Quantum cascade laser device

Abstract

A quantum cascade laser device 1 has a light-absorbing cover element 7, which is arranged between an emission end face 6a of a quantum cascade laser element 6 and an exit window 8 of a housing 2. The emission end face 6a and an opposite face 5c of a submount 5 are flush with the cover element 7. The cover element 7 has an opening 18 at a position opposite an emission end face 6a. The opening 18 has a conical first opening part 21, the diameter of which increases from the side of one emission end face 6a to the side of the exit window 8, and a second opening part 22 with a fixed diameter that is not smaller than the smallest diameter of the first opening part 21.

Description

Technical field

[0001] The present invention relates to a quantum cascade laser device. background

[0002] Mid-infrared light (e.g., where the wavelength is on the order of 5 μm to 30 μm) is an important wavelength range, for example, in the field of spectroscopic measurement. Attention has focused on quantum cascade lasers (QCLs) as high-power semiconductor light sources in such a wavelength range (see, for example, the published documents of Japanese patent applications Nos. H08-279647, 2008-177366, 2008-60396 and H10-4242).

[0003] Quantum cascade laser elements are monopolar laser elements that utilize a layered structure formed by subbands in a semiconductor quantum well to generate light according to the electronic transitions between the subbands. The quantum cascade laser element achieves extremely efficient, high power output through the cascaded connection of multiple stages of light-emitting quantum well layers, each consisting of a quantum well structure and serving as the active region. The cascaded connection of the light-emitting quantum well layers is achieved by employing electron injection layers to inject electrons to higher emission levels and by alternating the stacking of the light-emitting quantum well layers and the injection layers. Summary

[0004] When using a quantum cascade laser element as a single-mode laser for continuous wave operation with distributed feedback for, for example, spectroscopic measurement, it is common to connect a submount mounted on the quantum cascade laser element with a heat sink and a temperature control element and to arrange it in a nitrogen-filled housing to form an assembly and to stabilize the oscillation wavelength.

[0005] Such an assembly uses a structure in which laser light emitted from one end face of the quantum cascade laser element exits through an exit window provided in the housing. If laser light from the other end face of the quantum cascade laser element is accidentally reflected within the housing, causing stray light to escape, noise can be generated during the spectroscopic measurement. While this noise can be suppressed by operating the quantum cascade laser element in pulsed mode, interference from the stray light can compromise the basis of the measurement results and reduce the measurement sensitivity in the case of continuous-wave operation.

[0006] Therefore, prior art experiments have focused on structures in which the elements within the housing are coated with a black layer to prevent the emission of scattered light, or on structures in which a cover element with a pinhole is attached to the quantum cascade laser element. However, in practice, it is difficult to apply the black coating to all elements within the housing in the first case, while in the second case, the radiation angles of laser light in the mid-infrared range cannot be managed, thus blocking the laser light that is intended to escape.

[0007] To solve the problems mentioned above, one objective of the present invention is to provide a quantum cascade laser device that can prevent the escape of scattered light while maintaining the emission efficiency of the laser light.

[0008] To solve the aforementioned problems, the quantum cascade laser device, according to one aspect, comprises a hollow housing with an exit window for emitting laser light to the outside; wherein a heat sink is arranged in the housing, a submount is attached to the heat sink, a quantum cascade laser element is mounted on the submount, and a cover element opposite the submount is arranged between an emission end face of the quantum cascade laser element and the exit window and has a light absorption property for the laser light emitted by one emission end face and the other emission end face of the quantum cascade laser element; wherein one emission end face of the quantum cascade laser element and a surface opposite the cover element in the submount are flush with each other;the cover element has an opening located opposite one emission end face to direct laser light through it towards the exit window; the opening having a conical first opening part whose diameter increases from the side of one emission end face to the side of the exit window, and a second opening part with a fixed diameter that is not smaller than the smallest diameter of the first opening part on the side of one emission end face of the first opening part.

[0009] In this quantum cascade laser device, the light-absorbing cover element between one emission end face of the quantum cascade laser element and the exit window absorbs stray laser light within the housing, thus preventing stray light from escaping. The cover element has an opening located opposite one emission end face. Because the opening has a conical first part, the cover element prevents the laser light from being blocked, even if the laser light emitted from one emission end face has a large radiation angle, thus preserving the emission efficiency of the laser light exiting the window.Since the second aperture section, with a fixed diameter no smaller than the smallest diameter of the first aperture section, is located on the side of one emission end face of the first aperture section, that emission end face can be positioned closer to the aperture without coming into contact with the cover element. Even if the aperture diameter of the first aperture section is reduced, the cover element is prevented from blocking the laser light, thus suppressing the outward escape of stray light while maintaining the emission efficiency of the laser light.

[0010] The cover element can be in contact with the surface opposite the cover element in the submount, while one emission end face of the quantum cascade laser element is located at one end of the second aperture portion in the cover element. In this case, one emission end face can be positioned closer to the aperture portion. This allows for even more reliable prevention of stray light escaping.

[0011] The opening can further comprise a third opening section for positioning a lens on the side of the exit window of the first opening section. This allows the lens to be positioned with a simple structure.

[0012] The cover element can have an extended portion that stretches along a surface for mounting the quantum cascade laser element in the submount, on the heat sink side of the other emission end face. In this case, the laser light emitted from the other emission end face can be efficiently absorbed by the extended portion of the cover element. This further prevents stray light from escaping.

[0013] The heat sink can have an opposing surface that faces the other emission end face of the quantum cascade laser element in an inclined state. This prevents the laser light emitted from the other emission end face from being reflected back towards the quantum cascade laser element. This stabilizes the operation of the quantum cascade laser element.

[0014] The housing can consist of a lower main part and a lid part with the exit window, the lid part having a black inner surface. In this case, the inner surface of the lid part absorbs stray light, thus preventing the escape of stray light even more reliably.

[0015] The entire inner surface of the housing can be black. In this case, the entire inner surface of the housing absorbs stray light, thus preventing the escape of stray light even more reliably.

[0016] The housing can be filled with dry nitrogen. This prevents the formation of condensation inside the housing.

[0017] The quantum cascade laser element can be a distributed feedback continuous-wave laser. When the quantum cascade laser element is used for spectroscopic measurements, interference from scattered light can compromise the basis of the measurement results and thus reduce the measurement sensitivity. The structure described above prevents scattered light from escaping, thereby advantageously suppressing interference from scattered light during the spectroscopic measurement.

[0018] As explained above, one aspect of the present invention can prevent stray light from escaping while maintaining the emission efficiency of the laser light. Brief description of the drawings

[0019] Fig. Figure 1 is a sectional view of an embodiment of a quantum cascade laser device;

[0020] Fig. Figure 2 is a graph of an example of the radiation angles of the laser light emitted by a quantum cascade laser element;

[0021] Fig. 3 is a diagram of the transmittance characteristics of synthetic resin materials in a mid-infrared range;

[0022] Fig. Figure 4 is an enlarged cross-sectional view of a main part of the quantum cascade laser device made of Fig. 1;

[0023] Fig. 5 is a diagram of the results of an experiment on scattered light emission; and

[0024] Fig. Figure 6 is a sectional view of a modified example of the quantum cascade laser device. Detailed description

[0025] Preferred embodiments of the quantum cascade laser device according to the present invention are described below with reference to the drawings.

[0026] Fig. Figure 1 is a sectional view of an embodiment of the quantum cascade laser device. As shown in this drawing, the quantum cascade laser device comprises 1 a case 2 , a temperature control element 3 , a heat sink 4 , a submount 5 , a quantum cascade laser element 6 and a cover element 7 The quantum cascade laser device 1 It serves, for example, as a light source for spectroscopic measurement and uses a structure in which laser light L (see Fig. 4), which is generated by the quantum cascade laser element 6 is emitted from an exit window 8 of the case 2 exits.

[0027] The case 2 It has an essentially rectangular, parallel-flat shape, made of, for example, a metal. The housing 2 consists of a lower main part 9 and a lid part10 The main part 9 has a thick, flat base section 11 and a side panel 12 on, which is separated from the bottom part 11 raises.

[0028] The lower end of the side panel 12 For example, it is permanently attached to a surface side of the base part by welding. 11 connected. Feed-through terminals, conductors and the like, used to control the temperature control element. 3 and the quantum cascade laser element 6 They can be used as needed, for example on the side panel 12 arranged. The bottom part 11 is slightly larger than the lid part 10 and has a projecting section that is bordered by four surfaces of the side part 12 in the top view of the casing 2 It protrudes outwards. This ensures the mounting stability of the quantum cascade laser device. 1 .

[0029] The lid part 10It has a flat shape that is thinner than the bottom part. 11 is. A rim part of the lid part 10 For example, it is permanently attached to the front end of the side panel by welding. 12 connected. The housing 2 has an interior S, which is divided by the main part 9 and the lid part 10 It is hermetically sealed. The interior space S, for example, is filled with dry nitrogen, which prevents condensation from forming inside the housing. 2 forms. Near the center of the lid part. 10 is the round exit window 8 trained so that the quantum cascade laser element 6 emitted laser light L from the housing 2 can escape. Examples of materials suitable for the exit window. 8 Ge and ZnSe are among those that can be used.

[0030] The inner surfaces of the housing 2, i.e., the part that forms the interior space S in one area of ​​the floor part 11 facing the inner surface of the side panel 12 and the inner surface of the lid part 10 They are all finished in black. This black finish can be achieved, for example, by applying a black synthetic resin coating containing carbon. Such a black finish gives the inner surfaces of the housing a black appearance. 2 a light absorption property for the laser light L emitted by the quantum cascade laser element 6 is emitted.

[0031] The aforementioned temperature control element 3 , the heat sink 4 , the submount 5 , the quantum cascade laser element 6 and the cover element 7 are located in the interior S of the housing 2 contain.

[0032] The temperature control element 3is a part that controls the temperature of the quantum cascade laser element 6 according to an external control signal, in order to adjust the oscillation wavelength of the quantum cascade laser element. 6 to stabilize. As the temperature control element 3 For example, a Peltier element is used. A surface 3a of the temperature control element 3 for example, by soldering to the bottom part 11 of the case 2 attached.

[0033] The heat sink 4 , also known as a package heat sink, is a part through which the in the quantum cascade laser element 6 generated heat in the direction of the temperature control element 3 is dissipated. The heat sink 4 It consists of a material that has excellent thermal conductivity, such as copper. A surface 4a of the heat sink 4for example, by soldering on the other surface 3b of the temperature control element 3 attached. The heat sink 4 features a mounting part 13 on which the submount 5 is mounted, a positioning part 14 for positioning the submount 5 on the mounting part 13 , and an extension 15 , which differ from the assembly part 13 extends.

[0034] The assembly part 13 has a mounting surface 13a on, which are essentially parallel to a surface 4a of the heat sink 4 trained. The positioning part 14 rises essentially parallel to the side part 12 of the case 2 from the lower end of the mounting surface 13a and has a planting area 14a on, at which an end surface 5a of the submount 5 is pending. The extension 15has an opposite surface 15a on, which is an emission end surface 6b (which will be explained later) of the quantum cascade laser element 6 at a position opposite, one step lower than the front end of the mounting surface 13h is. The opposite surface 15a is at an obtuse angle to the emission end surface 6b (the optical axis of the laser light L from the emission end surface 6b ) inclined, so that they increase in distance from the emission end surface 6b further away from the optical axis of the emission end surface 6b is removed. Preferably the opposite surface. 15a as well as the inner surfaces of the case 2 trained illegally.

[0035] The submount 5 , also known as laser heat sink, is a part on which the quantum cascade laser element is mounted. 6is attached and which is in the quantum cascade laser element 6 generated heat in the direction of the heat sink 4 derives. The submount 5 It has an essentially rectangular, parallel-surface shape made of a material with excellent thermal conductivity, such as copper. The submount 5 is on the mounting surface 13a mounted so that an end surface 5a at the planting area 14a it rests against the heat sink and is secured, for example, by screws. 4 fixed.

[0036] The other end part of the submount 5 is a mounting surface 5b , at which the quantum cascade laser element 6 is attached. The mounting surface 5b is equipped with a step-side surface 13b between the mounting surface 13a and the opposite surface 15a at a position parallel to the exit window 8corresponds to the area opposite the mounting surface. 13a in the submount 5 is an opposite surface 5c , which belong to the cover element 7 opposite. The opposite surface 5c is with a front end surface 14b of the positioning part 14 Perfectly level. The electrode pads, which are used to control the quantum cascade laser element. 6 are used, which are connected to the electrode pads and the like, which is not shown, is also attached to the mounting surface. 5b attached.

[0037] The quantum cascade laser element 6 is a monopolar laser element that utilizes a plane structure formed by subbands in a semiconductor quantum well structure to generate light according to the electronic transitions between the subbands. The quantum cascade laser element 6It operates in continuous wave mode and features a distributed feedback structure that includes a diffraction grating to generate a longitudinal single-mode spectrum as a light source for spectroscopic measurement.

[0038] The quantum cascade laser element 6 is on the mounting surface 5b of the submount 5 attached so that one emission end surface 6a and the other emission end surface 6b the exit window 8 or the opposite surface 15a of the heat sink 4 opposite. The emission end surface 6a is with the front end surface 14b of the positioning part 14 in the heat sink 4 and the opposite surface 5c of the submount 5 Flight level. "Flight level" here means that the area from the emission end surface 6a emitted laser light L not on the mounting surface 5bthe submounts 5 encounters.

[0039] In the distributed feedback structure, only one wavelength corresponding to the period of the diffraction grating is selectively fed back to achieve a single-mode oscillation. In such a structure, an antireflective coating is applied to one emission end surface. 6a (or both on one emission end surface 6a as well as the other emission end surface 6b ) of the quantum cascade laser element 6 applied to avoid generating further Fabry-Perot modes. On the other emission end surface 6b A high-reflective coating can be applied to reduce stray light from the laser light L inside the housing. 2 to suppress

[0040] If the reflectivity of the emission end surface 6bWhile the high reflectivity is increased by the high-reflective coating, competition with other modes is more likely to occur, potentially preventing the achievement of stable single-mode oscillation. Therefore, the emission end surface is 6b of the quantum cascade laser element 6 Leave as a split end surface without the high-reflective coating.

[0041] The quantum cascade laser element 6 It also features a refractive index guide structure in which a light-emitting layer is arranged between cladding layers, while light that has propagated along the waveguide is directed from the end faces of the element (i.e., the emission end face). 6a , 6b) is beamed into free space. Since this refractive index guide structure can be considered a slit where the thickness portion of the active layer is an opening, the laser light L beamed into free space has a fixed radiation angle due to a refractive effect of the light, as in the case when light emerges from a tiny slit.

[0042] The refraction of light becomes even more pronounced with longer wavelengths. For spectroscopic measurements, the restriction to the transverse single mode exists partly to enhance the refraction of light. For example, the emission angle is approximately 30° (±15° if the perpendicular to the end face is considered 0°) in the near-infrared range, which serves as a communication wavelength band, but is 100° or more in the mid-infrared range with a wavelength of 3 μm or longer. Fig. Figure 2 is a diagram of a far-field pattern in one growth direction of a distributed feedback quantum cascade laser element with a wavelength of 7.2 μm. The diagram shows data obtained by fitting actual measured values ​​with a Gaussian function, indicating that the emission angle extends beyond 140°.

[0043] To extract the laser light L from the emission end surface 6a of the quantum cascade laser element 6 To obtain this, it is therefore necessary to clean the inside of the case. 2 to design it in such a way that the laser light with a wide emission angle is not blocked. The quantum cascade laser element 6 In contrast, the laser light L radiates from the emission end surface. 6b with a radiation angle similar to that of the emission end surface 6a from. Therefore, this can be determined from the emission end surface. 6b laser light L was emitted randomly in the housing 2be reflected, so that stray light from the exit window 8 Scattered light can escape and cause noise at the time of spectroscopic measurement. Therefore, a structure is needed that prevents the escape of scattered light while simultaneously reducing the emission efficiency L of the laser light from the exit window. 8 can be obtained.

[0044] The cover element 7 is a part that diffuses light within the housing 2 suppressed. As in Fig. The cover element is shown in Figure 1. 7 opposite the submount 5 , so that there is between an emission end surface 6a of the quantum cascade laser element 6 and the exit window 8 is arranged. The cover element 7 has a planar main part 16 on, which has an opening 18 is provided with a feature through which the laser light L is directed towards the exit window. 8can be accessed, as well as a planar extension part 17 , which is from a terminal part of the main part 16 at substantially right angles to the main part 16 branches off.

[0045] The main part 16 is arranged so that each has a front end face 14b of the positioning part 14 in the heat sink 4 and the opposite surface 5c of the submount 5 comes into contact at a position where the opening 18 the one emission end surface 6a opposite. The heat sink 4 has a mounting surface that is aligned with the opposite surface 5c of the submount 5 in the depth direction Fig. 1. The surface is level, while the main part 16 firmly attached to the mounting surface of the heat sink by screwing or gluing. 4 is attached. An end surface 16a of the main part16 is with the outer surface of the positioning part 14 in the heat sink 4 level with the ground, whereas the other end surface 16b of the main part 16 from the mounting surface 5b of the submount 5 protrudes, so that it is located on one side of the extension 15 of the heat sink 4 beyond the position of the exit window 8 is located.

[0046] The extended part 17 extends from the other end of the main part 16 to the opposite surface 15a of the heat sink 4 essentially parallel to the mounting surface 5b of the submount 5 , however, is distinguished from the quantum cascade laser element 6 separated. A front end face 17a of the extended part 17 is located on the opposite side of the surface 15a of the heat sink 4behind the position of the other emission end surface 6b of the quantum cascade laser element 6 The extended part 17 can be thicker than the main part 16 be.

[0047] As material for the cover element 7 Preferably, one with a light absorption property for wavelengths in the mid-infrared range is used. Fig. Figure 3 is a diagram of the transmission characteristics of synthetic resin materials in the mid-infrared range. The examples shown in the diagram, whose abscissa and ordinate respectively indicate the wavenumber (inverse of the wavelength) and transmittance, plot the transmission characteristics of acrylic (Graph A), polyoxymethylene (POM) (Graph B), and polyetheretherketone (PEEK) (Graph C).

[0048] The results in the diagram suggest that the POM or PEEK resin is preferably used as the material for forming the cover element in the mid-infrared range (where the wavelengths range, for example, from 3 μm to 11 μm). 7 The material is selected based on sufficient transmittance across the entire wavelength range. PEEK resin is particularly preferred due to its heat resistance, chemical resistance, mechanical strength, electrical insulation, ease of processing, and similar properties. Preferably, the front surface of the cover element... 7 as well as the inner surfaces of the case 2 trained illegally.

[0049] As material for forming the cover element 7 Not only synthetic resins but also ceramic materials can be used. In this case, the cover element can be... 7bformed from Al2O3 or AlN, with an anti-reflective coating subsequently being applied to the front surface.

[0050] As in Fig. As shown in 4, the opening 18 in the main part 16 specifically, a first opening section 21 , a second opening part 22 and a third opening part 23 The first part of the opening 21 It is located in the middle of the main part in the thickness direction and has a conical shape, the diameter of which is determined by an emission end surface. 6a towards the side of the exit window 8 (see Fig. 1) becomes larger.

[0051] The cone angle of the first opening part 21 is determined according to the emission angle L of the laser light emitted from the emission end surface. 6ais emitted. If the emission angle of the laser light L is, for example, 140°, the cone angle of the first aperture part becomes 21 at 140° (±70° when the perpendicular direction to the emission end surface 6a (taken as 0°) or more. If the thickness of the main part 16 of the cover element 7 If the diameter is 0.8 mm, the smallest diameter of the first aperture part (the diameter on the side of the emission end surface) will be 6a ) for example, set to approximately 1.5 mm ±0.5 mm. The length of the first opening part 21 in the thickness direction of the main part 16 (in the direction perpendicular to the emission end surface 6a ) is set to approximately 0.3 mm, for example.

[0052] The second opening part 22 is located on the side of the emission end surface 6aand is designed with a fixed diameter that is not smaller than the smallest diameter of the first opening part. 21 is. The diameter of the second opening 22 For example, the length of the second opening part is approximately 2.6 mm. 22 in the thickness direction of the main part 16 For example, it is set to approximately 0.2 mm.

[0053] The third opening part 23 It is located on the side of the exit window. 8 and is designed with a fixed diameter that is larger than the largest diameter of the second opening part. 22 is (the diameter on the side of the exit window) 8 ). The third opening part 23 It serves to position a lens, wherein in this embodiment a plano-convex lens 24 it is used therein. The laser light L from the emission end surface 6apasses through the opening at a predetermined radiation angle 18 , is then reflected by the plano-convex lens 24 aligned with parallel light and exits through the exit window 8 from the case 2 out. The area of ​​the plano-convex lens 24 on the side of the cover element 7 is preferably provided with an anti-reflective coating. The length of the third opening part 23 in the thickness direction of the main part 16 For example, it is set to approximately 0.3 mm.

[0054] As explained above, the light-absorbing cover element 7 between an emission end surface 6a of the quantum cascade laser element 6 and the exit window 8 in the quantum cascade laser device 1 arranged. As in Fig. As shown in section 4, the cover element absorbs 7Scattered light resulting from the reflection of the laser light L at the opposite surface 15a of the heat sink 4 is caused after it has passed from the other emission end surface 6b emitted, and scattered light resulting from the reflection of the laser light L on the inner surfaces of the housing 2 This is caused by preventing the escape of scattered light. By suppressing the escape of scattered light, the problem of scattered light interference affecting the basis of measurement results and thus reducing measurement sensitivity is advantageously eliminated when the quantum cascade laser element is used. 6 is of the type of continuous wave laser with distributed feedback used for spectroscopic measurement.

[0055] The cover element 7 is with an opening 18 at a position opposite an emission end surface 6a provided. Since the opening 18with the cone-shaped first opening part 21 If provided, it can prevent the cover element from 7 the laser light L is blocked, even if it is coming from the exit window 8 The emitted laser light L has a large radiation angle, so that the emission efficiency of the laser light L from the exit window 8 can be obtained.

[0056] In contrast, the second opening part 22 , which is designed with a fixed diameter that is not smaller than the smallest diameter of the first opening part 21 is, on the side of the emission end surface 6a of the first opening part 21 arranged. This allows the emission end surface to be 6a near the opening 18 can be arranged without interfering with the cover element 7 to come into contact. Even if the opening diameter of the first opening part 21When the cover element is reduced in size, it is prevented from... 7 The laser light L is blocked, thereby suppressing the escape of scattered light to the outside while maintaining the emission efficiency of the laser light L. Through the second aperture part 22 , whose diameter is not smaller than the smallest diameter of the first opening part 21 Furthermore, it can prevent the emission end surface from being affected. 6a during the installation of the cover element 7 on the submount 5 with the cover element 7 comes into contact.

[0057] In the quantum cascade laser device 1 The main part 16 of the cover element 7 with the opposite surface 5c of the submount 5 in contact while an end surface 6a of the quantum cascade laser element 6 at the opening end of the second opening part 22in the cover element 7 is arranged. This allows one emission end surface to be 6a closer to the opening 18 be ordered.

[0058] Fig. Figure 5 is a diagram of the results of an experiment on scattered light emission. In this experiment, a high-reflectivity coating was applied to an emission end surface. 6a of the quantum cascade laser element 6 applied so that the laser light L only from the other emission end surface 6b was emitted, and which is from the exit window 8 The emitted intensity of the laser light L was measured as scattered light emission, while the aperture diameter (the smallest diameter) of the first aperture part 21 was changed. The results in the diagram show that the stray light emission, which was 26 mW, was the cover element. 7 was not appropriate, gradually decreased as the opening diameter of the first opening part21 by attaching the cover element 7 was narrowed.

[0059] The stray light emission was approximately 16 mW and approximately 9.8 mW when the aperture diameter of the first aperture part 21 It had a size of 6 mm and 4 mm, respectively. The stray light output was approximately 4.6 mW and approximately 1.73 mW, respectively, when the aperture diameter of the first aperture part was... 21 It had a size of 2.6 mm or 1.6 mm. The stray light output was approximately 1.55 mW when the aperture diameter of the first aperture part was... 21 had a size of 0.8 mm. This was from one emission end surface. 6a emitted laser light L appears from the opening 18 to be blocked if the opening diameter of the first opening part 21 is less than 1 mm. Therefore, the opening diameter of the first opening part must be 21in an area of ​​at least 1 mm but not more than 2 mm, and can then advantageously prevent the escape of scattered light to the outside and maintain the emission efficiency of the laser light L.

[0060] In the quantum cascade laser device 1 The opening indicates 18 Furthermore, a third opening part 23 for arranging the plano-convex lens 24 on the side of the exit window 8 of the first opening part 21 on. Thus, the plano-convex lens can 24 They are positioned with a simple structure. The third opening part... 23 A positioned lens does not necessarily have to be a plano-convex lens. 24 be, but can be according to the specifications of the quantum cascade laser device 1 will be changed.

[0061] In the quantum cascade laser device 1 The cover element 7the extended part 17 on, which is located on the side of the heat sink 4 the other emission end surface 6b of the quantum cascade laser element 6 along the mounting surface 5b of the submount 5 extends. The extended part 17 of the cover element 7 can this be from the other emission end surface? 6b The emitted laser light L is efficiently absorbed. This makes it even more reliable to prevent stray light from escaping.

[0062] In the quantum cascade laser device 1 The heat sink has the opposite surface 15a on, which the other emission end surface 6b of the quantum cascade laser element 6 in an inclined state opposite each other. Since the opposite surface 15a If inclined, it can prevent the emission from the other emission end surface. 6bemitted laser light L regularly in the direction of the quantum cascade laser element 6 is reflected and returns there (see Fig. 4) This allows the operation of the quantum cascade laser element 6 to be stabilized. In this embodiment, the opposite surface is 15a It is black and can therefore suppress the influence of reflected light even more reliably.

[0063] In the quantum cascade laser device 1 are all the internal surfaces of the housing 2 The casing is black. This prevents stray light from escaping all internal surfaces of the housing. 2 absorbed and can be prevented from escaping even more reliably. Instead of all internal surfaces of the housing. 2 It can also just be the inside of the lid part. 10 black finish. If the inside of the lid part 10, which is equipped with the exit window and is black, it can efficiently absorb scattered light.

[0064] Fig. Figure 6 is a sectional view of the quantum cascade laser device according to a modified example. As shown in this drawing, the quantum cascade laser device deviates 1 According to the modified embodiment, it differs from the first embodiment in that the cover element 7 not with the extended part 17 is equipped. More precisely, it is located in the quantum cascade laser device. 1 the main part 16 in the cover element 7 over the mounting surface 5b of the submount 5 outwards, so that the other end surface 16b to the position of the front end surface 15b the extension 15 of the heat sink 4 about the position of the exit window 8extends beyond. In such a structure, this can be from the other emission end surface. 6b of the quantum cascade laser element 6 laser light emitted through the cover element 7 This allows for efficient absorption and prevents the escape of stray light. Furthermore, this allows for adjustments to the shape of the cover element. 7 to be simplified. List of reference symbols 1 : Quantum cascade laser device; 2 : Housing; 4 : Heat sink; 5 : Submount; 5b : Mounting surface; 5c : opposite surface; 6 : Quantum cascade laser element; 6a : an emission end surface; 6b : the other emission end surface; 7 : Cover element; 8 Exit window; 9 : Main part; 10 : Lid part; 15a : opposite surface; 17 : extended part; 18 : Opening; 21: first opening part; 22 : second opening part; 23 : third opening part; L: laser light. QUOTES INCLUDED IN THE DESCRIPTION

[0065] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0066] JP 08-279647

[0002] JP 2008-177366

[0002] JP 2008-60396

[0002] JP 10-4242

[0002]

Claims

[1] Quantum cascade laser device comprising a hollow housing with an exit window for emitting laser light to the outside; which is located inside the housing: a heat sink; a submount that is attached to the heat sink; a quantum cascade laser element mounted on the submount; and a cover element opposite the submount, which is to be arranged between an emission end face of the quantum cascade laser element and the exit window and has a light absorption property for the laser light emitted by one emission end face and the other emission end face of the quantum cascade laser element; wherein the emission end surface of the quantum cascade laser element and a surface opposite the cover element in the submount are flush with each other; the cover element has an opening that is positioned opposite one emission end face in order to direct laser light through it towards the exit window; wherein the opening has a conical first opening part, the diameter of which increases from the side of one emission end face to the side of the exit window, and a second opening part with a fixed diameter which is not smaller than the smallest diameter of the first opening part on the side of one emission end face of the first opening part. [2] Quantum cascade laser device according to claim 1, wherein the cover element is in contact with the surface opposite the cover element in the submount; and wherein one emission end surface of the quantum cascade laser element is located at an opening end of the second opening part in the cover element. [3] Quantum cascade laser device according to claim 1 or 2, which further comprises a third opening part for positioning a lens on the side of the exit window of the first opening part. [4] Quantum cascade laser device according to one of claims 1 to 3, wherein the cover element has an extended part which extends to the heat sink side of the other emission end face of the quantum cascade laser element along a surface for mounting the quantum cascade laser element in the submount. [5] Quantum cascade laser device according to one of claims 1 to 4, wherein the heat sink has an opposite surface which is opposite the other emission end surface of the quantum cascade laser element in an inclined state. [6] Quantum cascade laser device according to any one of claims 1 to 5, wherein the housing consists of a lower main part and a lid part in which the exit window is arranged; and wherein the lid part has a black interior. [7] Quantum cascade laser device according to one of claims 1 to 6, wherein the entire inner surface of the housing is black. [8] Quantum cascade laser device according to any one of claims 1 to 7, wherein the housing is filled with dry nitrogen. [9] Quantum cascade laser device according to any one of claims 1 to 8, wherein the quantum cascade laser element is a distributed feedback continuous wave laser.