External cavity laser module and method for manufacturing the same

Abstract

To provide an external resonant laser module capable of improving yield, and a method of manufacturing the same.SOLUTION: A laser module 1 includes a QCL element 2, a diffraction grating unit 5, lens holders 7A and 7B, and a mount member 4. A fourth mounting portion 44 of the mount member 4 is provided with a placement hole 44b into which a protruding portion 53c of the diffraction grating unit 5 is inserted. The placement hole 44b is longer than the protruding portion 53c so that the protruding portion 53c can be slid in an X-axis direction relative to the placement hole 44b. A wall surface 43c for positioning the diffraction grating unit 5 is provided between a third mounting portion 43 and the fourth mounting portion 44. The diffraction grating unit 5 has a positioning surface 53d facing the wall surface 43c. The diffraction grating unit 5 is fixed to the fourth mounting portion 44 in a state where the protruding portion 53c is inserted into the placement hole 44b and the positioning surface 53d is in surface contact with the wall surface 43c.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to an external cavity laser module and a method for manufacturing an external cavity laser module. [Background technology]

[0002] A known external cavity laser module includes a quantum cascade laser element, an oscillating diffraction grating, and a lens disposed between the quantum cascade laser element and the diffraction grating (see, for example, Patent Document 1). In such an external cavity laser module, light from the quantum cascade laser element is diffracted and reflected by the diffraction grating, and light of a specific wavelength from the light is fed back to the quantum cascade laser element. As a result, an external resonator is formed by the end face of the quantum cascade laser element and the diffraction grating, and the light of the specific wavelength is amplified and output to the outside. By oscillating the diffraction grating to change the wavelength of the output light, it is possible to sweep the wavelength within a predetermined wavelength range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2009 / 0225802 Summary of the Invention [Problem to be solved by the invention]

[0004] In the external cavity laser module described above, in order to generate laser oscillation by external resonance, components such as lenses and diffraction gratings must be mounted with high precision. If the mounting precision of the components is poor, there is a risk of the resulting product being defective and not generating laser oscillation by external resonance. In other words, when mass-producing external cavity laser modules, if the mounting precision of the components varies greatly, there is a risk of a decrease in yield.

[0005] Therefore, an object of one aspect of the present disclosure is to provide an external cavity laser module and a manufacturing method thereof that can improve yield. [Means for solving the problem]

[0006] An external cavity laser module according to one aspect of the present disclosure includes: a quantum cascade laser element; a diffraction grating unit including a movable diffraction grating that constitutes an external cavity of the quantum cascade laser element; a first lens holder that is arranged on the opposite side of the quantum cascade laser element from the side on which the movable diffraction grating is located and that holds a first lens that passes light emitted from the quantum cascade laser element; a second lens holder that is arranged between the quantum cascade laser element and the movable diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the movable diffraction grating to the quantum cascade laser element; and a mount member that mounts the quantum cascade laser element, the diffraction grating unit, the first lens holder, and the second lens holder, wherein the mount member includes a first mounting portion, a second mounting portion, a third mounting portion, and a fourth mounting portion that are arranged in this order from the first lens holder side toward the diffraction grating unit side along a direction in which the first lens holder and the second lens holder face each other. The diffraction grating unit has a mounting portion and a fourth mounting portion, wherein the first mounting portion has a first lens holder mounted thereon, the second mounting portion has a quantum cascade laser element mounted thereon, the third mounting portion has a third mounting surface on which the second lens holder is mounted, and the fourth mounting portion has a fourth mounting surface on which a diffraction grating unit is mounted, a protrusion is provided on a surface of the diffraction grating unit facing the fourth mounting surface, and the fourth mounting portion has a hole into which the protrusion is inserted, the length of the hole in the facing direction being longer than the length of the protrusion in the facing direction so that the protrusion can be slid in the facing direction relative to the hole, and a wall surface is provided between the third and fourth mounting portions, intersecting the facing direction, for positioning the diffraction grating unit, and the diffraction grating unit has a positioning surface facing the wall surface, and the diffraction grating unit is fixed to the fourth mounting portion with the protrusion inserted into the hole and the positioning surface in surface contact with the wall surface.

[0007] In the above-described external cavity laser module, the protrusion of the diffraction grating unit is inserted into the hole of the fourth mounting portion, and the positioning surface of the diffraction grating unit is fixed to the fourth mounting portion while in surface contact with the positioning wall surface. This allows the diffraction grating unit to be positioned accurately relative to the mount member. Furthermore, the protrusion is configured to be slidable in the opposing direction while inserted into the hole. This allows the diffraction grating unit to be easily positioned by inserting the protrusion into the hole and performing a sliding operation to push the diffraction grating unit toward the third mounting portion. That is, in the above-described external cavity laser module, the diffraction grating unit can be easily mounted to the mount member with high accuracy. As a result, variation in mounting accuracy of the diffraction grating unit 5 can be suppressed, thereby improving yield during mass production of external cavity laser modules.

[0008] The third mounting surface may be located higher than the fourth mounting surface, and the wall surface may be formed by a stepped surface connecting the third mounting surface and the fourth mounting surface. According to the above configuration, the stepped surface connecting the third mounting portion and the fourth mounting portion can function as a wall surface for positioning. In other words, there is no need to provide a separate wall portion dedicated solely to positioning the diffraction grating unit. This simplifies the structure of the mounting member, thereby reducing the manufacturing cost of the mounting member.

[0009] In a width direction that is parallel to the fourth mounting surface and perpendicular to the facing direction, the width of the wall surface and the positioning surface may be larger than the width of the protrusion. One possible method for positioning the diffraction grating unit with respect to the fourth mounting portion is to abut the end of the protrusion facing the third mounting portion against the end of the hole facing the third mounting portion, but by making the width of the wall surface and the positioning surface larger than the width of the protrusion and positioning the diffraction grating unit using the wall surface and the positioning surface, it is possible to position the diffraction grating unit with a larger width and with higher accuracy than when positioning the diffraction grating unit using the protrusion and the hole.

[0010] The hole may have a first portion extending along the facing direction, and the first portion may have a width parallel to the fourth mounting surface and substantially equal to the width of the protrusion in a width direction perpendicular to the facing direction. According to the above configuration, the first portion functions as a guide for smoothly sliding the protrusion in the facing direction. Therefore, with the protrusion inserted into the hole, the operation of sliding the diffraction grating unit toward the third mounting portion until the positioning surface makes surface contact with the wall surface can be performed easily and with high precision. As a result, the installation of the diffraction grating unit on the mount member can be facilitated and the installation precision of the diffraction grating unit can be improved.

[0011] The gap between the protrusion and the hole may be filled with a resin adhesive, the hole may have a second portion having a width greater than the first portion, and when the diffraction grating unit is fixed to the fourth mounting portion, the end of the protrusion facing the third mounting portion may be located within the first portion of the hole. According to the above configuration, the second portion can function as a region for allowing excess resin adhesive to escape. Furthermore, by locating the end of the protrusion facing the third mounting portion within the first portion, which has approximately the same width as the protrusion, it is possible to suppress deviation of the end of the protrusion in the width direction, thereby improving the mounting accuracy of the diffraction grating unit.

[0012] A method for manufacturing an external cavity laser module according to another aspect of the present disclosure includes the steps of: placing a resin adhesive made of a thermosetting resin inside a hole; inserting a protrusion into the hole after the placing step; sliding the diffraction grating unit in the opposing direction relative to the fourth mounting portion to bring the positioning surface into surface contact with the wall surface after the surface contact step; and fixing the diffraction grating unit to the fourth mounting portion by hardening the resin adhesive by heat treatment after the surface contact step.

[0013] According to the above manufacturing method, with the protrusion inserted into the hole, the diffraction grating unit is slid until the positioning surface comes into surface contact with the wall surface, and then the resin adhesive is thermally hardened, thereby making it possible to easily and accurately position and fix (mount) the diffraction grating unit to the mounting member. [Effects of the Invention]

[0014] According to one aspect of the present disclosure, it is possible to provide an external cavity laser module and a method for manufacturing the same that can improve yield. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of an external cavity laser module according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing the internal configuration of the external cavity laser module. [Figure 3] FIG. 3 is a cross-sectional view of the external cavity laser module taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the external cavity laser module taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a diagram showing the relationship between the mount member and the diffraction grating unit. [Figure 6] FIG. 6 is a front view of the MEMS diffraction grating. [Figure 7] FIG. 7 is a diagram showing an electrical connection configuration between the quantum cascade laser element and the electrode terminals. [Figure 8] FIG. 8 is a plan view of the mount member. [Figure 9] FIG. 9 is a diagram showing a manufacturing process of an external cavity laser module. [Figure 10] FIG. 10 is a diagram showing a manufacturing process of an external cavity laser module. [Figure 11] FIG. 11 is a diagram showing a structure for attaching a diffraction grating unit to a mount member according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, terms such as "upper" and "lower" are used for convenience based on the state shown in the drawings.

[0017] [Overall configuration of external cavity laser module] As shown in FIGS. 1 to 4, an external cavity laser module 1 (hereinafter referred to as the “laser module 1”) includes a quantum cascade laser element (hereinafter referred to as the “QCL ​​element”) 2 and a package 3 that hermetically houses the QCL element 2. The external cavity laser module 1 is a tunable light source that tunable the wavelength of output light (laser light L). The external cavity laser module 1 can be used, for example, for biomeasurements of glucose and the like, and for measuring the absorption spectrum of an analyte having an optical absorption band, such as a VOC gas (volatile organic compound). For example, when measuring such an absorption spectrum, the analyte contained in an optically transparent container is placed between the external cavity laser module 1 and a photodetector (not shown). The external cavity laser module 1 then rapidly changes the wavelength of the output light (laser light L) to sweep the wavelength within a predetermined wavelength range (for example, the mid-infrared region). The absorption spectrum is calculated based on the detection result of the photodetector. The analyte may be any of a gas, liquid, and solid.

[0018] The package 3 is a housing that houses the QCL element 2, the mount member 4, the diffraction grating unit 5, a lens holder 7A (first lens holder) that holds a lens 6A (first lens), and a lens holder 7B (second lens holder) that holds a lens 6B (second lens). In this embodiment, as an example, the package 3 is configured as a butterfly package. The package 3 has a bottom wall 31, side walls 32, and a top wall 33. In FIG. 2, the top wall 33 of the package 3 is not shown, and the portions of the lead terminals 10 that protrude outward beyond the protruding walls 34 are not shown.

[0019] The bottom wall 31 is a rectangular plate-shaped member. The bottom wall 31 is formed of a metal material such as copper tungsten. The bottom wall 31 is a base member on which the mount member 4 is mounted. For convenience, in this specification, the longitudinal direction of the bottom wall 31 is referred to as the X-axis direction, the lateral direction of the bottom wall 31 is referred to as the Y-axis direction, and the direction perpendicular to the bottom wall 31 (i.e., the direction perpendicular to the X-axis direction and the Y-axis direction) is referred to as the Z-axis direction. The X-axis direction is also the direction along the optical axis of the laser light L emitted from the QCL device 2 (optical axis direction).

[0020] The side wall 32 is erected on the bottom wall 31. When viewed from the Z-axis direction, the side wall 32 is formed in an annular shape so as to surround the internal space in which the QCL element 2 and the like are housed. In this embodiment, the side wall 32 is a rectangular tubular member. The side wall 32 is formed of a metal material such as Kovar. The side wall 32 is, for example, a Kovar frame plated with Ni / Au. In this embodiment, the side wall 32 is provided in the center of the bottom wall 31 in the longitudinal direction (X-axis direction). The width of the side wall 32 in the lateral direction (Y-axis direction) is the same as the width of the bottom wall 31 in the lateral direction, and the width of the side wall 32 in the longitudinal direction (X-axis direction) is shorter than the width of the bottom wall 31 in the longitudinal direction. In other words, protrusions 31a are formed on both sides of the bottom wall 31 in the longitudinal direction, protruding outward from the side walls 32. At the portions of the protruding portion 31a corresponding to the four corners of the bottom wall 31, screw holes 31b are provided for attaching the package 3 (bottom wall 31) to another member.

[0021] The top wall 33 is a member that closes the opening of the side wall 32 on the opposite side from the bottom wall 31. The top wall 33 has a rectangular plate shape. The outer shape (lengthwise and widthwise) of the top wall 33 when viewed from the Z-axis direction approximately matches the outer shape of the side wall 32. The top wall 33 is formed, for example, from the same metal material (e.g., Kovar) as the side wall 32. The top wall 33 is joined to the end of the side wall 32 on the opposite side from the bottom wall 31 by, for example, seam welding or the like.

[0022] A plurality of lead terminals 10 (14 in total, seven on each side in the lateral direction) are inserted into a pair of first side walls 321 (i.e., portions intersecting in the lateral direction (Y-axis direction)) of the side walls 32 extending along the longitudinal direction (X-axis direction) for passing current to components such as the QCL element 2 housed in the package 3. Each lead terminal 10 is a flat conductive member extending in the Y-axis direction.

[0023] Each of the pair of first side walls 321 is provided with a protruding wall 34 that protrudes from both the outer surface (the outer surface of the package 3) and the inner surface (the inner surface of the package 3) of the first side wall 321 (see FIG. 4 ). The protruding wall 34 is a canopy-shaped member that extends along the X-axis direction above (toward the top wall 33) the center position of the first side wall 321 in the Z-axis direction. The lead terminals 10 are arranged on the upper surfaces 34a of the protruding walls 34 at approximately equal intervals along the X-axis direction. The portions of the lead terminals 10 along the inner wall surfaces of the package 3 (the inner surfaces of the first side walls 321) (i.e., the portions located inside the package 3) function as electrode terminals 10a for supplying power to the components within the package 3 (e.g., the QCL element 2, the MEMS diffraction grating 51, the temperature sensor 9 described below, etc.). That is, the electrode terminals 10a and the components are electrically connected to each other via conductive wires W, thereby supplying power from an external power source to the components.

[0024] A light exit window 32a is provided on one of the second side walls 322 extending along the short-side direction (Y-axis direction) of the side wall 32 (i.e., the portion intersecting the long-side direction (X-axis direction)). The light exit window 32a passes through the laser light L emitted from one end face (first end face 2a) of the QCL device 2. The light exit window 32a is made of, for example, a material (e.g., germanium) that transmits the laser light L with a wavelength in the mid-infrared region. In this embodiment, as an example, the light exit window 32a is formed in a disk shape. The light exit window 32a is fixed to a circular opening formed in one of the second side walls 322.

[0025] Next, the components housed in the package 3 will be described. As shown in FIG. 3, the QCL element 2, the diffraction grating unit 5, and the lens holders 7A and 7B are disposed on the bottom wall 31 via a mount member 4. The mount member 4 is an optical stage for mounting the optical element described above. The wires W are not shown in FIG. 3. The mount member 4 is fixed to the bottom wall 31 by, for example, bonding or screwing. The mount member 4 is made of a material with excellent thermal conductivity, such as copper. In this embodiment, the mount member 4 is disposed directly on the bottom wall 31; however, the mount member 4 may be disposed on the bottom wall 31 via a cooling element, such as a Peltier module. In this embodiment, the mount member 4 is a single component; however, the mount member 4 may be a combination of multiple components (parts).

[0026] As shown in FIGS. 3, 5, and 8, the mount member 4 is a member that is elongated in the X-axis direction. The mount member 4 mounts the QCL element 2, the diffraction grating unit 5, the lens holder 7A, and the lens holder 7B. The mount member 4 has a first mounting portion 41, a second mounting portion 42, a third mounting portion 43, and a fourth mounting portion 44. The first mounting portion 41, the second mounting portion 42, the third mounting portion 43, and the fourth mounting portion 44 are arranged in this order from the lens holder 7A side toward the diffraction grating unit 5 side along the opposing direction (the X-axis direction in this embodiment) in which the lens holder 7A and the lens holder 7B face each other. The lens holder 7A is mounted on the first mounting portion 41 via an adhesive layer B1 (first adhesive layer) made of a photo-curable resin (e.g., a UV-curable resin) interposed therebetween. The QCL element 2 is mounted on the second mounting portion 42. The lens holder 7B is mounted on the third mounting portion 43 via an adhesive layer B2 (second adhesive layer) made of a photocurable resin (e.g., a UV-curable resin) similar to the adhesive layer B1. The diffraction grating unit 5 is mounted on the fourth mounting portion 44. That is, the light exit window 32a, the lens 6A (lens holder 7A), the QCL element 2, the lens 6B (lens holder 7B), and the diffraction grating unit 5 are arranged in this order along the X-axis direction.

[0027] The first mounting portion 41 and the third mounting portion 43 have the same thickness. That is, with the bottom wall 31 as the reference, the height position of the upper surface 41a (first mounting surface) of the first mounting portion 41 coincides with the height position of the upper surface 43a (third mounting surface) of the third mounting portion 43. The lens holder 7A is adhesively fixed to the upper surface 41a of the first mounting portion 41 via an adhesive layer B1. Similarly, the lens holder 7B is adhesively fixed to the upper surface 43a of the third mounting portion 43 via an adhesive layer B2. The length of the lens holders 7A and 7B in the X-axis direction is, for example, approximately 2.2 mm.

[0028] In this embodiment (FIGS. 3 and 5), the widths (lengths in the Y-axis direction) of the lens holders 7A and 7B are the same as the widths of the upper surfaces 41a and 43a, but the widths of the lens holders 7A and 7B may be smaller than the widths of the upper surfaces 41a and 43a. That is, the ends of the lens holders 7A and 7B in the Y-axis direction may be located more inward than the ends of the upper surfaces 41a and 43a in the Y-axis direction. For example, the widths of the upper surfaces 41a and 43a (i.e., the width of the mount member 4) may be set to approximately 6 mm, and the widths of the lens holders 7A and 7B may be set to approximately 5.7 mm.

[0029] In this embodiment (FIG. 3), the position in the X-axis direction of the end of the lens holder 7A on the light exit window 32a side coincides with the position in the X-axis direction of the end of the first mounting portion 41 (upper surface 41a) on the light exit window 32a side, but the end of the lens holder 7A on the light exit window 32a side may be located more inward (towards the second mounting portion 42) than the end of the first mounting portion 41 (upper surface 41a) on the light exit window 32a side. For example, the distance (length in the X-axis direction) between the end of the lens holder 7A on the light exit window 32a side and the end of the first mounting portion 41 (upper surface 41a) on the light exit window 32a side may be set to about 0.3 mm.

[0030] It is preferable to use a photocurable resin as the adhesive (adhesive layers B1, B2) for fixing the lens holders 7A, 7B to the mount member 4. The reason for this is as follows: When fixing the lens holders 7A, 7B to the mount member 4, it is necessary to align the lens holders 7A, 7B (lenses 6A, 6B) in the X, Y, and Z directions, as described below. For this reason, the process of curing the adhesive is not performed while the lens holders 7A, 7B are sufficiently pressed against the mount member 4. In such a case, using a photocurable resin as the adhesive allows the lens holders 7A, 7B to be bonded to the mount member 4 with higher positional accuracy than using a thermosetting resin. Furthermore, precision components such as the QCL element 2 are disposed between the lens holders 7A, 7B. If a thermosetting resin is used as the adhesive, the heat treatment for curing the adhesive may affect the quality of the QCL element 2. For the above reasons, in this embodiment, the lens holders 7A and 7B are fixed to the mount member 4 via adhesive layers B1 and B2 made of photocurable resin.

[0031] The second mounting section 42 is provided between the first mounting section 41 and the third mounting section 43. The second mounting section 42 is thicker than the first mounting section 41 and the third mounting section 43 and protrudes relative to the first mounting section 41 and the third mounting section 43. That is, the upper surface 42a (second mounting surface) of the second mounting section 42 is located higher than the upper surfaces 41a, 43a of the first mounting section 41 and the third mounting section 43. The QCL element 2 is fixed to the upper surface 42a of the second mounting section 42 via a submount 8. The submount 8 is a rectangular plate-shaped member on which the QCL element 2 is mounted. In this embodiment, the submount 8 is disposed at the center of the upper surface 42a in the Y-axis direction. As a result, the QCL element 2 is mounted approximately at the center of the upper surface 42a in the Y-axis direction. The submount 8 is made of a material (e.g., aluminum nitride) having a thermal expansion coefficient similar to that of the QCL element 2. The QCL element 2 is bonded to the submount 8 via, for example, an AuSn-based solder material. The submount 8 is bonded to the mount member 4 (upper surface 42a) via, for example, an In-based (InSn, InAg, etc.) solder material. As described above, the QCL element 2 is integrated with the submount 8, and therefore the combination of the QCL element 2 and the submount 8 can be considered the "QCL element."

[0032] In addition to the submount 8, a temperature sensor 9 and an electrode pad 11 are also arranged on the upper surface 42a of the second mounting part 42. The temperature sensor 9 and the electrode pad 11 are bonded to the mount member 4 (upper surface 42a) via, for example, a resin adhesive. In this embodiment, the temperature sensor 9 and the electrode pad 11 are arranged on opposite sides of the submount 8. The temperature sensor 9 is, for example, a thermistor. The electrode pad 11 relays the electrical connection between the electrode terminal 10a and the QCL element 2. In this embodiment, two electrode pads 11 are provided on the upper surface 42a of the second mounting part 42. Specifically, an electrode pad 11a electrically connected to the cathode of the QCL element 2 (in this embodiment, the upper surface (upper mesa surface) of the QCL element 2) and an electrode pad 11b electrically connected to the anode of the QCL element 2 (in this embodiment, the submount 8) are provided on the upper surface 42a of the second mounting part 42. Each of the electrode pads 11a and 11b has a substantially rectangular connection region (top surface). The electrode pads 11a and 11b are aligned along the X-axis direction. The electrode pad 11a is located closer to the light exit window 32a than the electrode pad 11b. With respect to the bottom wall 31 as a reference, the height of each of the electrode pads 11a and 11b is lower than the height of the electrode terminal 10a (i.e., the height of the upper surface 34a of the protruding wall 34) and higher than the height of the QCL element 2.

[0033] The fourth mounting portion 44 is thinner than the first mounting portion 41 and the third mounting portion 43. That is, an upper surface 44a (fourth mounting surface) of the fourth mounting portion 44 is located lower than the upper surfaces 41a, 43a of the first mounting portion 41 and the third mounting portion 43. An arrangement hole 44b (hole) is formed in the fourth mounting portion 44. As shown in FIG. 5, the diffraction grating unit 5 is fixed to the fourth mounting portion 44 using a resin adhesive B3 such as a thermosetting resin, with a protrusion 53c, which is part of a yoke 53 described later, inserted into the arrangement hole 44b.

[0034] The QCL 2 has a first end face 2a and a second end face 2b opposite to the first end face 2a. The QCL 2 emits light in the mid-infrared region (e.g., 4 μm to 12 μm) from each of the first end face 2a and the second end face 2b. The first end face 2a and the second end face 2b are flat surfaces perpendicular to the X-axis direction, for example, and the optical axis of the laser light L emitted from the QCL 2 is along the X-axis direction. The QCL 2 includes an active layer made of multiple quantum well layers (e.g., InGaAs) and multiple quantum barrier layers (e.g., InAlAs), and a pair of cladding layers (e.g., InP) sandwiching the active layer, and is capable of emitting light in the broadband described above. In this embodiment, the stacking direction of the stacked structure including the active layer and the cladding layers in the QCL 2 coincides with the direction in which the bottom wall 31 and the top wall 33 face each other (the Z-axis direction). The QCL 2 may include multiple active layers and a pair of cladding layers each having a different center wavelength, and in this case, the QCL 2 can still emit light over a wide bandwidth. The first end face 2a is coated with a low-reflection coating, and the second end face 2b is coated with an anti-reflection coating.

[0035] The lenses 6A and 6B are aspherical lenses made of, for example, zinc selenide (ZnSe), and the surfaces of the lenses 6A and 6B are coated with an anti-reflection coating.

[0036] The lens 6A is disposed on the opposite side of the QCL element 2 from the side on which the MEMS diffraction grating 51 (diffraction grating unit 5) is located. That is, the lens 6A is disposed at a position facing the first end face 2a of the QCL element 2. The lens 6A passes the light emitted from the QCL element 2 (light emitted from the first end face 2a). The lens 6A collimates the light emitted from the first end face 2a. The light collimated by the lens 6A passes through the light exit window 32a of the package 3 and is output to the outside as output light (laser light L).

[0037] The lens 6B is disposed between the QCL element 2 and the MEMS diffraction grating 51 (diffraction grating unit 5). That is, the lens 6B is disposed at a position facing the second end face 2b of the QCL element 2. The lens 6B passes the light emitted from the QCL element 2 (light emitted from the second end face 2b) and the light returning from the MEMS diffraction grating 51 to the QCL element 2. The lens 6B collimates the light emitted from the second end face 2b to the MEMS diffraction grating 51.

[0038] The lens holders 7A and 7B have a substantially rectangular parallelepiped shape. The lenses 6A and 6B are fixed to the lens holders 7A and 7B with a resin adhesive or the like. The surfaces of the lens holders 7A and 7B are blackened, for example, by anodizing.

[0039] The diffraction grating unit 5 includes a MEMS diffraction grating 51 (movable diffraction grating), a magnet 52, and a yoke 53. The MEMS diffraction grating 51 is formed in a substantially plate shape. The magnet 52 is disposed on the opposite side of the MEMS diffraction grating 51 from the QCL element 2. The MEMS diffraction grating 51 is fixed to the yoke 53, and the magnet 52 is housed within the yoke 53. As a result, the MEMS diffraction grating 51, the magnet 52, and the yoke 53 are integrated and form a single unit.

[0040] The light collimated by the lens 6B is incident on the MEMS diffraction grating 51 of the diffraction grating unit 5. The MEMS diffraction grating 51 diffracts and reflects the incident light, thereby returning light of a specific wavelength from the incident light to the second end face 2b of the QCL element 2 via the lens 6B. The MEMS diffraction grating 51 forms an external resonator for the QCL element 2. In this embodiment, the MEMS diffraction grating 51 and the first end face 2a form a Littrow-type external resonator. This allows the laser module 1 to amplify light of a specific wavelength and output it to the outside.

[0041] Furthermore, the MEMS diffraction grating 51 can rapidly change the orientation of the diffraction grating portion 64 that diffracts and reflects incident light. This makes it possible to change the wavelength of the light that returns from the MEMS diffraction grating 51 to the second end facet 2b of the QCL device 2, thereby changing the wavelength of the output light (laser light L) of the laser module 1. By changing the wavelength of the laser light L, it is possible to sweep the wavelength within the gain band of the QCL device 2, for example.

[0042] 6, the MEMS diffraction grating 51 includes a support portion 61, a pair of connecting portions 62, a movable portion 63, a diffraction grating portion 64, and a pair of coils 65 and 66. The MEMS diffraction grating 51 is configured as a MEMS device that oscillates the movable portion 63 around an axis A. A MEMS device is a device formed using microfabrication techniques (patterning, etching, etc.) known as MEMS technology, and includes semiconductor devices formed using semiconductor microfabrication techniques.

[0043] The support part 61 is a flat frame body having a rectangular shape in a plan view. The support part 61 supports the movable part 63 via a pair of connecting parts 62. Each connecting part 62 is a flat member having a rectangular rod shape in a plan view, and extends straight along the axis A. Each connecting part 62 connects the movable part 63 to the support part 61 on the axis A so that the movable part 63 can swing freely around the axis A.

[0044] The movable portion 63 is located inside the support portion 61. As described above, the movable portion 63 is capable of swinging around the axis A. The movable portion 63 is a flat member having a substantially rectangular shape in a plan view. In the present embodiment, as an example, the four corners of the movable portion 63 are chamfered in an R-shape. That is, the four corners of the movable portion 63 are curved in an arc shape in a plan view. This reduces the moment of inertia of the movable portion 63 and increases the swing speed of the movable portion 63. In this example, the movable portion 63 is formed in a substantially rectangular shape with its long sides parallel to the first direction D1 (a direction perpendicular to the axis A), and the length of the movable portion 63 in the first direction D1 is longer than the length of the movable portion 63 in the second direction D2 (a direction parallel to the axis A). As an example, the length of the support portion 61 in the first direction D1 is approximately 6 to 7 mm, and the length of the support portion 61 in the second direction D2 is approximately 6 mm. The length of the movable portion 63 in the first direction D1 is about 4 mm, the length of the movable portion 63 in the second direction D2 is about 3 mm, and the thickness is about 30 μm. The support portion 61, the connecting portion 62, and the movable portion 63 are integrally formed by being built into a single SOI (Silicon on Insulator) substrate, for example.

[0045] A diffraction grating unit 64 is provided on the surface of the movable unit 63 facing the QCL device 2. The diffraction grating unit 64 has a plurality of grating grooves (not shown) and diffracts and reflects light emitted from the QCL device 2. The diffraction grating unit 64 includes, for example, a resin layer provided on the surface of the movable unit 63 and having a diffraction grating pattern formed thereon, and a metal layer provided on the surface of the resin layer so as to follow the diffraction grating pattern. Alternatively, the diffraction grating unit 64 may be formed only by a metal layer provided on the movable unit 63 and having a diffraction grating pattern formed thereon. Examples of the diffraction grating pattern that can be used include a blazed grating with a sawtooth cross section, a binary grating with a rectangular cross section, and a holographic grating with a sinusoidal cross section. The diffraction grating pattern is formed on the resin layer by, for example, nanoimprint lithography. The metal layer is, for example, a metal reflective film made of gold and formed by vapor deposition.

[0046] The coils 65 and 66 are made of a metal material such as copper, and have a damascene structure embedded in grooves formed in the surface of the movable part 63. In a plan view, the coil 65 is arranged on one side (upper side in FIG. 6) of the axis A, and the coil 66 is arranged on the other side (lower side in FIG. 6) of the axis A. The coils 65 and 66 are drive coils that pass a current to drive the MEMS diffraction grating 51 (i.e., to oscillate the movable part 63).

[0047] Each of the coils 65, 66 is wound multiple times in a spiral shape in a plan view. The outer end of the coil 65 is electrically connected to an electrode pad 71 provided on the support portion 61 via a wiring 72. The wiring 72 extends across the support portion 61, one of the connecting portions 62, and the movable portion 63. The outer end of the coil 66 is electrically connected to an electrode pad 73 provided on the support portion 61 via a wiring 74. The wiring 74 extends across the support portion 61, the other connecting portion 62, and the movable portion 63. In this embodiment, a detection coil (first coil) (not shown) is provided on the surface of the movable portion 63 in addition to the coils 65, 66. Therefore, in addition to the electrode pads 71, 73 electrically connected to the coils 65, 66, the support portion 61 is also provided with electrode pads 75, 76 (first electrode pads) electrically connected to both ends of the detection coil via wiring (similar to the wiring 72, 74) (not shown) to extract the current detected by the detection coil to the outside.

[0048] The inner end of coil 65 is electrically connected to the inner end of coil 66. In this example, coils 65 and 66 are integrally formed with each other, and therefore the inner ends of coils 65 and 66 are electrically connected to each other. In other words, in MEMS diffraction grating 51, a single coil wiring (multilayer wiring) extends so as to be folded back in a figure-eight shape in plan view, thereby forming a pair of coils 65 and 66. Note that coils 65 and 66 may also be formed separately from each other. In this case, the inner end of coil 65 and the inner end of coil 66 may be electrically connected via wiring.

[0049] Magnet 52 generates a magnetic field (magnetic force) that acts on coils 65 and 66. As shown in Fig. 3, magnet 52 is a neodymium magnet (permanent magnet) formed in a substantially rectangular parallelepiped shape. For example, magnet 52 has an N pole on the side of MEMS diffraction grating 51 and an S pole on the side opposite MEMS diffraction grating 51.

[0050] The yoke 53 amplifies the magnetic force of the magnet 52 and forms a magnetic circuit together with the magnet 52. The surface of the yoke 53 is blackened, for example, by zinc plating. As shown in Fig. 3, the yoke 53 has an inclined surface 53a, a lower surface 53b, a protrusion 53c, and a positioning surface 53d.

[0051] The inclined surface 53a is inclined with respect to the second end face 2b of the QCL element 2. By fixing the MEMS diffraction grating 51 on the inclined surface 53a, the normal N of the diffraction grating portion 64 of the MEMS diffraction grating 51 can be inclined with respect to the second end face 2b. In this example, the diffraction grating portion 64 is inclined so as to face one side in the Z-axis direction (toward the top wall 33). However, the diffraction grating portion 64 may be inclined so as to face the other side in the Z-axis direction (toward the bottom wall 31). The inclination angle of the inclined surface 53a (the angle with respect to the second end face 2b of the QCL element 2) is set depending on the oscillation wavelength of the QCL element 2, the number of grating grooves in the diffraction grating portion 64, the blazed angle, and the like. For example, when the oscillation wavelength is in the 7 μm band and the number of grooves is 150 / mm, the inclination angle of the inclined surface 53a is set to approximately 60 degrees.

[0052] The yoke 53 is formed in a generally U-shape (inverted C-shape) when viewed from the Y-axis direction, and defines an arrangement space SP that opens to an inclined surface 53a. The magnet 52 is disposed in this arrangement space SP, and the magnet 52 is housed within the yoke 53. When viewed from the Y-axis direction, the yoke 53 surrounds the magnet 52. The MEMS diffraction grating 51 is fixed to the inclined surface 53a at the edge of the support portion 61 so as to cover the opening of the arrangement space SP.

[0053] The lower surface 53b is a surface facing the upper surface 44a of the fourth mounting portion 44. A protrusion 53c that protrudes downward is provided on the lower surface 53b. The positioning surface 53d is a surface that intersects with the X-axis direction so as to connect the inclined surface 53a and the lower surface 53b. In this embodiment, the positioning surface 53d is perpendicular to the X-axis direction. In other words, the positioning surface 53d is a surface that is parallel to the Y-axis direction and the Z-axis direction.

[0054] In the MEMS diffraction grating 51, when a current flows through the coils 65 and 66, a Lorentz force is generated in a predetermined direction on the electrons flowing through the coils 65 and 66 due to the magnetic field formed by the magnet 52 and the yoke 53. As a result, the coil 65 is subjected to a force in a predetermined direction. Therefore, by controlling the direction or magnitude of the current flowing through the coil 65, the movable part 63 (diffraction grating part 64) can be oscillated around the axis A. Furthermore, by passing a current having a frequency corresponding to the resonant frequency of the movable part 63 through the coils 65 and 66, the movable part 63 can be oscillated at high speed at the resonant frequency level (for example, at a frequency of 1 kHz or higher). In this way, the coils 65 and 66, the magnet 52, and the yoke 53 function as an actuator part that oscillates the movable part 63.

[0055] [Electrical connection configuration of QCL element] Next, the electrical connection configuration between the QCL element 2 and the electrode terminal 10a will be described with reference to FIGS. 2 and 7. As shown in FIGS. 2 and 7, the electrode terminal 10a and the QCL element 2 (in this embodiment, the cathode and anode of the QCL element 2) are electrically connected via a wire W. The wire W is formed, for example, by wire bonding. The end of the wire W on the QCL element 2 side is located between the lens holder 7A and the lens holder 7B when viewed from a direction perpendicular to the opposing direction (in this embodiment, the X-axis direction) between the lens holders 7A and 7B (in this embodiment, a direction parallel to a plane perpendicular to the X-axis direction, such as the Y-axis direction or Z-axis direction). In this embodiment, as an example, the end of the wire W on the QCL element 2 side is connected to the QCL element 2 or the submount 8. Furthermore, the wire W is connected to the electrode terminal 10a at a position between the lens holder 7A and the lens holder 7B when viewed from a direction perpendicular to the opposing direction. In other words, the wire W is connected to the electrode terminal 10a at a position that does not overlap with the lens holder 7A or the lens holder 7B when viewed from a direction perpendicular to the opposing direction. In this embodiment, two electrode terminals 10a1 and 10a2 are provided at positions that do not overlap with the lens holder 7A or the lens holder 7B when viewed from a direction perpendicular to the opposing direction. The above-mentioned arrangement configuration is achieved by using these two electrode terminals 10a1 and 10a2. The electrode terminals 10a1 and 10a2 are the second and third electrode terminals 10a, counting from the light exit window 32a side, on the protruding wall 34 on the side on which the electrode pad 11 is provided with respect to the QCL element 2.

[0056] The electrode terminal 10a1 is electrically connected to the cathode of the QCL element 2 (in this embodiment, the top surface of the QCL element 2). The electrode terminal 10a1 is connected to the top surface of the QCL element 2 via an electrode pad 11a. More specifically, the electrode terminal 10a1 is connected to the electrode pad 11a via multiple (six in this embodiment) wires W1 (first wires). The electrode pad 11a is also connected to the top surface of the QCL element 2 via multiple (six in this embodiment) wires W2 (second wires). Although the number of each wire W1 and W2 may be one, using multiple wires W1 and W2 ensures reliable electrical connection between the electrode terminal 10a1 and the cathode of the QCL element 2 (the top surface of the QCL element 2). Furthermore, as shown in FIG. 7, by arranging multiple wires W2 approximately evenly along the optical axis direction (X-axis direction) on the upper surface (upper surface of the mesa) of the QCL element 2, the amount of current injected into the QCL element 2 can be made approximately uniform along the optical axis direction, thereby improving the operational stability of the QCL element 2.

[0057] The electrode terminal 10a2 is electrically connected to the anode of the QCL element 2 (in this embodiment, the submount 8). The electrode terminal 10a2 is connected to the submount 8 via an electrode pad 11b. More specifically, the electrode terminal 10a2 is connected to the electrode pad 11b via a plurality of wires W3 (first wires) (six in this embodiment). The electrode pad 11b is connected to the submount 8 via a plurality of wires W4 (second wires) (six in this embodiment). Although the number of each of the wires W3 and W4 may be one, using multiple wires W3 and W4 ensures a reliable electrical connection between the electrode terminal 10a2 and the anode of the QCL element 2 (the submount 8).

[0058] As described above, in the laser module 1, the entire wire W (wires W1 to W4) that is connected to electrically connect the electrode terminal 10a and the QCL element 2 (anode or cathode) is configured to pass through the space between the lens holder 7A and the lens holder 7B when viewed from a direction (Y-axis direction, Z-axis direction, etc.) perpendicular to the opposing direction (X-axis direction).

[0059] In this embodiment, the temperature sensor 9 is also electrically connected to the electrode terminal 10a via wires W5a and W5b. Specifically, the wires W5 include a wire W5a connected to the temperature sensor 9 itself and a wire W5b connected to the mount member 4. The wires W5a and W5b are connected to the second and third electrode terminals 10a, counting from the light exit window 32a, on the protruding wall 34 on the side where the temperature sensor 9 is provided relative to the QCL element 2 (i.e., the electrode terminals 10a positioned so as not to overlap with the lens holder 7A or the lens holder 7B when viewed from a direction perpendicular to the facing direction). As a result, the wires W5a and W5b electrically connecting the temperature sensor 9 and the electrode terminals 10a are configured to pass through the space between the lens holder 7A and the lens holder 7B when viewed from a direction (such as the Y-axis direction or the Z-axis direction) perpendicular to the facing direction (the X-axis direction).

[0060] [Electrical connection configuration of MEMS diffraction grating] Next, referring to FIG. 2, the electrical connection configuration between the electrode terminal 10a and the MEMS diffraction grating 51 will be described. As described above, the MEMS diffraction grating 51 has two electrode pads 71 ​​and 73 electrically connected to the coils 65 and 66. More specifically, as shown in FIGS. 2 and 6, the electrode pads 71 ​​and 73 are provided at one corner of the support 61 on the top wall 33 side (the upper left corner when the MEMS diffraction grating 51 is viewed from the front). Each electrode pad 71 and 73 is connected to a corresponding electrode terminal 10a (electrode terminals 10a3 and 10a4) via a corresponding wire W (wires W6 and W7). The electrode terminals 10a3 and 10a4 are the third and second electrode terminals 10a, counting from the side opposite the light exit window 32a, on the protruding wall 34 on the side on which the electrode pad 11 is provided relative to the QCL element 2.

[0061] The electrode terminal 10a3 is connected to the electrode pad 71 via a plurality of wires W6 (two in this embodiment). The electrode terminal 10a4 is connected to the electrode pad 73 via a plurality of wires W7 (two in this embodiment). Although the number of wires W6 and W7 may be one each, using a plurality of wires W6 and W7 ensures reliable electrical connection between the electrode terminals 10a3 and 10a4 and the electrode pads 71 ​​and 73.

[0062] Here, the height positions of the electrode pads 71, 73 relative to the bottom wall 31 are equal to or higher than the height positions of the electrode terminals 10a3, 10a4 relative to the bottom wall 31. That is, the electrode pads 71, 73 do not extend deeper into the package 3 (towards the bottom wall 31) than the corresponding electrode terminals 10a3, 10a4. Therefore, when connecting the wires W6, W7 by wire bonding, it is not necessary to insert the capillary of the wire bonding device into the deeper side of the package 3. This makes it possible to appropriately prevent the capillary from coming into contact with other components (such as the lens holder 7B) inside the package 3 and to prevent damage to the components due to such contact.

[0063] In this embodiment, the electrode pads 75 and 76, which are provided on the opposite side of the electrode pads 71 ​​and 73 in the Y-axis direction, have the same electrical connection configuration as the electrode pads 71 ​​and 73. That is, the electrode pads 75 and 76 are provided on the other corner of the support 61 on the top wall 33 side (the upper right corner when the MEMS diffraction grating 51 is viewed from the front). Each electrode pad 75 and 76 is connected to a corresponding electrode terminal 10a (electrode terminals 10a5 and 10a6) via a corresponding wire W (wires W8 and W9). The electrode terminals 10a5 and 10a6 are the second and third electrode terminals 10a, counting from the side opposite the light exit window 32a, on the protruding wall 34 on the side where the temperature sensor 9 is provided with respect to the QCL element 2. The height positions of the electrode pads 75 and 76 relative to the bottom wall 31 are equal to or greater than the height positions of the electrode terminals 10a5 and 10a6 relative to the bottom wall 31. The electrode terminal 10a5 is connected to the electrode pad 75 via a plurality of wires W8 (two in this embodiment). The electrode terminal 10a6 is connected to the electrode pad 76 via a plurality of wires W8 (two in this embodiment). Although the number of wires W8 and W9 may be one, using a plurality of wires W8 and W9 ensures reliable electrical connection between the electrode terminals 10a5 and 10a6 and the electrode pads 75 and 76.

[0064] [Lens holder arrangement] Next, the arrangement of the lens holder 7B will be described with reference to Figures 3 and 4. The distance d (see Figure 4) between the top wall 33 and the surface 7a of the lens holder 7B facing the top wall is smaller than the thickness t (see Figure 3) of the lens holder 7B along the optical axis direction (X-axis direction) of the lens 6B. The distance d is, for example, about 0.64 mm. The thickness t is, for example, about 2.5 mm. Furthermore, the surface 7a of the lens holder 7B is located higher (closer to the top wall 33) than the electrode terminals 10a1 and 10a2 to which the wires W1 and W3 are connected.

[0065] [Lens holder mounting structure for mount] Next, the mounting structure of the lens holders 7A and 7B to the mount member 4 will be described in detail with reference to Figures 3, 4, 5, and 8. More specifically, the structures of the mount member 4 and the lens holders 7A and 7B for appropriately photo-curing the adhesive layers B1 and B2 will be described.

[0066] The lens holder 7A has a mounting surface 7Ab (first mounting surface) facing the upper surface 41a of the first mounting portion 41. The mounting surface 7Ab is bonded to the upper surface 41a via an adhesive layer B1. A recess 7Ac is formed in at least a portion of the mounting surface 7Ab of the lens holder 7A that is not bonded to the upper surface 41a via the adhesive layer B1. In this embodiment, the recess 7Ac is formed in the center of the mounting surface 7Ab in the width direction (Y-axis direction), and the mounting surface 7Ab is bonded to the upper surface 41a via the adhesive layer B1 on both sides of the recess 7Ac in the width direction (Y-axis direction). The recess 7Ac is provided so as to communicate with the space outside the lens holder 7A when the lens holder 7A is placed on the upper surface 41a. In other words, the recess 7Ac is provided so as to be able to guide light from the space outside the lens holder 7A to the space inside the recess 7Ac when the lens holder 7A is placed on the upper surface 41a. As an example, the recess 7Ac is formed as a groove extending along the X-axis direction from one end (the end on the light exit window 32a side) of the mounting surface 7Ab to the other end (the end on the lens holder 7B side). In this case, light can be guided from the external spaces on both sides of the lens holder 7A in the X-axis direction to the space inside the recess 7Ac.

[0067] According to the above configuration, when the adhesive layer B1 is irradiated with light to harden it, the light can be suitably guided from the space outside the lens holder 7A to the space within the recess 7Ac. This allows the adhesive layer B1 to harden appropriately. As a result, the lens holder 7A can be more reliably fixed to the upper surface 41a.

[0068] A recess 41b is formed on the upper surface 41a of the first mounting portion 41 so as to face the recess 7Ac of the lens holder 7A. The recess 41b is formed in at least a portion of the upper surface 41a that is not bonded to the attachment surface 7Ab of the lens holder 7A via the adhesive layer B1. The recess 41b is provided so as to communicate with the space outside the first mounting portion 41 when the lens holder 7A is placed on the upper surface 41a. That is, the recess 41b is provided so as to be able to guide light from the space outside the first mounting portion 41 to the space within the recess 41b when the lens holder 7A is placed on the upper surface 41a. As an example, the recess 41b is formed in the center of the upper surface 41a in the width direction (Y-axis direction). As shown in FIGS. 3 and 8, the recess 41b extends in the X-axis direction from the end of the upper surface 41a on the light exit window 32a side to the end of a curved surface 421b (described later). In this case, light can be guided from the external space on the light exit window 32a side of the first mounting portion 41 in the X-axis direction to the space within the recess 41b.

[0069] According to the above configuration, when the adhesive layer B1 is irradiated with light to harden it, the light can be suitably guided from the space outside the first mounting portion 41 to the space inside the recess 41b. This allows the adhesive layer B1 to harden appropriately. As a result, the lens holder 7A can be more reliably fixed to the upper surface 41a.

[0070] The lens holder 7B has a mounting surface 7Bb (second mounting surface) facing the upper surface 43a of the third mounting portion 43. The mounting surface 7Bb is bonded to the upper surface 43a via an adhesive layer B2. A recess 7Bc is formed in at least a portion of the mounting surface 7Bb of the lens holder 7B that is not bonded to the upper surface 43a via the adhesive layer B2. In this embodiment, the recess 7Bc is formed in the center of the mounting surface 7Bb in the width direction (Y-axis direction), and the mounting surface 7Bb is bonded to the upper surface 43a via the adhesive layer B2 on both sides of the recess 7Bc in the width direction (Y-axis direction). The recess 7Bc is provided so as to communicate with the space outside the lens holder 7B when the lens holder 7B is placed on the upper surface 43a. That is, the recess 7Bc is provided so as to be able to guide light from the space outside the lens holder 7B to the space within the recess 7Bc when the lens holder 7B is placed on the upper surface 43a. As an example, the recess 7Bc is formed as a groove extending along the X-axis direction from one end (the end on the lens holder 7A side) of the mounting surface 7Bb to the other end (the end on the diffraction grating unit 5 side). In this case, light can be guided from the external spaces on both sides of the lens holder 7B in the X-axis direction to the space within the recess 7Bc.

[0071] According to the above configuration, when the adhesive layer B2 is irradiated with light to harden it, the light can be suitably guided from the space outside the lens holder 7B to the space within the recess 7Bc. This allows the adhesive layer B2 to harden appropriately. As a result, the lens holder 7B can be more reliably fixed to the upper surface 43a.

[0072] A recess 43b is formed in the upper surface 43a of the third mounting portion 43 so as to face the recess 7Bc of the lens holder 7B. The recess 43b is formed in at least a portion of the upper surface 43a that is not bonded to the attachment surface 7Bb of the lens holder 7B via the adhesive layer B2. The recess 43b is provided so as to communicate with the space outside the third mounting portion 43 when the lens holder 7B is placed on the upper surface 43a. That is, the recess 43b is provided so as to be able to guide light from the space outside the third mounting portion 43 to the space within the recess 43b when the lens holder 7B is placed on the upper surface 43a. As an example, the recess 43b is formed in the center of the upper surface 43a in the width direction (Y-axis direction). As shown in FIGS. 3 and 8, the recess 43b extends in the X-axis direction from the end of the upper surface 43a on the diffraction grating unit 5 side to the end of a curved surface 422b (described later). In this case, light can be guided from the external space on the diffraction grating unit 5 side of the third mounting portion 43 in the X-axis direction to the space within the recess 43b.

[0073] According to the above configuration, when the adhesive layer B2 is irradiated with light to harden it, the light can be suitably guided from the space outside the third mounting portion 43 to the space inside the recess 43b. This allows the adhesive layer B2 to harden appropriately. As a result, the lens holder 7B can be more reliably fixed to the upper surface 43a.

[0074] The recess 7Ac and recess 41b also function as areas for allowing excess adhesive (i.e., adhesive layer B1) applied between the lens holder 7A and the upper surface 41a to escape. Similarly, the recess 7Bc and recess 43b also function as areas for allowing excess adhesive (i.e., adhesive layer B2) applied between the lens holder 7B and the upper surface 43a to escape.

[0075] [Detailed structure of the second mounting part of the mounting member] Next, the structure of the second mounting portion 42 will be described in detail with reference to Figures 3, 5, and 8. More specifically, the structure of the second mounting portion 42 for appropriately photo-curing the adhesive layers B1 and B2 will be described.

[0076] The second mounting portion 42 has an upper surface 42a, which is a mounting surface on which the QCL element 2 is mounted, a side surface 421 (first side surface), and a side surface 422 (second side surface). The side surface 421 faces the lens holder 7A. The side surface 421 intersects with the X-axis direction to connect the upper surface 42a of the second mounting portion 42 and the upper surface 41a of the first mounting portion 41. The side surface 422 is located on the opposite side from the side surface 421. In other words, the side surface 422 faces the lens holder 7B. The side surface 422 intersects with the X-axis direction to connect the upper surface 42a of the second mounting portion 42 and the upper surface 43a of the third mounting portion 43.

[0077] The side surface 421 has a notch 421a (first notch) extending from the upper surface 42a to the upper surface 41a of the first mounting portion 41 along a height direction (Z-axis direction) perpendicular to the upper surface 42a. The notch 421a is formed at an end of the side surface 421 in a width direction (Y-axis direction) parallel to the upper surface 42a and perpendicular to the facing direction (X-axis direction). In this embodiment, two notches 421a having similar shapes (symmetrical shapes) are provided at each end of the side surface 421 in the width direction (Y-axis direction). Such notches 421a have the following effect. That is, when viewed from the vertical direction (Z-axis direction), the notch 421a can increase the gap between the second mounting portion 42 and the lens holder 7A. As a result, when the adhesive layer B1 is irradiated with light to harden it, the light can be suitably guided to the adhesive layer B1 through the space formed by the notch 421a. More specifically, when the lens holder 7A is fixed to the mount member 4 while the mount member 4 is fixed in the package 3, light for curing the adhesive layer B1 must be irradiated from above the lens holder 7A through an opening in the top wall 33. In such a case, the notch 421a can effectively guide the light to the adhesive layer B1. As a result, the adhesive layer B1 can be appropriately cured, and the lens holder 7A can be more reliably fixed to the top surface 41a. Furthermore, by providing the notch 421a at the end of the second mounting portion 42 (side surface 421) in the width direction (Y-axis direction), the above-mentioned effect can be achieved without impairing the support stability of the QCL element 2 mounted approximately at the center of the second mounting portion 42 in the width direction (Y-axis direction). The distance (distance in the X-axis direction) between the side surface 421 and the lens holder 7A is, for example, 0.8 mm. The distance between the inner surface of the notch 421a (the portion farthest from the lens holder 7A) and the lens holder 7A is, for example, 1.15 mm.

[0078] A curved surface 421b is formed at a portion of the side surface 421 connected to the upper surface 41a of the first mounting portion 41 (i.e., at the base of the portion of the second mounting portion 42 that protrudes beyond the first mounting portion 41). The curved surface 421b curves in the height direction (Z-axis direction) from the upper surface 42a of the second mounting portion 42 toward the upper surface 41a of the first mounting portion 41, and approaches the lens holder 7A in the X-axis direction. In this embodiment, the curved surface 421b is provided at a portion of the side surface 421 where the notch 421a is not provided (i.e., the center of the side surface 421 in the Y-axis direction). With this curved surface 421b, when curing the adhesive layer B1, light irradiated from above the lens holder 7A can be reflected by the curved surface 421b toward the space between the lens holder 7A and the upper surface 41a of the first mounting portion 41. This improves the efficiency of light irradiation into the space between the lens holder 7A and the upper surface 41a, allowing the adhesive layer B1 to be properly cured. As a result, the lens holder 7A can be more reliably fixed to the upper surface 41a.

[0079] The side surface 422 has a notch 422a (second notch) extending from the upper surface 42a to the upper surface 43a of the third mounting portion 43 along the height direction (Z-axis direction). The notch 422a is formed at an end of the side surface 422 in the width direction (Y-axis direction). In this embodiment, two notches 422a having similar shapes (symmetrical shapes) are provided at each of both ends of the side surface 422 in the width direction (Y-axis direction). Such notches 422a have the following effect. That is, when viewed from the top-bottom direction (Z-axis direction), the notch 422a can increase the gap between the second mounting portion 42 and the lens holder 7B. As a result, when the adhesive layer B2 is irradiated with light to harden it, the light can be suitably guided to the adhesive layer B2 through the space formed by the notch 422a. More specifically, when the lens holder 7B is fixed to the mount member 4 while the mount member 4 is fixed in the package 3, light for curing the adhesive layer B2 must be irradiated from above the lens holder 7B through an opening in the top wall 33. In such a case, the notch 422a allows the light to be appropriately guided to the adhesive layer B2. As a result, the adhesive layer B2 can be appropriately cured, and the lens holder 7B can be more reliably fixed to the top surface 43a. Furthermore, by providing the notch 422a at the end of the second mounting portion 42 (side surface 422) in the width direction (Y-axis direction), the above-mentioned effect can be achieved without impairing the support stability of the QCL element 2 mounted approximately at the center of the second mounting portion 42 in the width direction (Y-axis direction). The distance (distance in the X-axis direction) between the side surface 422 and the lens holder 7B is, for example, 0.8 mm. The distance between the inner surface of the notch 422a (the portion farthest from the lens holder 7B) and the lens holder 7B is, for example, 1.15 mm.

[0080] A curved surface 422b is formed at a portion of the side surface 422 connected to the upper surface 43a of the third mounting portion 43 (i.e., at the base of the portion of the second mounting portion 42 that protrudes beyond the third mounting portion 43). The curved surface 422b curves in the height direction (Z-axis direction) from the upper surface 42a of the second mounting portion 42 toward the upper surface 43a of the third mounting portion 43, and approaches the lens holder 7B in the X-axis direction. In this embodiment, the curved surface 422b is provided at a portion of the side surface 422 where the notch 422a is not provided (i.e., the central portion of the side surface 422 in the Y-axis direction). With this curved surface 422b, when curing the adhesive layer B2, light irradiated from above the lens holder 7B can be reflected by the curved surface 422b toward the space between the lens holder 7B and the upper surface 43a of the third mounting portion 43. This improves the efficiency of light irradiation into the space between the lens holder 7B and the upper surface 43a, thereby properly curing the adhesive layer B2. As a result, the lens holder 7B can be more reliably fixed to the upper surface 43a.

[0081] Furthermore, the notches 421a and 422a that face each other in the X-axis direction are formed so as not to be continuous with each other. That is, as shown in FIG. 8, the notches 421a and 422a are independent of each other and are not connected in the X-axis direction. In other words, the width (length in the Y-axis direction) of the second mounting portion 42 with the notches 421a and 422a formed is the same as the width of the second mounting portion 42 without the notches 421a and 422a. That is, the width of the second mounting portion 42 is not reduced by the formation of the notches 421a and 422a. According to the above configuration, the width of the second mounting portion 42 disposed between the lens holder 7A and the lens holder 7B can be ensured while providing the notches 421a and 422a. This allows the second mounting portion 42 to function sufficiently as a barrier that prevents stray light components (i.e., light reflected by the MEMS diffraction grating 51 that does not return to the QCL device 2 via the lens 6B) from mixing into the laser light L emitted from the module via the lens 6A. In other words, the effect of the notches 421a and 422a described above (i.e., improved efficiency of light irradiation onto the adhesive layers B1 and B2) can be obtained without impairing the function as such a barrier.

[0082] [Diffraction grating unit mounting structure] Next, the mounting structure of the yoke 53 (diffraction grating unit 5) to the mount member 4 will be described in detail with reference to Figures 3 and 8. As described above, the protrusion 53c is provided on the lower surface 53b of the yoke 53, which faces the upper surface 44a of the fourth mounting portion 44. The fourth mounting portion 44 also has an arrangement hole 44b into which the protrusion 53c is inserted. In this embodiment, the arrangement hole 44b is configured as a through hole that passes through the fourth mounting portion 44 from top to bottom. However, the arrangement hole 44b may also be configured as a blind hole that opens only to the upper surface 44a of the fourth mounting portion 44.

[0083] 8, the length of the arrangement hole 44b in the X-axis direction is longer than the length of the protrusion 53c in the X-axis direction so that the protrusion 53c can slide relative to the arrangement hole 44b in the X-axis direction. Also, as shown in FIG. 3, the length of the arrangement hole 44b in the Z-axis direction (which corresponds to the thickness of the fourth mounting portion 44 in this embodiment) is longer than the protrusion length of the protrusion 53c. Thus, when the resin adhesive B3 is disposed in the arrangement hole 44b, the entire protrusion 53c is inserted into the arrangement hole 44b, and the lower surface 53b of the yoke 53 abuts against the upper surface 44a.

[0084] A wall surface 43c for positioning the yoke 53 (diffraction grating unit 5) is provided between the third mounting portion 43 and the fourth mounting portion 44. In this embodiment, the upper surface 43a of the third mounting portion 43 is located higher than the upper surface 44a of the fourth mounting portion 44, and the wall surface 43c is formed by the side surface of the third mounting portion 43 (i.e., the step surface connecting the upper surface 43a and the upper surface 44a). With the above configuration, the step surface connecting the third mounting portion 43 and the fourth mounting portion 44 can function as the positioning wall surface 43c. In other words, there is no need to provide a separate wall portion dedicated solely to positioning the yoke 53. This simplifies the structure of the mount member 4, thereby reducing the manufacturing cost of the mount member 4.

[0085] As shown in FIGS. 3 and 8, the yoke 53 (diffraction grating unit 5) is fixed to the fourth mounting portion 44 with the protrusion 53c inserted into the arrangement hole 44b and the positioning surface 53d in surface contact with the wall surface 43c. In this embodiment, the position and length of the protrusion 53c are adjusted so that in this state, both ends of the protrusion 53c in the X-axis direction do not contact either the end 44b3 of the arrangement hole 44b on the third mounting portion 43 side or the end 44b4 on the opposite side of the end 44b3. Note that, in this embodiment, as an example, both ends of the protrusion 53c in the X-axis direction have a rounded curved shape that convex outward. Both ends 44b3 and 44b4 of the arrangement hole 44b also have a curved shape similar to both ends of the protrusion 53c. By making both ends of protrusion 53c curved in this way, protrusion 53c can be prevented from getting caught on the inner surface of arrangement hole 44b when protrusion 53c is inserted into arrangement hole 44b and slid in the X-axis direction, which makes it possible to smoothly move protrusion 53c relative to arrangement hole 44b.

[0086] The arrangement hole 44b has a first portion 44b1 and a second portion 44b2. The first portion 44b1 is parallel to the upper surface 44a, has a width substantially equal to the width of the protrusion 53c in the width direction (Y-axis direction) perpendicular to the facing direction (X-axis direction), and extends along the X-axis direction. The second portion 44b2 is a portion having a width greater than that of the first portion 44b1. In this embodiment, the first portion 44b1 is formed in a portion excluding the central portion of the arrangement hole 44b in the X-axis direction (i.e., the portion where the second portion 44b2 is formed) and portions near both end portions 44b3, 44b4 of the arrangement hole 44b in the X-axis direction (i.e., the portions where the outwardly convex curved shapes are formed). The second portion 44b2 is formed in the central portion of the arrangement hole 44b in the X-axis direction. In other words, the second portion 44b2 is positioned away from the end portion 44b3 of the arrangement hole 44b. As an example, the second portion 44b2 is formed in a circular shape in a plan view (when viewed from the Z-axis direction). Furthermore, a resin adhesive B3 is filled in the gap between the protrusion 53c and the arrangement hole 44b.

[0087] In the above configuration, the first portion 44b1 functions as a guide portion for smoothly sliding the protrusion 53c in the X-axis direction. Therefore, with the protrusion 53c inserted into the arrangement hole 44b, the diffraction grating unit 5 can be easily and accurately slid toward the third mounting portion 43 until the positioning surface 53d comes into surface contact with the wall surface 43c. As a result, the installation of the diffraction grating unit 5 on the mount member 4 can be facilitated and the installation accuracy of the diffraction grating unit 5 can be improved.

[0088] In the above configuration, the second portion 44b2 can function as a region for allowing excess resin adhesive B3 to escape. Furthermore, as shown in FIG. 8 , when the diffraction grating unit 5 is fixed to the fourth mounting portion 44, the end 53c1 of the protrusion 53c on the third mounting portion 43 side is disposed within the first portion 44b1 of the arrangement hole 44b. If the end 53c1 of the protrusion 53c were disposed within the second portion 44b2, which is wider than the protrusion 53c, gaps would be formed on both sides of the end 53c1 of the protrusion 53c in the Y-axis direction. This could cause the end 53c1 of the protrusion 53c to deviate in the Y-axis direction when the positioning surface 53d is brought into surface contact with the wall surface 43c to position the diffraction grating unit 5. On the other hand, by arranging the end 53c1 of the protrusion 53c within the first portion 44b1 having approximately the same width as the protrusion 53c as described above, it is possible to prevent the end 53c1 of the protrusion 53c from wobbling in the Y-axis direction, thereby improving the mounting accuracy of the diffraction grating unit 5.

[0089] 8, the width (length in the Y-axis direction) of wall surface 43c and positioning surface 53d is greater than the width of protrusion 53c. One possible method for positioning diffraction grating unit 5 with respect to fourth mount portion 44 is to abut end 53c1 of protrusion 53c against end 44b3 of arrangement hole 44b. However, by making the width of wall surface 43c and positioning surface 53d greater than the width of protrusion 53c and positioning diffraction grating unit 5 using wall surface 43c and positioning surface 53d, it is possible to position diffraction grating unit 5 with greater accuracy and with a greater width than when positioning diffraction grating unit 5 using protrusion 53c and arrangement hole 44b. Furthermore, because the resin adhesive B3 is filled inside the arrangement hole 44b, when positioning is performed using the protrusion 53c and the arrangement hole 44b, there is a risk that a small amount of the resin adhesive B3 will be positioned between the end 53c1 of the protrusion 53c and the end 44b3 of the arrangement hole 44b, which may cause the position of the diffraction grating unit 5 to deviate from the designed position. By performing positioning using the wall surface 43c and the positioning surface 53d, the above-mentioned problem can be avoided.

[0090] [Manufacturing method for external cavity laser module] Next, a method for manufacturing the laser module 1 will be described. First, the QCL element 2 and the MEMS diffraction grating 51 (diffraction grating unit 5) are placed in the package 3 (first step). In this embodiment, the following processes are performed. The QCL element 2 is solder-bonded to the submount 8 using, for example, an AuSn-based solder material. Next, the submount 8 on which the QCL element 2 is mounted is bonded to the upper surface 42a of the second mounting portion 42 of the mount member 4 using, for example, an AuSn-based solder material. The temperature sensor 9 and electrode pads 11 are bonded to the upper surface 42a of the mount member 4 using, for example, a resin adhesive. The pre-assembled diffraction grating unit 5 is fixed to the fourth mounting portion 44 of the mount member 4 using resin adhesive B3, with the protrusion 53c of the yoke 53 positioned in the arrangement hole 44b of the fourth mounting portion 44. This completes the mounting member 4, with all components mounted thereon except for the lens holders 7A and 7B. The first step is completed by fixing the mount member 4 in this state onto the bottom wall 31 of the package 3 before the top wall 33 is attached. The mount member 4 may be initially fixed onto the bottom wall 31 without the above-mentioned components being mounted thereon. In this case, the above-mentioned components are mounted on the mount member 4 fixed to the bottom wall 31 through the opening in the side wall 32 on the top wall 33 side.

[0091] 9, a method for fixing the diffraction grating unit 5 to the mount member 4 in the first step will be described in detail. First, a resin adhesive B3 made of a thermosetting resin is placed inside the placement hole 44b (placement step). Next, after the placement step, the protrusion 53c is inserted into the placement hole 44b (insertion step). As shown in S1 of FIG. 9, when the protrusion 53c is first inserted into the placement hole 44b, a gap may be formed between the positioning surface 53d and the wall surface 43c. Therefore, as shown in S2 of FIG. 9, after the insertion step, the diffraction grating unit 5 is slid in the X-axis direction relative to the fourth mounting portion 44 to bring the positioning surface 53d into surface contact with the wall surface 43c (face-contacting step). After the surface-contacting step, the resin adhesive B3 is hardened by heat treatment, thereby fixing the diffraction grating unit 5 to the fourth mounting portion 44. According to the above method, with the protrusion 53c inserted into the arrangement hole 44b, the diffraction grating unit 5 is slid until the positioning surface 53d comes into surface contact with the wall surface 43c, and then the resin adhesive B3 is thermally cured, thereby enabling the diffraction grating unit 5 to be positioned and fixed (mounted) to the mounting member 4 easily and with high precision.

[0092] Next, wires W1 to W4 are formed by wire bonding to electrically connect the QCL element 2 (anode and cathode) arranged in the package 3 to the electrode terminals 10a1 and 10a2 (second step). In this embodiment, the QCL element 2 and the electrode terminals 10a1 and 10a2 are electrically connected via the electrode pads 11a and 11b, and the following process is performed, for example. First, multiple (six in this embodiment) wires W2 are formed by wire bonding from the top surface of the QCL element 2 (the cathode of the QCL element 2) to the electrode pad 11a, and multiple (six in this embodiment) wires W4 are formed from the submount 8 (the anode of the QCL element 2) to the electrode pad 11b. Next, multiple (six in this embodiment) wires W1 are formed from the electrode pad 11a to the electrode terminal 10a1, and multiple (six in this embodiment) wires W3 are formed from the electrode pad 11b to the electrode terminal 10a2. Here, the end of the wire W on the QCL element 2 side (in this embodiment, the end of the wire W2 connected to the top surface of the QCL element 2 and the end of the wire W4 connected to the submount 8) is located between the positions where the lens holder 7A and the lens holder 7B are to be located when viewed from a direction orthogonal to the X-axis direction (such as the Y-axis direction and the Z-axis direction). Furthermore, the wires W1 and W3 and the electrode terminals 10a1 and 10a2 are connected at a position between the positions where the lens holder 7A and the lens holder 7B are to be located when viewed from a direction orthogonal to the X-axis direction (such as the Y-axis direction and the Z-axis direction).

[0093] In the second step, the wires W5a and W5b that electrically connect the temperature sensor 9 and the electrode terminal 10a are also formed by wire bonding. The wires W6 to W9 that electrically connect the electrode pads 71, 73, 75, and 76 of the MEMS diffraction grating 51 to the electrode terminals 10a3 to 10a6 are also formed by wire bonding. As described above, the height positions of the electrode pads 71, 73, 75, and 76 are set equal to or higher than the height positions of the electrode terminals 10a3 to 10a6. This significantly improves the workability of wire bonding the electrode pads 71, 73, 75, and 76 compared to when the height positions of the electrode pads 71, 73, 75, and 76 are lower than the height positions of the electrode terminals 10a3 to 10a6 (i.e., when the electrode pads 71, 73, 75, and 76 are located toward the back (bottom wall 31) of the package 3). By carrying out the second step, as shown in FIG. 10, an intermediate product 1A is obtained in which components other than the lens holders 7A and 7B are arranged inside the package 3 before the top wall 33 is attached.

[0094] Next, the lens holder 7A holding the lens 6A and the lens holder 7B holding the lens 6B are placed inside the package 3 (third step). In this embodiment, the lens holder 7A is bonded to the upper surface 41a of the first mounting portion 41 of the mount member 4 via an adhesive layer B1. The lens holder 7B is bonded to the upper surface 43a of the third mounting portion 43 of the mount member 4 via an adhesive layer B2.

[0095] In the third step, a driving voltage is applied to the QCL element 2 via the electrode terminals 10a1 and 10a2 and the wires W1 to W4 to oscillate the laser beam, and the lenses 6A and 6B are aligned to fix the lens holders 7A and 7B within the package 3. Specifically, the lens holders 7A and 7B are positioned so that the optical axes of the lenses 6A and 6B coincide with the optical axis of the light emitted from the QCL element 2 while the laser is oscillating. After the positions of the lens holders 7A and 7B are determined, the adhesive layers B1 and B2 are hardened by irradiating the lens holders 7A and 7B with light from above through an opening in the top wall 33. In this embodiment, the light irradiated from above the lens holders 7A and 7B can be appropriately guided to the adhesive layers B1 and B2 by the above-described [attachment structure of the lens holder to the mount member] and [detailed structure of the second mounting portion].

[0096] After the third step is completed, the top wall 33 is joined to the upper end of the side wall 32 by seam welding or the like, thereby obtaining the laser module 1 shown in FIG.

[0097] [Action and effect] In the laser module 1, the protrusion 53c of the diffraction grating unit 5 is inserted into the arrangement hole 44b of the fourth mount portion 44, and the positioning surface 53d of the diffraction grating unit 5 is in surface contact with the positioning wall surface 43c, and the diffraction grating unit 5 is fixed to the fourth mount portion 44. This allows the diffraction grating unit 5 to be positioned with high precision relative to the mount member 4. Furthermore, the protrusion 53c is configured to be slidable in the X-axis direction while inserted into the arrangement hole 44b. This allows the diffraction grating unit 5 to be easily positioned by inserting the protrusion 53c into the arrangement hole 44b and performing a sliding operation to push the diffraction grating unit 5 toward the third mount portion 43. That is, in the laser module 1, the diffraction grating unit 5 can be easily mounted to the mount member 4 with high precision. As a result, variation in the mounting precision of the diffraction grating unit 5 can be suppressed, and the yield rate during mass production of the laser module 1 can be improved.

[0098] The above effects will be further explained with reference to FIGS. 8 and 11. FIG. 11 is a diagram showing the mounting structure of a diffraction grating unit 5A according to a comparative example relative to the mount member 4. The yoke 153 of the diffraction grating unit 5A according to the comparative example has a protrusion 153c whose length in the X-axis direction is equivalent to that of the arrangement hole 44b. That is, in the comparative example, the protrusion 153c is not configured to be slidable in the X-axis direction relative to the arrangement hole 44b. That is, the protrusion 153c is configured to fit snugly into the arrangement hole 44b. Furthermore, to ensure that the diffraction grating unit 5A can be reliably positioned on the fourth mounting portion 44, a slight gap (clearance) is provided between the side surface 153d (the surface corresponding to the positioning surface 53d) of the diffraction grating unit 5A and the wall surface 43c. In this comparative example, the mounting accuracy (positioning accuracy) of the diffraction grating unit 5A relative to the mount member 4 depends on the processing accuracy of the protrusion 153c and the arrangement hole 44b. The inventors mounted the diffraction grating units on the mount members 20 times (for 20 products) for each of the mounting structure (Example) of FIG. 8 and the mounting structure (Comparative Example) of FIG. 11, and calculated the deviation angle (mounting error) of the diffraction grating units for each mounting. Here, the "deviation angle" refers to the angle by which the line along which the positioning surface 53d (or side surface 153d) of the diffraction grating unit is aligned deviates from the design line (i.e., the line along the Y-axis direction) when viewed from the Z-axis direction. As a result, the average deviation angle for the 20 mountings in the Comparative Example was "0.52 degrees," while the average deviation angle for the 20 mountings in the Example was "-0.05 degrees." In other words, it was confirmed that by adopting the mounting structure of this embodiment (FIG. 8), the average deviation angle can be reduced to approximately one-tenth of that in the Comparative Example.

[0099] In the laser module 1, the lens holder 7A is mounted on the first mounting portion 41 via an adhesive layer B1 made of a photocurable resin, and the lens holder 7B is mounted on the third mounting portion 43 via an adhesive layer B2 made of a photocurable resin. If a notch 421a is formed in the side surface 421, the notch 421a can increase the gap between the second mounting portion 42 (side surface 421) and the lens holder 7A. This allows light to be appropriately guided to the adhesive layer B1 through the space formed by the notch 421a when irradiating the lens holder 7A from above to harden the adhesive layer B1. As a result, the adhesive layer B1 can be appropriately hardened, and the lens holder 7A can be more reliably fixed to the upper surface 41a of the first mounting portion 41. If a notch 422a is formed in the side surface 422, the notch 422a can increase the gap between the second mounting portion 42 (side surface 422) and the lens holder 7B. As a result, when light is irradiated from above the lens holder 7B to harden the adhesive layer B2, the light can be suitably guided to the adhesive layer B2 through the space formed by the notch 422a. As a result, the adhesive layer B2 can be properly hardened, and the lens holder 7B can be more reliably fixed to the upper surface 43a of the third mounting portion 43. As described above, according to the laser module 1, it is possible to suppress variations in the mounting accuracy of the optical members (lenses 6A, 6B) that constitute the laser module 1, thereby improving the yield when the laser module 1 is mass-produced.

[0100] In addition, in the laser module 1, lens holders 7A and 7B are arranged on both sides of the QCL element 2. An electrode terminal 10a arranged along the inner wall surface of the package 3 is electrically connected to the QCL element 2 (in this embodiment, both the anode and cathode of the QCL element 2) by a wire W. The end of the wire W on the QCL element 2 side is located between the lens holder 7A and the lens holder 7B when viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) perpendicular to the opposing direction (X-axis direction) in which the lens holder 7A and the lens holder 7B face each other. As a result, as shown in FIG. 7 , a configuration can be realized in which at least a portion of the wire W (including the end on the QCL element 2 side) is located in the space between the lens holder 7A and the lens holder 7B, between the electrode terminal 10a and the QCL element 2 (in this embodiment, both the upper surface of the QCL element 2 as the cathode and the submount 8 as the anode). As a result, it is possible to suitably suppress interference between the wire W for supplying power to the QCL element 2 and components inside the package 3 (especially the lens holders 7A and 7B arranged on both sides of the QCL element 2). As a result, the reliability of the laser module 1 and the workability during assembly are improved.

[0101] Furthermore, when viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) orthogonal to the opposing direction (the X-axis direction), the wire W is connected to the electrode terminal 10a at a position between the lens holder 7A and the lens holder 7B. This makes it possible to realize a configuration in which the entire wire W is disposed in the space between the lens holder 7A and the lens holder 7B between the electrode terminal 10a and the QCL element 2 (in this embodiment, the upper surface of the QCL element 2 as the cathode and the submount 8 as the anode). This makes it possible to more effectively suppress interference between the wire W and components within the package 3 (particularly the lens holders 7A and 7B).

[0102] Furthermore, the height of the electrode terminal 10a relative to the bottom wall 31 is higher than the height of the QCL element 2 relative to the bottom wall 31. This configuration makes it easy to connect the wire W with an appropriate tension from the QCL element 2 to the electrode terminal 10a. As a result, loosening of the wire W can be effectively suppressed, and interference between the wire W and components inside the package 3 can be more effectively suppressed. In this embodiment, the QCL element 2 and the electrode terminal 10a are connected by two wires (a combination of wires W1 and W2 or a combination of wires W3 and W4) via the electrode pad 11. However, as described below, the above-described effect can be achieved by arranging the electrode pad 11 at a height intermediate between the QCL element 2 and the electrode terminal 10a. Furthermore, the above-described effect can be achieved naturally when the QCL element 2 and the electrode terminal 10a are directly connected by a single wire without using the electrode pad 11.

[0103] In this embodiment, the wires W include a wire W1 that connects the electrode terminal 10a1 to the electrode pad 11a and a wire W2 that connects the electrode pad 11a to the QCL element (the upper surface of the QCL element 2 as the cathode). Similarly, the wires W include a wire W3 that connects the electrode terminal 10a2 to the electrode pad 11b and a wire W4 that connects the electrode pad 11b to the QCL element (the submount 8 as the anode). With this configuration, the length of each of the wires W1 to W4 can be shortened compared to when the electrode terminals 10a1 and 10a2 are directly connected to the QCL element (the upper surface of the QCL element 2 or the submount 8). This effectively prevents the wires W1 to W4 from loosening and effectively prevents interference between the wires W1 to W4 and components within the package 3.

[0104] Furthermore, electrode pads 11a and 11b are provided at a position between lens holder 7A and lens holder 7B when viewed from a direction (e.g., Y-axis direction or Z-axis direction) perpendicular to the opposing direction (X-axis direction). This configuration allows all of wires W1 to W4 to pass through the space between lens holder 7A and lens holder 7B. Furthermore, by shortening the path from electrode terminals 10a1 and 10a2 to the QCL element (the upper surface of QCL element 2 or submount 8) via electrode pads 11a and 11b as much as possible, the length of each wire W1 to W4 can be shortened. This effectively prevents interference between wires W1 to W4 and components within package 3.

[0105] Furthermore, the height positions of the electrode pads 11a and 11b relative to the bottom wall 31 are lower than the height positions of the electrode terminals 10a1 and 10a2 relative to the bottom wall 31 and higher than the height position of the QCL element 2 relative to the bottom wall 31. According to the above configuration, the height positions of the electrode terminals 10a1 and 10a2, the electrode pads 11a and 11b, and the QCL element 2 on the package 3 side are set to gradually decrease. This facilitates connecting wires W2 and W4 with appropriate tension from the QCL element 2 to the electrode pads 11a and 11b, and also facilitates connecting wires W1 and W3 with appropriate tension from the electrode pads 11a and 11b to the electrode terminals 10a1 and 10a2. As a result, loosening of the wires W1 to W4 can be effectively suppressed, and interference between the wires W1 to W4 and components within the package 3 can be effectively suppressed.

[0106] Furthermore, in the above manufacturing method (first to third steps), in the second step, the end of the wire W on the QCL element 2 side is positioned between the lens holder 7A and the lens holder 7B when viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) perpendicular to the opposing direction (X-axis direction) in which the lens holders 7A and 7B face each other. This allows for a configuration in which at least a portion of the wire W (including the end on the QCL element 2 side) is positioned in the space between the lens holder 7A and the lens holder 7B, between the electrode terminals 10a1 and 10a2 and the QCL element 2 (in this embodiment, the upper surface of the QCL element 2 as the cathode and the submount 8 as the anode). As a result, when the lens holders 7A and 7B are positioned in the third step, interference between the wire W and the lens holders 7A and 7B can be suitably suppressed. As a result, the reliability of the laser module 1 and the workability during assembly are improved.

[0107] Furthermore, in the third step, a drive voltage is applied to the QCL element 2 via the electrode terminals 10a1, 10a2 and the wire W to align the lenses 6A, 6B while laser oscillation is occurring, thereby fixing the lens holders 7A, 7B within the package 3. According to the manufacturing method described above, by performing alignment while laser oscillation is occurring in the third step, the lens holders 7A, 7B can be appropriately positioned within the package 3. Furthermore, since wire bonding is performed in the second step so that the wire W does not interfere with the lens holders 7A, 7B, alignment in the third step (i.e., adjusting the positions of the lens holders 7A, 7B) can be easily performed.

[0108] Furthermore, in the laser module 1, the distance d (see FIG. 4) between the top wall 33 and the surface 7a of the lens holder 7B facing the top wall 33 is smaller than the thickness t (see FIG. 3) of the lens holder 7B along the optical axis direction (X-axis direction) of the lens 6B. That is, the lens holder 7B is disposed in the package 3 so that the distance d (gap) between the top wall 33 and the lens holder 7B is smaller than the thickness t of the lens holder 7B. This makes it difficult for stray light, which is reflected by the MEMS diffraction grating 51 and deviates from the lens 6B toward the top wall 33, to pass through the space between the top wall 33 and the lens holder 7B, even if the stray light enters between the top wall 33 and the lens holder 7B. That is, it is possible to effectively prevent stray light from entering the space S2 (see FIG. 3) on the side where the MEMS diffraction grating 51 is disposed relative to the lens holder 7B, into the space S1 (see FIG. 3) on the side where the QCL element 2 is disposed relative to the lens holder 7B. As a result, it is possible to prevent stray light components from being mixed into the laser light L emitted from the QCL device 2 to the outside, and to ensure appropriate laser quality.

[0109] Preferably, the top wall 33 and the surface 7a of the lens holder 7B are arranged so that their surfaces face each other. More preferably, the top wall 33 and the surface 7a of the lens holder 7B are arranged so that they face each other in parallel. As shown in FIG. 4, it is preferable that the outer shape of the lens 6B in the YZ plane is circular and the outer shape of the lens holder 7B is rectangular. The thickness t of the lens holder 7B is the overall length of the lens holder 7B in the X-axis direction. When the outer shape of the lens holder 7B is a rectangular parallelepiped, the thickness t of the lens holder 7B is the length of the surface 7a of the lens holder 7B along the X-axis direction. From the viewpoint of improving the stability of the lens 6B, it is preferable that the thickness t of the lens holder 7B is equal to or greater than the thickness of the lens 6B along the optical axis direction (X-axis direction). It is also preferable that the distance d is equal to or less than the thickness of the lens 6B.

[0110] Furthermore, there may be cases where the top wall 33 and the surface 7a are not parallel when viewed from the X-axis direction (for example, the surface 7a is inclined with respect to the top wall 33 when viewed from the X-axis direction), and the distance between the top wall 33 and the surface 7a varies at each position along the Y-axis direction. In this case, a statistical value (for example, minimum, maximum, average, etc.) of the distance between the top wall 33 and the surface 7a at each position along the Y-axis direction (the distance along the Z-axis) may be used as the above-mentioned distance d between the top wall 33 and the surface 7a of the lens holder 7B.

[0111] Furthermore, there may be cases where the top wall 33 and the surface 7a are not parallel when viewed from the Y-axis direction (for example, the surface 7a is inclined with respect to the top wall 33 when viewed from the Y-axis direction), and the distance between the top wall 33 and the surface 7a varies at each position along the X-axis direction. In this case, a statistical value (for example, a minimum value, a maximum value, an average value, etc.) of the distance between the top wall 33 and the surface 7a at each position along the X-axis direction may be used as the above-mentioned distance d between the top wall 33 and the surface 7a of the lens holder 7B.

[0112] Furthermore, when the top wall 33 and the surface 7a are not parallel when viewed from either the X-axis direction or the Y-axis direction, a statistical value (for example, a minimum value, a maximum value, an average value, or the like) of the distance between each position on the surface 7a in the XY plane and the top wall 33 may be used as the distance d between the top wall 33 and the surface 7a of the lens holder 7B. Furthermore, it is preferable that a relationship similar to the relationship between the top wall 33 and the lens holder 7B be established between the top wall 33 and the lens holder 7A.

[0113] When viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) perpendicular to the optical axis direction (X-axis direction), the wires W (wires W1 and W3) are connected to the electrode terminals 10a1 and 10a2 in a region of the lens holder 7B on the side where the QCL element 2 is disposed. The electrode terminals 10a1 and 10a2 are disposed closer to the top wall 33 than the QCL element 2, and the surface 7a of the lens holder 7B facing the top wall 33 is closer to the top wall 33 than the electrode terminals 10a1 and 10a2. According to the above configuration, when viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) perpendicular to the optical axis direction (X-axis direction), the electrode terminals 10a1 and 10a2 are connected to the wires W (wires W1 and W3 in this embodiment) in a space closer to the QCL element 2 than the lens holder 7B. This suppresses interference between the wires W and the lens holder 7B, and allows the surface 7a of the lens holder 7B facing the top wall 33 to be closer to the top wall 33 than the electrode terminals 10a1 and 10a2. This allows the lens holder 7B to be positioned so that the gap (distance d) between the top wall 33 and the lens holder 7B is as small as possible. As a result, it is possible to more effectively suppress stray light generated in the space S2 from passing between the top wall 33 and the lens holder 7B and entering the space S1.

[0114] Furthermore, the stacking direction of the stacked structure including the active layer and cladding layer in the QCL 2 coincides with the direction in which the bottom wall 31 and the top wall 33 face each other (the Z-axis direction). In the above configuration, the beam shape of the light emitted from the end faces (the first end face 2a and the second end face 2b) of the QCL 2 is an ellipse with its major axis aligned with the stacking direction (the Z-axis direction). In this case, the light emitted from the end faces of the QCL 2 tends to spread in the vertical direction (the Z-axis direction), which tends to generate stray light that is reflected by the MEMS diffraction grating 51 and directed toward the top wall 33. However, the positional relationship between the top wall 33 and the lens holder 7B (the relationship between the distance d and the thickness t) prevents the stray light from entering the space S1. That is, by setting the positional relationship between the top wall 33 and the lens holder 7B, the QCL 2 can be positioned so that the stacking direction of the QCL 2 coincides with the Z-axis direction while favorably suppressing degradation of laser quality due to stray light.

[0115] The surface of the lens holder 7B is also blackened. In this embodiment, the surface of the lens holder 7B is blackened by anodizing or the like. With the above configuration, a portion of the stray light reflected by the MEMS diffraction grating 51 and deflected from the lens 6B is absorbed by the blackened surface of the lens holder 7B, thereby more effectively suppressing the intrusion of stray light into the space S1. In this embodiment, the surface of the yoke 53 is also blackened by zinc plating or the like to enhance the effect of reducing the stray light.

[0116] Furthermore, the height positions of the electrode pads 71, 73 of the MEMS diffraction grating 51 relative to the bottom wall 31 are equal to or higher than the height positions of the electrode terminals 10a3, 10a4 relative to the bottom wall 31 (see FIGS. 2 and 3). That is, in the laser module 1, the electrode pads 71, 73 of the MEMS diffraction grating 51 are disposed within the package 3 at height positions equal to or higher than the electrode terminals 10a3, 10a4 disposed along the side wall 32 (first side wall 321) of the package 3. In this embodiment, of the two electrode pads 71, 73, the upper electrode pad 73 (closer to the top wall 33) is disposed at a position slightly higher than the height positions of the electrode terminals 10a3, 10a4, and the lower electrode pad 71 (closer to the bottom wall 31) is disposed at a position substantially the same as the height positions of the electrode terminals 10a3, 10a4. By positioning the electrode pads 71, 73 in this manner, compared to when the electrode pads 71, 73 are positioned lower than the electrode terminals 10a3, 10a4 on the package 3 side (i.e., at the back (bottom wall 31) side of the package 3), forming the wires W6, W7 by wire bonding becomes easier and the required wire length can be shortened. By shortening the wire length, the wires W6, W7 can be given appropriate tension and interference between the wires W6, W7 and components inside the package 3 (for example, components included in the diffraction grating unit 5) can be appropriately suppressed. As a result, the reliability of the laser module 1 and the workability during assembly are improved.

[0117] Furthermore, even when a MEMS diffraction grating 51 is used in which the ratio of the width of the optical surface (movable portion 63) to the width of the accommodation space of the package 3 (width in the Y-axis direction) is relatively large, wire bonding between the electrode terminals 10a3 and 10a4 and the electrode pads 71 ​​and 73 can be easily performed. This allows for a greater distance between the lens 6B and the MEMS diffraction grating 51 than when a MEMS diffraction grating 51 in which the ratio of the width of the optical surface is relatively small is used, thereby significantly reducing the difficulty of assembly. This will be described in detail below. In this embodiment, to suppress interference between the movable portion 63 and the wires W6 to W9, the electrode pads 71, 73, 75, and 76 are arranged on both sides of the movable portion 63 on the support portion 61. In this configuration, as the width of the movable portion 63 is increased, the electrode pads 71, 73, 75, and 76 are positioned closer to the first side wall 321 in the Y-axis direction. In such a case, if the electrode pads 71, 73, 75, and 76 were positioned deep inside the package 3, wire bonding would be difficult. That is, it would be extremely difficult for a capillary to access the electrode pads 71, 73, 75, and 76 during wire bonding. In contrast, by positioning the electrode pads 71, 73, 75, and 76 at a height equal to or higher than that of the electrode terminals 10a on the package 3, as in this embodiment, wire bonding can be performed more easily. This advantage is particularly significant when the width of the movable portion 63 is increased. Furthermore, the lens 6B does not necessarily completely collimate the light emitted from the second end face 2b of the QCL element 2 to the movable portion 63. Therefore, the light transmitted through the lens 6B may have a slight divergence angle. Therefore, when the width of the movable portion 63 is small, it is necessary to position the MEMS diffraction grating 51 as close as possible to the lens 6B. In contrast to this, in this embodiment, as described above, it is possible to use a MEMS diffraction grating 51 having a movable portion 63 that is as wide as possible, and therefore it is possible to increase the distance between the lens 6B and the MEMS diffraction grating 51.Furthermore, by using a MEMS diffraction grating 51 that is as large as possible relative to the storage space within the package 3 (i.e., a MEMS diffraction grating 51 in which the width of the movable part 63 is as close as possible to the horizontal width (width along the Y-axis direction) of the package 3), the loss of light fed back to the QCL element 2 can be reduced, and the output power of the laser module 1 can be increased.

[0118] The MEMS diffraction grating 51 also has a rectangular frame-shaped support portion 61 that supports the diffraction grating portion 64. The electrode pads 71 ​​and 73 are provided at one corner of the support portion 61 on the top wall 33 side. In this embodiment, the electrode pads 71 ​​and 73 are provided at the upper left corner (see FIG. 6 ) when the MEMS diffraction grating 51 is viewed from the front. This configuration allows electrical connection at the corner of the support portion 61, which is relatively far from the center of the diffraction grating portion 64. This reduces the generation of stray light due to the wires W6 and W7 and the electrode pads 71 ​​and 73, thereby effectively improving the reliability of the laser module 1. This will be described in detail below. Typically, the movable portion 63 is made as large as possible so that the entire beam of light emitted from the second end face 2b of the QCL element 2 can be received by the diffraction grating portion 64. However, when a high current is injected into the QCL element 2, the beam of light from the QCL element 2 has a large divergence angle, and the entire beam of light (total luminous flux) cannot necessarily be received by the diffraction grating portion 64. In such a case, light passing through the gap between the movable part 63 (diffraction grating part 64) and the support part 61 may be diffused by the surface of the magnet 52 arranged on the back side of the movable part 63, and may strike the electrode pads 71, 73, the wire W, etc., causing stray light. As described above, by arranging the electrode pads 71, 73 in the corners of the support part 61, which are relatively far from the center of the diffraction grating part 64, it is possible to prevent the diffusely reflected light from striking the electrode pads 71, 73, the wire W, etc. This makes it possible to effectively reduce the occurrence of stray light.

[0119] The MEMS diffraction grating 51 also has electrode pads 75 and 76 (first electrode pads) electrically connected to a coil (a detection coil or a first coil, not shown) different from the coils 65 and 66 (drive coils). The electrode pads 75 and 76 are provided at the other corner of the support 61 on the top wall 33 side (i.e., the corner opposite the side on which the electrode pads 71 ​​and 73 are provided). According to the above configuration, even when two types of coils (the drive coils 65 and 66 and the detection coil in this embodiment) are provided in the MEMS diffraction grating 51, the electrode pads 71, 73, 75, and 76 corresponding to the respective coils are provided at a pair of corners of the rectangular frame-shaped support 61 on the top wall 33 side (i.e., the upper left corner and the upper right corner when the support 61 is viewed from the front with the top wall 33 side facing upward), thereby achieving the above-mentioned effect (i.e., improved reliability of the laser module 1 and ease of assembly).

[0120] Furthermore, the MEMS diffraction grating 51 and the magnet 52 that generates a magnetic field acting on the coils 65 and 66 constitute a diffraction grating unit 5. The magnet 52 is disposed on the side of the MEMS diffraction grating 51 opposite to the side on which the QCL element 2 is disposed. This configuration improves the degree of freedom in arranging the electrode pads 71, 73, 75, and 76. More specifically, by providing the magnet 52 on the back side of the MEMS diffraction grating 51, there is no need to worry about interference between the magnet 52 and the electrode pads 71, 73, 75, and 76 (and the wires W connected to the electrode pads 71, 73, 75, and 76), and the electrode pads 71, 73, 75, and 76 can be freely disposed on the surface of the support 61 (the surface facing the QCL element 2).

[0121] [Variations] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment. The materials and shapes of each component are not limited to those described above, and various materials and shapes can be used. Furthermore, some components included in the laser module 1 according to the above embodiment may be omitted or modified as appropriate. For example, the electrode pad 11 may be omitted. In this case, the electrode terminal 10a and the QCL element (the upper surface of the QCL element 2 and the submount 8) may be directly connected by a single wire. Furthermore, if the detection coil is omitted in the MEMS diffraction grating 51, the electrode pads 75 and 76 may be omitted.

[0122] In the above embodiment, the notches 421a and 422a are provided on both side surfaces (side surface 421 and side surface 422) of the second mounting portion 42. However, if it is desired to improve the light irradiation efficiency for one of the adhesive layers B1 and B2, the notches may be provided on only one of the side surfaces 421 and 422. For example, if the arrangement of components in the package 3 results in a difference between the light irradiation efficiency for the adhesive layer B1 and the light irradiation efficiency for the adhesive layer B2, only the notch (e.g., notch 421a) corresponding to the adhesive layer with lower irradiation efficiency (e.g., adhesive layer B1) may be provided. In the above embodiment, the notches 421a and 422a are provided at both end portions of the side surfaces 421 and 422 in the width direction (Y-axis direction). However, the notches may be provided on only one of the side surfaces 421 and 422 in the width direction. For example, if the arrangement of components within package 3 results in differences in irradiation efficiency between the areas of adhesive layers B1 and B2, it is possible to provide only a notch corresponding to the area of ​​the adhesive layer with lower irradiation efficiency (for example, part of adhesive layer B1).

[0123] Furthermore, in the above embodiment, each notch 421a, 422a is formed in an L-shape at the end of each side surface 421, 422 in the width direction (Y-axis direction), but each notch 421a, 422a may be formed in a U-shape (groove-like) at a position spaced apart from the end of each side surface 421, 422 in the width direction.

[0124] Furthermore, in the above embodiment, the curved surfaces 421b, 422b are formed only in the portions where the notches 421a, 421b are not formed (the central portions in the width direction of each side surface 421, 422), but the curved surfaces 421b, 422b may also be formed at the boundary portions between the notches 421a, 421b and the upper surfaces 41a, 43a.

[0125] Alternatively, instead of the curved surface 421b, an inclined surface (i.e., a surface including a non-curved flat portion) may be provided that slopes toward the lens holder 7A in the facing direction (X-axis direction) as it moves from the upper surface 42a of the second mounting portion 42 to the upper surface 41a of the first mounting portion 41 in the height direction (Z-axis direction). Similarly, instead of the curved surface 422b, an inclined surface (i.e., a surface including a non-curved flat portion) may be provided that slopes toward the lens holder 7B in the facing direction (X-axis direction) as it moves from the upper surface 42a of the second mounting portion 42 to the upper surface 43a of the third mounting portion 43 in the height direction (Z-axis direction). [Explanation of symbols]

[0126] 1...external cavity laser module, 2...quantum cascade laser element, 4...mounting member, 5...diffraction grating unit, 6A...lens (first lens), 6B...lens (second lens), 7A...lens holder (first lens holder), 7B...lens holder (second lens holder), 41...first mounting portion, 42...second mounting portion, 43...third mounting portion, 43a...top surface (third mounting surface), 43c...wall surface, 44...fourth mounting portion, 44a...top surface (fourth mounting surface), 44b...positioning hole (hole portion), 44b1...first part, 44b2...second part, 51...MEMS diffraction grating (movable diffraction grating), 53c...protrusion, 53c1...end, 53d...positioning surface, B3...resin adhesive.

Claims

1. a quantum cascade laser element; a diffraction grating unit including a movable diffraction grating that constitutes an external resonator of the quantum cascade laser element; a first lens holder that is disposed on the opposite side of the quantum cascade laser element from the side on which the movable diffraction grating is located, and that holds a first lens that passes light emitted from the quantum cascade laser element; a second lens holder that is disposed between the quantum cascade laser element and the movable diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the movable diffraction grating to the quantum cascade laser element; a mount member for mounting the quantum cascade laser element, the diffraction grating unit, the first lens holder, and the second lens holder, the mount member includes a first mounting portion, a second mounting portion, a third mounting portion, and a fourth mounting portion that are arranged in this order from the first lens holder side toward the diffraction grating unit side along an opposing direction in which the first lens holder and the second lens holder face each other, the first lens holder is mounted on the first mounting portion, the quantum cascade laser element is mounted on the second mounting portion, the third mounting portion has a third mounting surface on which the second lens holder is mounted, the fourth mounting portion has a fourth mounting surface on which the diffraction grating unit is mounted, a protrusion is provided on a surface of the diffraction grating unit facing the fourth mounting surface, the fourth mounting portion is provided with a hole into which the protrusion is inserted, a length of the hole in the opposing direction is longer than a length of the protrusion in the opposing direction so that the protrusion can slide relative to the hole in the opposing direction; a wall surface is provided between the third mounting portion and the fourth mounting portion, the wall surface intersecting the opposing direction and used to position the diffraction grating unit; the diffraction grating unit has a positioning surface facing the wall surface, the diffraction grating unit is fixed to the fourth mounting portion in a state in which the protrusion is inserted into the hole and the positioning surface is in surface contact with the wall surface. External cavity laser module.

2. the third mounting surface is located higher than the fourth mounting surface, the wall surface is formed by a step surface connecting the third mounting surface and the fourth mounting surface.

2. The external cavity laser module according to claim 1.

3. a width of the wall surface and the positioning surface in a width direction parallel to the fourth mounting surface and perpendicular to the opposing direction is greater than a width of the protrusion; 3. The external cavity laser module according to claim 1 or 2.

4. The hole has a first portion extending along the opposing direction to function as a guide portion for sliding the protrusion in the opposing direction.

4. The external cavity laser module according to claim 1.

5. A resin adhesive is filled in the gap between the protrusion and the hole, the aperture has a second portion having a width greater than the first portion; an end portion of the protrusion on the third mounting portion side is disposed within the first portion of the hole when the diffraction grating unit is fixed to the fourth mounting portion; 5. The external cavity laser module according to claim 4.

6. A method for manufacturing an external cavity laser module according to any one of claims 1 to 5, comprising the steps of: placing a resin adhesive made of a thermosetting resin inside the hole; a step of inserting the protrusion into the hole after the step of placing; after the inserting step, sliding the diffraction grating unit in the opposing direction relative to the fourth mounting portion to bring the positioning surface into surface contact with the wall surface; a step of fixing the diffraction grating unit to the fourth mounting portion by hardening the resin adhesive through a heat treatment after the step of bringing the surfaces into surface contact; A method for manufacturing an external cavity laser module, comprising:

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