JP4402030B2 - External cavity semiconductor laser - Google Patents

Description

  The present invention relates to an external resonant semiconductor laser, and more particularly to an external resonant semiconductor laser using a semiconductor laser element that emits laser light in at least two directions from the same end face.

  Conventionally, a semiconductor laser is used as a small coherent light source for various applications such as optical communication technology, optical measurement technology, and optical processing technology. However, semiconductor lasers generally have a small optical output, and the wavelength and light quantity are likely to shift depending on temperature changes. Furthermore, increasing the semiconductor laser drive current to increase the optical output widens the spectrum width. There is a point.

On the other hand, the external resonance type semiconductor laser is known to feed back a part of laser light (specific wavelength light) emitted from the semiconductor laser element to the semiconductor laser element to stabilize the optical output. For example, as shown in Patent Document 1, there has been proposed a method in which only a specific wavelength light in a beam is fed back to the semiconductor laser element by using a lens and a holographic diffraction grating for the back beam of the semiconductor laser element.
JP 58-71687 A

  In recent years, an external resonance type semiconductor laser utilizing the high output characteristics of a gain waveguide type semiconductor laser has been proposed. In the gain waveguide type semiconductor laser, the laser light emitted from the same end face is emitted in two directions off the optical axis of the waveguide in the laser element, so that one of the laser lights is fed back to the semiconductor laser element, The other laser beam is used as output light.

Examples of the external resonance type semiconductor laser using the gain waveguide type semiconductor laser include Non-Patent Documents 1 and 2 and Patent Document 2.
Volker Raab, etal., "External resonator design for high-power laser diodes that yield 400 mW of TEM00 power", p167-169, Vol.27, No.3, OPTICS LETTERS, February 1,2002 Volker Raab, etal., "Tuning high-power laser diodes with as much as 0.38 W of power and M2 = 1.2 over a range of 32 nm with 3-GHz bandwidth", p1995-1997, Vol.27, No.22, OPTICS LETTERS, November 15,2002 WO03 / 055018 A1

  FIG. 1 shows an external cavity semiconductor laser described in Non-Patent Document 1. Output light 8 and 9 are emitted from a gain-guided semiconductor laser (Gain-guided diode laser) in two directions away from the optical axis 7 of the waveguide in the laser element. In order to collimate the emitted light, a fast axis collimator (FAC) 2 and a slow axis collimator (SAC) 3 are provided. A part of the laser light passes through the aperture 5, is reflected by the high reflection (HR) mirror 4, passes again through the aperture 5, SAC and FAC, and returns to the semiconductor laser 1, and the external resonance laser light 8 is returned. Form. On the other hand, the output laser beam 9 is emitted through the FAC, SAC and the aperture 6.

  Non-Patent Document 2 is intended to narrow the spectrum width of laser light emitted from an external resonant semiconductor laser. Regarding the external resonant laser light 18, a part of the laser light emitted from the semiconductor laser element 10 is used. The FAC 11 and the lens 12 pass through the aperture 13, and the lens 14 corrects the light into parallel light. The etalon 15 and the diffraction grating 16 constitute a resonance optical system for specific wavelength light. In FIG. 2, the device is devised to increase wavelength selectivity by adjusting the etalon 15 and adjusting the angle of the diffraction grating 16. Reference numeral 17 denotes reflection means for leading the output laser beam 19 to the outside.

  The external resonance type semiconductor laser of Patent Document 2 is basically similar in configuration to that shown in FIG. 2, and a part 24 of the laser light emitted from the semiconductor laser 20 is diffracted through the cylinder lens 21 and the etalon 22. The light enters the grating 23 and returns the reflected light 25 to the semiconductor laser 20. The other laser beam from the semiconductor laser 20 is emitted as the output laser beam 26.

  However, even in the external resonance type semiconductor laser using the gain waveguide type semiconductor laser as described above, the phenomenon that the spectrum width is widened occurs when the drive current of the laser element is increased. Such a phenomenon occurs when, for example, laser light emitted from an external resonant laser is converted into SHG light when used as an excitation laser for wavelength conversion to obtain second harmonic generation (SHG light). It also causes a decrease in efficiency. Further, in spectroscopic measurement applications and wavelength conversion applications, it is necessary to secure a stable and high-power laser beam and to narrow the spectral width of the output laser beam as much as possible. It is necessary to set it to 1 nm or less, preferably 0.05 nm or less.

  The problem to be solved by the present invention is to solve the above-mentioned problems, and can output a laser beam having a high output and an extremely narrow spectrum width, and the external resonance type with a small number of parts without complicating the configuration. A semiconductor laser is provided.

In the invention according to claim 1, a semiconductor laser element that emits laser light in at least two directions from the same end face, a part of the emitted laser light is used as external resonance laser light, and the other laser light is used as an output laser. In the external resonance type semiconductor laser used as light, the semiconductor laser element is a gain waveguide type semiconductor laser, and is at least one or more arranged across the optical paths of the external resonance laser beam and the output laser beam A beam shaping element, a reflection mirror that reflects only the external resonance laser beam, and a specific arrangement that is disposed between the beam shaping element and the reflection mirror and that is disposed in the optical path of the external resonance laser beam. A wavelength transmission filter and a specific wavelength transmission filter having a wavelength characteristic similar to that of the specific wavelength transmission filter disposed in the optical path of the output laser beam, and an external resonant semiconductor laser Rutotomoni spectral width of the laser light emitted from The is narrowed to 0.1nm or less, a specific wavelength transmitting filter that is disposed in an optical path of the external resonator laser light, it is disposed in an optical path of the output laser beam The specific wavelength transmission filter is composed of one specific wavelength transmission filter .

In the invention according to claim 2 , in the external resonance semiconductor laser according to claim 1, the external resonance laser light and the output laser light are interposed between the beam shaping element and the specific wavelength transmission filter. It has at least one or more apertures arranged across each optical path.

According to a third aspect of the present invention, in the external resonant semiconductor laser according to the second aspect , a light absorption film or an antireflection film is formed on the semiconductor laser element side of the aperture. .

According to a fourth aspect of the present invention, in the external resonant semiconductor laser according to the first aspect, the beam shaping element includes a fast axis collimator and a slow axis collimator.

In the invention according to claim 5 , in the external cavity semiconductor laser according to claim 1, the specific wavelength transmission filter is a dielectric multilayer filter or a transmission Fabry-Perot etalon. .

According to a sixth aspect of the present invention, in the external resonant semiconductor laser according to the first or fifth aspect , the specific wavelength transmission filter has an incident surface on the semiconductor laser element side having the external resonant laser beam and the output. It is characterized by being arranged with an inclination from a plane perpendicular to each optical axis with respect to the laser beam for use.

In the invention according to claim 7 , in the external resonance type semiconductor laser according to claim 6 , the inclination of the specific wavelength transmission filter is parallel to a plane including the external resonance laser light and the output laser light. And a rotation axis perpendicular to the central optical axis of the external resonance laser beam and the output laser beam.

According to an eighth aspect of the present invention, in the external resonance type semiconductor laser according to the first aspect, the reflection mirror is a partial reflection in which a reflection surface is formed only in a region irradiated with the external resonance laser beam. It is a mirror.

In the invention according to claim 9 , in the external resonance semiconductor laser according to claim 1, the reflection mirror has a filter film that reflects only light of a specific wavelength on a reflection surface of the laser light for external resonance. It is characterized by.

According to the first aspect of the invention, the specific wavelength transmission filter is interposed in the optical path of the external resonance laser beam and the output laser beam, so that the wavelength selectivity is improved and the spectral width is further narrowed. It becomes possible. In addition, since the semiconductor laser element is a gain waveguide type semiconductor laser, it is possible to obtain high-power laser light.
Further , since the specific wavelength transmission filter is composed of one specific wavelength transmission filter disposed across the optical paths of the external resonance laser beam and the output laser beam, only one specific wavelength transmission filter is provided. Therefore, it is possible to improve the constriction, and further, there is no need to adjust a subtle difference in characteristics for each filter. Therefore, it is possible to provide an external resonant semiconductor laser that can suppress the complexity of the device configuration and can be easily assembled. It becomes possible.

According to the second aspect of the present invention, at least one aperture is disposed between the beam shaping element and the specific wavelength transmission filter so as to straddle the optical paths of the external resonance laser beam and the output laser beam. In addition to adjusting the beam shape by the aperture, it is possible to limit the beam incident on the specific wavelength transmission filter to only the component parallel to the beam optical axis, thereby further improving the wavelength selectivity. Further, when the driving current of the semiconductor laser device is increased, a high-order or low-order spectrum shifted from a specific wavelength is likely to be generated around the beam, and by blocking the ambient light of the beam by the aperture, the spectral width of these spectra is reduced. Higher or lower order spectra leading to an increase can be cut. In addition, since the aperture is configured to straddle the optical paths of the external resonance laser beam and the output laser beam, the number of parts can be reduced. In addition, since the aperture can be placed at a position equidistant from the semiconductor laser element with respect to the external resonance laser beam and the output laser beam, the wavelength distribution and spatial characteristics of both laser beams can be approximated, and the wavelength selectivity Can be further improved.

According to the invention of claim 3 , since the light absorbing film or the antireflection film is formed on the semiconductor laser element side of the aperture, the laser light blocked by the aperture is fed back to the semiconductor laser element, and the semiconductor laser element It is possible to prevent the operation from becoming unstable.

According to the invention of claim 4 , since the beam shaping element includes a fast axis collimator and a slow axis collimator, it is possible to efficiently collimate the external resonance laser beam and the output laser beam with a common optical system. It becomes.

According to the invention of claim 5 , the specific wavelength transmission filter is a dielectric multilayer filter or a transmission type Fabry-Perot etalon. Therefore, in the case of a dielectric multilayer filter, the wavelength selectivity is affected by the temperature change. Since it is difficult to receive, and the parts can be easily manufactured and the parts themselves can be formed compactly, the entire apparatus can be configured at low cost. On the other hand, in the case of an etalon, it is possible to vary the wavelength selection of the specific wavelength light in a wider range than the dielectric multilayer filter.

According to the invention of claim 6 , the specific wavelength transmission filter is arranged such that the incident surface on the semiconductor laser element side is inclined with respect to the respective optical axes of the external resonance laser beam and the output laser beam from a plane perpendicular thereto. Therefore, it is possible to suppress the spectral light not selected by the specific wavelength transmission filter from returning to the semiconductor laser element and destabilizing the operation of the semiconductor laser element.

According to the invention of claim 7 , the inclination of the specific wavelength transmission filter is parallel to a plane including the external resonance laser beam and the output laser beam, and is on the central optical axis of the external resonance laser beam and the output laser beam. Since it has a vertical rotation axis, even when the external resonance laser beam and the output laser beam deviate from the parallel light when passing through the specific wavelength transmission filter 33, the external resonance laser beam and the output laser beam are not affected. The transmission wavelength of the specific wavelength transmission filter can always be maintained at the same wavelength, and the amount of laser output from the external resonant semiconductor laser can be stabilized.

According to the eighth aspect of the present invention, since the reflecting mirror is a partially reflecting mirror in which the reflecting surface is formed only in the region irradiated with the laser beam for external resonance, the operation of setting the reflecting mirror to the mirror state can be simplified. . Furthermore, the beam shape can be adjusted in the same manner as the aperture by adjusting the area of the reflecting surface. In this case, it is possible to further improve the beam shape adjusting function by forming a light absorption film or an antireflection film in addition to the reflection surface.

According to the invention of claim 9 , since the reflection mirror is formed with a filter film that reflects only the specific wavelength light on the reflection surface of the external resonance laser light, the wavelength selectivity is improved and the spectral width of the output laser light is increased. It becomes possible to narrow down.

The external cavity semiconductor laser according to the present invention will be described in detail below.
FIG. 4 is a diagram showing an outline of an external cavity semiconductor laser according to the present invention.
Reference numeral 30 denotes a semiconductor laser element. In the present invention, a gain waveguide type semiconductor laser that emits laser light in at least two directions from the same end face is used. The gain waveguide type semiconductor laser has a laser active layer having a wide width of about 50 μm to 400 μm along the junction surface with the p-type semiconductor and the n-type semiconductor. This semiconductor laser has a characteristic that the refractive index of both end portions of the active layer increases as the drive current increases, so that the active layer itself has the effect of a concave lens and the emitted laser light is bent in two directions.

  Laser beams 35 and 36 emitted from the semiconductor laser element 30 pass through a fast axis collimator (FAC) 31 and a slow axis collimator (SAC) 32 which are beam shaping elements, and are collimated into parallel beams. The laser beam 35 is used as an external resonance laser beam that serves as excitation light for the semiconductor laser element. The collimated laser light 35 enters the specific wavelength transmission filter 33, passes only the beam having a specific wavelength component, passes through the filter 33, and is reflected by the reflection mirror 34. The reflected beam again passes through the specific wavelength transmission filter 33, further increases the wavelength selectivity, and further passes through the SAC 32 and FAC 31, and returns to the semiconductor laser element. Thus, by increasing the wavelength selectivity of the external resonance laser beam, the spectral width of the laser beam generated by the semiconductor laser element can be narrowed.

  On the other hand, the laser beam 36 passes through the FAC 31 and the SAC 32 as an output laser beam, then passes through the specific wavelength transmission filter 33, and is output to the outside in a state where the wavelength selectivity is further enhanced. As shown in FIG. 4, since the specific wavelength transmission filter is disposed across the optical paths of the external resonance laser beam 35 and the output laser beam 36, only one specific wavelength transmission filter can be used for both beams. Improvement of constriction can be realized, and the wavelength selected by both is the same. Therefore, subtle differences in characteristics of each filter that occur when multiple filters are configured are performed by adjusting the angle of the filter. There is no need.

The specific wavelength transmission filter 33 includes a dielectric multilayer filter in which a plurality of dielectric films made of a low refractive index material such as TiO ₂ / SiO ₂ or Ta ₂ O ₅ / SiO ₂ and a high refractive index material are stacked on a support. Alternatively, a transmission type Fabry-Perot type etalon can be used.
In the dielectric multilayer filter, the wavelength selectivity is not easily affected by temperature changes, the parts can be easily manufactured, and the parts themselves can be formed compactly, so that the entire apparatus can be configured at low cost. On the other hand, the transmission type Fabry-Perot type etalon has the disadvantage that the transmission wavelength characteristics are likely to change due to temperature changes, but the wavelength selection of specific wavelength light can be varied in a wider range than the dielectric multilayer filter. There are advantages to doing.

  Further, the specific wavelength transmission filter 33 is arranged such that the incident surface on the semiconductor laser element 30 side is inclined with respect to each optical axis with respect to the external resonance laser beam 35 and the output laser beam 36 from a plane perpendicular thereto. . With this configuration, it is possible to prevent laser light having a spectrum that is not selected by the specific wavelength transmission filter from returning to the semiconductor laser element 30 through the reverse path, and the operation of the semiconductor laser element caused by such unnecessary laser light is prevented. It becomes possible to suppress destabilization.

As shown in FIG. 6, when the external resonance laser beam 35 and the output laser beam 36 deviate from the parallel light when passing through the specific wavelength transmission filter 33, the external resonance laser beam and the output laser beam are temporarily output. When the specific wavelength transmission filter 33 is rotated about a rotation axis perpendicular to the plane including the laser beam to form an inclined surface for each laser beam, the incident angle θ ₁ of the output laser beam 36 with respect to the specific wavelength transmission filter 33 and the outside The incident angle θ ₂ of the resonance laser beam 35 is different from each other.

When the transmission wavelength of the specific wavelength transmission filter 33 is λ ₀ , the transmission wavelength λ ₁ = λ ₀ / cos θ ₁ with respect to the output laser light is obtained when the difference in refractive index between the filter and the surroundings is not considered. Similarly, the transmission wavelength λ ₂ = λ ₀ / cos θ ₂ with respect to the external resonance laser beam. For this reason, as shown in FIG. 7, the transmission spectrum intensity distribution A for the output laser light of the specific wavelength transmission filter 33 and the transmission spectrum intensity distribution B for the external resonance laser light are relatively shifted, and the external resonance type The light amount of the laser output from the semiconductor laser is an output light amount corresponding to the portion C where both overlap.

  Therefore, as the specific wavelength transmission filter 33 is tilted from the state perpendicular to the center optical axis a of the external resonance laser beam and the output laser beam shown in FIG. 6, as shown in the graph D of FIG. Corresponding to the increase in the rotation angle, the resonator output, which is the laser light amount output from the external resonant semiconductor laser, tends to decrease.

In order to solve this problem, as shown in FIG. 9, the plane is parallel to the plane including the external resonance laser beam and the output laser beam, and is perpendicular to the central optical axis a between the external resonance laser beam and the output laser beam. By tilting the specific wavelength transmission filter 33 with an appropriate rotation axis, the incident angle of the output laser beam 36 and the incident angle of the external resonance laser beam 35 with respect to the specific wavelength transmission filter 33 can be maintained at the same value. Thus, two transmission spectrum intensity distributions A and B as shown in FIG. 7 can be matched.
As a result, it is possible to suppress a decrease in the resonator output as shown by a graph E in FIG.

Next, another embodiment of the external cavity semiconductor laser according to the present invention will be described.
FIG. 5 is a schematic view showing another embodiment. One of the features of the embodiment of FIG. 5 is that the optical path between the external resonance laser beam 42 and the output laser beam 43 extends between the beam shaping element (FAC31 and SAC32) and the specific wavelength transmission filter 33. Having an aperture 38 to be arranged.

  This aperture 38 not only shapes the beam shape of each laser beam, but also limits the beam incident on the specific wavelength transmission filter 33 to only a component parallel to the beam optical axis, thereby improving the wavelength selectivity of the filter. Have. In order to further enhance this function, it is possible to arrange a plurality of apertures along the optical axes of the laser beams 42 and 43. As the shape of the aperture opening (laser beam transmitting portion), various shapes such as an ellipse and a rectangle can be adopted in addition to a circle, and a plurality of differently shaped apertures can be combined to obtain a desired shape. Is also possible.

In a gain waveguide type semiconductor laser, when the driving current of the semiconductor laser element is increased, a high-order or low-order spectrum shifted from a specific wavelength tends to be generated around the beam, and the aperture 38 blocks the ambient light of the beam. Thus, higher-order or lower-order spectra that lead to an increase in the spectrum width can be cut.
In addition, since the aperture is configured to straddle the optical paths of the external resonance laser beam and the output laser beam, the number of parts can be reduced.
Furthermore, since the spatial distribution of the light intensity for each wavelength in the external resonance laser beam 42 and the output laser beam 43 has substantially the same shape, the external resonance laser beam 42 and the output laser beam 43 are Since the aperture 38 can be arranged at a position equidistant from the semiconductor laser element 30, it is possible to approximate the wavelength distribution and spatial characteristics of both laser beams, and the wavelength selectivity can be further improved.

  Further, on the semiconductor laser element 30 side of the aperture 38, a light absorption film or an antireflection film (black paint or the like) or a surface is roughened to form a diffusion surface, so that the laser light blocked by the aperture is transmitted to the semiconductor laser element. It is also possible to prevent the operation of the semiconductor laser element from destabilizing (preventing return light).

Next, the reflection mirrors 34 and 40 will be described. As these reflection mirrors, it is preferable to use a partial reflection mirror in which a mirror-like reflection surface is formed only in a region irradiated with the external resonance laser beams 35 and 42. Thereby, it becomes possible to simplify the operation | work which makes a reflective mirror a mirror surface state.
Furthermore, the beam shape can be adjusted in the same manner as the aperture 38 by adjusting the formation area of the reflecting surface. In this case, the beam shape can be adjusted more effectively by forming a light absorption film or an antireflection film in addition to the reflection surface.

  Further, like the reflection mirror 40, a filter film 41 that reflects only the specific wavelength light is formed on the reflection surface of the external resonance laser light 42 of the reflection mirror 40, and the wavelength selectivity is further increased, and the spectrum of the output laser light is increased. It is also possible to narrow the width.

Actually, in the optical system shown in FIG. 4, EYP-BAE-1120, manufactured by Eagleyard Photonics (Germany) is used as the gain waveguide type semiconductor laser 30, FAC31 having a focal length of 0.9 mm, SAC32 having a focal length of 30 mm, and a specific wavelength. As the transmission filter 33, a dielectric multilayer film filter in which 44 layers of Ta ₂ O ₅ / SiO ₂ are laminated on a glass substrate (the wavelength of transmitted light is 1130 nm in the direction perpendicular to the filter), and the reflection mirror 34 is a reflection mirror. An external resonant semiconductor laser was configured using a reflection mirror having a mirror finished surface of 3 mm long by 0.5 mm wide from the end. The semiconductor laser was driven at 350 mW (drive voltage 1.21 V, drive current 800 mA), the position of each optical component was adjusted, and the output laser beam 36 was observed with a spectrum analyzer Q8347, manufactured by Advantes. A single mode laser beam having an optical spectrum width of about 0.05 nm and an output of 210 mW could be obtained.

  As described above, according to the present invention, there is provided an external resonant semiconductor laser capable of outputting a laser beam having a high output and an extremely narrow spectrum width and having a small number of parts without complicating the configuration. Is possible.

1 is a schematic diagram of an external resonant semiconductor laser according to Non-Patent Document 1. FIG. 6 is a schematic diagram of an external resonant semiconductor laser according to Non-Patent Document 2. FIG. 6 is a schematic diagram of an external resonant semiconductor laser according to Patent Document 2. FIG. It is a figure which shows the Example of the external cavity semiconductor laser which concerns on this invention. It is a figure which shows the other Example of the external cavity semiconductor laser which concerns on this invention. It is a figure which shows a mode when the laser beam for external resonance and the laser beam for output remove | deviate from parallel light, when passing through a specific wavelength transmission filter. It is a figure which shows the transmission spectrum intensity distribution of the specific wavelength transmission filter with respect to the laser beam for external resonance and the laser beam for output in the state of FIG. It is a graph which shows the mode of the optical output change of an external resonance type semiconductor laser. FIG. 6 is a diagram illustrating an appropriate rotation direction of a specific wavelength transmission filter when external resonance laser light and output laser light deviate from parallel light when passing through the specific wavelength transmission filter.

Explanation of symbols

30 Semiconductor Laser Element 31 Fast Axis Collimator (FAC)
32 Collimator for slow axis (SAC)
33 Specific wavelength transmission filter 34 Reflection mirrors 35, 42 External resonance laser light 36, 43 Output laser light 38 Aperture

Claims (9)

A semiconductor laser element that emits laser light in at least two directions from the same end face, and an external resonant semiconductor laser that uses part of the emitted laser light as external resonance laser light and the other laser light as output laser light In
The semiconductor laser element is a gain waveguide type semiconductor laser,
At least one beam shaping element disposed across each optical path of the external resonance laser beam and the output laser beam;
A reflection mirror that reflects only the external resonance laser beam;
A specific wavelength transmission filter disposed between the beam shaping element and the reflection mirror and disposed in an optical path of the external resonance laser beam;
A specific wavelength transmission filter having the same wavelength characteristics as the specific wavelength transmission filter disposed in the optical path of the output laser beam,
Spectral width of the laser light emitted from the external cavity semiconductor laser is narrowed to 0.1nm or less Rutotomoni a specific wavelength transmitting filter that is disposed in an optical path of the external resonator laser light, the optical path of the output laser beam An external resonance type semiconductor laser, wherein the specific wavelength transmission filter disposed in the laser diode is constituted by one specific wavelength transmission filter . 2. The external resonant semiconductor laser according to claim 1 , wherein the external resonant semiconductor laser is disposed between the beam shaping element and the specific wavelength transmission filter across at least the optical paths of the external resonant laser beam and the output laser beam. An external cavity type semiconductor laser having one or more apertures. 3. The external cavity semiconductor laser according to claim 2 , wherein a light absorption film or an antireflection film is formed on the semiconductor laser element side of the aperture.   2. The external cavity semiconductor laser according to claim 1, wherein the beam shaping element includes a fast axis collimator and a slow axis collimator.   2. The external cavity semiconductor laser according to claim 1, wherein the specific wavelength transmission filter is a dielectric multilayer filter or a transmission Fabry-Perot etalon. In external cavity semiconductor laser according to claim 1 or 5, wherein the specific wavelength transmitting filter for each optical axis between the semiconductor incident surface of the laser element side external resonant laser beam and the output laser beam An external cavity semiconductor laser characterized by being arranged with an inclination from a vertical plane. 7. The external resonant semiconductor laser according to claim 6 , wherein the inclination of the specific wavelength transmission filter is parallel to a plane including the external resonant laser beam and the output laser beam, and the external resonant laser beam and the external resonant laser beam. An external resonance type semiconductor laser having a rotation axis perpendicular to a central optical axis with an output laser beam.   2. The external resonance semiconductor laser according to claim 1, wherein the reflection mirror is a partial reflection mirror in which a reflection surface is formed only in a region irradiated with the external resonance laser beam. Type semiconductor laser.   2. The external resonance type semiconductor laser according to claim 1, wherein the reflection mirror is formed with a filter film that reflects only light of a specific wavelength on a reflection surface of the external resonance laser beam. Semiconductor laser.

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