External cavity laser module and method for manufacturing the same

Abstract

To provide an external resonance type laser module capable of improving reliability and operability at assembling, and a manufacturing method.SOLUTION: A laser module 1 comprises: a QCL element 2; a MEMS diffraction grating 51; lens holders 7A and 7B arranged while nipping the QCL element 2; a package 3; an electrode terminal 10a arranged along an inner wall surface of the package 3; and a wire W for electrically connecting the electrode terminal 10a and the QCL element 2. The end part of the QCL element 2 side in the wire W is arranged between the lens holders 7A and 7B in the case of viewing it from a direction orthogonal to an opposite direction where the lens holders 7A and 7B are opposite. A height position of the electrode terminal 10a is higher than the height position of the QCL element 2. The distance between the end part on the electrode terminal 10a side of the wire W in a width direction and the end part on the QCL element 2 side is smaller than a width of the lens holder 7A in the width direction or the width of the lens holder 7B.SELECTED DRAWING: Figure 2

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] The external cavity laser module as described above may be housed in a package (housing). In this case, wires for supplying power to the quantum cascade laser element are housed in the package together with the various components. From the viewpoint of improving the operational stability (reliability) of the external cavity laser module and workability during assembly, it is necessary to appropriately suppress interference between the wires and the various components.

[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 reliability and workability during assembly. [Means for solving the problem]

[0006] an external cavity laser module according to one aspect of the present disclosure, comprising: a quantum cascade laser element; a MEMS diffraction grating constituting an external cavity of the quantum cascade laser element; a first lens holder arranged on the opposite side of the quantum cascade laser element from the side on which the MEMS diffraction grating is located, and holding a first lens that passes light emitted from the quantum cascade laser element; a second lens holder arranged between the quantum cascade laser element and the MEMS diffraction grating, and holding a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element; a package that houses the quantum cascade laser element, the MEMS diffraction grating, the first lens holder, and the second lens holder; electrode terminals arranged along an inner wall surface of the package; and a wire for electrically connecting the electrode terminal and the quantum cascade laser element, wherein the end of the wire on the quantum cascade laser element side is located between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction in which the first lens holder and the second lens holder face each other.

[0007] In the above-mentioned external cavity laser module, lens holders (first lens holder and second lens holder) are arranged on both sides of the quantum cascade laser element. Furthermore, electrode terminals arranged along the inner wall surface of the package are electrically connected to the quantum cascade laser element by wires. Here, the end of the wire on the quantum cascade laser element side is arranged between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction of the first lens holder and the second lens holder. This makes it possible to realize a configuration in which at least a part of the wire (a part including the end on the quantum cascade laser element side) is arranged in the space between the first lens holder and the second lens holder from the electrode terminal to the quantum cascade laser element. As a result, interference between the wire for supplying power to the quantum cascade laser element and components inside the package (particularly the first lens holder and the second lens holder arranged on both sides of the quantum cascade laser element) can be suitably suppressed. As a result, the reliability of the external cavity laser module and the workability during assembly are improved.

[0008] The wire may be connected to the electrode terminal at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction. According to the above configuration, it is possible to realize a configuration in which the entire wire is disposed in the space between the first lens holder and the second lens holder between the electrode terminal and the quantum cascade laser element. This makes it possible to more effectively suppress interference between the wire and components inside the package (particularly the first lens holder and the second lens holder).

[0009] The package may have a bottom wall, a side wall extending from the bottom wall and having an annular shape so as to surround the area in which the quantum cascade laser element is housed when viewed perpendicularly to the bottom wall, and a top wall covering an opening on the side wall opposite the bottom wall, and the electrode terminals may be positioned higher in height relative to the bottom wall than the quantum cascade laser element in height relative to the bottom wall. This configuration facilitates connecting wires with appropriate tension from the quantum cascade laser element to the electrode terminals. As a result, slack in the wires can be effectively suppressed, and interference between the wires and components within the package can be effectively suppressed.

[0010] The device may further include an electrode pad that relays electrical connection between the electrode terminal and the quantum cascade laser element, and the wire may include a first wire that connects the electrode terminal and the electrode pad and a second wire that connects the electrode pad and the quantum cascade laser element. According to the above configuration, the length of each wire (first wire and second wire) can be shortened compared to when the electrode terminal and the quantum cascade laser element are directly connected by wire. This effectively prevents the wires from loosening and effectively prevents interference between the wires and components inside the package.

[0011] The electrode pad may be provided at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction. This configuration allows the entire first wire and the second wire to pass through the space between the first lens holder and the second lens holder, and shortens the length of each wire (the first wire and the second wire) by shortening the path from the electrode terminal via the electrode pad to the quantum cascade laser element as much as possible. This effectively reduces interference between the wires and components inside the package.

[0012] The package may have a bottom wall, a side wall extending from the bottom wall and having an annular shape so as to surround an area in which the quantum cascade laser device is housed when viewed perpendicularly to the bottom wall, and a top wall covering an opening on the side wall opposite the bottom wall. The height of the electrode pad relative to the bottom wall may be lower than the height of the electrode terminal relative to the bottom wall and higher than the height of the quantum cascade laser device relative to the bottom wall. According to the above configuration, the heights of the electrode terminal, electrode pad, and quantum cascade laser device on the package side are set to gradually decrease. This facilitates connecting a second wire with appropriate tension from the quantum cascade laser device to the electrode pad, and connecting a first wire with appropriate tension from the electrode pad to the electrode terminal. As a result, loosening of the first wire and the second wire can be effectively suppressed, and interference between the first wire and the second wire and components within the package can be effectively suppressed.

[0013] A method for manufacturing an external cavity laser module according to another aspect of the present disclosure includes a quantum cascade laser element, a MEMS 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 MEMS diffraction grating 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 MEMS diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element, a package that houses the quantum cascade laser element, the MEMS diffraction grating, and the second lens holder, and electrodes that are arranged along an inner wall surface of the package. and a terminal, the method for manufacturing an external cavity laser module including: a first step of arranging a quantum cascade laser element and a MEMS diffraction grating in a package; a second step of forming a wire by wire bonding to electrically connect the quantum cascade laser element arranged in the package to the electrode terminal; and a third step of arranging, after the second step, a first lens holder holding a first lens and a second lens holder holding a second lens in the package, wherein in the second step, the end of the wire on the quantum cascade laser element side is arranged at a position between the position where the first lens holder is to be arranged and the position where the second lens holder is to be arranged when viewed from a direction perpendicular to the opposing direction in which the first lens holder and the second lens holder are opposed to each other.

[0014] In the above manufacturing method, in the second step, the end of the wire on the quantum cascade laser element side is positioned between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction of the first lens holder and the second lens holder. This makes it possible to realize a configuration in which at least a portion of the wire (a portion including the end on the quantum cascade laser element side) is positioned in the space between the first lens holder and the second lens holder from the electrode terminal to the quantum cascade laser element. As a result, when the first lens holder and the second lens holder are positioned in the third step, interference between the wire and the first lens holder and the second lens holder can be suitably suppressed. As a result, the reliability of the external cavity laser module and the workability during assembly are improved.

[0015] In the third step, the first lens and the second lens may be aligned while a driving voltage is applied to the quantum cascade laser element via the electrode terminals and the wire to cause laser oscillation, thereby fixing the first lens holder and the second lens holder in the package. According to the above manufacturing method, by performing alignment while causing laser oscillation in the third step, the first lens holder and the second lens holder can be appropriately positioned in the package. Furthermore, since wire bonding is performed in the second step so as to suppress interference between the wire and the first lens holder and the second lens holder, alignment in the third step (i.e., adjusting the positions of the first lens holder and the second lens holder) can be easily performed. [Effects of the Invention]

[0016] 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 reliability and workability during assembly. [Brief explanation of the drawings]

[0017] [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 diagram showing a manufacturing process of an external cavity laser module. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 (width 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 (vertical 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).

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] 3 and 5, the mount member 4 is a member that is elongated in the X-axis direction. The mount member 4 has, in order from the side closest to the light exit window 32a, a first mounting portion 41 on which the lens holder 7A is mounted, a second mounting portion 42 on which the QCL element 2 is mounted, a third mounting portion 43 on which the lens holder 7B is mounted, and a fourth mounting portion 44 on which the diffraction grating unit 5 is mounted. 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.

[0029] The first mounting portion 41 and the third mounting portion 43 have the same thickness. That is, the height position of the upper surface 41a of the first mounting portion 41 coincides with the height position of the upper surface 43a of the third mounting portion 43, with the bottom wall 31 as the reference. The lens holder 7A is adhesively fixed to the upper surface 41a of the first mounting portion 41 via a resin adhesive B (e.g., a photocurable resin). Similarly, the lens holder 7B is adhesively fixed to the upper surface 43a of the third mounting portion 43 via a resin adhesive B (e.g., a photocurable resin).

[0030] 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 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. The submount 8 is located 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 joined 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 as the "QCL element."

[0031] 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.

[0032] The fourth mounting portion 44 is thinner than the first mounting portion 41 and the third mounting portion 43. That is, the top surface 44a of the fourth mounting portion 44 is located lower than the top surfaces 41a, 43a of the first mounting portion 41 and the third mounting portion 43. An arrangement hole 44b 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 or the like, with a portion of a yoke 53 (described later) disposed in the arrangement hole 44b.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] The diffraction grating unit 5 includes a MEMS diffraction grating 51, 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.

[0039] 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.

[0040] 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.

[0041] 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. The MEMS diffraction grating 51 is formed by processing a semiconductor substrate using MEMS technology (patterning, etching, etc.).

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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. The inclined surface 53a is inclined relative 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 relative 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 (the top wall 33 side). However, the diffraction grating portion 64 may also be inclined so as to face the other side in the Z-axis direction (the bottom wall 31 side). The inclination angle of the inclined surface 53a (the angle relative 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 about 60 degrees.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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).

[0055] 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).

[0056] 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).

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 then fixed to the fourth mounting portion 44 using, for example, a resin adhesive, with a portion of the yoke 53 positioned in the placement hole 44b of the fourth mounting portion 44 of the mount member 4. 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.

[0063] 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).

[0064] 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. 8, an intermediate product 1A is obtained in which members other than the lens holders 7A and 7B are arranged inside the package 3 before the top wall 33 is attached.

[0065] 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 a resin adhesive B. The lens holder 7B is also bonded to the upper surface 43a of the third mounting portion 43 of the mount member 4 via a resin adhesive B.

[0066] In the third step, a drive voltage is applied to the QCL element 2 via the electrode terminals 10a1, 10a2 and wires W1 to W4 to cause laser oscillation, and then the lenses 6A, 6B are aligned to fix the lens holders 7A, 7B in the package 3. That is, the lens holders 7A, 7B are positioned so that the optical axes of the lenses 6A, 6B coincide with the optical axis of the light emitted from the QCL element 2 while the laser is oscillating.

[0067] 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.

[0068] [Action and effect] In the laser module 1 described above, lens holders 7A and 7B are arranged on either side 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, 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 the components inside the package 3 (particularly 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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).

[0088] 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).

[0089] [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. [Explanation of symbols]

[0090] 1...external cavity laser module, 2...quantum cascade laser element, 3...package, 6A...lens (first lens), 6B...lens (second lens), 7A...lens holder (first lens holder), 7B...lens holder (second lens holder), 10a, 10a1 to 10a6...electrode terminals, 11, 11a, 11b...electrode pads, 31...bottom wall, 32...side wall, 33...top wall, 51...MEMS diffraction grating, 61...support portion, 64...diffraction grating portion, 65, 66...coil, 71, 73...electrode pads, 75, 76...electrode pads (first electrode pads), W, W5a, W5b, W6 to W9...wires, W1, W3...wires (first wires), W2, W4...wires (second wires).

Claims

1. a quantum cascade laser element; a MEMS diffraction grating that constitutes an external cavity 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 MEMS 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 MEMS diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element; a package that accommodates the quantum cascade laser element, the MEMS diffraction grating, the first lens holder, and the second lens holder; electrode terminals arranged along an inner wall surface of the package; a wire for electrically connecting the electrode terminal and the quantum cascade laser element; an end of the wire on the quantum cascade laser element side is disposed at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to a direction in which the first lens holder and the second lens holder face each other; the package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround a region in which the quantum cascade laser element is housed when viewed in a vertical direction perpendicular to the bottom wall, and a top wall closing an opening of the side wall on the opposite side to the bottom wall, a height position of the electrode terminal relative to the bottom wall is higher than a height position of the quantum cascade laser element relative to the bottom wall; a distance between an end of the wire on the electrode terminal side and an end of the wire on the quantum cascade laser element side in a width direction perpendicular to the facing direction and the vertical direction is smaller than a width of the first lens holder or a width of the second lens holder in the width direction; An external cavity laser module, wherein in at least one pair of lenses and lens holders in the pair of the first lens and the first lens holder and the pair of the second lens and the second lens holder, at the vertical height position where the width of the lens in the width direction is maximum, the distance between the outer edge of the lens in the width direction and the end of the lens holder is smaller than the width of the lens in the width direction.

2. a quantum cascade laser element; a MEMS diffraction grating that constitutes an external cavity 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 MEMS 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 MEMS diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element; a package that accommodates the quantum cascade laser element, the MEMS diffraction grating, the first lens holder, and the second lens holder; electrode terminals arranged along an inner wall surface of the package; a wire for electrically connecting the electrode terminal and the quantum cascade laser element; an end of the wire on the quantum cascade laser element side is disposed at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to a direction in which the first lens holder and the second lens holder face each other; the package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround a region in which the quantum cascade laser element is housed when viewed in a vertical direction perpendicular to the bottom wall, and a top wall closing an opening of the side wall on the opposite side to the bottom wall, a height position of the electrode terminal relative to the bottom wall is higher than a height position of the quantum cascade laser element relative to the bottom wall; a distance between the inner wall surface of the package and the first lens holder or the second lens holder when viewed from the opposing direction is smaller than a width of the first lens holder or a width of the second lens holder when viewed from the opposing direction, An external cavity laser module, wherein in at least one pair of lenses and lens holders in the pair of the first lens and the first lens holder and the pair of the second lens and the second lens holder, at the height position in the vertical direction where the width of the lens in the width direction perpendicular to the opposing direction and the vertical direction is maximum, the distance between the outer edge of the lens in the width direction and the end of the lens holder is smaller than the width of the lens in the width direction.

3. 3. The external cavity laser module according to claim 1, wherein the wire is connected to the electrode terminal at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction.

4. further comprising an electrode pad for relaying an electrical connection between the electrode terminal and the quantum cascade laser element; 4. An external cavity laser module according to claim 1, wherein the wire comprises a first wire connecting the electrode terminal and the electrode pad, and a second wire connecting the electrode pad and the quantum cascade laser element.

5. 5. The external cavity laser module according to claim 4, wherein the electrode pad is provided at a position between the first lens holder and the second lens holder when viewed from a direction perpendicular to the opposing direction.

6. 6. The external cavity laser module according to claim 4, wherein the height position of the electrode pad relative to the bottom wall is lower than the height position of the electrode terminal relative to the bottom wall, and higher than the height position of the quantum cascade laser element relative to the bottom wall.

7. a quantum cascade laser element; a MEMS diffraction grating that constitutes an external cavity 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 MEMS diffraction grating 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 MEMS diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element; a package that accommodates the quantum cascade laser element, the MEMS diffraction grating, the first lens holder, and the second lens holder; electrode terminals arranged along an inner wall surface of the package; a wire for electrically connecting the electrode terminal and the quantum cascade laser element; the package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround a region in which the quantum cascade laser element is housed when viewed in a vertical direction perpendicular to the bottom wall, and a top wall closing an opening of the side wall on the opposite side to the bottom wall, a distance between an end of the wire on the electrode terminal side and an end of the wire on the quantum cascade laser element side in a direction in which the first lens holder and the second lens holder face each other and in a width direction perpendicular to the vertical direction is smaller than a width of the first lens holder or a width of the second lens holder in the width direction; a method for manufacturing an external cavity laser module, wherein in at least one pair of the lens and lens holder in the pair of the first lens and the first lens holder and the pair of the second lens and the second lens holder, a distance between an outer edge of the lens in the width direction and an end of the lens holder is smaller than a width of the lens in the width direction at a height position in the vertical direction where the width of the lens in the width direction is maximum; a first step of placing the quantum cascade laser device and the MEMS diffraction grating in the package; a second step of forming the wires by wire bonding to electrically connect the quantum cascade laser element disposed in the package to the electrode terminals; a third step of, after the second step, placing the first lens holder holding the first lens and the second lens holder holding the second lens in the package, In the first step, the quantum cascade laser element is disposed at a position lower than a height position of the electrode terminal relative to the bottom wall, A method for manufacturing an external cavity laser module, wherein in the second step, the end of the wire on the quantum cascade laser element side is positioned at a position between the position where the first lens holder is intended to be positioned and the position where the second lens holder is intended to be positioned when viewed from a direction perpendicular to the opposing direction.

8. a quantum cascade laser element; a MEMS diffraction grating that constitutes an external cavity 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 MEMS diffraction grating 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 MEMS diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element; a package that accommodates the quantum cascade laser element, the MEMS diffraction grating, the first lens holder, and the second lens holder; electrode terminals arranged along the inner wall surface of the package, the package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround a region in which the quantum cascade laser element is housed when viewed in a vertical direction perpendicular to the bottom wall, and a top wall closing an opening of the side wall on the opposite side to the bottom wall, when viewed from a direction in which the first lens holder and the second lens holder face each other, a distance between the inner wall surface of the package and the first lens holder or the second lens holder is smaller than a width of the first lens holder or a width of the second lens holder when viewed from the direction in which the first lens holder and the second lens holder face each other, a method for manufacturing an external cavity laser module, wherein in at least one pair of the lens and lens holder in the pair of the first lens and the first lens holder and the pair of the second lens and the second lens holder, at a height position in the vertical direction where the width of the lens in the width direction perpendicular to the facing direction and the vertical direction is maximum, a distance between an outer edge of the lens in the width direction and an end of the lens holder is smaller than the width of the lens in the width direction; a first step of placing the quantum cascade laser device and the MEMS diffraction grating in the package; a second step of forming wires by wire bonding to electrically connect the quantum cascade laser element disposed in the package to the electrode terminals; a third step of, after the second step, placing the first lens holder holding the first lens and the second lens holder holding the second lens in the package, In the first step, the quantum cascade laser element is disposed at a position lower than a height position of the electrode terminal relative to the bottom wall, A method for manufacturing an external cavity laser module, wherein in the second step, the end of the wire on the quantum cascade laser element side is positioned at a position between the position where the first lens holder is intended to be positioned and the position where the second lens holder is intended to be positioned when viewed from a direction perpendicular to the opposing direction.

9. 9. The method for manufacturing an external cavity laser module according to claim 7, wherein in the third step, the first lens and the second lens are aligned while a driving voltage is applied to the quantum cascade laser element via the electrode terminals and the wires to cause laser oscillation, thereby fixing the first lens holder and the second lens holder in the package.

Images