External Cavity Laser Module

Abstract

To provide an external resonant laser module capable of improving yield, and a method of manufacturing the same.SOLUTION: A laser module 1 includes a QCL element 2, a diffraction grating unit 5, lens holders 7A and 7B, and a mount member 4. The mount member 4 has a first mounting portion 41, a second mounting portion 42, and a third mounting portion 43. The first mounting portion has a top surface 41a on which the lens holder 7A is mounted via an adhesive layer B1. The third mounting portion has a top surface 43a on which the lens holder 7B is mounted via an adhesive layer B2. The second mounting portion has: a top surface 42a located higher than the top surfaces 41a and 43a; a side surface 421 connecting the top surface 42a and the top surface 41a; and a side surface 422 connecting the top surface 42a and the top surface 43a. A notch 421a or a notch 422a extending from the top surface 42a to the top surface 41a or the top surface 43a along a Z-axis direction is formed in at least one of the side surfaces 421 and 422.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an external resonance type laser module.

Background Art

[0002] As an external resonance type 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 resonance type laser module, light from the quantum cascade laser element is diffracted and reflected by the diffraction grating, and light having a specific wavelength among the light is returned to the quantum cascade laser element. Thereby, an external resonator is configured by the end face of the quantum cascade laser element and the diffraction grating, and light having a specific wavelength is amplified and output to the outside. By changing the wavelength of the output light by swinging the diffraction grating, 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] In the external resonance type laser module as described above, in order to cause laser oscillation by external resonance, it is required to mount members such as a lens and a diffraction grating with high accuracy. If the mounting accuracy of the above members is poor, there is a risk of becoming a defective product in which laser oscillation is not caused by external resonance. That is, when mass-producing an external resonance type laser module, if the variation in the mounting accuracy of the above members is large, the yield may decrease.

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

[0006] An external cavity laser module according to one aspect of the present disclosure includes: a quantum cascade laser element; a diffraction grating unit including a movable diffraction grating that constitutes an external cavity of the quantum cascade laser element; a first lens holder that is arranged on the opposite side of the quantum cascade laser element from the side on which the movable diffraction grating is located and that holds a first lens that passes light emitted from the quantum cascade laser element; a second lens holder that is arranged between the quantum cascade laser element and the movable diffraction grating and that holds a second lens that passes light emitted from the quantum cascade laser element and light returning from the movable diffraction grating to the quantum cascade laser element; and a mount member that mounts the quantum cascade laser element, the first lens holder, and the second lens holder, wherein the mount member is configured to mount the first lens along a direction in which the first lens holder and the second lens holder face each other. The optical element has a first mounting portion, a second mounting portion, and a third mounting portion arranged in that order from the lens holder side to the second lens holder side, the first mounting portion having a first mounting surface on which the first lens holder is mounted via a first adhesive layer made of a photocurable resin, the third mounting portion having a third mounting surface on which the second lens holder is mounted via a second adhesive layer made of a photocurable resin, the second mounting portion having a second mounting surface that is higher than the first and third mounting surfaces and on which a quantum cascade laser element is mounted, a first side surface that intersects with the opposing direction to connect the second mounting surface and the first mounting surface, and a second side surface that intersects with the opposing direction to connect the second mounting surface and the third mounting surface, and at least one of the first side surface and the second side surface has a notch formed in it that extends from the second mounting surface to the first mounting surface or the third mounting surface along a height direction perpendicular to the second mounting surface.

[0007] In the above-described external cavity laser module, the first lens holder is mounted on the first mounting portion via a first adhesive layer made of a photocurable resin, and the second lens holder is mounted on the third mounting portion via a second adhesive layer made of a photocurable resin. If a notch is formed on the first side surface, the notch can increase the gap between the second mounting portion (first side surface) and the first lens holder. As a result, when light is irradiated from above the first lens holder to harden the first adhesive layer, the light can be suitably guided to the first adhesive layer through the space formed by the notch. As a result, the first adhesive layer can be suitably hardened, and the first lens holder can be more reliably fixed to the first mounting surface. Furthermore, if a notch is formed on the second side surface, the notch can increase the gap between the second mounting portion (second side surface) and the second lens holder. This allows light to be suitably guided to the second adhesive layer through the space formed by the notch when light is irradiated from above the second lens holder to harden the second adhesive layer. As a result, the second adhesive layer can be properly hardened, and the second lens holder can be more reliably fixed to the third mounting surface. As a result, according to the above-mentioned external cavity laser module, it is possible to suppress variations in the mounting accuracy of the optical members (at least one of the first lens and the second lens) that constitute the external cavity laser module, thereby improving the yield when mass-producing external cavity laser modules.

[0008] The quantum cascade laser element may be mounted at a substantially central portion of the second mounting surface in the width direction that is parallel to the second mounting surface and orthogonal to the opposing direction. The notch may include a first notch formed at an end of the first side surface in the width direction that is parallel to the second mounting surface and orthogonal to the opposing direction. According to the above configuration, the gap between the second mounting portion and the first lens holder can be increased by the first notch. Thereby, when irradiating the first adhesive layer with light for curing, the light can be suitably guided to the first adhesive layer through the space formed by the first notch. As a result, the first adhesive layer can be appropriately cured, and the fixing of the first lens holder to the first mounting surface can be made more reliable. Further, by providing the first notch at the end in the width direction of the second mounting portion (first side surface), the above effects can be obtained without impairing the support stability of the quantum cascade laser element mounted at the substantially central portion in the width direction of the second mounting portion.

[0009] The quantum cascade laser element may be mounted at a substantially central portion of the second mounting surface in the width direction that is parallel to the second mounting surface and orthogonal to the opposing direction. The notch may include a second notch formed at an end of the second side surface in the width direction that is parallel to the second mounting surface and orthogonal to the opposing direction. According to the above configuration, the gap between the second mounting portion and the second lens holder can be increased by the second notch. Thereby, when irradiating the second adhesive layer with light for curing, the light can be suitably guided to the second adhesive layer through the space formed by the second notch. As a result, the second adhesive layer can be appropriately cured, and the fixing of the second lens holder to the third mounting surface can be made more reliable. Further, by providing the second notch at the end in the width direction of the second mounting portion (second side surface), the above effects can be obtained without impairing the support stability of the quantum cascade laser element mounted at the substantially central portion in the width direction of the second mounting portion.

[0010] The notch may include a first notch formed at an end of the first side surface in the width direction that is parallel to the second mounting surface and orthogonal to the opposing direction, and a second notch formed at an end of the second side surface in the width direction. The first notch and the second notch may be formed so as not to be continuous with each other. According to the above configuration, while providing the first notch and the second notch, it is possible to secure the width of the second mounting portion disposed between the first lens holder and the second lens holder. Thereby, the second mounting portion can function sufficiently as a barrier for suppressing the mixing of stray light components (that is, light that is reflected by the diffraction grating and does not return to the quantum cascade laser element through the second lens) in the laser light emitted from the module through the first lens.

[0011] The first lens holder may have a first mounting surface joined to the first mounting surface via a first adhesive layer. At least a part of the portion of the first mounting surface that is not joined to the first mounting surface via the first adhesive layer may be provided with a recess formed so as to communicate with the space outside the first lens holder when the first lens holder is placed on the first mounting surface. According to the above configuration, when irradiating the first adhesive layer with light to cure it, the light can be preferably guided from the space outside the first lens holder to the space inside the recess. Thereby, the first adhesive layer can be appropriately cured. As a result, the fixing of the first lens holder to the first mounting surface can be made more reliable.

[0012] The first lens holder may have a first mounting surface facing the first mounting surface via a first adhesive layer. At least a part of the portion of the first mounting surface that is not joined to the first mounting surface via the first adhesive layer may be provided with a recess formed so as to communicate with the space outside the first mounting portion when the first lens holder is placed on the first mounting surface. According to the above configuration, when irradiating the first adhesive layer with light to cure it, the light can be preferably guided from the space outside the first mounting portion to the space inside the recess. Thereby, the first adhesive layer can be appropriately cured. As a result, the fixing of the first lens holder to the first mounting surface can be made more reliable.

[0013] In a portion connected to the first mounting surface of the first side surface, a surface that is inclined or curved so as to approach the first lens holder in the facing direction as it goes from the second mounting surface to the first mounting surface in the height direction may be formed. According to the above configuration, when curing the first adhesive layer, the light irradiated from above the first lens holder can be reflected by the inclined or curved surface toward the space between the first lens holder and the first mounting surface. Thereby, the irradiation efficiency of light to the space between the first lens holder and the first mounting surface can be improved, and the first adhesive layer can be appropriately cured. As a result, the fixing of the first lens holder to the first mounting surface can be made more reliable.

[0014] The second lens holder may have a second mounting surface joined to the third mounting surface via a second adhesive layer, and at least a part of the portion of the second mounting surface that is not joined to the third mounting surface via the second adhesive layer may be provided with a recess formed so as to communicate with the space outside the second lens holder in a state where the second lens holder is placed on the third mounting surface. According to the above configuration, when irradiating the second adhesive layer with light for curing, the light can be preferably guided from the space outside the second lens holder to the space inside the recess. Thereby, the second adhesive layer can be appropriately cured. As a result, the fixing of the second lens holder to the third mounting surface can be made more reliable.

[0015] The second lens holder may have a second mounting surface joined to the third mounting surface via a second adhesive layer, and at least a part of the portion of the third mounting surface that is not joined to the second mounting surface via the second adhesive layer may be provided with a recess formed so as to communicate with the space outside the third mounting portion in a state where the second lens holder is placed on the third mounting surface. According to the above configuration, when irradiating the second adhesive layer with light for curing, the light can be preferably guided from the space outside the third mounting portion to the space inside the recess. Thereby, the second adhesive layer can be appropriately cured. As a result, the fixing of the second lens holder to the third mounting surface can be made more reliable.

[0016] In a portion connected to the third mounting surface of the second side surface, a surface that slopes or curves so as to approach the second lens holder in the opposing direction as it goes from the second mounting surface to the third mounting surface in the height direction may be formed. According to the above configuration, when curing the second adhesive layer, the light irradiated from above the second lens holder can be reflected by the sloping or curved surface toward the space between the second lens holder and the third mounting surface. Thereby, the irradiation efficiency of light to the space between the second lens holder and the third mounting surface can be improved, and the second adhesive layer can be cured appropriately. As a result, the fixing of the second lens holder to the third mounting surface can be made more reliable.

Advantages of the Invention

[0017] According to one aspect of the present disclosure, it is possible to provide an external resonance type laser module capable of improving the yield and a method for manufacturing the same.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted. Also, terms such as "upper" and "lower" are for convenience based on the state shown in the drawings.

[0020] [Overall Configuration of External Resonance Type Laser Module] As shown in FIGS. 1 to 4, an external resonance type laser module 1 (hereinafter referred to as "laser module 1") includes 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 resonance type laser module 1 is a wavelength tunable light source in which the wavelength of the output light (laser light L) is variable. The external resonance type laser module 1 can be used, for example, for biological measurement such as glucose or measurement of an absorption spectrum of an analysis target having an optical absorption band such as a VOC gas (volatile organic compound). For example, when measuring such an absorption spectrum, the analysis target accommodated in a light-transmissive container is disposed between the external resonance type laser module 1 and a photodetector (not shown). Then, the external resonance type laser module 1 performs wavelength sweeping in a predetermined wavelength range (for example, the mid-infrared region) by rapidly changing the wavelength of the output light (laser light L). Thereby, an absorption spectrum is calculated based on the detection result of the photodetector. Note that the analysis target may be any of a gas, a liquid, and a solid.

[0021] Package 3 is a housing that houses the QCL element 2, the mounting member 4, the diffraction grating unit 5, the lens holder 7A (first lens holder) that holds the lens 6A (first lens), and the lens holder 7B (second lens holder) that holds the 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 FIG. 2, the illustration of the top wall 33 of Package 3 is omitted, and the illustration of the portion of the lead terminal 10 that protrudes outside the protruding wall 34 is omitted.

[0022] 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.

[0023] The side walls 32 are erected on the bottom wall 31. The side walls 32 are formed in an annular shape so as to surround the internal space in which the QCL element 2 and the like are housed when viewed from the Z-axis direction. In this embodiment, the side walls 32 are rectangular tubular members. The side walls 32 are formed of a metal material such as kovar. The side walls 32 are, for example, kovar frames plated with Ni / Au. In this embodiment, the side walls 32 are 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 walls 32 coincides with the width of the bottom wall 31 in the short-side direction, and the width along the longitudinal direction (X-axis direction) of the side walls 32 is shorter than the width of the bottom wall 31 in the longitudinal direction. That is, protruding portions 31a that protrude and extend outward from the side walls 32 are formed on both sides of the bottom wall 31 in the longitudinal direction. Screw 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 protruding portions 31a.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] As shown in FIGS. 3, 5, and 8, the mount member 4 is a member elongated in the X-axis direction. The mount member 4 mounts the QCL element 2, the diffraction grating unit 5, the lens holder 7A, and the lens holder 7B. The mount member 4 has a first mounting portion 41, a second mounting portion 42, a third mounting portion 43, and a fourth mounting portion 44. The first mounting portion 41, the second mounting portion 42, the third mounting portion 43, and the fourth mounting portion 44 are arranged in order from the lens holder 7A side toward the diffraction grating unit 5 side along the facing direction (in this embodiment, the X-axis direction) in which the lens holder 7A and the lens holder 7B face each other. The lens holder 7A is mounted on the first mounting portion 41 via an adhesive layer B1 (first adhesive layer) made of a photocurable resin (for example, a UV curable resin or the like). The QCL element 2 is mounted on the second mounting portion 42. The lens holder 7B is mounted on the third mounting portion 43 via an adhesive layer B2 (second adhesive layer) made of a photocurable resin similar to the adhesive layer B1 (for example, a UV curable resin or the like). The diffraction grating unit 5 is mounted on the fourth mounting portion 44. That is, the light emission 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.

[0030] The first mounting portion 41 and the third mounting portion 43 have the same thickness. That is, with reference to the bottom wall 31, the height position of the upper surface 41a (first mounting surface) of the first mounting portion 41 coincides with the height position of the upper surface 43a (third mounting surface) of the third mounting portion 43. The lens holder 7A is adhesively fixed to the upper surface 41a of the first mounting portion 41 via the adhesive layer B1. Similarly, the lens holder 7B is adhesively fixed to the upper surface 43a of the third mounting portion 43 via the adhesive layer B2. The length of the lens holders 7A and 7B in the X-axis direction is, for example, about 2.2 mm.

[0031] In this embodiment (Figs. 3 and 5), the widths (lengths in the Y-axis direction) of the lens holders 7A and 7B are the same as the widths of the upper surfaces 41a and 43a, but the widths of the lens holders 7A and 7B may be smaller than the widths of the upper surfaces 41a and 43a. That is, the ends of the lens holders 7A and 7B in the Y-axis direction may be located inside the ends of the upper surfaces 41a and 43a in the Y-axis direction. For example, the width of the upper surfaces 41a and 43a (i.e., the width of the mount member 4) may be set to about 6 mm, and the widths of the lens holders 7A and 7B may be set to about 5.7 mm.

[0032] In this embodiment (Fig. 3), the position in the X-axis direction of the end of the lens holder 7A on the light-emitting window 32a side coincides with the position in the X-axis direction of the end of the first mounting portion 41 (upper surface 41a) on the light-emitting window 32a side, but the end of the lens holder 7A on the light-emitting window 32a side may be located inside (on the side of the second mounting portion 42) the end of the first mounting portion 41 (upper surface 41a) on the light-emitting window 32a side. For example, the distance (length in the X-axis direction) between the end of the lens holder 7A on the light-emitting window 32a side and the end of the first mounting portion 41 (upper surface 41a) on the light-emitting window 32a side may be set to about 0.3 mm.

[0033] It is preferable to use a photocurable resin as the adhesive (adhesive layers B1, B2) for fixing the lens holders 7A, 7B to the mount member 4. The reason for this is as follows: When fixing the lens holders 7A, 7B to the mount member 4, it is necessary to align the lens holders 7A, 7B (lenses 6A, 6B) in the X, Y, and Z directions, as described below. For this reason, the process of curing the adhesive is not performed while the lens holders 7A, 7B are sufficiently pressed against the mount member 4. In such a case, using a photocurable resin as the adhesive allows the lens holders 7A, 7B to be bonded to the mount member 4 with higher positional accuracy than using a thermosetting resin. Furthermore, precision components such as the QCL element 2 are disposed between the lens holders 7A, 7B. If a thermosetting resin is used as the adhesive, the heat treatment for curing the adhesive may affect the quality of the QCL element 2. For the above reasons, in this embodiment, the lens holders 7A and 7B are fixed to the mount member 4 via adhesive layers B1 and B2 made of photocurable resin.

[0034] The second mounting section 42 is provided between the first mounting section 41 and the third mounting section 43. The second mounting section 42 is thicker than the first mounting section 41 and the third mounting section 43 and protrudes relative to the first mounting section 41 and the third mounting section 43. That is, the upper surface 42a (second mounting surface) of the second mounting section 42 is located higher than the upper surfaces 41a, 43a of the first mounting section 41 and the third mounting section 43. The QCL element 2 is fixed to the upper surface 42a of the second mounting section 42 via a submount 8. The submount 8 is a rectangular plate-shaped member on which the QCL element 2 is mounted. In this embodiment, the submount 8 is disposed at the center of the upper surface 42a in the Y-axis direction. As a result, the QCL element 2 is mounted approximately at the center of the upper surface 42a in the Y-axis direction. The submount 8 is made of a material (e.g., aluminum nitride) having a thermal expansion coefficient similar to that of the QCL element 2. The QCL element 2 is bonded to the submount 8 via, for example, an AuSn-based solder material. The submount 8 is bonded to the mount member 4 (upper surface 42a) via, for example, an In-based (InSn, InAg, etc.) solder material. As described above, the QCL element 2 is integrated with the submount 8, and therefore the combination of the QCL element 2 and the submount 8 can be considered the "QCL element."

[0035] On the upper surface 42a of the second mounting portion 42, in addition to the submount 8, a temperature sensor 9 and electrode pads 11 are arranged. The temperature sensor 9 and the electrode pads 11 are joined to the mounting member 4 (upper surface 42a) via, for example, a resin adhesive or the like. In the present embodiment, the temperature sensor 9 and the electrode pads 11 are arranged on opposite sides of each other with the submount 8 interposed therebetween. The temperature sensor 9 is, for example, a thermistor. The electrode pads 11 relay the electrical connection between the electrode terminals 10a and the QCL element 2. In the present embodiment, two electrode pads 11 are provided on the upper surface 42a of the second mounting portion 42. Specifically, an electrode pad 11a that is electrically connected to the cathode of the QCL element 2 (in the present 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 the present embodiment, the submount 8) are provided on the upper surface 42a of the second mounting portion 42. Each of the electrode pads 11a, 11b has a substantially rectangular connection region (upper surface). The electrode pads 11a, 11b are arranged side by side along the X-axis direction. The electrode pad 11a is located closer to the light emission window 32a side than the electrode pad 11b. Based on the bottom wall 31, the height positions of the electrode pads 11a, 11b are lower than the height position of the electrode terminal 10a (that is, the height position of the upper surface 34a of the protruding wall 34) and higher than the height position of the QCL element 2.

[0036] The fourth mounting portion 44 is thinner than the first mounting portion 41 and the third mounting portion 43. That is, the upper surface 44a (fourth mounting surface) of the fourth mounting portion 44 is at a lower position than the upper surfaces 41a, 43a of the first mounting portion 41 and the third mounting portion 43. An arrangement hole 44b (hole portion) is formed in the fourth mounting portion 44. As shown in FIG. 5, the diffraction grating unit 5 is fixed to the fourth mounting portion 44 using a resin adhesive B3 such as a thermosetting resin with a protruding portion 53c, which is a part of a yoke 53 described later, inserted into the arrangement hole 44b.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] The diffraction grating unit 5 includes a MEMS diffraction grating 51 (movable diffraction grating), a magnet 52, and a yoke 53. The MEMS diffraction grating 51 is formed in a substantially plate shape. The magnet 52 is disposed on the opposite side of the MEMS diffraction grating 51 from the QCL element 2. The MEMS diffraction grating 51 is fixed to the yoke 53, and the magnet 52 is housed within the yoke 53. As a result, the MEMS diffraction grating 51, the magnet 52, and the yoke 53 are integrated and form a single unit.

[0043] 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.

[0044] 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.

[0045] 6, the MEMS diffraction grating 51 includes a support portion 61, a pair of connecting portions 62, a movable portion 63, a diffraction grating portion 64, and a pair of coils 65 and 66. The MEMS diffraction grating 51 is configured as a MEMS device that oscillates the movable portion 63 around an axis A. A MEMS device is a device formed using microfabrication techniques (patterning, etching, etc.) known as MEMS technology, and includes semiconductor devices formed using semiconductor microfabrication techniques.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The yoke 53 amplifies the magnetic force of the magnet 52 and forms a magnetic circuit together with the magnet 52. The surface of the yoke 53 is blackened, for example, by zinc plating. As shown in Fig. 3, the yoke 53 has an inclined surface 53a, a lower surface 53b, a protrusion 53c, and a positioning surface 53d.

[0054] The inclined surface 53a is inclined with respect to the second end face 2b of the QCL element 2. By fixing the MEMS diffraction grating 51 on the inclined surface 53a, the normal N of the diffraction grating portion 64 of the MEMS diffraction grating 51 can be inclined with respect to the second end face 2b. In this example, the diffraction grating portion 64 is inclined so as to face one side in the Z-axis direction (toward the top wall 33). However, the diffraction grating portion 64 may be inclined so as to face the other side in the Z-axis direction (toward the bottom wall 31). The inclination angle of the inclined surface 53a (the angle with respect to the second end face 2b of the QCL element 2) is set depending on the oscillation wavelength of the QCL element 2, the number of grating grooves in the diffraction grating portion 64, the blazed angle, and the like. For example, when the oscillation wavelength is in the 7 μm band and the number of grooves is 150 / mm, the inclination angle of the inclined surface 53a is set to approximately 60 degrees.

[0055] 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.

[0056] The following surface 53b is a surface facing the upper surface 44a of the fourth mounting portion 44. A protruding portion 53c protruding downward is provided on the lower surface 53b. The positioning surface 53d is a surface intersecting in the X-axis direction so as to connect the inclined surface 53a and the lower surface 53b. In the present embodiment, the positioning surface 53d is orthogonal to the X-axis direction. That is, the positioning surface 53d is a surface parallel to the Y-axis direction and the Z-axis direction.

[0057] In the MEMS diffraction grating 51, when current flows through the coils 65 and 66, a Lorentz force is generated in a predetermined direction on the electrons flowing in the coils 65 and 66 by the magnetic field formed by the magnet 52 and the yoke 53. As a result, the coil 65 receives a force in a predetermined direction. Therefore, by controlling the direction or magnitude of the current flowing through the coil 65, the movable portion 63 (diffraction grating portion 64) can be swung around the axis A. Further, by flowing a current having a frequency corresponding to the resonance frequency of the movable portion 63 through the coils 65 and 66, the movable portion 63 can be swung at a high speed at the resonance frequency level (for example, at a frequency of 1 kHz or higher). Thus, the coils 65 and 66, the magnet 52, and the yoke 53 function as an actuator unit that swings the movable portion 63.

[0058] [Electrical Connection Configuration of QCL Element] Next, the electrical connection configuration between the QCL element 2 and the electrode terminal 10a will be described with reference to FIGS. 2 and 7. As shown in FIGS. 2 and 7, the electrode terminal 10a and the QCL element 2 (in this embodiment, the cathode and anode of the QCL element 2) are electrically connected via a wire W. The wire W is formed, for example, by wire bonding. The end of the wire W on the QCL element 2 side is located between the lens holder 7A and the lens holder 7B when viewed from a direction perpendicular to the opposing direction (in this embodiment, the X-axis direction) between the lens holders 7A and 7B (in this embodiment, a direction parallel to a plane perpendicular to the X-axis direction, such as the Y-axis direction or Z-axis direction). In this embodiment, as an example, the end of the wire W on the QCL element 2 side is connected to the QCL element 2 or the submount 8. Furthermore, the wire W is connected to the electrode terminal 10a at a position between the lens holder 7A and the lens holder 7B when viewed from a direction perpendicular to the opposing direction. In other words, the wire W is connected to the electrode terminal 10a at a position that does not overlap with the lens holder 7A or the lens holder 7B when viewed from a direction perpendicular to the opposing direction. In this embodiment, two electrode terminals 10a1 and 10a2 are provided at positions that do not overlap with the lens holder 7A or the lens holder 7B when viewed from a direction perpendicular to the opposing direction. The above-mentioned arrangement configuration is achieved by using these two electrode terminals 10a1 and 10a2. The electrode terminals 10a1 and 10a2 are the second and third electrode terminals 10a, counting from the light exit window 32a side, on the protruding wall 34 on the side on which the electrode pad 11 is provided with respect to the QCL element 2.

[0059] 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.

[0060] 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).

[0061] 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.) orthogonal to the opposing direction (X-axis direction).

[0062] Also, in the present embodiment, the temperature sensor 9 is also electrically connected to the electrode terminal 10a via wires W5a and W5b. Specifically, the wire W5 has 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 electrode terminals 10a located 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 with respect to the QCL element 2 (that is, the electrode terminals 10a arranged at positions that do not overlap with the lens holder 7A or the lens holder 7B when viewed from the direction orthogonal to the opposing direction). Thereby, the wires W5a and W5b that electrically connect the temperature sensor 9 and the electrode terminal 10a are also 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.) orthogonal to the opposing direction (X-axis direction).

[0063] [Electrical Connection Configuration of MEMS Diffraction Grating] Next, referring to FIG. 2, the electrical connection configuration between the electrode terminal 10a and the MEMS diffraction grating 51 will be described. As described above, the MEMS diffraction grating 51 has two electrode pads 71 and 73 electrically connected to the coils 65 and 66. More specifically, as shown in FIGS. 2 and 6, the electrode pads 71 and 73 are provided at one corner of the support 61 on the top wall 33 side (the upper left corner when the MEMS diffraction grating 51 is viewed from the front). Each electrode pad 71 and 73 is connected to a corresponding electrode terminal 10a (electrode terminals 10a3 and 10a4) via a corresponding wire W (wires W6 and W7). The electrode terminals 10a3 and 10a4 are the third and second electrode terminals 10a, counting from the side opposite the light exit window 32a, on the protruding wall 34 on the side on which the electrode pad 11 is provided relative to the QCL element 2.

[0064] 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.

[0065] 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.

[0066] In addition, in the present embodiment, the electrode pads 75 and 76 provided on the side opposite to the electrode pads 71 and 73 in the Y-axis direction also have the same electrical connection configuration as the electrode pads 71 and 73. That is, the 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 of the electrode pads 75 and 76 is connected to the corresponding electrode terminal 10a (electrode terminals 10a5 and 10a6) via the corresponding wire W (wires W8 and W9). The electrode terminals 10a5 and 10a6 are the electrode terminals 10a located second and third from the side opposite to the side where the light emission window 32a is provided 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 with respect to the bottom wall 31 are equal to or higher than the height positions of the electrode terminals 10a5 and 10a6 with respect to the bottom wall 31. The electrode terminal 10a5 is connected to the electrode pad 75 via a plurality (two in the present embodiment) of wires W8. Also, the electrode terminal 10a6 is connected to the electrode pad 76 via a plurality (two in the present embodiment) of wires W8. The number of each of the wires W8 and W9 may be one, but by using a plurality of wires W8 and W9 respectively, the electrical connection between each of the electrode terminals 10a5 and 10a6 and each of the electrode pads 75 and 76 can be ensured.

[0067] [Arrangement configuration of the lens holder] Next, with reference to FIGS. 3 and 4, the arrangement configuration of the lens holder 7B will be described. The distance d (see FIG. 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 FIG. 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 at a position higher (closer to the top wall 33) than the electrode terminals 10a1 and 10a2 to which the wires W1 and W3 are connected.

[0068] [Mounting structure of the lens holder to the mounting member] Next, with reference to FIGS. 3, 4, 5, and 8, the attachment structure of the lens holders 7A and 7B to the mount member 4 will be described in detail. More specifically, the structures of the mount member 4 and the lens holders 7A and 7B for appropriately photocuring the adhesive layers B1 and B2 will be described.

[0069] The lens holder 7A has an attachment surface 7Ab (first attachment surface) facing the upper surface 41a of the first mounting portion 41. The attachment surface 7Ab is joined to the upper surface 41a via the adhesive layer B1. At least a part of the attachment surface 7Ab of the lens holder 7A that is not joined to the upper surface 41a via the adhesive layer B1 is formed with a recess 7Ac. In the present embodiment, the recess 7Ac is formed at the central portion in the width direction (Y-axis direction) of the attachment surface 7Ab, and the attachment surface 7Ab is joined to the upper surface 41a via the adhesive layer B1 at both side portions of the recess 7Ac in the width direction (Y-axis direction). The recess 7Ac is provided so as to communicate with the space outside the lens holder 7A when the lens holder 7A is placed on the upper surface 41a. That is, the recess 7Ac is provided so that light can be guided from the space outside the lens holder 7A to the space inside the recess 7Ac when the lens holder 7A is placed on the upper surface 41a. As an example, the recess 7Ac is formed in a concave groove shape extending along the X-axis direction from one end portion in the X-axis direction (the end portion on the light-emitting window 32a side) of the attachment surface 7Ab to the other end portion (the end portion on the lens holder 7B side). In this case, light can be guided from the external spaces on both sides of the lens holder 7A in the X-axis direction to the space inside the recess 7Ac.

[0070] According to the above configuration, when irradiating the adhesive layer B1 with light for curing, light can be suitably guided from the space outside the lens holder 7A to the space inside the recess 7Ac. Thereby, the adhesive layer B1 can be appropriately cured. As a result, the fixing of the lens holder 7A to the upper surface 41a can be made more reliable.

[0071] A recess 41b is formed on the upper surface 41a of the first mounting portion 41 so as to face the recess 7Ac of the lens holder 7A. The recess 41b is formed in at least a portion of the upper surface 41a that is not bonded to the attachment surface 7Ab of the lens holder 7A via the adhesive layer B1. The recess 41b is provided so as to communicate with the space outside the first mounting portion 41 when the lens holder 7A is placed on the upper surface 41a. That is, the recess 41b is provided so as to be able to guide light from the space outside the first mounting portion 41 to the space within the recess 41b when the lens holder 7A is placed on the upper surface 41a. As an example, the recess 41b is formed in the center of the upper surface 41a in the width direction (Y-axis direction). As shown in FIGS. 3 and 8, the recess 41b extends in the X-axis direction from the end of the upper surface 41a on the light exit window 32a side to the end of a curved surface 421b (described later). In this case, light can be guided from the external space on the light exit window 32a side of the first mounting portion 41 in the X-axis direction to the space within the recess 41b.

[0072] According to the above configuration, when the adhesive layer B1 is irradiated with light to harden it, the light can be suitably guided from the space outside the first mounting portion 41 to the space inside the recess 41b. This allows the adhesive layer B1 to harden appropriately. As a result, the lens holder 7A can be more reliably fixed to the upper surface 41a.

[0073] The lens holder 7B has a mounting surface 7Bb (second mounting surface) facing the upper surface 43a of the third mounting portion 43. The mounting surface 7Bb is joined to the upper surface 43a via an adhesive layer B2. A recess 7Bc is formed in at least a part of the mounting surface 7Bb of the lens holder 7B that is not joined to the upper surface 43a via the adhesive layer B2. In the present embodiment, the recess 7Bc is formed at the center in the width direction (Y-axis direction) of the mounting surface 7Bb, and the mounting surface 7Bb is joined to the upper surface 43a via the adhesive layer B2 at both side portions of the recess 7Bc in the width direction (Y-axis direction). The recess 7Bc is provided so as to communicate with the space outside the lens holder 7B when the lens holder 7B is placed on the upper surface 43a. That is, the recess 7Bc is provided so that light can be guided from the space outside the lens holder 7B to the space inside the recess 7Bc when the lens holder 7B is placed on the upper surface 43a. As an example, the recess 7Bc is formed in a concave groove shape extending along the X-axis direction from one end portion in the X-axis direction (the end portion on the lens holder 7A side) to the other end portion (the end portion on the diffraction grating unit 5 side) of the mounting surface 7Bb. In this case, light can be guided from the external spaces on both sides of the lens holder 7B in the X-axis direction to the space inside the recess 7Bc.

[0074] According to the above configuration, when irradiating the adhesive layer B2 with light to cure it, light can be suitably guided from the space outside the lens holder 7B to the space inside the recess 7Bc. Thereby, the adhesive layer B2 can be cured appropriately. As a result, the fixing of the lens holder 7B to the upper surface 43a can be made more reliable.

[0075] On the upper surface 43a of the third mounting portion 43, a recess 43b is formed so as to face the recess 7Bc of the lens holder 7B. The recess 43b is formed in at least a part of the portion of the upper surface 43a that is not joined to the mounting surface 7Bb of the lens holder 7B via the adhesive layer B2. The recess 43b is provided so as to communicate with the space outside the third mounting portion 43 when the lens holder 7B is placed on the upper surface 43a. That is, the recess 43b is provided so that light can be guided from the space outside the third mounting portion 43 into the space within the recess 43b when the lens holder 7B is placed on the upper surface 43a. As an example, the recess 43b is formed at the center of the upper surface 43a in the width direction (Y-axis direction). Further, as shown in FIGS. 3 and 8, the recess 43b extends in the X-axis direction from the end of the upper surface 43a on the diffraction grating unit 5 side to the end of the curved surface 422b described later. In this case, light can be guided from the external space on the diffraction grating unit 5 side of the third mounting portion 43 in the X-axis direction into the space within the recess 43b.

[0076] According to the above configuration, when irradiating and curing the adhesive layer B2 with light, light can be preferably guided from the space outside the third mounting portion 43 into the space within the recess 43b. Thereby, the adhesive layer B2 can be appropriately cured. As a result, the fixing of the lens holder 7B to the upper surface 43a can be made more reliable.

[0077] Note that the above-described recesses 7Ac and 41b also function as regions for discharging the excess of the adhesive (i.e., the adhesive layer B1) applied between the lens holder 7A and the upper surface 41a. Similarly, the above-described recesses 7Bc and 43b also function as regions for discharging the excess of the adhesive (i.e., the adhesive layer B2) applied between the lens holder 7B and the upper surface 43a.

[0078] [Detailed Structure of the Second Mounting Portion of the Mounting Member] Next, with reference to FIGS. 3, 5, and 8, the structure of the second mounting portion 42 will be described in detail. More specifically, the structure of the second mounting portion 42 for appropriately photocuring the adhesive layers B1 and B2 will be described.

[0079] The second mounting portion 42 has an upper surface 42a, which is a mounting surface on which the QCL element 2 is mounted, a side surface 421 (first side surface), and a side surface 422 (second side surface). The side surface 421 faces the lens holder 7A. The side surface 421 intersects with the X-axis direction to connect the upper surface 42a of the second mounting portion 42 and the upper surface 41a of the first mounting portion 41. The side surface 422 is located on the opposite side from the side surface 421. In other words, the side surface 422 faces the lens holder 7B. The side surface 422 intersects with the X-axis direction to connect the upper surface 42a of the second mounting portion 42 and the upper surface 43a of the third mounting portion 43.

[0080] On the side surface 421, a notch 421a (first notch) extending from the upper surface 42a to the upper surface 41a of the first mounting portion 41 along the height direction (Z-axis direction) orthogonal to the upper surface 42a is formed. The notch 421a is formed at the end of the side surface 421 in the width direction (Y-axis direction) that is parallel to the upper surface 42a and orthogonal to the opposing direction (X-axis direction). In the present embodiment, two notches 421a having the same shape (symmetrical shape) are provided at each of both ends of the side surface 421 in the width direction (Y-axis direction). Such a notch 421a produces the following effects. That is, when viewed from the vertical direction (Z-axis direction), the gap between the second mounting portion 42 and the lens holder 7A can be enlarged by the notch 421a. Thereby, when irradiating the adhesive layer B1 with light to cure it, the light can be suitably guided to the adhesive layer B1 through the space formed by the notch 421a. More specifically, when fixing the lens holder 7A to the mount member 4 with the mount member 4 fixed in the package 3, it is necessary to irradiate light for curing the adhesive layer B1 from above the lens holder 7A through the opening provided with the top wall 33. In such a case, the notch 421a can suitably guide the light to the adhesive layer B1. As a result, the adhesive layer B1 can be appropriately cured, and the fixing of the lens holder 7A to the upper surface 41a can be made more reliable. Further, by providing the notch 421a at the end of the second mounting portion 42 (side surface 421) in the width direction (Y-axis direction), the above effects can be obtained without impairing the support stability of the QCL element 2 mounted at the substantially central portion in the width direction (Y-axis direction) of the second mounting portion 42. The distance between the side surface 421 and the lens holder 7A (distance in the X-axis direction) is, for example, 0.8 mm. The distance between the inner surface of the notch 421a (the portion farthest from the lens holder 7A) and the lens holder 7A is, for example, 1.15 mm.

[0081] The portion connected to the upper surface 41a of the first mounting portion 41 of the side surface 421 (i.e., the base portion of the portion of the second mounting portion 42 that protrudes with respect to the first mounting portion 41) is curved in the X-axis direction so as to approach the lens holder 7A as it goes from the upper surface 42a of the second mounting portion 42 toward the upper surface 41a of the first mounting portion 41 in the height direction (Z-axis direction). A curved surface 421b is formed. In the present embodiment, the curved surface 421b is provided in a portion of the side surface 421 where the notch 421a is not provided (i.e., the central portion of the side surface 421 in the Y-axis direction). According to such a curved surface 421b, when curing the adhesive layer B1, the light irradiated from above the lens holder 7A can be reflected by the curved surface 421b toward the space between the lens holder 7A and the upper surface 41a of the first mounting portion 41. Thereby, the irradiation efficiency of light to the space between the lens holder 7A and the upper surface 41a can be improved, and the adhesive layer B1 can be appropriately cured. As a result, the fixing of the lens holder 7A to the upper surface 41a can be made more reliable.

[0082] On the side surface 422, a notch 422a (second notch) extending from the upper surface 42a to the upper surface 43a of the third mounting portion 43 along the height direction (Z-axis direction) is formed. The notch 422a is formed at the end of the side surface 422 in the width direction (Y-axis direction). In the present embodiment, two notches 422a having the same shape (symmetrical shape) are provided at each of both ends of the side surface 422 in the width direction (Y-axis direction). Such a notch 422a produces the following effects. That is, when viewed from the vertical direction (Z-axis direction), the gap between the second mounting portion 42 and the lens holder 7B can be enlarged by the notch 422a. Thereby, when irradiating the adhesive layer B2 with light to cure it, the light can be suitably guided to the adhesive layer B2 through the space formed by the notch 422a. More specifically, when fixing the lens holder 7B to the mount member 4 with the mount member 4 fixed in the package 3, it is necessary to irradiate light for curing the adhesive layer B2 from above the lens holder 7B through the opening provided with the top wall 33. In such a case, the light can be suitably guided to the adhesive layer B2 by the notch 422a. As a result, the adhesive layer B2 can be appropriately cured, and the fixing of the lens holder 7B to the upper surface 43a can be made more reliable. Further, by providing the notch 422a at the end of the second mounting portion 42 (side surface 422) in the width direction (Y-axis direction), the above effect can be obtained without impairing the support stability of the QCL element 2 mounted at the substantially central portion of the second mounting portion 42 in the width direction (Y-axis direction). The distance between the side surface 422 and the lens holder 7B (distance in the X-axis direction) is, for example, 0.8 mm. The distance between the inner surface of the notch 422a (the portion farthest from the lens holder 7B) and the lens holder 7B is, for example, 1.15 mm.

[0083] The portion connected to the upper surface 43a of the third mounting portion 43 of the side surface 422 (i.e., the base portion of the portion of the second mounting portion 42 that protrudes with respect to the third mounting portion 43) is curved in the X-axis direction so as to approach the lens holder 7B as it goes from the upper surface 42a of the second mounting portion 42 to the upper surface 43a of the third mounting portion 43 in the height direction (Z-axis direction). A curved surface 422b is formed. In the present embodiment, the curved surface 422b is provided in a portion of the side surface 422 where the notch 422a is not provided (i.e., the central portion of the side surface 422 in the Y-axis direction). According to such a curved surface 422b, when the adhesive layer B2 is cured, the light irradiated from above the lens holder 7B can be reflected by the curved surface 422b toward the space between the lens holder 7B and the upper surface 43a of the third mounting portion 43. Thereby, the irradiation efficiency of light to the space between the lens holder 7B and the upper surface 43a can be improved, and the adhesive layer B2 can be appropriately cured. As a result, the fixing of the lens holder 7B to the upper surface 43a can be made more reliable.

[0084] In addition, the notches 421a and 422a facing each other in the X-axis direction are formed so as not to be continuous with each other. That is, as shown in FIG. 8, the notches 421a and 422a are independent of each other and are not connected in the X-axis direction. In other words, the width of the second mounting portion 42 (the length in the Y-axis direction) in the state where the notches 421a and 422a are formed is the same as the width of the second mounting portion 42 when the notches 421a and 422a are not formed. That is, the width of the second mounting portion 42 is not reduced by the formation of the notches 421a and 422a. According to the above configuration, while providing the notches 421a and 422a, it is possible to secure the width of the second mounting portion 42 disposed between the lens holder 7A and the lens holder 7B. Thereby, the second mounting portion 42 can function sufficiently as a barrier for suppressing the mixing of stray light components (that is, light that is not returned to the QCL element 2 via the lens 6B among the light reflected by the MEMS diffraction grating 51) into the laser light L emitted from the module via the lens 6A. That is, the effects of the notches 421a and 422a described above (that is, the improvement in the light irradiation efficiency to the adhesive layers B1 and B2) can be obtained without impairing the function as such a barrier.

[0085] [Mounting Structure of Diffraction Grating Unit] Next, with reference to FIGS. 3 and 8, the mounting structure of the yoke 53 (diffraction grating unit 5) to the mount member 4 will be described in detail. As described above, a protruding portion 53c is provided on the lower surface 53b of the yoke 53 facing the upper surface 44a of the fourth mounting portion 44. In addition, the fourth mounting portion 44 is provided with an arrangement hole 44b into which the protruding portion 53c is inserted. In the present embodiment, the arrangement hole 44b is configured as a through hole that penetrates the fourth mounting portion 44 vertically. However, the arrangement hole 44b may be configured as a non-through hole that opens only on the upper surface 44a of the fourth mounting portion 44.

[0086] As shown in FIG. 8, the length of the placement hole 44b in the X-axis direction is made longer than the length of the protruding portion 53c in the X-axis direction so that the protruding portion 53c can be slid in the X-axis direction with respect to the placement hole 44b. Further, as shown in FIG. 3, the length of the placement hole 44b in the Z-axis direction (which coincides with the thickness of the fourth mounting portion 44 in the present embodiment) is longer than the protruding length of the protruding portion 53c. Thereby, in a state where the resin adhesive B3 is disposed in the placement hole 44b, the entire protruding portion 53c is inserted into the placement hole 44b, and the lower surface 53b of the yoke 53 is configured to contact the upper surface 44a.

[0087] A wall surface 43c for positioning the yoke 53 (diffraction grating unit 5) is provided between the third mounting portion 43 and the fourth mounting portion 44. In the present embodiment, the upper surface 43a of the third mounting portion 43 is at a position higher than the upper surface 44a of the fourth mounting portion 44, and the wall surface 43c is formed by a side surface of the third mounting portion 43 (that is, a stepped surface connecting the upper surface 43a and the upper surface 44a). According to the above configuration, the stepped surface connecting the third mounting portion 43 and the fourth mounting portion 44 can function as the positioning wall surface 43c. That is, there is no need to separately provide a dedicated wall portion only for positioning the yoke 53. Thereby, the structure of the mount member 4 can be simplified, and thus the manufacturing cost of the mount member 4 can be reduced.

[0088] As shown in FIGS. 3 and 8, the yoke 53 (diffraction grating unit 5) is fixed to the fourth mounting portion 44 in a state where the protruding portion 53c is inserted into the placement hole 44b and the positioning surface 53d is in surface contact with the wall surface 43c. In the present embodiment, in this state, both ends of the protruding portion 53c in the X-axis direction do not contact either the end portion 44b3 on the third mounting portion 43 side of the placement hole 44b or the end portion 44b4 on the opposite side of the end portion 44b3. The position and length of the protruding portion 53c are adjusted. In the present embodiment, as an example, both ends of the protruding portion 53c in the X-axis direction have a curved shape with a convex curvature outward. Both end portions 44b3 and 44b4 of the placement hole 44b also have the same curved shape as both ends of the protruding portion 53c. By forming both ends of the protruding portion 53c in such a curved shape, when the protruding portion 53c is inserted into the placement hole 44b and slid in the X-axis direction, it is possible to prevent the protruding portion 53c from being caught on the inner surface of the placement hole 44b. As a result, the protruding portion 53c can be smoothly moved with respect to the placement hole 44b.

[0089] The placement hole 44b has a first portion 44b1 and a second portion 44b2. The first portion 44b1 is parallel to the upper surface 44a and has a width substantially equal to the width of the protruding portion 53c in the width direction (Y-axis direction) perpendicular to the facing direction (X-axis direction), and is a portion extending along the X-axis direction. The second portion 44b2 is a portion having a width larger than that of the first portion 44b1. In the present embodiment, the first portion 44b1 is formed in a portion excluding the central portion of the placement hole 44b in the X-axis direction (that is, the portion where the second portion 44b2 is formed) and the vicinity portions of both end portions 44b3 and 44b4 of the placement hole 44b in the X-axis direction (that is, the portions where the convex curved shape is formed outward). The second portion 44b2 is formed in the central portion of the placement hole 44b in the X-axis direction. That is, the second portion 44b2 is disposed at a position separated from the end portion 44b3 of the placement hole 44b. As an example, the second portion 44b2 is formed in a circular shape in a plan view (when viewed from the Z-axis direction). The gap between the protruding portion 53c and the placement hole 44b is filled with a resin adhesive B3.

[0090] In the above configuration, the first portion 44b1 functions as a guide portion for smoothly sliding the protruding portion 53c in the X-axis direction. Therefore, with the protruding portion 53c inserted into the placement hole 44b, the operation of sliding the diffraction grating unit 5 toward the third mounting portion 43 until the positioning surface 53d is in surface contact with the wall surface 43c can be performed easily and with high precision. As a result, the workability of mounting the diffraction grating unit 5 to the mount member 4 can be improved, and the mounting accuracy of the diffraction grating unit 5 can be enhanced.

[0091] In the above configuration, the second portion 44b2 can be made to function as a region for discharging the excess of the resin adhesive B3. Further, as shown in FIG. 8, in a state where the diffraction grating unit 5 is fixed to the fourth mounting portion 44, the end portion 53c1 of the protruding portion 53c on the side of the third mounting portion 43 is disposed within the first portion 44b1 of the placement hole 44b. If the end portion 53c1 of the protruding portion 53c were disposed within the second portion 44b2 that is wider than the protruding portion 53c, gaps would be formed on both sides of the end portion 53c1 of the protruding portion 53c in the Y-axis direction, and there would be a possibility that the end portion 53c1 of the protruding portion 53c would move in the Y-axis direction when positioning the diffraction grating unit 5 with the positioning surface 53d in surface contact with the wall surface 43c. On the other hand, by disposing the end portion 53c1 of the protruding portion 53c within the first portion 44b1 having substantially the same width as the protruding portion 53c as described above, movement of the end portion 53c1 of the protruding portion 53c in the Y-axis direction can be suppressed, and the mounting accuracy of the diffraction grating unit 5 can be improved.

[0092] Also, as shown in FIG. 8, in the Y-axis direction, the widths (lengths in the Y-axis direction) of the wall surface 43c and the positioning surface 53d are larger than the width of the protruding portion 53c. Here, as a method of positioning the diffraction grating unit 5 with respect to the fourth mounting portion 44, a method of abutting the end portion 53c1 of the protruding portion 53c against the end portion 44b3 of the placement hole 44b can be considered. However, by making the widths of the wall surface 43c and the positioning surface 53d larger than the width of the protruding portion 53c and positioning the diffraction grating unit 5 using the wall surface 43c and the positioning surface 53d, it is possible to position with higher accuracy at a larger width than when positioning the diffraction grating unit 5 using the protruding portion 53c and the placement hole 44b. Further, since the resin adhesive B3 is filled in the placement hole 44b, when positioning is performed using the protruding portion 53c and the placement hole 44b, there is a possibility that the resin adhesive B3 is slightly disposed between the end portion 53c1 of the protruding portion 53c and the end portion 44b3 of the placement hole 44b, and the position of the diffraction grating unit 5 may deviate from the designed position by that amount. By performing positioning using the wall surface 43c and the positioning surface 53d, the above problems can also be avoided.

[0093] [Method of manufacturing external resonance type laser module] Next, a method for manufacturing the laser module 1 will be described. First, the QCL element 2 and the MEMS diffraction grating 51 (diffraction grating unit 5) are arranged in the package 3 (first step). In the present embodiment, the following processing is executed. The QCL element 2 is soldered to the submount 8 with, for example, an AuSn-based solder material. Subsequently, the submount 8 mounted with the QCL element 2 is joined to the upper surface 42a of the second mounting portion 42 of the mount member 4 with, for example, an AuSn-based solder material. Further, the temperature sensor 9 and the electrode pad 11 are joined to the upper surface 42a of the mount member 4 via, for example, a resin adhesive or the like. Also, the pre-assembled diffraction grating unit 5 is fixed to the fourth mounting portion 44 using the resin adhesive B3 in a state where the protruding portion 53c of the yoke 53 is disposed in the arrangement hole 44b of the fourth mounting portion 44 of the mount member 4. Thereby, the mount member 4 is in a state of mounting all members other than the lens holders 7A and 7B. By fixing the mount member 4 in such a state onto the bottom wall 31 of the package 3 in a state where the top wall 33 is not attached, the first step is completed. Note that the mount member 4 may be first fixed onto the bottom wall 31 in a state where the above-described members are not mounted. In this case, the above-described members are mounted on the mount member 4 fixed to the bottom wall 31 through the opening on the top wall 33 side in the side wall 32.

[0094] 9, a method for fixing the diffraction grating unit 5 to the mount member 4 in the first step will be described in detail. First, a resin adhesive B3 made of a thermosetting resin is placed inside the placement hole 44b (placement step). Next, after the placement step, the protrusion 53c is inserted into the placement hole 44b (insertion step). As shown in S1 of FIG. 9, when the protrusion 53c is first inserted into the placement hole 44b, a gap may be formed between the positioning surface 53d and the wall surface 43c. Therefore, as shown in S2 of FIG. 9, after the insertion step, the diffraction grating unit 5 is slid in the X-axis direction relative to the fourth mounting portion 44 to bring the positioning surface 53d into surface contact with the wall surface 43c (face-contacting step). After the surface-contacting step, the resin adhesive B3 is hardened by heat treatment, thereby fixing the diffraction grating unit 5 to the fourth mounting portion 44. According to the above method, with the protrusion 53c inserted into the arrangement hole 44b, the diffraction grating unit 5 is slid until the positioning surface 53d comes into surface contact with the wall surface 43c, and then the resin adhesive B3 is thermally cured, thereby enabling the diffraction grating unit 5 to be positioned and fixed (mounted) to the mounting member 4 easily and with high precision.

[0095] 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).

[0096] In the second step, the wires W5a and W5b that electrically connect the temperature sensor 9 and the electrode terminals 10a are also formed by wire bonding. Also, the wires W6 to W9 that electrically connect the electrode pads 71, 73, 75, 76 of the MEMS diffraction grating 51 and the electrode terminals 10a3 to 10a6 are also formed by wire bonding. As described above, the height positions of the respective electrode pads 71, 73, 75, 76 are equal to or higher than the height positions of the electrode terminals 10a3 to 10a6. Thereby, when the height positions of the respective electrode pads 71, 73, 75, 76 are lower than the height positions of the electrode terminals 10a3 to 10a6 (that is, when the respective electrode pads 71, 73, 75, 76 are located on the back side (bottom wall 31 side) of the package 3), the workability of wire bonding to the respective electrode pads 71, 73, 75, 76 is significantly improved. By implementing the second step, as shown in FIG. 10, an intermediate product 1A in a state where members other than the lens holders 7A and 7B are arranged in the package 3 before the top wall 33 is attached is obtained.

[0097] Subsequently, the lens holder 7A holding the lens 6A and the lens holder 7B holding the lens 6B are arranged in the package 3 (third step). In the present embodiment, the lens holder 7A is joined to the upper surface 41a of the first mounting portion 41 of the mount member 4 via the adhesive layer B1. Also, the lens holder 7B is joined to the upper surface 43a of the third mounting portion 43 of the mount member 4 via the adhesive layer B2.

[0098] In the third step, with the driving voltage applied to the QCL element 2 via the electrode terminals 10a1 and 10a2 and the wires W1 to W4 to cause laser oscillation, the lens holders 7A and 7B are fixed in 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 emitted light from the QCL element 2. After the positions of the lens holders 7A and 7B are determined, the adhesive layers B1 and B2 are cured by irradiating light from above the lens holders 7A and 7B through the openings provided with the top wall 33. In the present embodiment, the above-described [mounting structure of the lens holder to the mounting member] and [detailed structure of the second mounting portion] enable the light irradiated from above the lens holders 7A and 7B to be suitably guided to the adhesive layers B1 and B2.

[0099] After completion of the third step, the top wall 33 is joined to the upper end portion of the side wall 32 by seam welding or the like, thereby obtaining the laser module 1 shown in FIG. 1.

[0100] [Operation and Effect] In the laser module 1, the protruding portion 53c of the diffraction grating unit 5 is inserted into the placement hole 44b of the fourth mounting portion 44 and the positioning surface 53d of the diffraction grating unit 5 is in surface contact with the positioning wall surface 43c, and then it is fixed to the fourth mounting portion 44. Thereby, the diffraction grating unit 5 can be accurately positioned with respect to the mounting member 4. Further, the protruding portion 53c is configured to be slidable in the X-axis direction in a state of being inserted into the placement hole 44b. Thereby, by performing a slide operation of inserting the protruding portion 53c into the placement hole 44b and pushing the diffraction grating unit 5 toward the third mounting portion 43 side, the diffraction grating unit 5 can be easily positioned. That is, in the laser module 1, the diffraction grating unit 5 can be easily and highly accurately mounted with respect to the mounting member 4. As a result, variations in the mounting accuracy of the diffraction grating unit 5 can be suppressed, and the yield can be improved when mass-producing the laser module 1.

[0101] Regarding the above effects, supplementary explanations will be given with reference to FIGS. 8 and 11. FIG. 11 is a diagram showing the mounting structure of the diffraction grating unit 5A according to the comparative example with respect to the mounting member 4. The yoke 153 of the diffraction grating unit 5A according to the comparative example has a protruding portion 153c having the same length as the arrangement hole 44b in the X-axis direction. That is, in the comparative example, the protruding portion 153c is not configured to be slidable in the X-axis direction with respect to the arrangement hole 44b. That is, the protruding portion 153c is configured to fit exactly into the arrangement hole 44b. Further, in order to ensure that the diffraction grating unit 5A can be reliably arranged on the fourth mounting portion 44, a slight gap (clearance) is provided between the side surface 153d (the surface corresponding to the positioning surface 53d) of the diffraction grating unit 5A and the wall surface 43c. In such a comparative example, the mounting accuracy (positioning accuracy) of the diffraction grating unit 5A with respect to the mounting member 4 depends on the machining accuracy of the protruding portion 153c and the arrangement hole 44b. The inventor performed the mounting of the diffraction grating unit with respect to the mounting member 20 times (for 20 products) for each of the mounting structures (embodiment) of FIG. 8 and the mounting structure (comparative example) of FIG. 11, and calculated the deviation angle (mounting error) of the diffraction grating unit for each mounting. Here, the "deviation angle" is the magnitude of the angle by which the line along which the positioning surface 53d (or side surface 153d) of the diffraction grating unit is displaced with respect to the design line (that is, the line along the Y-axis direction) when viewed from the Z-axis direction. As a result, in the comparative example, the average deviation angle of the 20 mountings was "0.52 degrees", whereas in the embodiment, the average deviation angle of the 20 mountings was "-0.05 degrees". That is, it was confirmed that by adopting the mounting structure (FIG. 8) of the present embodiment, the average deviation angle can be reduced to about one-tenth or less compared to the comparative example.

[0102] Also, in the laser module 1, the lens holder 7A is mounted on the first mounting portion 41 via an adhesive layer B1 made of a photocurable resin, and the lens holder 7B is mounted on the third mounting portion 43 via an adhesive layer B2 made of a photocurable resin. When a notch 421a is formed in the side surface 421, the notch 421a can increase the gap between the second mounting portion 42 (side surface 421) and the lens holder 7A. Thereby, when light is irradiated from above the lens holder 7A to cure the adhesive layer B1, the light can be suitably guided to the adhesive layer B1 through the space formed by the notch 421a. As a result, the adhesive layer B1 can be appropriately cured, and the fixing of the lens holder 7A to the upper surface 41a of the first mounting portion 41 can be made more reliable. Also, when a notch 422a is formed in the side surface 422, the notch 422a can increase the gap between the second mounting portion 42 (side surface 422) and the lens holder 7B. Thereby, when light is irradiated from above the lens holder 7B to cure the adhesive layer B2, the light can be suitably guided to the adhesive layer B2 through the space formed by the notch 422a. As a result, the adhesive layer B2 can be appropriately cured, and the fixing of the lens holder 7B to the upper surface 43a of the third mounting portion 43 can be made more reliable. As described above, according to the laser module 1, variations in the mounting accuracy of the optical members (lenses 6A, 6B) constituting the laser module 1 can be suppressed, so that the yield can be improved when mass-producing the laser module 1.

[0103] In addition, in the laser module 1, lens holders 7A and 7B are arranged on both sides of the QCL element 2. An electrode terminal 10a arranged along the inner wall surface of the package 3 is electrically connected to the QCL element 2 (in this embodiment, both the anode and cathode of the QCL element 2) by a wire W. The end of the wire W on the QCL element 2 side is located between the lens holder 7A and the lens holder 7B when viewed from a direction (e.g., the Y-axis direction or the Z-axis direction) perpendicular to the opposing direction (X-axis direction) in which the lens holder 7A and the lens holder 7B face each other. As a result, as shown in FIG. 7 , a configuration can be realized in which at least a portion of the wire W (including the end on the QCL element 2 side) is located in the space between the lens holder 7A and the lens holder 7B, between the electrode terminal 10a and the QCL element 2 (in this embodiment, both the upper surface of the QCL element 2 as the cathode and the submount 8 as the anode). As a result, it is possible to suitably suppress interference between the wire W for supplying power to the QCL element 2 and components inside the package 3 (especially the lens holders 7A and 7B arranged on both sides of the QCL element 2). As a result, the reliability of the laser module 1 and the workability during assembly are improved.

[0104] 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).

[0105] Also, the height position of the electrode terminal 10a with respect to the bottom wall 31 is higher than the height position of the QCL element 2 with respect to the bottom wall 31. According to the above configuration, it becomes easy to connect the wire W having an appropriate tension from the QCL element 2 to the electrode terminal 10a. As a result, the slack of the wire W can be preferably suppressed, and the interference between the wire W and the members in the package 3 can be more preferably suppressed. In the present 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) by relaying through the electrode pad 11. However, as will be described later, by arranging the electrode pad 11 at a height position intermediate between the QCL element 2 and the electrode terminal 10a, the above-described effect can be obtained. Further, in the case where the QCL element 2 and the electrode terminal 10a are directly connected by one wire without relaying the electrode pad 11, the above-described effect can of course be obtained.

[0106] Also, in the present embodiment, the wire W includes a wire W1 that connects the electrode terminal 10a1 and the electrode pad 11a, and a wire W2 that connects the electrode pad 11a and the QCL element (the upper surface of the QCL element 2 serving as a cathode). Similarly, the wire W includes a wire W3 that connects the electrode terminal 10a2 and the electrode pad 11b, and a wire W4 that connects the electrode pad 11b and the QCL element (the submount 8 serving as an anode). According to the above configuration, the lengths of the wires W1 to W4 can be shortened as compared with 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 wire-connected. Thereby, the slack of the wires W1 to W4 can be preferably suppressed, and the interference between the wires W1 to W4 and the members in the package 3 can be preferably suppressed.

[0107] Also, the electrode pads 11a and 11b are provided at positions between the lens holder 7A and the lens holder 7B when viewed from a direction (for example, the Y-axis direction, the Z-axis direction, etc.) orthogonal to the facing direction (X-axis direction). According to the above configuration, it is possible to realize a configuration in which the entire wires W1 to W4 pass 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 lengths of the respective wires W1 to W4 can be shortened. Thereby, the interference between the wires W1 to W4 and the members in the package 3 can be preferably suppressed.

[0108] Also, the height positions of the electrode pads 11a and 11b with respect to the bottom wall 31 are lower than the height positions of the electrode terminals 10a1 and 10a2 with respect to the bottom wall 31, and higher than the height position of the QCL element 2 with respect 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 be gradually lower. Thereby, it becomes easy to connect the wires W2 and W4 having an appropriate tension from the QCL element 2 to the electrode pads 11a and 11b, and it also becomes easy to connect the wires W1 and W3 having an appropriate tension from the electrode pads 11a and 11b to the electrode terminals 10a1 and 10a2. As a result, the slack of the wires W1 to W4 can be preferably suppressed, and the interference between the wires W1 to W4 and the members in the package 3 can be preferably suppressed.

[0109] 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.

[0110] 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.

[0111] Also, 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 on the side of 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, in the package 3, the lens holder 7B is arranged 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. Thereby, even if stray light that deviates from the lens 6B and travels toward the top wall 33 among the light reflected by the MEMS diffraction grating 51 enters between the top wall 33 and the lens holder 7B, it is difficult for the 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 FIG. 3) on the side where the MEMS diffraction grating 51 is arranged with respect to the lens holder 7B to the space S1 (see FIG. 3) on the side where the QCL element 2 is arranged with respect to the lens holder 7B can be effectively suppressed. As described above, it is possible to suppress the mixing of stray light components into the laser light L emitted from the QCL element 2 to the outside and appropriately ensure the laser quality.

[0112] Note that the top wall 33 and the surface 7a of the lens holder 7B are preferably arranged so as to face each other (be opposite to each other) with surfaces. More preferably, the top wall 33 and the surface 7a of the lens holder 7B are arranged so as to face each other in parallel. Further, 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. Also, 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 shape, the thickness t of the lens holder 7B is the length along the X-axis direction of the surface 7a of the lens holder 7B. Further, the thickness t of the lens holder 7B is preferably equal to or greater than the thickness along the optical axis direction (X-axis direction) of the lens 6B from the viewpoint of improving the stability of the lens 6B. Also, the distance d is preferably equal to or less than the thickness of the lens 6B.

[0113] Also, 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 is inclined with respect 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 value (for example, the minimum value, the maximum value, the average value, 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 direction) may be used as the distance d between the top wall 33 and the surface 7a of the lens holder 7B described above.

[0114] Also, 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 is inclined with respect 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 value (for example, the minimum value, the maximum value, the 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 distance d between the top wall 33 and the surface 7a of the lens holder 7B described above.

[0115] Also, 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, the statistical value (for example, the minimum value, the maximum value, the average value, etc.) of the distance between each position of 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 described above. Also, it is preferable that the same relationship as the relationship between the top wall 33 and the lens holder 7B described above holds for the space between the top wall 33 and the lens holder 7A.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.In addition, by using a MEMS diffraction grating 51 that is as large as possible with respect to the accommodation space in the package 3 (that is, a MEMS diffraction grating 51 in which the width of the movable part 63 is made as close as possible to the lateral width of the package 3 (the width along the Y-axis direction)), the loss of light fed back to the QCL element 2 can be reduced, and the high output of the laser module 1 can be achieved.

[0121] In addition, the MEMS diffraction grating 51 has a rectangular frame-shaped support part 61 that supports the diffraction grating part 64, and the electrode pads 71 and 73 are provided at one corner part on the top wall 33 side in the support part 61. In the present embodiment, the electrode pads 71 and 73 are provided at the upper left corner part (see FIG. 6) when the MEMS diffraction grating 51 is viewed from the front. According to the above configuration, electrical connection is achieved at the corner part of the support part 61, which is a position relatively far from the center of the diffraction grating part 64. Thereby, the generation of stray light caused by the wires W6 and W7 and the electrode pads 71 and 73 can be reduced, so that the reliability of the laser module 1 can be effectively improved. Hereinafter, the above will be described in detail. Usually, the movable part 63 is made as large as possible so that the entire beam light emitted from the second end face 2b of the QCL element 2 can be received by the diffraction grating part 64. However, when a high current is injected into the QCL element 2, the divergence angle of the beam light from the QCL element 2 becomes large, and it is not always possible to receive the entire beam light (total luminous flux) by the diffraction grating part 64. In such a case, the light that passes through the gap between the movable part 63 (diffraction grating part 64) and the support part 61 is specularly reflected on the surface of the magnet 52 arranged on the back side of the movable part 63, and there is a risk of generating stray light when hitting the electrode pads 71 and 73 and the wires W and the like. As described above, by arranging the electrode pads 71 and 73 at the corner part of the support part 61, which is a position relatively far from the center of the diffraction grating part 64, it is possible to suppress the light specularly reflected as described above from hitting the electrode pads 71 and 73 and the wires W and the like. Thereby, the generation of the above-described stray light can be effectively reduced.

[0122] 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).

[0123] 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).

[0124] [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.

[0125] In the above embodiment, the notches 421a and 422a are provided on both side surfaces (side surface 421 and side surface 422) of the second mounting portion 42. However, if it is desired to improve the light irradiation efficiency for one of the adhesive layers B1 and B2, the notches may be provided on only one of the side surfaces 421 and 422. For example, if the arrangement of components in the package 3 results in a difference between the light irradiation efficiency for the adhesive layer B1 and the light irradiation efficiency for the adhesive layer B2, only the notch (e.g., notch 421a) corresponding to the adhesive layer with lower irradiation efficiency (e.g., adhesive layer B1) may be provided. In the above embodiment, the notches 421a and 422a are provided at both end portions of the side surfaces 421 and 422 in the width direction (Y-axis direction). However, the notches may be provided on only one of the side surfaces 421 and 422 in the width direction. For example, if the arrangement of components within package 3 results in differences in irradiation efficiency between the areas of adhesive layers B1 and B2, it is possible to provide only a notch corresponding to the area of the adhesive layer with lower irradiation efficiency (for example, part of adhesive layer B1).

[0126] Furthermore, in the above embodiment, each notch 421a, 422a is formed in an L-shape at the end of each side surface 421, 422 in the width direction (Y-axis direction), but each notch 421a, 422a may be formed in a U-shape (groove-like) at a position spaced apart from the end of each side surface 421, 422 in the width direction.

[0127] Furthermore, in the above embodiment, the curved surfaces 421b, 422b are formed only in the portions where the notches 421a, 421b are not formed (the central portions in the width direction of each side surface 421, 422), but the curved surfaces 421b, 422b may also be formed at the boundary portions between the notches 421a, 421b and the upper surfaces 41a, 43a.

[0128] Alternatively, instead of the curved surface 421b, an inclined surface (i.e., a surface including a non-curved flat portion) may be provided that slopes toward the lens holder 7A in the facing direction (X-axis direction) as it moves from the upper surface 42a of the second mounting portion 42 to the upper surface 41a of the first mounting portion 41 in the height direction (Z-axis direction). Similarly, instead of the curved surface 422b, an inclined surface (i.e., a surface including a non-curved flat portion) may be provided that slopes toward the lens holder 7B in the facing direction (X-axis direction) as it moves from the upper surface 42a of the second mounting portion 42 to the upper surface 43a of the third mounting portion 43 in the height direction (Z-axis direction). [Explanation of symbols]

[0129] 1...External cavity laser module, 2...Quantum cascade laser element, 4...Mounting member, 5...Diffraction grating unit, 6A...Lens (first lens), 6B...Lens (second lens), 7A...Lens holder (first lens holder), 7Ab...Mounting surface (first mounting surface), 7Ac...Recess, 7B...Lens holder (second lens holder), 7Bb...Mounting surface (second mounting surface), 7Bc...Recess, 41...First mounting portion, 41a...Top surface (first mounting surface) , 41b...recess, 42...second mounting portion, 42a...top surface (second mounting surface), 43...third mounting portion, 43a...top surface (third mounting surface), 43b...recess, 51...MEMS diffraction grating (movable diffraction grating), 421...side surface (first side surface), 421a...notch (first notch), 421b...curved surface, 422...side surface (second side surface), 422a...notch (second notch), 422b...curved surface, B1...adhesive layer (first adhesive layer), B2...adhesive layer (second adhesive layer).

Claims

1. A quantum cascade laser element, a diffraction grating unit including a movable diffraction grating that constitutes an external resonator of the quantum cascade laser element, a first lens holder that is disposed on a side opposite to the side where the movable diffraction grating is located with respect to the quantum cascade laser element and holds a first lens that allows the light emitted from the quantum cascade laser element to pass therethrough, a second lens holder that is disposed between the quantum cascade laser element and the movable diffraction grating and holds a second lens that allows the light emitted from the quantum cascade laser element and the light that is returned from the movable diffraction grating to the quantum cascade laser element to pass therethrough, a mount member on which the quantum cascade laser element, the first lens holder, and the second lens holder are mounted, wherein the mount member has a first mounting portion, a second mounting portion, and a third mounting portion that are sequentially arranged from the first lens holder side toward the second lens holder side along an opposing direction in which the first lens holder and the second lens holder face each other, the first mounting portion has a first mounting surface on which the first lens holder is mounted via a first adhesive layer made of a photocurable resin, the third mounting portion has a third mounting surface on which the second lens holder is mounted via a second adhesive layer made of a photocurable resin, the second mounting portion, has a second mounting surface that is located at a position higher than the first mounting surface and the third mounting surface and on which the quantum cascade laser element is mounted, a first side surface that intersects the opposing direction so as to connect the second mounting surface and the first mounting surface, a second side surface that intersects the opposing direction so as to connect the second mounting surface and the third mounting surface, wherein at least one of the first side surface and the second side surface is formed with a notch that extends from the second mounting surface to the first mounting surface or the third mounting surface along a height direction perpendicular to the second mounting surface, an external resonance type laser module.

2. The quantum cascade laser element is mounted at a substantially central portion of the second mounting surface in a width direction that is parallel to the second mounting surface and perpendicular to the opposing direction, the notch includes a first notch formed at an end of the first side surface in a width direction that is parallel to the second mounting surface and perpendicular to the opposing direction, The external resonance type laser module according to Claim 1.

3. The quantum cascade laser element is mounted at a substantially central portion of the second mounting surface in the width direction that is parallel to the second mounting surface and orthogonal to the facing direction. The notch includes a second notch formed at an end portion of the second side surface in the width direction that is parallel to the second mounting surface and orthogonal to the facing direction. The external resonance type laser module according to claim 1 or 2.

4. The notch includes a first notch formed at an end portion of the first side surface in the width direction that is parallel to the second mounting surface and orthogonal to the facing direction, and a second notch formed at an end portion of the second side surface in the width direction, and the first notch and the second notch are formed so as not to be continuous with each other. The external resonance type laser module according to any one of claims 1 to 3.

5. The first lens holder has a first mounting surface joined to the first mounting surface via the first adhesive layer. At least a part of the portion of the first mounting surface that is not joined to the first mounting surface via the first adhesive layer is provided with a recess formed so as to communicate with the space outside the first lens holder in a state where the first lens holder is placed on the first mounting surface. The external resonance type laser module according to any one of claims 1 to 4.

6. The first lens holder has a first mounting surface facing the first mounting surface via the first adhesive layer. At least a part of the portion of the first mounting surface that is not joined to the first mounting surface via the first adhesive layer is provided with a recess formed so as to communicate with the space outside the first mounting portion in a state where the first lens holder is placed on the first mounting surface. The external resonance type laser module according to any one of claims 1 to 5.

7. On a portion of the first side surface connected to the first mounting surface, a surface that inclines or curves so as to approach the first lens holder in the facing direction as it goes from the second mounting surface toward the first mounting surface in the height direction is formed. The external resonance type laser module according to any one of claims 1 to 6.

8. The second lens holder has a second mounting surface joined to the third mounting surface via the second adhesive layer. At least a part of the portion of the second mounting surface that is not joined to the third mounting surface via the second adhesive layer is provided with a recess formed so as to communicate with the space outside the second lens holder in a state where the second lens holder is placed on the third mounting surface. The external resonance type laser module according to any one of claims 1 to 7.

9. The second lens holder has a second mounting surface that is joined to the third mounting surface via the second adhesive layer. At least a part of the portion of the third mounting surface that is not joined to the second mounting surface via the second adhesive layer is provided with a recess formed so as to communicate with the space outside the third mounting portion in a state where the second lens holder is placed on the third mounting surface. The external resonance type laser module according to any one of claims 1 to 8.

10. On the portion of the second side surface that is connected to the third mounting surface, a surface that is inclined or curved so as to approach the second lens holder in the facing direction as it goes from the second mounting surface toward the third mounting surface in the height direction is formed. The external resonance type laser module according to any one of claims 1 to 9.

Images