Narrow linewidth external cavity laser

Abstract

The narrow linewidth external cavity laser of the present invention includes a gain chip having laser gain, a lens that collimates light emitted from the gain chip into parallel light, and a wavelength selective filter that transmits light of a specific wavelength from the light collimated through the lens, and may further include a dual heat transfer member disposed on both sides of at least one of the lens and the wavelength selective filter, the dual heat transfer member being made of a material having a higher thermal conductivity than the lens and the wavelength selective filter.

Description

[Technical Field]

[0001] The present invention relates to an external cavity laser, and more particularly to an external cavity laser having a narrow linewidth that can minimize the oscillation linewidth of laser light by improving the temperature uniformity of a wavelength selection filter and a lens in the external cavity laser. [Background technology]

[0002] Recently, optical coherent signal processing has been utilized in laser-based object recognition methods such as Lidar, using lasers with narrow linewidths. This optical coherent object recognition requires a laser light source with a very narrow linewidth, because the laser linewidth determines the optical coherence length, and this optical coupling length is directly related to the sensing distance. Therefore, external cavity lasers with narrow linewidths have been developed and used.

[0003] FIG. 1 is a diagram for explaining a conventional external cavity laser.

[0004] As shown in Figure 1, this is disclosed in US Patent Publication US2003 / 0231666A1, in which spontaneously emitted light from a gain chip 12 having a laser gain is collimated into parallel light via a lens 22 and passes through a wavelength selective filter 32. The light of the wavelength that passes through the wavelength selective filter 32 is reflected by a reflecting mirror 14, passes through the wavelength selective filter 32 again, and returns to the gain chip 12.

[0005] That is, the general structure of an external cavity laser is shown, which operates as a laser by causing spontaneous emission light generated from the gain chip 12 to undergo stimulated emission into laser light while passing through a wavelength selective filter 32.

[0006] During this process, the light of wavelength components that cannot pass through the wavelength selective filter 32 in the spontaneous emission mode of the gain chip 12 is reflected by the wavelength selective filter 32 in a direction that prevents it from returning to the gain chip 12, and is lost without being able to return to the gain chip 12. As a result, the external cavity laser consisting of the gain chip 12, wavelength selective filter 32, and reflector 14 oscillates only with the wavelength components that pass through the wavelength selective filter 32.

[0007] In this way, a single-mode external cavity laser is manufactured, and such a narrow linewidth single-mode external cavity laser is adopted and used in LIDAR and the like.

[0008] FIG. 2 is a diagram showing the heat transfer process in a conventional external cavity laser placed on a thermoelectric element.

[0009] 2, thermoelectric cooler 500 is a component used to maintain a constant temperature for components placed above it, and heats or cools the upper plate of the thermoelectric cooler depending on the direction and magnitude of the electric current. Since the entire component on which thermoelectric cooler 500 is placed is exposed to the external ambient temperature, the temperature of the outside of thermoelectric cooler 500 and the upper plate of the thermoelectric cooler may differ, and as a result, heat transfer from parts other than thermoelectric cooler 500 may occur to components placed above thermoelectric cooler 500.

[0010] Heat is transferred from the outside of the thermoelectric element 500 to the upper plate of the thermoelectric element (600) by convection or radiation. Therefore, in the case of components (e.g., gain chip 100, lens 200, wavelength selective filter 300, reflector 400) arranged on the upper part of the thermoelectric element 500, the direction of heat transfer from the outside is different from that of the upper plate of the thermoelectric element below, so the components arranged on the upper plate of the thermoelectric element have different temperatures depending on the position of the component (e.g., top or bottom). As a result, the internal temperature of the components arranged on the upper plate of the thermoelectric element is non-uniform depending on the position, resulting in an increase in the laser linewidth.

[0011] FIG. 3 is a diagram for explaining the operating principle of a conventional general Fabry-Perot semiconductor laser.

[0012] The Fabry-Perot type semiconductor laser in FIG. 3 is a laser having a structure in which the wavelength selective filter 300 is removed from the external cavity type laser in FIG.

[0013] As shown in Figure 3, an external cavity semiconductor laser oscillates in the oscillation laser mode shown in Figure 3 due to feedback amplification with the strong gain part of the Fabry-Perot mode of the cavity consisting of the semiconductor gain chip 100 and the reflecting mirror 400, as the semiconductor gain chip 100 has gain characteristics that match the semiconductor bandgap characteristics (see the bottom diagram). Normally, a Fabry-Perot laser operates as a multimode laser, which oscillates with multiple oscillation peaks.

[0014] FIG. 4 is a diagram for explaining the operating principle of the external cavity laser of FIG.

[0015] The external cavity laser in FIG. 2 is a laser having a structure in which a wavelength selective filter 300 is further arranged in addition to the laser in FIG. 3, and exhibits a single oscillation mode.

[0016] The additional wavelength-selective filter 300 selectively transmits one of the Fabry-Perot modes to resonate within the cavity, thereby allowing the external cavity laser to have a single oscillation mode (see the bottom drawing).

[0017] 5 and 6 are diagrams for explaining the influence of temperature non-uniformity of a general wavelength selective filter on the linewidth of an oscillating laser.

[0018] As shown in FIG. 5, in this embodiment, the wavelength selective filter has a width of 0.5 mm, a length of 1.5 mm, and a height of 1.5 mm, and heat (W) (e.g., 2 mW, 5 mW, 10 mW, 15 mW, 20 mW) is uniformly generated on the upper surface, the lower surface is at room temperature, and the material is glass. However, this description is not limited to this example.

[0019] Wavelength-selective filters are typically fabricated by alternately depositing multiple materials with different dielectric constants onto a substrate. However, since all materials have different refractive indices depending on the temperature, temperature changes at different locations on the wavelength-selective filter result in changes in the wavelength of light passing through the wavelength-selective filter.

[0020] In other words, in the external cavity laser structure of FIG. 2, heat is applied to the wavelength selective filter 300 in different directions, which causes temperature non-uniformity inside the wavelength selective filter.

[0021] Figure 5 shows the temperature non-uniformity ("AC") inside the wavelength selective filter when 2mW, 5mW, 10mW, 15mW, and 20mW of heat is transferred to the top of the wavelength selective filter. With respect to heat transfer, the wavelength selective filter shows a temperature difference of approximately 2.3 (Kelvin) to approximately 20 degrees depending on the position ("Position A, Position B, Position C").

[0022] In wavelength-selective filters, a temperature difference of 1 degree causes a wavelength change of 2 pm to 10 pm, so a temperature difference of 20 degrees causes a difference in transmitted wavelength of 200 pm.

[0023] 6 shows the curve of the transmitted wavelength depending on the position of the wavelength-selective filter, and it can be seen that the transmitted wavelength differs depending on the temperature difference according to the position ("A, B, C") of the wavelength-selective filter. In other words, if the temperature differs depending on the position even in one wavelength-selective filter, the wavelength of the transmitted light will differ depending on the position, which may cause the problem of increasing the linewidth.

[0024] Although the explanation in FIG. 6 is based on a wavelength-selective filter, similarly in the case of a lens, if the temperature differs depending on the position, the wavelength of light passing through the lens may differ.

[0025] FIG. 7 is a diagram for explaining the influence of a wavelength selective filter with a non-uniform temperature on the oscillation characteristics of an external cavity laser.

[0026] As shown in FIG. 7, when the temperature differs depending on the position ("A, B") of the wavelength selective filter, the transmission characteristics (700) of the wavelength selective filter corresponding to "A" differ from the transmission characteristics (710) of the wavelength selective filter corresponding to "B", which may cause the linewidth of the oscillation characteristics of the external cavity laser to increase (720).

[0027] FIG. 8 is a diagram for explaining the influence of a lens with a non-uniform temperature on the oscillation characteristics of an external cavity laser.

[0028] The collimating lens 200 is typically made of glass, a material with low thermal conductivity. However, because this lens also exchanges heat with the upper plate of the thermoelectric element at the bottom and with the outside air at the top, the temperature varies at different positions on the lens, resulting in different optical lengths depending on the position on the lens itself. This is because the optical length of a lens is determined by the length of the lens on the optical path multiplied by the refractive index, and the refractive index is a function of temperature. Therefore, the optical lengths of each part of the lens differ due to temperature non-uniformity, unlike when the temperature is uniform. This results in slightly different lengths of the optical path passing through each part of the lens.

[0029] As shown in Figure 8, when the temperature varies depending on the lens position ("A, B"), the refractive index changes depending on the lens position, causing a difference in the optical path ("difference in optical path length"), which can change the characteristics of the Fabry-Perot mode. For example, the wavelength characteristics of the Fabry-Perot mode allowed by the lens corresponding to "A" (800) and the wavelength characteristics of the Fabry-Perot mode allowed by the lens corresponding to "B" (810) change, which causes the linewidth of the external cavity laser oscillation characteristics to increase (820).

[0030] This application is the result of the following national research and development projects: [National research and development project that supported this invention] [Project unique number]1711193908 [Project Number] 2022-0-00523-003 [Ministry name] Ministry of Science, ICT and Communication [Name of issue management (specialized) organization] Information and Communications Planning and Evaluation Agency [Research Project Name] Broadcasting and Communications Industry Technology Development [Research title] Development of 25Gbps-based 4-channel 100Gbps NG-PON2+ transceiver [Name of project executing organization] PHOVEL Co., Ltd. [Research period] 2022.04.01~2024.12.31. [Prior art documents] [Patent documents]

[0031] [Patent Document 1] U.S. Patent Application Publication No. 2003 / 0231666 (published December 18, 2003) Summary of the Invention [Problem to be solved by the invention]

[0032] The present invention has been proposed to solve the problems caused by the oscillation characteristics of conventional external cavity lasers, and an object of the present invention is to provide an external cavity laser having a narrow linewidth that can improve the temperature uniformity of the wavelength selection filter and lens of the external cavity laser. [Means for solving the problem]

[0033] In order to solve the above-mentioned problems, an external cavity laser having a narrow linewidth is devised. The external cavity laser includes a gain chip having laser gain, a lens that collimates the light emitted from the gain chip into parallel light, and a wavelength selective filter that transmits light of a specific wavelength from the light collimated through the lens. The external cavity laser is characterized by including a double heat transfer member disposed on both sides of at least one of the lens and the wavelength selective filter, the double heat transfer member being made of a material having a higher thermal conductivity than the lens and the wavelength selective filter.

[0034] The narrow linewidth external cavity laser may further include an upper heat transfer member disposed on an upper surface of the lens and the wavelength selective filter, the upper heat transfer member being made of a material having a higher thermal conductivity than the lens and the wavelength selective filter.

[0035] The two heat transfer members and the upper heat transfer member may be disposed apart from the lens and the wavelength selective filter to form a space.

[0036] The narrow linewidth external cavity laser may further include a lens fixing member coupled to the lens and having a structure for allowing the lens to stand vertically, and the heat transfer member may be disposed on a side portion of the lens fixing member.

[0037] The heat transfer member is made of a material having a thermal conductivity of 50 W / (m2°C) or more, and is characterized in that it is a semiconductor material containing one of silicon (Si), gallium arsenide (GaAs), and germanium (Ge), or a metal material containing one of aluminum (Al) and copper (Cu).

[0038] The heat transfer member is attached via epoxy mixed with powder containing at least one of silver, copper, and carbon nanotubes.

[0039] One or more of the gain chip, the lens, the wavelength selective filter, and the heat transfer member are arranged in thermal contact with the thermoelectric element. [Effects of the Invention]

[0040] According to the present invention, by improving the temperature uniformity of the wavelength selection filter and lens in an external cavity laser, the coherent path is lengthened, which has the effect of increasing the measurement distance in products that use the interference of laser light, such as LIDAR. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a diagram for explaining a conventional external cavity laser. [Figure 2] 1 is a diagram showing a heat transfer process in an external cavity laser placed on a conventional thermoelectric element. [Figure 3] FIG. 1 is a diagram for explaining the operating principle of a conventional general Fabry-Perot semiconductor laser. [Figure 4] FIG. 3 is a diagram for explaining the operating principle of the external cavity laser of FIG. 2. [Figure 5-6] 1 is a diagram for explaining the influence of temperature non-uniformity of a general wavelength selective filter on the linewidth of an oscillating laser. [Figure 7] 10A and 10B are diagrams for explaining the influence of a wavelength selective filter with a non-uniform temperature on the oscillation characteristics of an external cavity laser. [Figure 8] 10A and 10B are diagrams for explaining the influence of a lens with a non-uniform temperature on the oscillation characteristics of an external cavity laser. [Figures 9a-9c]1 is a diagram illustrating an external cavity laser including a heat transfer member disposed in a wavelength selective filter according to an embodiment of the present invention. [Figures 10a-10c] 10 is a diagram illustrating an external cavity laser including a heat transfer member disposed in a wavelength selective filter according to another embodiment of the present invention. [Figures 11a-11c] 10 is a diagram illustrating an external cavity laser including a heat transfer member disposed in a wavelength selective filter according to another embodiment of the present invention. [Figures 12a-12c] 1 is a diagram illustrating an external cavity laser including a heat transfer member disposed on a lens according to an embodiment of the present invention; [Figures 13a-13c] 10 is a diagram illustrating an external cavity laser including a heat transfer member disposed on a lens according to yet another embodiment of the present invention. [Figures 14a-14c] 10 is a view illustrating an external cavity laser including a heat transfer member disposed on a lens according to another embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, specific details for carrying out the invention will be described in detail with reference to the accompanying drawings.

[0043] 9a, 9b and 9c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a wavelength selective filter according to an embodiment of the present invention.

[0044] Figure 9a is an oblique view of the wavelength selective filter and heat transfer member, Figure 9b is a front view of the wavelength selective filter and heat transfer member in Figure 9a as viewed from a second direction (930), and Figure 9c is a side view of the wavelength selective filter and heat transfer member in Figure 9a as viewed from a third direction (940).

[0045] Referring to Figures 2, 9a, 9b and 9c, light can be transmitted through wavelength selective filter 900 in a first direction (920).

[0046] The heat transfer member 910 may include a side heat transfer member 910. The side heat transfer member 910 is disposed on both sides of the wavelength selective filter 900, rather than on the surface of the wavelength selective filter 900 in the first direction (920) through which light passes, and the lower surface can be coupled to the thermoelectric element 500 and may be a member having a better heat transfer coefficient than the wavelength selective filter 900. By using a material with a good heat transfer coefficient, heat transferred from the upper part can be transferred to the lower part via the heat transfer member 910, rather than to the wavelength selective filter 900.

[0047] For example, if the wavelength selective filter 900 is made of a glass material with a thermal conductivity of 1 W / (m²°C), the heat transfer member 910 can be made of any material with a thermal conductivity higher than that of the glass material. Examples of such materials include semiconductor substrates such as GaAs, Ge (germanium), and silicon, and metal materials such as aluminum and copper. Any material with a thermal conductivity of 50 W / (m²°C) and that can be attached can also be used as the member.

[0048] For example, epoxy containing powder of silver, copper, carbon nanotubes, etc. may be used to attach the heat transfer member 910 to the outer periphery of the wavelength selective filter 900. The heat transfer member 910 must be thermally coupled to the wavelength selective filter 900 and at the same time be in thermal contact with the upper plate of the thermoelectric element 500 to make the temperature of the entire wavelength selective filter 900 uniform, and the adhesive used for this may be epoxy containing silver, copper, carbon nanotubes, etc.

[0049] As a result, heat from the upper portion is not transferred to the wavelength selective filter 900 or the transfer is minimized, thereby eliminating the temperature variation depending on the position of the wavelength selective filter 900 described above in Figures 6 and 7, and thus preventing an increase in the linewidth. In other words, according to the present invention, by applying the heat transfer member 910, the temperature of the wavelength selective filter 900 can be made uniform, and therefore the wavelength of light transmitted through the wavelength selective filter 900 does not change depending on the position, which has the effect of narrowing the linewidth of the oscillation laser mode.

[0050] 10a, 10b and 10c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a wavelength selective filter according to still another embodiment of the present invention.

[0051] Figure 10a is an oblique view of the wavelength selective filter and heat transfer member, Figure 10b is a front view of the wavelength selective filter and heat transfer member in Figure 10a as viewed from a second direction (1030), and Figure 10c is a side view of the wavelength selective filter and heat transfer member in Figure 10a as viewed from a third direction (1040).

[0052] Referring to Figures 2, 10a, 10b and 10c, light can be transmitted through wavelength selective filter 1000 in a first direction (1020).

[0053] The heat transfer members may include a double heat transfer member 1010 and an upper heat transfer member 1015 .

[0054] The heat transfer members 1010 on both sides are disposed on both sides of the wavelength selective filter 1000 rather than on the surface of the wavelength selective filter 900 in the first direction (1020) through which light passes, and the lower surface can be coupled to the thermoelectric element 500.

[0055] The upper heat transfer member 1015 may be disposed on the upper surface of the wavelength selective filter 1000, rather than on the surface of the wavelength selective filter 1000 in the first direction (1020) through which light passes. The upper heat transfer member 1015 may be disposed only on the upper portion of the wavelength selective filter 1000, or may be disposed from the two side heat transfer members 1010 to the upper portion of the wavelength selective filter 1000.

[0056] At this time, the upper heat transfer member 1015 may be in thermal contact with the wavelength selective filter 900 and the two-sided heat transfer members 1010, and the attachment method may be the same as that described in FIG. 9a.

[0057] In addition, the two heat transfer members 1010 and the upper heat transfer member 1015 may be provided separately or integrally, and may be realized in various ways.

[0058] Furthermore, the widths of the two heat transfer members 1010 and the upper heat transfer member 1015 may be the same as or larger than the width of the wavelength selective filter 1000 .

[0059] The two heat transfer members 1010 and the upper heat transfer member 1015 may be members having a better heat transfer coefficient than the wavelength selective filter 300. By using a material with a good heat transfer coefficient, heat transferred from the upper part can be transferred to the lower part via the heat transfer member 910, rather than to the wavelength selective filter 900.

[0060] According to this embodiment, by further including the upper heat transfer member 1015, there is an effect that the heat transferred from the upper part can be additionally prevented from being directly transferred to the wavelength selective filter 1000.

[0061] 11a, 11b and 11c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a wavelength selective filter according to still another embodiment of the present invention.

[0062] Figure 11a is an oblique view of the wavelength selective filter and heat transfer member, Figure 11b is a front view of the wavelength selective filter and heat transfer member in Figure 11a as viewed from a second direction (1130), and Figure 11c is a side view of the wavelength selective filter and heat transfer member in Figure 11a as viewed from a third direction (1140).

[0063] Referring to Figures 2, 11a, 11b and 11c, light can be transmitted through wavelength selective filter 1100 in a first direction (1120).

[0064] The heat transfer member 1110 is positioned at a distance from the wavelength selective filter 1100, wrapping both sides and the upper side of the wavelength selective filter 1100 rather than the surface of the wavelength selective filter 1100 in the first direction (1120) through which light passes (the ``light-transmitting surface''), and the lower side can be coupled to the thermoelectric element 500.

[0065] Also, the heat transfer member 1110 can be variously realized, for example, it can be provided as an integrated member or as a plurality of members attached to one another.

[0066] The width of the heat transfer member 1110 may be the same as or larger than the width of the wavelength selective filter 1100 .

[0067] According to this embodiment, the heat transfer member 1110 is positioned at a distance from the wavelength selective filter 1100, and heat transfer due to thermal radiation is blocked by the air layer formed at the distance, thereby having the effect of blocking or reducing the heat transferred to the wavelength selective filter 1100.

[0068] 12a, 12b and 12c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a lens according to an embodiment of the present invention.

[0069] Figure 12a is a perspective view of the lens and heat transfer member, Figure 12b is a front view of the lens and heat transfer member in Figure 12a as viewed from a second direction (1240), and Figure 12c is a side view of the wavelength selective filter and heat transfer member in Figure 12a as viewed from a third direction (1250).

[0070] Referring to Figures 2, 12a, 12b and 12c, light can be transmitted through lens 1200 in a first direction (1220).

[0071] The lens fixing member 1210 is coupled to the lens 1200 so that the lens 1200 can stand vertically on the thermoelectric element 500. The lens fixing member 1210 can have any shape as long as it can stand the lens 1200.

[0072] The heat transfer member 1230 may include a side heat transfer member 1230. The side heat transfer member 1230 is disposed on both sides of the lens 1200 or the lens fixing member 1210, rather than on the surface of the lens 1200 in the first direction (1220) through which light passes (the "light transmitting surface"). The lower surface can be coupled to the thermoelectric element 500 and may be a member having a better heat transfer coefficient than the lens 1200 or the lens fixing member 1210. By using a material with a good heat transfer coefficient, heat transferred from the upper part can be transferred to the lower part via the heat transfer member 1230, rather than the lens fixing member 1210.

[0073] For example, the heat transfer member 910 may be attached to the outer periphery of the lens fixing member 1210 using epoxy containing powder of silver, copper, carbon nanotubes, etc. The heat transfer member 1230 must be thermally coupled to the lens fixing member 1210 and at the same time be in thermal contact with the upper plate of the thermoelectric element 500 to make the temperature of the entire lens 1200 uniform, and the adhesive used for this may be epoxy containing silver, copper, carbon nanotubes, etc.

[0074] As a result, heat from the upper portion is not transferred to the lens fixing member 1210 and the lens 1200, or the transfer is minimized, thereby eliminating the temperature variation due to the position of the lens 1200 described above in Figures 6 and 7, and thus preventing an increase in linewidth. In other words, according to the present invention, the application of the heat transfer member 1230 makes the temperature of the lens 1200 uniform, and the wavelength of the light transmitted through the lens 1200 does not change depending on the position, which has the effect of narrowing the linewidth of the oscillation laser mode.

[0075] 13a, 13b and 13c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a lens according to still another embodiment of the present invention.

[0076] Figure 13a is a perspective view of the lens and heat transfer member, Figure 13b is a front view of the lens and heat transfer member in Figure 13a as viewed from a second direction (1350), and Figure 13c is a side view of the lens and heat transfer member in Figure 13a as viewed from a third direction (1360).

[0077] Referring to Figures 2, 13a, 13b and 13c, light can be transmitted through lens 1300 in a first direction (1320).

[0078] The lens fixing member 1310 is coupled to the lens 1300 so that the lens 1300 can stand vertically on the thermoelectric element 500. The lens fixing member 1310 can have any shape as long as it can stand the lens 1300.

[0079] The heat transfer members may include a double heat transfer member 1330 and an upper heat transfer member 1340 .

[0080] The two-sided heat transfer members 1330 are disposed on both sides of the lens 1300 or the lens fixing member 1310 rather than on the surface of the lens 1300 in the first direction (1320) through which light passes, and the lower surface can be coupled to the thermoelectric element 500.

[0081] The upper heat transfer member 1340 may be disposed on the upper surface of the lens fixing member 1310, not on the surface of the lens 1300 in the first light transmitting direction (1320). The upper heat transfer member 1340 may be disposed only on the upper part of the lens fixing member 1310, or may be disposed from the two side heat transfer members 1330 to the upper part of the lens fixing member 1310.

[0082] At this time, the upper heat transfer member 1340 may be in thermal contact with the lens fixing member 1310 and the two side heat transfer members 1330, and the attachment method may be the same as that described in FIG. 9a.

[0083] In addition, the two heat transfer members 1330 and the upper heat transfer member 1340 may be provided separately or integrally, and may be realized in various ways.

[0084] Furthermore, the widths of the two heat transfer members 1330 and the upper heat transfer member 1340 may be equal to or greater than the width of the lens fixing member 1310 .

[0085] The two heat transfer members 1330 and the upper heat transfer member 1340 may be members having a better heat transfer coefficient than the lens 1300 or the lens fixing member 1310. By using a material with a good heat transfer coefficient, heat transferred from the upper part can be transferred to the lower part via the heat transfer members 1330 and 1340, rather than the lens fixing member 1310 or the lens 1300.

[0086] According to this embodiment, by further including the upper heat transfer member 1340, it is possible to additionally prevent heat transferred from above from being directly transferred to the lens fixing member 1310 or the lens 1300.

[0087] 14a, 14b and 14c are diagrams illustrating an external cavity laser including a heat transfer member disposed on a lens according to another embodiment of the present invention.

[0088] Figure 14a is a perspective view of the lens and heat transfer member, Figure 14b is a front view of the lens and heat transfer member in Figure 14a as viewed from a second direction (1440), and Figure 14c is a side view of the lens and heat transfer member in Figure 14a as viewed from a third direction (1450).

[0089] Referring to Figures 2, 14a, 14b and 14c, light can be transmitted through lens 1400 in a first direction (1420).

[0090] The lens fixing member 1410 is coupled to the lens 1400 so that the lens 1400 can stand vertically on the thermoelectric element 500. The lens fixing member 1410 can have any shape as long as it can stand the lens 1400.

[0091] The heat transfer member 1410 is positioned at a distance from the lens fixing member 1410 while wrapping both sides and the upper side of the lens 1400 or the lens fixing member 1410, rather than the surface of the lens 1400 in the first direction (1420) through which light passes (the "light-transmitting surface"), and the lower side can be coupled to the thermoelectric element 500.

[0092] The heat transfer member 1410 can be implemented in various ways, such as being provided as an integrated member or being provided by attaching a plurality of members.

[0093] Also, the width of the heat transfer member 1410 may be the same as or greater than the width of the lens fixing member 1410.

[0094] According to this embodiment, the heat transfer member 1110 is positioned at a distance from the wavelength selective filter 1100, and heat transfer due to thermal radiation is blocked by the air layer formed at the distance, thereby having the effect of blocking or reducing the heat transferred to the wavelength selective filter 1100.

[0095] The method of applying the heat transfer member applicable to the wavelength selective filter or lens described above can be applied to the wavelength selective filter or lens in various ways, either alone or in combination.

[0096] The above-described embodiments may be configured by selectively combining all or part of each embodiment to allow for various modifications.

[0097] It should be noted that the embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention, and that those skilled in the art will understand that various embodiments are possible within the scope of the technical concept of the present invention.

Claims

1. An external cavity laser including a gain chip having a laser gain, a lens for collimating light emitted from the gain chip into parallel light, and a wavelength selective filter for transmitting light of a specific wavelength from the light collimated through the lens, An external cavity laser having a narrow linewidth, comprising a double heat transfer member arranged on both sides of at least one of the lens and the wavelength selective filter, the double heat transfer member being made of a material having a higher heat transfer coefficient than the lens and the wavelength selective filter.

2. 2. The narrow linewidth external cavity laser of claim 1, further comprising an upper heat transfer member disposed on an upper surface of the lens and the wavelength selective filter and made of a material having a higher heat transfer coefficient than the lens and the wavelength selective filter.

3. The two heat transfer members and the upper heat transfer member are 3. The narrow linewidth external cavity laser according to claim 2, wherein the lens and the wavelength selective filter are spaced apart to form a space.

4. a lens fixing member coupled to the lens and having a structure for allowing the lens to stand vertically; 2. The external cavity laser having a narrow linewidth according to claim 1, wherein the heat transfer member is disposed on a side surface of the lens fixing member.

5. 2. The narrow linewidth external cavity laser according to claim 1, wherein the heat transfer member is made of a material having a thermal conductivity of 50 W / (m²°C) or more, and is a semiconductor material including one of silicon (Si), gallium arsenide (GaAs), and germanium (Ge), or a metal material including one of aluminum (Al) and copper (Cu).

6. 2. The narrow linewidth external cavity laser according to claim 1, wherein the heat transfer member is attached via epoxy mixed with powder containing at least one of silver, copper, and carbon nanotubes.

7. 2. The narrow linewidth external cavity laser of claim 1, wherein at least one of the gain chip, the lens, the wavelength selective filter, and the heat transfer member is disposed in thermal contact with a thermoelectric element.

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