Embodiment 4 FIG.
4A and 4B are configuration diagrams showing a semiconductor laser device according to Embodiment 4 of the present invention, in which FIG. 4, the same reference numerals as those in FIG. 1 denote the same or similar parts.

  The difference between the fourth embodiment and the first to third embodiments is that the beam divergence angle correcting element 51 has an isotropic spherical lens around the optical axis, that is, the same refractive power in the X direction and the Y direction. It is a lens. The beam divergence angle correction elements 5 and 31 in the other first to third embodiments are cylindrical lenses having refractive power only in the X direction, but the beam divergence angle correction element 51 in the fourth embodiment is a spherical lens. Thus, it also has refractive power in the Y direction.

The centers of the light beam 11 directed from the semiconductor laser element 1 to the reflective wavelength dispersion element 6 and the beam divergence angle correction element 51 are shifted in the Y direction (hereinafter, the shift amount is δ, see FIG. 4B). . At this time, the beam is deflected in the Y direction by the refractive power of the beam divergence angle correcting element 51 in the Y direction. The deflected angle is determined by using the focal length fb of the beam divergence angle correcting element 51 and the shift amount δ.
Y direction deflection angle = tan ⁻¹ (δ / fb) (4)
It is represented by

  Since the light beam 11 is deflected in the Y direction and enters the reflection type wavelength dispersion element 6, the light emitted from the reflection type wavelength dispersion element 6 travels in the direction opposite to the Y direction as shown in FIG. . That is, even when the reflective wavelength dispersion element 6 is installed in the vertical direction without being inclined, the incident beams (light beams 11a, 11b, 11c) and the outgoing beams (superimposed light beam 12) to the reflective wavelength dispersion element 6 are not affected. The optical path is easily separated. Since the reflective wavelength dispersion element 6 is not tilted, it is possible to suppress a decrease in diffraction efficiency. On the other hand, when the reflection-type wavelength dispersion element 6 is inclined, the emission angle in the Y direction changes depending on the wavelength as the dispersion axis is inclined with respect to the light traveling direction. Although this effect is smaller as the tilt angle Ψ is smaller, the beam quality (condensability) of the laser output from the external resonator is slightly degraded. According to the present embodiment, it is possible to suppress the deterioration of the light collecting property due to this phenomenon, and as a result, it is possible to obtain a laser output with high output and good beam quality.

  When fb = L, the light beam 12 superimposed on the light beam 11 becomes a parallel beam. When fb ≠ L, the light beam 11 superimposed on the light beam 11 does not become parallel, and the beam has a divergence angle in the Y direction. Therefore, the divergence angle is corrected to change the incident beam to the partial reflection mirror 7. A Y-direction relay lens 52 may be inserted for parallelization. Further, in order to adjust the distance of the partial reflection mirror 7, an X-direction relay lens may be further installed as in the third embodiment, or a refractive power is provided in both the X direction and the Y direction so that the X direction It is also possible to configure the relay lens and the Y-direction relay lens as a single sheet.

  As described above, according to the present embodiment, the light beam 12 superimposed on the light beam 11 can be separated even if the reflective wavelength dispersion element 6 is installed without being tilted. There is a remarkable effect that it is possible to obtain a laser output with little deterioration.

1a, 1b, 1c semiconductor laser element, 2a, 2b, 2c light emitting point,
3 beam collimating optics, 4 beam combining element, 5 beam divergence angle correcting element,
6 reflection type wavelength dispersion element, 7 partial reflection mirror,
11a, 11b, 11c light beams, 12 superimposed light beams,
21 Laser output, 31 Beam divergence angle correction element.
41 X-direction relay lens, 51 Beam divergence angle correction element,
52 Y direction relay lens.

Claims (8)

A semiconductor laser device having a plurality of light emitting points that emit light beams having different wavelengths;
A reflective wavelength dispersion element that reflects the light beam emitted from each light emitting point at a wavelength-dependent diffraction angle;
An external resonator together with the end face of the semiconductor laser element, and a partially reflecting mirror that partially reflects the light beam diffracted by the reflective wavelength dispersion element;
A beam combining element disposed on the emission side of the semiconductor laser element for superimposing a light beam emitted from each light emitting point on the reflective wavelength dispersion element;
The light beam incident on the reflection type wavelength dispersive element and the light beam diffracted by the reflection type wavelength dispersive element are arranged to pass, and the light beam diverges so that the light beam incident on the partial reflection mirror is parallel. A semiconductor laser device comprising: a beam divergence angle correction element for correcting an angle. The plurality of light emitting points are arranged linearly along the first direction,
2. The semiconductor laser device according to claim 1, wherein the beam combining element includes a cylindrical lens having a refractive power only in the first direction.   3. The semiconductor laser device according to claim 2, wherein the beam divergence angle correcting element includes a cylindrical lens having a refractive power only in the first direction.   The distance from the beam divergence angle correction element to the partial reflection mirror is greater than 0.6 × fb and less than 1.4 × fb, where fb is the focal length of the beam divergence angle correction element in the first direction. 4. The semiconductor laser device according to claim 3, wherein:   4. The semiconductor laser device according to claim 3, wherein a focal length in the first direction of the beam divergence angle correcting element is at least twice as long as a distance from a light emitting point to the beam divergence angle correcting element.   2. The semiconductor laser device according to claim 1, wherein the reflective wavelength dispersion element is inclined in a direction intersecting with a plane including an optical axis of a light beam emitted from each light emitting point.   7. The semiconductor laser device according to claim 2, further comprising a lens disposed between the beam divergence angle correcting element and the partial reflection mirror and having a refractive index in a first direction. .   The semiconductor laser device according to claim 1, wherein the beam divergence angle correction element is an isotropic lens around an optical axis.

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