JP3212182U - External cavity semiconductor laser device - Google Patents

Abstract

An external resonator type semiconductor laser device capable of suppressing fluctuations in the frequency of output laser light is provided. An external resonator type semiconductor laser device includes an external resonator and a sealed structure. The external resonator 3 resonates by partially returning laser light having a specific wavelength out of the light emitted from the semiconductor laser 1 to the semiconductor laser 1, and outputs the resonated laser light partially outside. The plurality of optical components 5 to 8 are included. The sealed structure 11 forms an internal space 12 in which the plurality of optical components 5 to 8 are arranged. The sealed structure 11 forms the internal space 12 in an airtight manner with respect to the outside. [Selection] Figure 1

Description

  The present invention relates to an external resonator type semiconductor laser device.

  The external cavity semiconductor laser device is called ECDL (External Cavity Diode Laser). In ECDL, only the laser light having a specific wavelength out of the light emitted from the semiconductor laser element passes through the wavelength selective element in the external resonator, and resonates by partially returning to the semiconductor laser element. The laser beam is partially output to the outside. For example, Patent Document 1 and Non-Patent Document 1 describe an external resonator type semiconductor laser device using a bandpass filter as a wavelength selective element.

JP-A-6-21549

P. Zorabedian and W. R. Trutna, “Interference-filter-tuned, alignment-stabilized, semiconductor external-cavity laser”, Optics Letters Vol. 13, Issue 10, pp. 826-828 (1988)

  By the way, the external resonator type semiconductor laser device can be used as a laser light source of an optical lattice clock. In an optical lattice clock, atoms are confined in a lattice of light produced by interference of laser light of a specific wavelength from a laser light source, and thermal motion of the atoms is suppressed. Laser light is applied to these atoms, and the frequency (resonance frequency) of the absorbed light is precisely measured. The vibration of this light is counted to determine the length of 1 second.

When the external resonator type semiconductor laser device is used as a laser light source of an optical lattice clock, the following is required.
Fluctuations in the frequency (that is, the above-mentioned specific wavelength) of the output laser light from the external resonator type semiconductor laser device are minimized.

  Even when an external resonator type semiconductor laser device is used for other purposes, it is sometimes required to minimize fluctuations in the frequency of the output laser light.

  Accordingly, an object of the present invention is to provide an external resonator type semiconductor laser device that can suppress fluctuations in the frequency of output laser light.

In order to achieve the above-described object, according to the present invention, among laser beams emitted from a semiconductor laser, a laser beam having a specific wavelength is resonated by partially returning the laser beam to the semiconductor laser. An external resonator including a plurality of optical components for outputting externally,
A sealed structure that forms an internal space in which the plurality of optical components are arranged, and
The sealed structure provides an external cavity semiconductor laser device in which the internal space is formed airtight with respect to the outside.

  According to the above-described present invention, the internal space in which the plurality of optical components constituting the external resonator are arranged is formed airtight with respect to the outside by the sealed structure. Thereby, fluctuations in the frequency (wavelength) of the output laser light of the external resonator type semiconductor laser device can be suppressed with respect to pressure fluctuations in the ambient atmosphere.

1 shows a configuration of an external resonator type semiconductor laser device according to an embodiment of the present invention. (A) is a 2A-2A arrow directional view of FIG. 1, (B) is the figure which abbreviate | omitted illustration of the adjustment structure part in (A). It is explanatory drawing of the coupling structure of the external resonator type semiconductor laser apparatus by embodiment of this invention. (A) is 4A-4A sectional drawing of FIG. 3, (B) is 4B-4B sectional drawing of FIG. It is experimental data which shows the short-term frequency fluctuation of an output laser beam. It is experimental data which shows long-term frequency fluctuation of the output laser beam.

  An embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 shows a configuration of an external cavity semiconductor laser device 10 according to an embodiment of the present invention. The external resonator type semiconductor laser device 10 includes an external resonator 3 that resonates laser light from the semiconductor laser 1 and outputs it to the outside.

  The semiconductor laser 1 has a cover 1a that houses therein a semiconductor laser element (not shown) including an active layer 1d that generates light, and a base portion 1b to which the cover 1a is attached. The active layer 1d has an output end face 1e and a reflection end face 1f located on opposite sides. An antireflection film (AR coat) is formed on the output end face 1e, and a high reflection film (HR coat) is formed on the reflection end face 1f. Thereby, the light in the active layer 1d is reflected by the reflection end face 1f toward the output end face 1e and passes through the output end face 1e. A transmission window (not shown) for transmitting the laser light emitted from the output end face 1e to the output side (right side in FIG. 1) of the external resonator 3 is formed on the front surface (right end face in FIG. 1) of the cover 1a. Has been. The terminal 1c of the semiconductor laser 1 penetrates the base portion 1b in an airtight manner and is electrically connected to the above-described semiconductor laser element. The cover 1a may be omitted.

(Configuration of external resonator)
The external resonator 3 resonates the laser beam by partially returning the laser beam having a specific wavelength out of the laser beam emitted from the semiconductor laser 1 to the semiconductor laser 1, and partially resonates the resonated laser beam to the outside. A plurality of optical components for output to More details are as follows. Laser light is emitted from the output end face 1e of the active layer 1d. In the external resonator 3, only a laser beam having a specific wavelength out of the laser beam passes through an optical component (for example, a bandpass filter 6 described later) as a wavelength selective element, and then is output to the active layer 1d to the output end face 1e. Resonates by returning through. The laser beam thus resonated is partially output to the outside of the external resonator 3.
As shown in FIG. 1, the resonator length L of the external resonator 3 is the length from the reflection end face 1f of the active layer 1d to the output position of the external resonator 3 (for example, the reflection surface 8a of the partial reflection mirror 8 described later). That's it.

  In the present embodiment, a first collimator lens 5, a band pass filter 6, a condenser lens 7, and a partial reflection mirror 8 are provided as a plurality of optical components.

  The first collimating lens 5 is disposed between the semiconductor laser 1 and the bandpass filter 6. The first collimating lens 5 adjusts the laser light from the semiconductor laser 1 to parallel light.

  The band-pass filter 6 transmits laser light having a specific wavelength out of laser light from the semiconductor laser 1 (parallel light after passing through the first collimating lens 5 in the embodiment). The bandpass filter 6 has a rotation angle around the rotation axis C1 adjusted. The wavelength of the laser beam that passes through the band-pass filter 6 changes as the incident angle of the laser beam with respect to the band-pass filter 6 changes according to the rotation angle. In the present embodiment, the rotation angle is adjusted so that the wavelength of the laser light transmitted through the bandpass filter 6 becomes a specific wavelength.

  The condenser lens 7 is disposed between the bandpass filter 6 and the partial reflection mirror 8. The condensing lens 7 condenses the laser light that has passed through the bandpass filter 6 on the reflection surface 8 a of the partial reflection mirror 8.

  The partial reflection mirror 8 partially reflects the laser light transmitted through the bandpass filter 6 (in the embodiment, the laser light further transmitted through the condensing lens 7) by the reflection surface 8a and returns it to the semiconductor laser 1 as well as the output laser. The light is partially transmitted to the output side.

  The external resonator type semiconductor laser device 10 includes a second collimating lens 9 that converts the output laser light transmitted through the partial reflection mirror 8 into parallel light.

(Configuration of sealed structure)
The external resonator type semiconductor laser device 10 includes a sealed structure 11 that forms an internal space 12 in which a plurality of optical components of the external resonator 3 are arranged. The sealed structure 11 forms the internal space 12 in an airtight manner with respect to the outside. In the example of FIG. 1, a part of the semiconductor laser 1 (cover 1 a) is also arranged in the internal space 12.

  The sealed structure 11 includes a plurality of structural parts 13, 15, and 17 that are separate from each other. The plurality of structural portions 13, 15, and 17 are arranged in the direction of the optical axis C0 (hereinafter simply referred to as the optical axis direction) of the external resonator 3 (the plurality of optical components described above) and are coupled to each other. In the example of FIG. 1, first to third structure parts 13, 15, 17 are provided as the plurality of structure parts 13, 15, 17. The plurality of structural portions 13, 15, and 17 extend in the circumferential direction surrounding the optical axis C <b> 0 and make one round and surround the internal space 12. In the following, the circumferential direction surrounding the optical axis C0 is simply referred to as the circumferential direction.

  The plurality of structural portions 13, 15, and 17 are welded to each other at a plurality of locations in the circumferential direction. In the entire range in the circumferential direction other than the plurality of locations, the gaps between the plurality of structural portions 13, 15, 17 are hermetically sealed with a sealant. The welding at the plurality of locations may be laser welding. Here, the laser welding may be welding with a YAG laser (Yttrium Aluminum Garnet laser). In the following description, welding may mean laser welding, and in the following, laser welding may mean welding with a YAG laser.

  The internal space 12 has an opening 12 a on the output side of the external resonator 3. The partial reflection mirror 8 is coupled to the sealed structure 11 so as to hermetically close the opening 12a.

  The sealed structure 11 includes a piezoelectric element 21 (piezo element). The piezoelectric element 21 is located between the band pass filter 6 and the partial reflection mirror 8. The piezoelectric element 21 has a through hole 21a through which a laser beam passes. The through hole 21a is located on the optical axis C0 and penetrates the piezoelectric element 21 in the optical axis direction.

  The size of the piezoelectric element 21 slightly changes in the optical axis direction when a voltage is applied. That is, even if the resonator length L of the external resonator 3 changes minutely due to, for example, thermal expansion or other causes, the resonator length L is made constant by changing the dimension in the optical axis direction of the piezoelectric element 21 minutely. Thus, the frequency of the output laser beam can be kept constant.

  The piezoelectric element 21 forms a part of the sealed structure 11. That is, the sealed structure 11 includes the piezoelectric element 21. The through hole 21 a forms a part of the internal space 12. The opening 12 a of the internal space 12 is an opening of the through hole 21 a on the output side of the external resonator 3. The partial reflection mirror 8 is coupled to the piezoelectric element 21 so as to airtightly close the opening 12a.

  In the example of FIG. 1, the internal space 12 has an opening 12 b on the semiconductor laser 1 side. The base portion 1b of the semiconductor laser 1 is coupled to the sealed structure 11 so as to hermetically close the opening 12b. In the example of FIG. 1, the openings 12a and 12b face the optical axis direction.

  The sealed structure 11 includes an adjustment structure 23 to which the bandpass filter 6 is coupled. 2A is a view taken in the direction of arrows 2A-2A in FIG. FIG. 2B corresponds to FIG. 2A, but shows a state before the adjustment structure portion 23 is attached to the second structure portion 15. As shown in FIG. 2B, the second structure portion 15 has an insertion hole 25 into which the adjustment structure portion 23 is inserted from the outside. The outer peripheral surface of the second structure portion 15 may be rectangular (for example, a square) when viewed from the optical axis direction, and the insertion hole 25 may be opened in the flat portion 15a of the outer peripheral surface. The insertion hole 25 communicates with the internal space 12.

  With the adjustment structure 23 inserted into the insertion hole 25, the bandpass filter 6 is positioned on the optical axis C0, and the rotation angle around the rotation axis C1 is set with the central axis of the insertion hole 25 as the rotation axis C1. It can be adjusted. For example, the rotation angle of the adjustment structure portion 23 can be adjusted by inserting a tool into an elongated groove 23a formed on the outer surface of the adjustment structure portion 23 and turning the tool. After this adjustment, the adjustment structure 23 is fixed to the sealing structure 11 so as to block the insertion hole 25 in an airtight manner.

(Bonded structure)
FIG. 3 shows a hermetic coupling structure of the external cavity semiconductor laser device 10. In FIG. 3, at positions P1 and P2 surrounded by a broken line, coupling is performed by both laser welding and a sealant (in this example, an adhesive). In the places Q1 to Q4 surrounded by the broken line, the laser welding is not performed and the bonding is performed by the adhesive. In the locations R1 to R4 surrounded by the broken line, the bonding is performed by laser welding without using the sealant.

  The first and second structural parts 13 and 15 are hermetically sealed at the joint P1 as follows. 4A is a cross-sectional view taken along the line 4A-4A in FIG. 3 (illustration of the semiconductor laser 1 is omitted in this figure). The first and second structural portions 13 and 15 have axial surfaces 13a and 15b that face each other in the optical axis direction. Each axial direction surface 13a, 15b is extended in the circumferential direction, and makes one round. With the axial surfaces 13a and 15b butting each other, the first and second structural portions 13 and 15 are laser welded at a plurality of locations in the circumferential direction (four locations in FIG. 4A). It is firmly joined by the weld W made. After this laser welding is performed, the gap between the axial surface 13a and the axial surface 15b is applied from the outside of the first and second structural portions 13 and 15 in the entire circumferential range other than the welded portion W. It is hermetically sealed with a sealing agent S (adhesive in this example). As a result, the boundary between the first and second structure portions 13 and 15 is hermetically closed to the outside over the entire circumferential range.

  The connection with the second and third structural portions 15 and 17 is made airtight at the connection point P2 as follows. 4B is a cross-sectional view taken along the line 4B-4B of FIG. 3 (the second holding member 39 is not shown in this figure). The second and third structure portions 15 and 17 have axial surfaces 15c and 17a that face each other in the optical axis direction. Each axial direction surface 15c, 17a extends in the circumferential direction and makes one round. With the axial surfaces 15c and 17a being in contact with each other, the second and third structural portions 15 and 17 are laser-welded at a plurality of locations in the circumferential direction (four locations in FIG. 4B). It is firmly joined by the weld W made. After this laser welding is performed, the gap between the axial surface 15c and the axial surface 17a is applied from the outside of the second and third structural portions 15 and 17 in the entire circumferential range other than the welded portion W. It is hermetically sealed with a sealing agent S (adhesive in this example). Thereby, the boundary between the second and third structural portions 15 and 17 is hermetically closed to the outside over the entire circumferential range.

  The coupling between the piezoelectric element 21 and the partial reflection mirror 8 is airtight at the coupling point Q1 as follows. The piezoelectric element 21 has an axial surface 21b in which an opening 12a is formed. The axial surface 21b faces the optical axis direction, and extends around the circumference so as to surround the opening 12a. An adhesive as a sealing agent is applied between the axial surface 21b and the partial reflection mirror 8 over the entire circumferential range of the axial surface 21b. With this adhesive, the partial reflection mirror 8 is coupled to the piezoelectric element 21 so as to close the opening 12a in an airtight manner with respect to the outside. When viewed from the optical axis direction, the opening 12a may be circular, and the piezoelectric element 21 may be annular.

  The coupling between the piezoelectric element 21 and the third structure portion 17 is airtight at the coupling location Q2 as follows. The piezoelectric element 21 and the third structure portion 17 have axial surfaces 21c and 17b that face each other in the optical axis direction. Each of the axial surfaces 21c and 17b extends in the circumferential direction so as to surround the internal space 12, and makes one round. An adhesive as a sealant is applied between the axial surface 21c and the axial surface 17b over the entire circumferential range of the axial surfaces 21c and 17b. With this adhesive, the piezoelectric element 21 and the third structure portion 17 are coupled to each other so that the boundary between the axial surfaces 21c and 17b is airtightly closed to the outside.

  The adjustment structure portion 23 and the second structure portion 15 are airtightly connected at the connection portion Q3 as follows. The gap between the adjustment structure portion 23 and the second structure portion 15 is hermetically sealed by an adhesive applied from the outside over the entire circumferential range in the direction surrounding the insertion hole 25 (the rotation axis C1). Moreover, the adjustment structure part 23 is fixed to the second structure part 15 by this adhesive so as to close the insertion hole 25 in an airtight manner.

  The coupling between the base portion 1b of the semiconductor laser 1 and the first structure portion 15 is made airtight at the coupling location Q4 as follows. The first structure portion 15 has an axial surface 13b in which an opening 12b is formed. The axial surface 13b faces the optical axis direction and extends around the circumference so as to surround the opening 12b. ing. The base portion 1b has an axial surface 2 that faces the axial surface 13b. An adhesive as a sealing agent is applied between the axial surface 13b and the axial surface 2 over the entire circumferential range of the axial surfaces 13b and 2. With this adhesive, the base portion 1b is coupled to the first structure portion 15 so as to close the opening 12b in an airtight manner with respect to the outside. When viewed from the optical axis direction, the opening 12b may be circular.

  Alternatively, the coupling between the base portion 1b of the semiconductor laser 1 and the first structure portion 13 may be made airtight at the coupling point Q4 as follows. The base portion 1 b has an outer peripheral surface 4 extending in the circumferential direction, and the first structure portion 13 has an inner peripheral surface 13 c extending in the circumferential direction so as to surround the outer peripheral surface 4. Between the outer peripheral surface 4 and the inner peripheral surface 13c, an adhesive as a sealing agent is applied over the entire range in the circumferential direction. With this adhesive, the base portion 1b is coupled to the first structure portion 13 so as to close the opening 12b in an airtight manner with respect to the outside.

A first cover member 31 is coupled to the first structure portion 13. This connection may be made by a screw or an adhesive. The first cover member 31 has a hole through which the terminal 1c passes.
The external resonator type semiconductor laser device 10 is provided with a second cover member 33 that covers the piezoelectric element 21 and the partial reflection mirror 8. The second cover member 33 is coupled to the third structure portion 17 by laser welding at the coupling location R1. This welding is performed at a plurality of locations in the circumferential direction. In order to apply a voltage to the piezoelectric element 21, a conductor hole 33 a through which a conductor (not shown) extending from the piezoelectric element 21 passes is formed in the second cover member 33.

  The first collimating lens 5 is attached and held in advance on the first holding member 35. The first holding member 35 has a through hole penetrating in the optical axis direction, and the first collimating lens 5 is disposed in the through hole. The first holding member 35 may be coupled to the first structure portion 13 by laser welding at the coupling location R2. This welding is performed at a plurality of locations in the circumferential direction. At the time of this welding, the first structure portion 13 is not yet assembled to the second structure portion 15.

  The bandpass filter 6 is attached and held in advance on the holding unit 37. The holding part 37 has a through hole penetrating in the optical axis direction, and the bandpass filter 6 is disposed in the through hole. The holding part 37 is fixed to the adjustment structure part 23. For example, the holding part 37 is integrated with the adjustment structure part 23 in advance by integral molding.

  The condenser lens 7 is attached to the second holding member 39 in advance. The second holding member 39 has a through hole penetrating in the optical axis direction, and the condenser lens 7 is disposed in the through hole. The second holding member 39 may be coupled to the third structure portion 17 by laser welding at the coupling location R3. This welding is performed at a plurality of locations in the circumferential direction. At the time of this welding, the third structure portion 17 is not yet assembled to the second structure portion 15.

  The second collimating lens 9 is attached to the third holding member 41 in advance. The third holding member 41 has a through hole penetrating in the optical axis direction, and the second collimating lens 9 is disposed in the through hole. The third holding member 41 may be coupled to the third structure portion 17 by laser welding at the coupling location R4. This welding is performed at a plurality of locations in the circumferential direction.

(Effect of embodiment)
According to the above-described embodiment, the internal space 12 in which the plurality of optical components of the external resonator 3 are arranged is formed airtight with respect to the outside by the sealed structure 11. Thereby, fluctuations in the frequency (wavelength) of the output laser light of the external resonator type semiconductor laser device 10 can be suppressed with respect to pressure fluctuations in the ambient atmosphere.

  FIG. 5 is experimental data showing short-term frequency fluctuations of the output laser light. 5A shows the air pressure around the sealed structure 11, and FIG. 5B shows the frequency fluctuation of the laser light output from the external resonator type semiconductor laser device. In FIG. 5B, M1 is the measurement data of the present embodiment, and M2 is the measurement data of the comparative example in which the optical components of the external resonator are arranged in the non-sealed space without using the sealed structure 11. . The measurement data M1 and the measurement data M2 were obtained by making the other conditions in the present embodiment and the comparative example the same.

  FIG. 6 is experimental data showing long-term frequency fluctuations. 6A shows the air pressure around the sealed structure 11, and FIG. 6B shows the frequency fluctuation of the laser light output from the external resonator type semiconductor laser device. In FIG. 6B, M3 is the measurement data of the present embodiment, and M4 is the measurement data of the comparative example in which the optical components of the external resonator are arranged in the non-sealed space without using the sealed structure. The measurement data M3 and the measurement data M4 were obtained by making the other conditions in the present embodiment and the comparative example the same.

  In the case of the comparative example, the refractive index of the air in the optical path of the external resonator 3 changes due to fluctuations in the surrounding air pressure. As a result, the effective resonator length L of the external resonator 3 changes, and the frequency of the output laser beam fluctuates greatly as in the measurement data M2 and M4. On the other hand, in this embodiment, since the sealed structure 11 is not affected by fluctuations in the surrounding air pressure, the frequency fluctuation of the output laser beam is affected by the fluctuations in the surrounding air pressure as in the measurement data M1 and M3. Very small.

  Further, according to the present embodiment, the partial reflection mirror 8 is arranged on the output side of the piezoelectric element 21 in order to close the opening 12 a of the internal space 12 with the partial reflection mirror 8. This arrangement is the reverse of the prior art. That is, in the past (for example, Non-Patent Document 1), the partial reflection mirror is arranged on the semiconductor laser side with respect to the piezoelectric element. With the arrangement of the partial reflection mirror 8 according to the present embodiment, the internal space 12 can be more reliably and easily sealed from the outside.

  Further, according to the present embodiment, the first and second structure parts 13 and 15, the second and third structure parts 15 and 17, and the third structure part 17 and the second cover member 33 are The semiconductor laser 1, the first collimator lens 5, the band-pass filter 6, which are coupled to the first to third structure parts 13, 15, 17 and the second cover member 33, because they are firmly coupled by laser welding. The optical axis C0 of the condensing lens 7, the partial reflection mirror 8, and the second collimating lens 9 is not shaken, and the shake of the resonator length L with respect to mechanical shock is small.

  Further, at least the first to third structure parts 13, 15, and 17 and the second cover member 33 are made of a metal material and are firmly coupled to each other by laser welding as described above. Therefore, superiority of the mechanical characteristics of the external cavity semiconductor laser device 10 can be expected. Therefore, mechanical deterioration of the external cavity semiconductor laser device 10 (especially the sealed structure 11) due to vibration or aging can be prevented.

  The boundary between the first and second structural parts 13 and 15 and the boundary between the second and third structural parts 15 and 17 are the sealing agent (adhesive) in the entire circumferential range that is not laser welded. ). Thereby, airtightness at these boundaries can be secured. That is, since the plurality of structural portions 13, 15, and 17 are coupled to each other by laser welding and a sealing agent, the internal space 12 can be sealed while eliminating the fluctuation of the resonator length L with respect to mechanical shock.

  The present invention is not limited to the above-described embodiment, and various changes can be made within the scope of the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser, 1a cover, 1b base part, 1c terminal, 1d active layer, 1e Output end surface, 1f Reflective end surface, 2 Axial direction surface, 3 External resonator, 5 1st collimating lens (optical component), 4 outer peripheral surface, 6 Band pass filter (optical component), 7 Condensing lens, 8 Partial reflection mirror (optical component), 8a Reflecting surface, 9 Second collimating lens, 10 External resonator type semiconductor laser device, 11 Sealed structure, 12 Internal space , 12a opening, 12b opening, 13 first structure portion, 13a, 13b axial surface, 13c inner peripheral surface, 15 second structure portion, 15a planar portion of outer peripheral surface, 15b, 15c axial surface, 17 third , 17a, 17b axial surface, 21 piezoelectric element, 21a through hole, 21b, 21c axial surface, 23 adjustment structure, 23a groove, 25 insertion hole, 31 first cover member, 3 The second cover member, 33a conductor hole, 35 the first holding member 37 holding portion, 39 the second holding member, 41 third holding member, C0 optical axis, C1 rotation axis, W welds, S sealant (adhesive)

Claims (5)

Includes a plurality of optical components for resonating a laser beam having a specific wavelength out of the light emitted from the semiconductor laser by partially returning the laser beam to the semiconductor laser and partially outputting the resonated laser beam to the outside An external resonator,
A sealed structure that forms an internal space in which the plurality of optical components are arranged, and
The external cavity semiconductor laser device, wherein the sealed structure forms the internal space in an airtight manner with respect to the outside. The sealed structure includes a plurality of separate structural parts,
The plurality of structures are arranged in the direction of the optical axis of the external resonator and coupled to each other, extend in a circumferential direction surrounding the optical axis and surround the internal space,
The plurality of structural portions are welded to each other at a plurality of locations in the circumferential direction, and gaps between the plurality of structural portions are hermetically sealed with a sealing agent in a range in the circumferential direction other than the plurality of locations. The external cavity semiconductor laser device according to claim 1. The plurality of optical components are:
A bandpass filter that transmits laser light having a specific wavelength among laser light from the semiconductor laser;
A partially reflecting mirror that partially reflects the laser beam that has passed through the bandpass filter and returns the laser beam to the semiconductor laser, and partially transmits the laser beam as an output laser beam to the output side,
The internal space has an opening on the output side;
The external cavity semiconductor laser device according to claim 1, wherein the partial reflection mirror is coupled to the hermetic structure so as to hermetically close the opening. Comprising a piezoelectric element positioned between the bandpass filter and the partial reflection mirror;
The piezoelectric element has a through hole, the through hole is located on the optical axis, and penetrates the piezoelectric element in the direction of the optical axis;
The piezoelectric element changes its size in the direction of the optical axis when a voltage is applied,
The piezoelectric element forms part of the sealed structure, and the through hole forms part of the internal space;
The opening of the internal space is an opening of the through hole on the output side,
The external cavity semiconductor laser device according to claim 3, wherein the partial reflection mirror is coupled to the piezoelectric element so as to hermetically close the opening. An adjustment structure unit coupled with the bandpass filter;
The sealing structure is formed with an insertion hole into which the adjustment structure portion is inserted from the outside, and the insertion hole communicates with the internal space.
With the adjustment structure inserted into the insertion hole, the band-pass filter is positioned on the optical axis and can adjust the rotation angle around the central axis of the insertion hole. 5. The external resonator type semiconductor laser device according to claim 3, wherein the adjustment structure portion is fixed to the sealing structure so as to hermetically close the insertion hole.

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