External resonant laser module

Abstract

To provide a laser module that can adequately ensure laser quality.SOLUTION: A laser module includes a mount member disposed on a cooling element, a QCL element disposed on the mount member, a lens holder that holds a lens disposed on the mount member, and a package. The package includes a bottom wall, a side wall that is erected on the bottom wall and is formed in an annular shape so as to surround an area in which the QCL element is housed when viewed from a direction perpendicular to the bottom wall, and a top wall that closes an opening on the side wall opposite the bottom wall. The top wall faces the bottom wall in a direction perpendicular to the optical axis direction of the lens, and the distance between the top wall and the surface of the lens holder on the top wall side is smaller than the thickness of the lens holder along the optical axis direction of the lens.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a laser module.

Background Art

[0002] As an external resonant laser module, there is known one including a quantum cascade laser element, a swingable 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 resonant laser module, light from the quantum cascade laser element is diffracted and reflected by the diffraction grating, and light of a specific wavelength among the light is fed back to the quantum cascade laser element. Thereby, an external resonator is constituted by the end face of the quantum cascade laser element and the diffraction grating, and light of a specific wavelength is amplified and output to the outside. By swinging the diffraction grating to change the wavelength of the output light, wavelength sweeping can be performed within a predetermined wavelength range.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The external resonant laser module as described above may be housed in a package (housing). In such a configuration, when light that is not fed back to the quantum cascade laser element through the lens among the light reflected by the diffraction grating (that is, stray light components that deviate from the lens) is generated, the stray light components may be mixed into the laser light emitted from the quantum cascade laser element to the outside, which may deteriorate the laser quality.

[0005] Therefore, an aspect of the present disclosure aims to provide a laser module that can appropriately ensure laser quality. [Means for solving the problem]

[0006] A laser module relating to one aspect of this disclosure comprises a quantum cascade laser element, a MEMS diffraction grating constituting an external resonator of the quantum cascade laser element, a lens holder positioned between the quantum cascade laser element and the MEMS diffraction grating and holding a lens through which light emitted from the quantum cascade laser element and light returning from the MEMS diffraction grating to the quantum cascade laser element pass, and a package housing the quantum cascade laser element, the MEMS diffraction grating, and the lens holder, wherein the package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround the region in which the quantum cascade laser element is housed when viewed from a direction perpendicular to the bottom wall, and a top wall that closes the opening on the side wall opposite to the bottom wall, the top wall facing the bottom wall in a direction perpendicular to the optical axis direction of the lens, and the distance between the top wall and the top wall side surface of the lens holder is smaller than the thickness of the lens holder along the optical axis direction of the lens.

[0007] In the above laser module, the lens holder is positioned within the package such that the distance (gap) between the top wall and the lens holder is smaller than the thickness of the lens holder. This makes it difficult for stray light, which is reflected from the MEMS diffraction grating and deviates from the lens towards the top wall, to pass through the space between the top wall and the lens holder, even if it enters the space between the top wall and the lens holder. In other words, it is possible to effectively suppress the intrusion of stray light from the space on the side of the lens holder where the MEMS diffraction grating is positioned to the space on the side of the lens holder where the quantum cascade laser element is positioned. As a result, it is possible to suppress the mixing of stray light components into the laser light emitted from the quantum cascade laser element and ensure appropriate laser quality.

[0008] The above laser module may further include electrode terminals arranged along the side wall within the package, and a wire for electrically connecting the electrode terminals to the quantum cascade laser element. The wire may be connected to the electrode terminals in the region on the side of the lens holder where the quantum cascade laser element is positioned when viewed from a direction perpendicular to the optical axis. The electrode terminals may be positioned closer to the top wall than the quantum cascade laser element, and the top wall side of the lens holder may be positioned closer to the top wall than the electrode terminals. With the above configuration, by connecting the electrode terminals and the wire in the space on the quantum cascade laser element side of the lens holder when viewed from a direction perpendicular to the optical axis, interference between the wire and the lens holder can be suppressed, while the top wall side of the lens holder can be positioned closer to the top wall than the electrode terminals. This allows the lens holder to be positioned so that the gap between the top wall and the lens holder is as small as possible. As a result, stray light generated in the space where the MEMS diffraction grating is positioned relative to the lens holder can be more effectively suppressed from passing between the top wall and the lens holder and entering the space where the quantum cascade laser element is positioned relative to the lens holder.

[0009] The stacking direction of the stacked structure, including the active layer and cladding layer, in the quantum cascade laser element may coincide with the direction in which the bottom wall and top wall face each other. In the above configuration, the beam shape of the light emitted from the end face of the quantum cascade laser element is an ellipse shape with a major axis along the stacking direction. In this case, stray light is likely to be reflected by the MEMS diffraction grating and directed towards the top wall, but the positional relationship between the top wall and the lens holder described above can suppress the intrusion of such stray light into the space where the quantum cascade laser element is arranged relative to the lens holder. That is, by setting the positional relationship between the top wall and the lens holder as described above, it is possible to arrange the quantum cascade laser element so that the stacking direction of the quantum cascade laser element coincides with the direction in which the bottom wall and top wall face each other, while suitably suppressing the deterioration of laser quality due to stray light.

[0010] The surface of the lens holder may be blackened. With the above configuration, some of the stray light reflected by the MEMS diffraction grating and missing the lens can be absorbed by the blackened surface of the lens holder, thereby more effectively suppressing the intrusion of stray light into the space on the side of the lens holder where the quantum cascade laser element is positioned. [Effects of the Invention]

[0011] According to one aspect of this disclosure, it is possible to provide a laser module that can adequately ensure laser quality. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view of an external resonant laser module according to one embodiment. [Figure 2] Figure 2 is a perspective view showing the internal configuration of an external resonant laser module. [Figure 3] Figure 3 is a cross-sectional view of an external resonant laser module along the line III-III in Figure 2. [Figure 4] Figure 4 is a cross-sectional view of the external resonant laser module along the IV-IV line in Figure 3. [Figure 5] Figure 5 shows the relationship between the mounting member and the diffraction grating unit. [Figure 6] Figure 6 is a front view of the MEMS diffraction grating. [Figure 7] Figure 7 shows the electrical connection configuration between the quantum cascade laser element and the electrode terminal. [Figure 8] Figure 8 shows the manufacturing process of an external resonant laser module. [Modes for carrying out the invention]

[0013] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used for the same or equivalent elements, and redundant explanations will be omitted. Also, terms such as "upper" and "lower" are for convenience based on the state shown in the drawings.

[0014] As shown in Figures 1 to 4, the external resonant laser module 1 (hereinafter referred to as "laser module 1") comprises a quantum cascade laser element (hereinafter referred to as "QCL element") 2 and a package 3 that hermetically houses the QCL element 2. The external resonant laser module 1 is a tunable light source in which the wavelength of the output light (laser light L) is variable. The external resonant laser module 1 can be used, for example, for biological measurements of glucose, or for measuring the absorption spectrum of analytes having optical absorption bands, such as VOC gases (volatile organic compounds). For example, when measuring such an absorption spectrum, the analyte housed in a light-transmitting container is placed between the external resonant laser module 1 and a photodetector (not shown). The external resonant laser module 1 then rapidly changes the wavelength of the output light (laser light L) to perform a wavelength sweep in a predetermined wavelength range (e.g., the mid-infrared region). Based on the detection result of the photodetector, the absorption spectrum is calculated. The analyte may be a gas, liquid, or solid.

[0015] Package 3 is a housing that contains the QCL element 2, a mounting member 4, a diffraction grating unit 5, a lens holder 7A (first lens holder) that holds lens 6A (first lens), and a lens holder 7B (second lens holder) that holds lens 6B (second lens). In this embodiment, as an example, package 3 is configured as a butterfly package. Package 3 has a bottom wall 31, side walls 32, and a top wall 33. In Figure 2, the top wall 33 of package 3 is not shown, and the portion of the lead terminals 10 that protrudes outward from the protruding wall 34 is not shown.

[0016] The bottom wall 31 is a rectangular plate-shaped member. The bottom wall 31 is formed of a metal material such as copper tungsten, for example. The bottom wall 31 is a base member on which the mounting member 4 is mounted. In this specification, for convenience, the longitudinal direction of the bottom wall 31 is represented as the X-axis direction, the short-side direction of the bottom wall 31 is represented as the Y-axis direction, and the direction perpendicular to the bottom wall 31 (that is, the direction orthogonal to the X-axis direction and the Y-axis direction) is represented as the Z-axis direction. The X-axis direction is also the direction (optical axis direction) along the optical axis of the laser beam L emitted from the QCL element 2.

[0017] The side wall 32 stands upright on the bottom wall 31. 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 accommodated when viewed from the Z-axis direction. In the present 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 the present embodiment, the side wall 32 is provided at the central portion in the longitudinal direction (X-axis direction) of the bottom wall 31. The width along the short-side direction (Y-axis direction) of the side wall 32 coincides with the width in the short-side direction of the bottom wall 31, and the width along the longitudinal direction (X-axis direction) of the side wall 32 is shorter than the width in the longitudinal direction of the bottom wall 31. That is, projecting portions 31a that project and extend outward from the side wall 32 are formed on both sides in the longitudinal direction of the bottom wall 31. Thread holes 31b for attaching the package 3 (bottom wall 31) to other members are provided at portions corresponding to the four corners of the bottom wall 31 in the projecting portions 31a.

[0018] The top wall 33 is a member that closes the opening on the side opposite to the bottom wall 31 side of the side wall 32. The top wall 33 has a rectangular plate shape. The outer shape (width in the longitudinal direction and the short-side direction) of the top wall 33 when viewed from the Z-axis direction substantially coincides with the outer shape of the side wall 32. The top wall 33 is formed of, for example, the same metal material (such as kovar) as the side wall 32. The top wall 33 is joined to the end portion on the side opposite to the bottom wall 31 side of the side wall 32 by, for example, seam welding or the like.

[0019] A pair of first side walls 321 (i.e., the portions intersecting the short side direction (Y-axis direction)) that extend along the longitudinal direction (X-axis direction) of the side walls 32 have a plurality (in this embodiment, a total of 14, seven on each side in the short side direction) of lead terminals 10 for passing an electric current to members such as the QCL element 2 housed in the package 3 inserted therethrough. Each lead terminal 10 is a flat plate-shaped conductive member that extends in the Y-axis direction.

[0020] Also, each of the pair of first side walls 321 is provided with a protruding wall 34 that protrudes on both the outer surface (the outer side surface of the package 3) side and the inner surface (the inner side surface of the package 3) side of the first side wall 321 (see FIG. 4). The protruding wall 34 is a roof-shaped member provided so as to extend along the X-axis direction above (toward the top wall 33 side) the central position of the first side wall 321 in the Z-axis direction. Each lead terminal 10 is arranged on the upper surface 34a of the protruding wall 34 at substantially equal intervals along the X-axis direction. The portion of the lead terminal 10 along the inner wall surface of the package 3 (the inner surface of the first side wall 321) (i.e., the portion located inside the package 3) functions as an electrode terminal 10a for supplying power to each member in the package 3 (for example, the QCL element 2, the MEMS diffraction grating 51, the temperature sensor 9 described later, etc.). That is, by electrically connecting the electrode terminal 10a and each member via a conductive wire W, power is supplied from an external power source to each member.

[0021] On one of the second side walls 322 (i.e., the portion intersecting the longitudinal direction (X-axis direction)) that extend along the short side direction (Y-axis direction) of the side walls 32, a light emission window 32a for passing the laser light L emitted from one end face (the first end face 2a) of the QCL element 2 is provided. The light emission window 32a is formed of a material (for example, germanium, etc.) that transmits laser light L having a wavelength in the mid-infrared region, for example. In this embodiment, as an example, the light emission window 32a is formed in a disc shape. The light emission window 32a is fixed to a circular opening formed in one of the second side walls 322.

[0022] Next, the components housed in package 3 will be described. As shown in Figure 3, the QCL element 2, diffraction grating unit 5, and lens holders 7A and 7B are arranged on the bottom wall 31 via a mounting member 4. The mounting member 4 is an optical stage on which the optical elements described above are mounted. In Figure 3, the wire W is not shown. The mounting member 4 is fixed to the bottom wall 31 by, for example, joining or screwing. The mounting member 4 is made of a material with excellent thermal conductivity, such as copper. In this embodiment, the mounting member 4 is directly arranged on the bottom wall 31, but the mounting member 4 may also be arranged on the bottom wall 31 via a cooling element such as a Peltier module. In this embodiment, the mounting member 4 is a single component, but the mounting member 4 may be a combination of multiple components.

[0023] As shown in Figures 3 and 5, the mounting member 4 is a long member in the X-axis direction. The mounting member 4 has, in order from the side closest to the light emission window 32a, a first mounting section 41 on which the lens holder 7A is mounted, a second mounting section 42 on which the QCL element 2 is mounted, a third mounting section 43 on which the lens holder 7B is mounted, and a fourth mounting section 44 on which the diffraction grating unit 5 is mounted. That is, the light emission window 32a, lens 6A (lens holder 7A), QCL element 2, lens 6B (lens holder 7B), and diffraction grating unit 5 are arranged in this order along the X-axis direction.

[0024] The first mounting section 41 and the third mounting section 43 have the same thickness. That is, with respect to the bottom wall 31, the height position of the upper surface 41a of the first mounting section 41 coincides with the height position of the upper surface 43a of the third mounting section 43. The lens holder 7A is bonded and fixed to the upper surface 41a of the first mounting section 41 via a resin adhesive B (e.g., a photocurable resin). Similarly, the lens holder 7B is bonded and fixed to the upper surface 43a of the third mounting section 43 via a resin adhesive B (e.g., a photocurable resin).

[0025] 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 from 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 and 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 positioned at the center of the upper surface 42a in the Y-axis direction. The submount 8 is made of a material having a similar coefficient of thermal expansion to the QCL element 2 (for example, aluminum nitride). The QCL element 2 is joined to the submount 8 via, for example, an AuSn-based solder material. Furthermore, the submount 8 is joined to the mounting member 4 (upper surface 42a) via a soldering material, such as In-based (InSn, InAg, etc.). As described above, since the QCL element 2 is integrated with the submount 8, the QCL element 2 and the submount 8 together can be considered as the "QCL element".

[0026] On the upper surface 42a of the second mounting section 42, in addition to the submount 8, a temperature sensor 9 and an electrode pad 11 are arranged. The temperature sensor 9 and the electrode pad 11 are joined to the mounting 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 section 42. Specifically, an electrode pad 11a that is electrically connected to the cathode of the QCL element 2 (in this embodiment, the upper surface (mesa upper surface) of the QCL element 2) and an electrode pad 11b that is 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 section 42. Each electrode pad 11a, 11b has a substantially rectangular connection area (top surface). Each electrode pad 11a, 11b is aligned along the X-axis. Electrode pad 11a is located closer to the light emission window 32a than electrode pad 11b. With respect to the bottom wall 31, the height of each electrode pad 11a, 11b is lower than the height of the electrode terminal 10a (i.e., the height of the top surface 34a of the protruding wall 34) and higher than the height of the QCL element 2.

[0027] The fourth mounting section 44 is thinner than the first mounting section 41 and the third mounting section 43. That is, the upper surface 44a of the fourth mounting section 44 is lower than the upper surfaces 41a and 43a of the first mounting section 41 and the third mounting section 43. An arrangement hole 44b is formed in the fourth mounting section 44. As shown in Figure 5, the diffraction grating unit 5 is fixed to the fourth mounting section 44 using a resin adhesive or the like, with a portion of the yoke 53 (described later) positioned in the arrangement hole 44b.

[0028] The QCL element 2 has a first end face 2a and a second end face 2b opposite to the first end face 2a. The QCL element 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, for example, flat surfaces perpendicular to the X-axis direction, and the optical axis of the laser light L emitted from the QCL element 2 is along the X-axis direction. The QCL element 2 includes an active layer consisting of a plurality of quantum well layers (e.g., InGaAs) and a plurality of quantum barrier layers (e.g., InAlAs), and a pair of cladding layers (e.g., InP) sandwiching the active layer, and is capable of emitting broadband light as described above. In this embodiment, the stacking direction of the stacked structure including the active layer and cladding layers in the QCL element 2 coincides with the direction in which the bottom wall 31 and the top wall 33 face each other (Z-axis direction). The QCL element 2 may also include multiple active layers having different central wavelengths and a pair of cladding layers, and even in this case, it can emit broadband light as described above. The first end face 2a is coated with a low-reflection coating, and the second end face 2b is coated with an anti-reflective coating.

[0029] Lenses 6A and 6B are aspherical lenses made of, for example, zinc selenide (ZnSe). The surfaces of lenses 6A and 6B are coated with an anti-reflective coating.

[0030] Lens 6A is positioned on the opposite side of the QCL element 2 from the side where the MEMS diffraction grating 51 (diffraction grating unit 5) is located. That is, lens 6A is positioned opposite the first end face 2a of the QCL element 2. Lens 6A allows the light emitted from the QCL element 2 (light emitted from the first end face 2a) to pass through. Lens 6A collimates the light emitted from the first end face 2a. The light collimated by lens 6A passes through the light emission window 32a of package 3 and is output to the outside as output light (laser light L).

[0031] Lens 6B is positioned between the QCL element 2 and the MEMS diffraction grating 51 (diffraction grating unit 5). That is, lens 6B is positioned opposite the second end face 2b of the QCL element 2. Lens 6B allows light emitted from the QCL element 2 (light emitted from the second end face 2b) and light returning from the MEMS diffraction grating 51 to the QCL element 2 to pass through. Lens 6B collimates the light emitted from the second end face 2b to the MEMS diffraction grating 51.

[0032] The lens holders 7A and 7B have a roughly rectangular parallelepiped shape. The lenses 6A and 6B are fixed to the lens holders 7A and 7B by a resin adhesive or the like. The surfaces of the lens holders 7A and 7B are blackened, for example by anodizing.

[0033] The diffraction grating unit 5 comprises 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 positioned 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, magnet 52, and yoke 53 are integrated and constitute a single unit.

[0034] Light collimated by lens 6B is incident on the MEMS diffraction grating 51 of diffraction grating unit 5. The MEMS diffraction grating 51 diffracts and reflects this incident light, thereby feeding back light of a specific wavelength from the incident light to the second end face 2b of the QCL element 2 via lens 6B. The MEMS diffraction grating 51 constitutes an external resonator for the QCL element 2. In this embodiment, a Littrow-type external resonator is formed by the MEMS diffraction grating 51 and the first end face 2a. As a result, the laser module 1 can amplify light of a specific wavelength and output it externally.

[0035] Furthermore, the MEMS diffraction grating 51 allows for rapid changes in the orientation of the diffraction grating portion 64 that diffracts and reflects incident light. This makes the wavelength of the light returned from the MEMS diffraction grating 51 to the second end face 2b of the QCL element 2 variable, and consequently, the wavelength of the output light (laser light L) of the laser module 1 variable. By changing the wavelength of the laser light L, for example, wavelength sweeping can be performed within the gain band range of the QCL element 2.

[0036] As shown in Figure 6, the MEMS diffraction grating 51 comprises 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 axis A. The MEMS diffraction grating 51 is formed by processing a semiconductor substrate using MEMS technology (patterning, etching, etc.).

[0037] The support portion 61 is a flat, plate-shaped frame that has a rectangular shape in plan view. The support portion 61 supports the movable portion 63 via a pair of connecting portions 62. Each connecting portion 62 is a flat, plate-shaped member that has a rectangular rod shape in plan view and extends straight along axis A. Each connecting portion 62 connects the movable portion 63 to the support portion 61 on axis A so that the movable portion 63 can swing freely around axis A.

[0038] The movable part 63 is located inside the support part 61. As described above, the movable part 63 is capable of swinging around axis A. The movable part 63 is a flat plate-shaped member that is substantially rectangular in plan view. In this embodiment, as an example, the four corners of the movable part 63 are chamfered in an R shape. That is, the four corners of the movable part 63 are curved in an arc shape in plan view. This reduces the moment of inertia of the movable part 63 and allows the swing of the movable part 63 to be accelerated. In this example, the movable part 63 is formed in a substantially rectangular shape with its long side parallel to the first direction D1 (the direction perpendicular to axis A), and the length of the movable part 63 in the first direction D1 is longer than the length of the movable part 63 in the second direction D2 (the direction parallel to axis A). As an example, the length of the support part 61 in the first direction D1 is about 6 to 7 mm, and the length of the support part 61 in the second direction D2 is about 6 mm. Furthermore, the length of the movable part 63 in the first direction D1 is approximately 4 mm, the length of the movable part 63 in the second direction D2 is approximately 3 mm, and the thickness is approximately 30 μm. The support part 61, the connecting part 62, and the movable part 63 are integrally formed, for example, by being fabricated on a single SOI (Silicon on Insulator) substrate.

[0039] A diffraction grating portion 64 is provided on the surface of the movable portion 63 on the side facing the QCL element 2. The diffraction grating portion 64 has a plurality of grating grooves (not shown) and diffracts and reflects light emitted from the QCL element 2. The diffraction grating portion 64 includes, for example, a resin layer provided on the surface of the movable portion 63 with a diffraction grating pattern formed thereon, and a metal layer provided across the surface of the resin layer along the diffraction grating pattern. Alternatively, the diffraction grating portion 64 may consist only of a metal layer provided on the movable portion 63 with a diffraction grating pattern formed thereon. As the diffraction grating pattern, for example, a blazed grating with a sawtooth cross-section, a binary grating with a rectangular cross-section, a holographic grating with a sinusoidal cross-section, etc., can be used. 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 is formed by vapor deposition.

[0040] Coils 65 and 66 are made of a metal material such as copper and have a damascene structure embedded in grooves formed on the surface of the movable part 63. In a plan view, coil 65 is positioned on one side of axis A (upper side in Figure 6), and coil 66 is positioned on the other side of axis A (lower side in Figure 6). Coils 65 and 66 are drive coils that carry current to drive the MEMS diffraction grating 51 (i.e., to oscillate the movable part 63).

[0041] Each of the coils 65 and 66 is wound multiple times in a spiral shape in a plan view. The outer end of coil 65 is electrically connected to an electrode pad 71 provided on the support portion 61 via wiring 72. The wiring 72 extends across the support portion 61, one connecting portion 62, and the movable portion 63. The outer end of coil 66 is electrically connected to an electrode pad 73 provided on the support portion 61 via 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 along with the coils 65 and 66. Therefore, in addition to the electrode pads 71 ​​and 73 electrically connected to the coils 65 and 66, the support portion 61 is also provided with electrode pads 75 and 76 (first electrode pads) electrically connected to both ends of the detection coil via wiring (similar to wiring 72 and 74) to extract the current detected by the detection coil to the outside.

[0042] The inner end of coil 65 is electrically connected to the inner end of coil 66. In this example, coils 65 and 66 are formed integrally with each other, so their inner ends are electrically connected. In other words, in the MEMS diffraction grating 51, a pair of coils 65 and 66 are formed by a single coil wiring (multilayer wiring) extending in a figure-eight shape in a plan view. Note that coils 65 and 66 may be formed separately. In this case, the inner end of coil 65 and the inner end of coil 66 may be electrically connected via wiring.

[0043] The magnet 52 generates a magnetic field (magnetic force) that acts on the coils 65 and 66. As shown in Figure 3, the magnet 52 is a neodymium magnet (permanent magnet) formed in a roughly rectangular parallelepiped shape. For example, the magnet 52 has a north pole on the side facing the MEMS diffraction grating 51 and a south pole on the opposite side from the MEMS diffraction grating 51.

[0044] 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 Figure 3, the yoke 53 has an inclined surface 53a. The inclined surface 53a is inclined with respect to the second end face 2b of the QCL element 2. By fixing the MEMS diffraction grating 51 on such an inclined surface 53a, the normal N of the diffraction grating portion 64 of the MEMS diffraction grating 51 can be inclined with respect to the second end face 2b. In this example, the diffraction grating portion 64 is inclined to face one side in the Z-axis direction (towards the top wall 33), but the diffraction grating portion 64 may also be inclined to face the other side in the Z-axis direction (towards the bottom wall 31). The inclination angle of the inclined surface 53a (angle with respect to the second end face 2b of the QCL element 2) is set according to the oscillation wavelength of the QCL element 2, as well as the number of grooves and blazed angle of the grating grooves in the diffraction grating portion 64. For example, if the oscillation wavelength is in the 7 μm band and the number of grooves is 150 grooves / mm, the inclination angle of the inclined surface 53a is set to approximately 60 degrees.

[0045] The yoke 53 is formed in a roughly U-shape (inverted C-shape) when viewed from the Y-axis direction, defining a placement space SP that opens onto the inclined surface 53a. The magnet 52 is placed within this placement space SP, and the magnet 52 is housed within the yoke 53. The yoke 53 surrounds the magnet 52 when viewed from the Y-axis direction. 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 placement space SP.

[0046] In the MEMS diffraction grating 51, when current flows through coils 65 and 66, the magnetic field formed by the magnet 52 and yoke 53 generates a Lorentz force in a predetermined direction on the electrons flowing through coils 65 and 66. As a result, coil 65 experiences a force in a predetermined direction. Therefore, by controlling the direction or magnitude of the current flowing through coil 65, the movable part 63 (diffraction grating part 64) can be oscillated around axis A. Furthermore, by flowing a current with a frequency corresponding to the resonant frequency of the movable part 63 through 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, coils 65 and 66, magnet 52, and yoke 53 function as actuators that oscillate the movable part 63.

[0047] Next, the electrical connection configuration between the QCL element 2 and the electrode terminal 10a will be described with reference to Figures 2 and 7. As shown in Figures 2 and 7, the electrode terminal 10a and the QCL element 2 (in this embodiment, the cathode and anode of the QCL element 2, respectively) 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 positioned between lens holder 7A and lens holder 7B when viewed from a direction perpendicular to the opposing direction in which lens holder 7A and lens holder 7B face each other (in this embodiment, the X-axis direction) (in this embodiment, a direction parallel to the plane perpendicular to the X-axis direction, for example, the Y-axis direction and the 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. Also, the wire W is connected to the electrode terminal 10a at a position between lens holder 7A and lens holder 7B when viewed from a direction perpendicular to the above 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 lens holder 7B when viewed from a direction perpendicular to the above 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 lens holder 7B when viewed from a direction perpendicular to the above opposing direction. The above arrangement configuration is realized by using these two electrode terminals 10a1 and 10a2. The electrode terminals 10a1 and 10a2 are the second and third electrode terminals 10a on the protruding wall 34 on the side where the electrode pad 11 is provided relative to the QCL element 2, counting from the light emission window 32a side.

[0048] 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 the electrode pad 11a. More specifically, the electrode terminal 10a1 is connected to the electrode pad 11a via a plurality of (six in this embodiment) wires W1 (first wires). The electrode pad 11a is connected to the top surface of the QCL element 2 via a plurality of (six in this embodiment) wires W2 (second wires). The number of wires W1 and W2 may be one each, but by using multiple wires W1 and W2, reliable electrical connection between the electrode terminal 10a1 and the cathode of the QCL element 2 (top surface of the QCL element 2) can be ensured. Furthermore, as shown in Figure 7, by arranging multiple wires W2 approximately uniformly along the optical axis direction (X-axis direction) on the upper surface (mesa surface) 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.

[0049] The electrode terminal 10a2 is electrically connected to the anode of the QCL element 2 (submount 8 in this embodiment). The electrode terminal 10a2 is connected to the submount 8 via the electrode pad 11b. More specifically, the electrode terminal 10a2 is connected to the electrode pad 11b via a plurality (six in this embodiment) of wires W3 (first wires). The electrode pad 11b is connected to the submount 8 via a plurality (six in this embodiment) of wires W4 (second wires). The number of wires W3 and W4 may be one each, but by using multiple wires W3 and W4, reliable electrical connection between the electrode terminal 10a2 and the anode (submount 8) of the QCL element 2 can be ensured.

[0050] As described above, in the laser module 1, the entirety of the wires W (wires W1 to W4) 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 perpendicular to the opposing direction (X-axis direction) (Y-axis direction, Z-axis direction, etc.).

[0051] In this embodiment, the temperature sensor 9 is also electrically connected to the electrode terminals 10a via wires W5a and W5b. Specifically, wire W5 has wire W5a connected to the temperature sensor 9 itself and wire W5b connected to the mounting member 4. Wires W5a and W5b are connected to the electrode terminals 10a located as the second and third from the light emission window 32a side on the protruding wall 34 on the side where the temperature sensor 9 is provided relative to the QCL element 2 (i.e., electrode terminals 10a positioned so as not to overlap with lens holder 7A or lens holder 7B when viewed from a direction perpendicular to the opposing direction). As a result, wires W5a and W5b that electrically connect the temperature sensor 9 and the electrode terminals 10a are configured to pass through the space between lens holder 7A and lens holder 7B when viewed from a direction perpendicular to the opposing direction (X-axis direction) (Y-axis direction, Z-axis direction, etc.).

[0052] Next, with reference to Figure 2, the electrical connection configuration between the electrode terminals 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 that are electrically connected to the coils 65 and 66. More specifically, as shown in Figures 2 and 6, the electrode pads 71 ​​and 73 are provided at one corner of the support portion 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 its corresponding electrode terminal 10a (electrode terminals 10a3 and 10a4) via its corresponding wire W (wires W6 and W7). Electrode terminals 10a3 and 10a4 are the third and second electrode terminals 10a located on the protruding wall 34 on the side where the electrode pads 11 are provided relative to the QCL element 2, counting from the side opposite to the side where the light emission window 32a is provided.

[0053] Electrode terminal 10a3 is connected to electrode pad 71 via multiple (two in this embodiment) wires W6. Similarly, electrode terminal 10a4 is connected to electrode pad 73 via multiple (two in this embodiment) wires W7. While one wire each of W6 and W7 may be used, using multiple wires W6 and W7 ensures reliable electrical connection between each electrode terminal 10a3, 10a4 and each electrode pad 71, 73.

[0054] Here, the height of the electrode pads 71 ​​and 73 relative to the bottom wall 31 is equal to or greater than the height of the electrode terminals 10a3 and 10a4 relative to the bottom wall 31. In other words, the electrode pads 71 ​​and 73 do not penetrate to the back side (bottom wall 31 side) of the package 3 relative to the corresponding electrode terminals 10a3 and 10a4. Therefore, when connecting wires W6 and W7 by wire bonding, it is not necessary to insert the capillary of the wire bonding device into the back side of the package 3. This effectively prevents the capillary from contacting other components within the package 3 (e.g., the lens holder 7B) and prevents damage to those components due to such contact.

[0055] Furthermore, in this embodiment, electrode pads 75 and 76, which are provided on the opposite side of electrode pads 71 ​​and 73 in the Y-axis direction, also have the same electrical connection configuration as electrode pads 71 ​​and 73. That is, electrode pads 75 and 76 are provided at the other corner on the top wall 33 side of the support portion 61 (the upper right corner when the MEMS diffraction grating 51 is viewed from the front). Each electrode pad 75 and 76 is connected to its corresponding electrode terminal 10a (electrode terminals 10a5 and 10a6) via its corresponding wire W (wires W8 and W9). Electrode terminals 10a5 and 10a6 are the second and third electrode terminals 10a located on the protruding wall 34 on the side of the QCL element 2 where the temperature sensor 9 is provided, counting from the side opposite to where the light emission window 32a is provided. The height position of electrode pads 75 and 76 relative to the bottom wall 31 is equal to or greater than the height position of electrode terminals 10a5 and 10a6 relative to the bottom wall 31. Electrode terminal 10a5 is connected to electrode pad 75 via multiple (two in this embodiment) wires W8. Similarly, electrode terminal 10a6 is connected to electrode pad 76 via multiple (two in this embodiment) wires W8. While each of the wires W8 and W9 may be represented by a single wire, using multiple wires W8 and W9 ensures reliable electrical connection between each electrode terminal 10a5 and 10a6 and each electrode pad 75 and 76.

[0056] Next, the arrangement configuration 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 top wall-side surface 7a of the lens holder 7B 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. Also, 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.

[0057] Next, the manufacturing method of the laser module 1 will be described. First, the QCL element 2 and the MEMS diffraction grating 51 (diffraction grating unit 5) are placed inside the package 3 (first step). In this embodiment, the following process is performed. The QCL element 2 is soldered to the submount 8 using, for example, an AuSn-based solder material. Subsequently, the submount 8 on which the QCL element 2 is mounted is joined 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 pad 11 are also joined 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 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. As a result, the mount member 4 is in a state where all components except the lens holders 7A and 7B are mounted. The first step is completed by fixing the mounting member 4 in this state onto the bottom wall 31 of the package 3, which does not yet have the top wall 33 attached. In this case, the mounting member 4 may be initially fixed onto the bottom wall 31 before the aforementioned components are mounted.

[0058] Next, wire bonding is performed to form wires W1 to W4 that electrically connect the QCL element 2 (anode and cathode) and electrode terminals 10a1 and 10a2, which are located inside the package 3 (second step). In this embodiment, the QCL element 2 and each electrode terminal 10a1 and 10a2 are electrically connected via each electrode pad 11a and 11b, so as an example, the following process is performed. First, by wire bonding, multiple wires (six in this embodiment) W2 are formed from the top surface of the QCL element 2 (cathode of the QCL element 2) to the electrode pad 11a, and multiple wires (six in this embodiment) W4 are formed from the submount 8 (anode of the QCL element 2) to the electrode pad 11b. Subsequently, multiple wires (six in this embodiment) W1 are formed from the electrode pad 11a to the electrode terminal 10a1, and multiple wires (six in this embodiment) W3 are formed from the electrode pad 11b to the electrode terminal 10a2. Here, the QCL element 2 side end of wire W (in this embodiment, the end of wire W2 connected to the upper surface of the QCL element 2, and the end of wire W4 connected to the submount 8) is positioned between the position where lens holder 7A is planned to be placed and the position where lens holder 7B is planned to be placed, when viewed from a direction perpendicular to the X-axis direction (such as the Y-axis and Z-axis directions). Also, wires W1 and W3 and electrode terminals 10a1 and 10a2 are connected at a position between the position where lens holder 7A is planned to be placed and the position where lens holder 7B is planned to be placed, when viewed from a direction perpendicular to the X-axis direction (such as the Y-axis and Z-axis directions).

[0059] In the second step, wires W5a and W5b, which electrically connect the temperature sensor 9 and the electrode terminal 10a, are also formed by wire bonding. Wires W6 to W9, which 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 of each electrode pad 71, 73, 75, and 76 is set to be equal to or greater than the height of the electrode terminals 10a3 to 10a6. This significantly improves the workability of wire bonding to each electrode pad 71, 73, 75, and 76 compared to the case where the height of each electrode pad 71, 73, 75, and 76 is lower than the height of the electrode terminals 10a3 to 10a6 (i.e., when each electrode pad 71, 73, 75, and 76 is located towards the back of the package 3 (towards the bottom wall 31)). As a result of the second step, an intermediate product 1A is obtained, as shown in Figure 8, in which components other than the lens holders 7A and 7B are arranged inside the package 3 before the top wall 33 is attached.

[0060] Next, the lens holder 7A holding lens 6A and the lens holder 7B holding lens 6B are placed inside the package 3 (third step). In this embodiment, the lens holder 7A is joined to the upper surface 41a of the first mounting portion 41 of the mount member 4 via resin adhesive B. The lens holder 7B is joined to the upper surface 43a of the third mounting portion 43 of the mount member 4 via resin adhesive B.

[0061] In the third step, a driving voltage is applied to the QCL element 2 via the electrode terminals 10a1, 10a2 and wires W1 to W4 to cause laser oscillation, and the lens holders 7A and 7B are fixed inside the package 3 by aligning the lenses 6A and 6B. That is, with the laser oscillating, the lens holders 7A and 7B are positioned so that the optical axes of the lenses 6A and 6B coincide with the optical axis of the light emitted from the QCL element 2.

[0062] After the completion of the third step, 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 Figure 1.

[0063] [Effects and Effects] In the laser module 1 described above, lens holders 7A and 7B are arranged on both sides of the QCL element 2. Furthermore, the electrode terminal 10a, which is arranged along the inner wall surface of the package 3, and the QCL element 2 (in this embodiment, both the anode and cathode of the QCL element 2) are electrically connected by a wire W. Here, 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 perpendicular to the opposing direction (X-axis direction) in which the lens holders 7A and 7B face each other (for example, the Y-axis and Z-axis directions). As a result, as shown in Figure 7, it is possible to realize 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 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, interference between the wire W for supplying power to the QCL element 2 and the components within the package 3 (especially the lens holders 7A and 7B located on both sides of the QCL element 2) can be effectively suppressed. This improves the reliability of the laser module 1 and the ease of assembly.

[0064] Furthermore, when viewed from a direction perpendicular to the opposing direction (X-axis direction) (for example, the Y-axis direction and the Z-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 placed 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 the components within the package 3 (especially the lens holders 7A and 7B).

[0065] Furthermore, the height position of the electrode terminal 10a relative to the bottom wall 31 is higher than the height position of the QCL element 2 relative to the bottom wall 31. With the above configuration, it becomes easy to connect a wire W with appropriate tension from the QCL element 2 to the electrode terminal 10a. As a result, slack in the wire W can be suitably suppressed, and interference between the wire W and the components inside the package 3 can be more suitably 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 an electrode pad 11, but the above-mentioned effects can be obtained by arranging the electrode pad 11 at a height position intermediate between the QCL element 2 and the electrode terminal 10a, as will be described later. Also, when the QCL element 2 and the electrode terminal 10a are connected directly with a single wire without using the electrode pad 11 as an intermediary, the above-mentioned effects can naturally be obtained.

[0066] Furthermore, in this embodiment, the wire W includes a wire W1 connecting the electrode terminal 10a1 and the electrode pad 11a, and a wire W2 connecting the electrode pad 11a and the QCL element (the upper surface of the QCL element 2 as the cathode). Similarly, the wire W includes a wire W3 connecting the electrode terminal 10a2 and the electrode pad 11b, and a wire W4 connecting the electrode pad 11b and the QCL element (the submount 8 as the anode). With the above configuration, the length of each wire W1 to W4 can be shortened compared to the case where the electrode terminals 10a1 and 10a2 and the QCL element (the upper surface of the QCL element 2 or the submount 8) are directly connected with wires. This effectively suppresses slack in the wires W1 to W4 and effectively suppresses interference between the wires W1 to W4 and the components inside the package 3.

[0067] Furthermore, the electrode pads 11a and 11b are positioned between the lens holder 7A and the lens holder 7B when viewed from a direction perpendicular to the opposing direction (X-axis direction) (for example, the Y-axis direction and the Z-axis direction). With the above configuration, it is possible to realize a configuration in which the entire length of wires W1 to W4 passes through the space between the lens holder 7A and the lens holder 7B, and by making the path from the electrode terminals 10a1 and 10a2 to the QCL element (the upper surface of the QCL element 2 or the submount 8) via the electrode pads 11a and 11b as short as possible, the length of each wire W1 to W4 can be shortened. This effectively suppresses interference between wires W1 to W4 and components inside the package 3.

[0068] 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. With the above configuration, the height positions of the electrode terminals 10a1 and 10a2, electrode pads 11a and 11b, and QCL element 2 on the package 3 side are set to decrease in stages. This makes it easy to connect wires W2 and W4 with appropriate tension from the QCL element 2 to the electrode pads 11a and 11b, and also makes it easy to connect wires W1 and W3 with appropriate tension from the electrode pads 11a and 11b to the electrode terminals 10a1 and 10a2. As a result, slack in the wires W1 to W4 can be suitably suppressed, and interference between the wires W1 to W4 and the components inside the package 3 can be suitably suppressed.

[0069] Furthermore, in the above manufacturing method (steps 1 to 3), in step 2, the end of the wire W on the QCL element 2 side is positioned between lens holder 7A and lens holder 7B when viewed from a direction perpendicular to the opposing direction (X-axis direction) in which lens holder 7A and lens holder 7B face each other (for example, the Y-axis direction and Z-axis direction). This makes it possible to realize 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 lens holder 7A and lens holder 7B between the electrode terminals 10a1, 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, interference between the wire W and lens holders 7A, 7B can be suitably suppressed when arranging lens holders 7A, 7B in step 3. Thus, the reliability of the laser module 1 and the workability during assembly are improved.

[0070] Furthermore, in the third step described above, the lens holders 7A and 7B are fixed inside the package 3 by aligning the lenses 6A and 6B while a driving voltage is applied to the QCL element 2 via the electrode terminals 10a1 and 10a2 and the wire W to cause laser oscillation. According to the above manufacturing method, the lens holders 7A and 7B can be properly positioned inside the package 3 by performing alignment while the laser is oscillating in the third step. In addition, since wire bonding is performed in the second step so that the wire W and the lens holders 7A and 7B do not interfere with each other, alignment in the third step (i.e., adjustment of the position of the lens holders 7A and 7B) can be easily performed.

[0071] Furthermore, in the laser module 1, the distance d (see Figure 4) between the top wall 33 and the surface 7a of the lens holder 7B on the top wall 33 side 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. In other words, within the package 3, the lens holder 7B is positioned such 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. As a result, even if stray light reflected from the MEMS diffraction grating 51 that deviates from the lens 6B and heads towards the top wall 33 enters the space between the top wall 33 and the lens holder 7B, it is difficult for this stray light to pass through the space between the top wall 33 and the lens holder 7B. That is, the intrusion of stray light from the space S2 (see Figure 3) on the side where the MEMS diffraction grating 51 is positioned relative to the lens holder 7B to the space S1 (see Figure 3) on the side where the QCL element 2 is positioned relative to the lens holder 7B can be effectively suppressed. As a result, the inclusion of stray light components in the laser beam L emitted from the QCL element 2 is suppressed, and the laser quality can be appropriately ensured.

[0072] Furthermore, it is preferable that the top wall 33 and the surface 7a of the lens holder 7B are arranged to face each other. More preferably, the top wall 33 and the surface 7a of the lens holder 7B are arranged to face each other parallel to each other. Also, as shown in Figure 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 total length of the lens holder 7B in the X-axis direction. If 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. Furthermore, from the viewpoint of improving the stability of the lens 6B, it is preferable that the thickness t of the lens holder 7B is greater than or equal to the thickness along the optical axis direction (X-axis direction) of the lens 6B. Also, it is preferable that the distance d is less than or equal to the thickness of the lens 6B.

[0073] Furthermore, when viewed from the X-axis direction, the top wall 33 and the surface 7a may not be parallel (for example, when viewed from the X-axis direction, the surface 7a may be inclined relative to the top wall 33), and there may be variations in the distance between the top wall 33 and the surface 7a at each position along the Y-axis direction. In this case, the statistical values ​​(e.g., minimum value, maximum value, average value, etc.) of the distance between the top wall 33 and the surface 7a at each position along the Y-axis direction (distance along the Z-axis direction) may be used as the distance d between the top wall 33 and the surface 7a of the lens holder 7B as described above.

[0074] Furthermore, when viewed from the Y-axis direction, the top wall 33 and the surface 7a may not be parallel (for example, when viewed from the Y-axis direction, the surface 7a may be inclined relative to the top wall 33), and there may be variations in the distance between the top wall 33 and the surface 7a at each position along the X-axis direction. In this case, the statistical values ​​of the distance between the top wall 33 and the surface 7a at each position along the X-axis direction (for example, minimum value, maximum value, average value, etc.) may be used as the distance d between the top wall 33 and the surface 7a of the lens holder 7B as described above.

[0075] Furthermore, if the top wall 33 and the surface 7a are not parallel when viewed from either the X-axis or Y-axis direction, the statistical values ​​of the distance between each position of the surface 7a in the XY plane and the top wall 33 (e.g., minimum value, maximum value, average value, etc.) may be used as the distance d between the top wall 33 and the surface 7a of the lens holder 7B described above. It is also preferable that the same relationship as between the top wall 33 and the lens holder 7A described above holds true for the relationship between the top wall 33 and the lens holder 7B.

[0076] Furthermore, the wires W (wires W1, W3) are connected to electrode terminals 10a1, 10a2 in the region of the lens holder 7B on the side where the QCL element 2 is positioned, when viewed from a direction perpendicular to the optical axis direction (X axis direction) (for example, the Y axis direction and Z axis direction, etc.). The electrode terminals 10a1, 10a2 are positioned closer to the top wall 33 than the QCL element 2, and the surface 7a of the lens holder 7B on the top wall 33 side is positioned closer to the top wall 33 than the electrode terminals 10a1, 10a2. According to the above configuration, by connecting the electrode terminals 10a1, 10a2 and wires W (wires W1, W3 in this embodiment) in the space on the QCL element 2 side of the lens holder 7B when viewed from a direction perpendicular to the optical axis direction (X axis direction) (for example, the Y axis direction and Z axis direction, etc.), it is possible to bring the surface 7a of the lens holder 7B on the top wall 33 side closer to the top wall 33 than the electrode terminals 10a1, 10a2, while suppressing interference between wires W and the lens holder 7B. As a result, the lens holder 7B can be positioned so that the gap (d) between the top wall 33 and the lens holder 7B is as small as possible. Consequently, it is possible to more effectively suppress stray light generated in the above space S2 from passing between the top wall 33 and the lens holder 7B and entering the above space S1.

[0077] Furthermore, the stacking direction of the stacked structure including the active layer and cladding layer in the QCL element 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 (first end face 2a and second end face 2b) of the QCL element 2 is an ellipse shape with a major axis along the stacking direction (Z-axis direction). In this case, since the light emitted from the end faces of the QCL element 2 tends to spread in the vertical direction (Z-axis direction), stray light is likely to be reflected by the MEMS diffraction grating 51 and directed towards the top wall 33. On the other hand, the positional relationship between the top wall 33 and the lens holder 7B (relationship between distance d and thickness t) described above suppresses the intrusion of such stray light into the space S1. That is, by setting the positional relationship between the top wall 33 and the lens holder 7B described above, the QCL element 2 can be arranged so that the stacking direction of the QCL element 2 coincides with the Z-axis direction while suitably suppressing the deterioration of laser quality due to stray light.

[0078] Furthermore, the surface of the lens holder 7B is blackened. In this embodiment, the surface of the lens holder 7B is blackened by anodizing or the like. With the above configuration, some of the stray light that is reflected by the MEMS diffraction grating 51 and misses the lens 6B is absorbed by the blackened surface of the lens holder 7B, thus more effectively suppressing the intrusion of stray light into the space S1. In addition, in this embodiment, in order to enhance the stray light reduction effect, the surface of the yoke 53 is also blackened by zinc plating or the like.

[0079] Furthermore, the height positions of the electrode pads 71 ​​and 73 of the MEMS diffraction grating 51 relative to the bottom wall 31 are equal to or greater than the height positions of the electrode terminals 10a3 and 10a4 relative to the bottom wall 31 (see Figures 2 and 3). In other words, in the laser module 1, the electrode pads 71 ​​and 73 of the MEMS diffraction grating 51 are positioned at a height equal to or greater than the height positions of the electrode terminals 10a3 and 10a4 arranged along the side wall 32 (first side wall 321) of the package 3 within the package 3. In this embodiment, of the two electrode pads 71 ​​and 73, the upper electrode pad 73 (on the top wall 33 side) is positioned slightly higher than the height positions of the electrode terminals 10a3 and 10a4, while the lower electrode pad 71 (on the bottom wall 31 side) is positioned at approximately the same height position as the electrode terminals 10a3 and 10a4. By setting the positions of the electrode pads 71 ​​and 73 in this manner, compared to the case where the height position of the electrode pads 71 ​​and 73 is lower than the height position of the electrode terminals 10a3 and 10a4 on the package 3 side (i.e., on the back side of the package 3 (bottom wall 31 side)), the formation of wires W6 and W7 by wire bonding becomes easier, and the required wire length can be shortened. By shortening the wire length, the wires W6 and W7 can be given appropriate tension, and interference between the wires W6 and W7 and components inside the package 3 (for example, each component 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.

[0080] Furthermore, even when a MEMS diffraction grating 51 is used in which the ratio of the width of the optical surface (movable part 63) to the width of the housing space of package 3 (width in the Y-axis direction) is relatively large, wire bonding between the electrode terminals 10a3, 10a4 and the electrode pads 71, 73 can be easily performed. As a result, the distance between the lens 6B and the MEMS diffraction grating 51 can be made larger compared to when a MEMS diffraction grating 51 with a relatively small ratio of the width of the optical surface is used, thereby significantly reducing the difficulty of assembly. The above will be explained in detail below. In this embodiment, in order to suppress interference between the movable part 63 and the wires W6~W9, the electrode pads 71, 73, 75, and 76 are arranged on both sides of the movable part 63 in the support part 61. In this configuration, as the width of the movable part 63 is increased, the electrode pads 71, 73, 75, and 76 will be positioned in a location close to the first side wall 321 in the Y-axis direction. In such cases, if the electrode pads 71, 73, 75, and 76 are positioned at a deep location at the back of the package 3, wire bonding becomes difficult. In other words, it becomes extremely difficult to allow the 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 greater than that of the electrode terminals 10a on the package 3 side, as in this embodiment, wire bonding can be easily performed. This advantage is particularly significant when the width of the movable part 63 is increased. Furthermore, the lens 6B cannot necessarily completely collimate the light emitted from the second end face 2b of the QCL element 2 to the movable part 63. Therefore, the light transmitted through the lens 6B may have a slight divergence angle. Consequently, when the width of the movable part 63 is small, it becomes necessary to bring the MEMS diffraction grating 51 as close as possible to the lens 6B. In contrast, in this embodiment, as described above, a MEMS diffraction grating 51 having a movable part 63 with as large a width as possible can be used, making it 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 housing space within package 3 (i.e., a MEMS diffraction grating 51 in which the width of the movable part 63 is made as close as possible to the width of package 3 (width along the Y-axis)), 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.

[0081] Furthermore, the MEMS diffraction grating 51 has a rectangular frame-shaped support portion 61 that supports the diffraction grating portion 64, and the electrode pads 71 ​​and 73 are provided at one corner of the support portion 61 on the side of the top wall 33. In this embodiment, the electrode pads 71 ​​and 73 are provided at the upper left corner (see Figure 6) when the MEMS diffraction grating 51 is viewed from the front. With the above configuration, electrical connections are made 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 caused by the wires W6 and W7 and the electrode pads 71 ​​and 73, thereby effectively improving the reliability of the laser module 1. The above will be described in detail below. Normally, 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 divergence angle from the QCL element 2 increases, and the diffraction grating portion 64 cannot necessarily receive the entire beam of light (total luminous flux). In such cases, light passing through the gap between the movable part 63 (diffraction grating part 64) and the support part 61 may be diffusely reflected by the surface of the magnet 52 located on the back side of the movable part 63, and may strike the electrode pads 71, 73 and the wire W, etc., causing stray light. As described above, by arranging the electrode pads 71, 73 at the corners of the support part 61, which are relatively far from the center of the diffraction grating part 64, it is possible to suppress the diffusely reflected light striking the electrode pads 71, 73 and the wire W, etc. This effectively reduces the generation of stray light as described above.

[0082] Furthermore, the MEMS diffraction grating 51 also has electrode pads 75, 76 (first electrode pads) that are electrically connected to a coil different from the coils 65, 66 (driving coils) (a detection coil, first coil, not shown). The electrode pads 75, 76 are provided at the other corner on the top wall 33 side of the support portion 61 (i.e., the corner opposite to the side where the electrode pads 71, 73 are provided). With the above configuration, even when the MEMS diffraction grating 51 is provided with two types of coils (in this embodiment, driving coils 65, 66 and a detection coil), the above-mentioned effects (i.e., improved reliability of the laser module 1 and improved workability during assembly) can be obtained by providing the electrode pads 71, 73, 75, 76 corresponding to each coil at a pair of corners on the top wall 33 side of the rectangular frame-shaped support portion 61 (i.e., the upper left corner and the upper right corner when the support portion 61 is viewed from the front side with the top wall 33 side facing upwards).

[0083] Furthermore, the MEMS diffraction grating 51, together with a magnet 52 that generates a magnetic field acting on coils 65 and 66, constitutes the diffraction grating unit 5. The magnet 52 is positioned on the side of the MEMS diffraction grating 51 opposite to the side on which the QCL element 2 is provided. With the above configuration, the degree of freedom in arranging the electrode pads 71, 73, 75, and 76 can be improved. 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 arranged on the surface of the support part 61 (the side facing the QCL element 2).

[0084] [Differentiation] 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. In addition, 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, respectively) may be directly connected by a single wire. Also, if the detection coil is omitted in the MEMS diffraction grating 51, the electrode pads 75 and 76 may be omitted. [Explanation of symbols]

[0085] 1...External resonant laser module, 2...Quantum cascade laser element, 3...Package, 6B...Lens, 7a...Face, 7B...Lens holder, 10a, 10a1~10a6...Electrode terminals, 11, 11a, 11b...Electrode pads, 31...Bottom wall, 32...Side wall, 33...Top wall, 51...MEMS diffraction grating.

Claims

1. Cooling element, A mounting member disposed on the cooling element, A quantum cascade laser element arranged on the mounting member, A lens holder is positioned on the mounting member and holds a lens through which light emitted from the quantum cascade laser element passes; The external resonator of the aforementioned quantum cascade laser element, The package comprises the cooling element, the mounting member, the quantum cascade laser element, the external resonator, and the lens holder, The package has a bottom wall, a side wall erected on the bottom wall and formed in an annular shape to surround the region in which the quantum cascade laser element is housed when viewed from a direction perpendicular to the bottom wall, and a top wall that closes the opening of the side wall on the side opposite to the bottom wall. The top wall faces the bottom wall in a direction perpendicular to the optical axis direction of the lens. The distance between the top wall and the top wall-side surface of the lens holder is smaller than the thickness of the lens holder along the optical axis of the lens. The aforementioned side wall is provided with a light-emitting window that allows the emitted light to pass through, The lens holder is an externally resonant laser module positioned between the external resonator and the light emission window.

2. The external resonant laser module according to claim 1, wherein the package is configured as a butterfly package.

3. The external resonant laser module according to claim 1 or 2, wherein the bottom wall is formed of copper tungsten.

4. The external resonant laser module according to any one of claims 1 to 3, wherein the light emission window is formed of germanium.

5. The external resonant laser module according to any one of claims 1 to 4, wherein the lens holder is fixed to the mounting member via a resin adhesive.

6. The external resonant laser module according to any one of claims 1 to 5, wherein the lens is an aspherical lens made of zinc selenide.

7. The external resonant laser module according to any one of claims 1 to 6, wherein, when viewed from the optical axis direction, the outer shape of the lens is circular and the outer shape of the lens holder is rectangular.

8. Within the package, electrode terminals arranged along the side wall, The system further comprises a wire for electrically connecting the electrode terminal and the quantum cascade laser element, The wire is connected to the electrode terminal in the region of the lens holder on the side where the quantum cascade laser element is positioned, when viewed from a direction perpendicular to the optical axis. The electrode terminals are positioned closer to the ceiling wall than the quantum cascade laser element. The external resonant laser module according to any one of claims 1 to 7, wherein the surface of the lens holder on the top wall side is located closer to the top wall than the electrode terminals.

9. The external resonant laser module according to any one of claims 1 to 8, wherein the stacking direction of the stacked structure including the active layer and the cladding layer in the quantum cascade laser element coincides with the direction in which the bottom wall and the top wall face each other.

10. The surface of the lens holder is blackened, as described in any one of claims 1 to 9, for the external resonant laser module.

11. The mounting member is formed by combining a plurality of members, as described in any one of claims 1 to 10.

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