Lens integrated coupling structure of semiconductor external cavity narrow linewidth laser

Abstract

The invention relates to the technical field of laser coupling and packaging, in particular to a lens integrated coupling structure of a semiconductor external cavity narrow linewidth laser, which solves the problems of small coupling tolerance, high debugging difficulty and low coupling efficiency in the prior art, and comprises a tube shell and an output tail fiber, the optical assembly comprises a collimating lens and a focusing lens, the focusing lens is integrally arranged at the position of a tube shell output hole of the tube shell, an isolator is arranged between the collimating lens and the focusing lens, the collimating lens, the isolator and the focusing lens are mutually coupled to form an integrated lens, and the output tail fiber is fixedly coupled with the tube shell. And the output tail fiber is aligned with an output focusing light spot of the integrated lens. The beneficial effects are that the coupling tolerance is obviously increased, the output tail fiber is independently arranged relative to the focusing lens, the micro angle deviation of the focusing lens can be compensated by performing three-dimensional adjustment on the output tail fiber, the focus point deviation tolerance is effectively increased, the angle deviation is increased, and the requirement for high assembly precision of preorder components is reduced.

Description

Technical Field

[0001] This invention relates to the field of laser coupling and packaging technology, and in particular to a lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser. Background Technology

[0002] Semiconductor external cavity narrow-linewidth lasers are widely used in optical communication, lidar, and spectral analysis due to their narrow linewidth, stable output power, and tunable wavelength. Their core principle involves selecting and feeding back the laser wavelength through an external cavity grating, using a RSOA (Reflective Semiconductor Optical Amplifier) ​​as the gain medium, and forming a resonant cavity through the coupling of optical elements to achieve narrow-linewidth laser output.

[0003] In existing technologies, the output coupling structure of semiconductor external cavity narrow linewidth lasers often adopts an integrated design of the focusing lens and the pigtail. While this design simplifies initial assembly to some extent, it has significant drawbacks: because the relative positions of the focusing lens and the pigtail are fixed, the tolerance for coupling alignment is extremely small, requiring very high assembly precision. This not only increases the difficulty of debugging but also leads to low yield during production, making it difficult to meet the needs of large-scale automated production. Furthermore, in this integrated structure, the coupling process of discrete components (such as collimating lenses and isolators) along the optical signal transmission path is complex, easily introducing additional losses and resulting in low overall coupling efficiency. In addition, the layout of optical components in existing structures is relatively compact. If devices such as beam splitters for monitoring wavelengths need to be embedded in the optical path, the space in the optical path will be limited, resulting in poor system functional expandability.

[0004] For example, CN107861197A discloses an optical emitting component and packaging process, which realizes optical signal transmission through a combination of flexible circuit board, coupling lens, isolator and adapter. Although the connection method between the optical emitting component and the multiplexing component is optimized in the packaging process, the problem of small coupling tolerance and insufficient optical path scalability caused by the integrated design of focusing lens and pigtail has not been solved. Its coupling structure still relies on the precise alignment of discrete components, and there is still room for improvement in coupling efficiency and system scalability.

[0005] Therefore, in view of the problems of small coupling tolerance, high debugging difficulty, low coupling efficiency and limited functional scalability in the existing coupling structure of semiconductor external cavity narrow linewidth lasers, there is an urgent need for an optimized coupling structure to improve the reliability, production efficiency and system scalability of the device. Summary of the Invention

[0006] This invention proposes a lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser, which solves the problems of small coupling tolerance, high debugging difficulty, and low coupling efficiency caused by the integrated design of the focusing lens and the pigtail in the prior art.

[0007] The technical solution of this invention is implemented as follows: A lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser includes a housing and an output pigtail. Optical components are housed within the housing, including a collimating lens and a focusing lens. The focusing lens is integrated into the output aperture of the housing. An isolator is positioned between the collimating lens and the focusing lens. The collimating lens, isolator, and focusing lens are coupled together to form an integrated lens. The output pigtail is fixedly coupled to the housing and aligned with the focused beam of the integrated lens. This dual-lens coupling structure, consisting of a collimating lens and a focusing lens, significantly improves coupling efficiency and enhances the output power for narrow linewidth lasers. Furthermore, the output pigtail is independently positioned relative to the focusing lens; adjusting the pigtail compensates for minute angular deviations in the focusing lens, increasing the focal point deviation tolerance and reducing the high-precision requirements of preceding components.

[0008] The center of the focusing lens is coaxially aligned with the output hole of the tube housing. The focusing lens is fixed to the output hole of the tube housing through precision injection molding, laser welding, or glass sintering processes to form an integrated structure, ensuring the optical axis alignment accuracy.

[0009] The inner side of the tube housing has a groove, and the isolator is installed in the groove. The optical axis of the isolator is aligned with the output optical axis of the external cavity grating. The isolator is used to suppress backlight interference and prevent backlight from affecting the stability of laser resonance. The groove positions and fixes the isolator, ensuring that the isolator is accurately installed inside the tube housing.

[0010] The optical components also include an RSOA and an external cavity grating. The output light from the RSOA is coupled to the external cavity grating, and the output light from the external cavity grating is transmitted sequentially through a collimating lens and an isolator to a focusing lens at the output aperture of the tube shell. The RSOA serves as a gain medium, and its output light coupled to the external cavity grating constitutes the gain source for the laser resonance. The external cavity grating reflects and provides feedback for light of a specific wavelength, working in conjunction with the RSOA to form a narrow linewidth laser resonance.

[0011] The focal length of the focusing lens is matched to the divergence angle of the output light from the external cavity grating. The focusing lens employs an aberration-correcting design; it is made of optical glass or high-transmittance plastic to ensure efficient focusing of the light field onto the output fiber.

[0012] The optical assembly also includes a single lens located between the RSOA and the external cavity grating. The output light from the RSOA is coupled to the external cavity grating via the single lens.

[0013] The housing contains a TEC (Transmission Temperature Regulator), which houses a heat sink for supporting the single lens, external cavity grating, and collimating lens. The TEC enables temperature control of the optical components, ensuring operational stability.

[0014] A substrate is mounted on the heat sink, and the RSOA is mounted on the substrate. The substrate is a COC substrate, and the substrate is attached to the heat sink to achieve stable installation and heat dissipation of the RSOA.

[0015] The output pigtail is coupled to the output port of the housing via a pigtail bracket. The output pigtail is aligned with the output focused spot of the integrated lens.

[0016] The output pigtail is fixed to the pigtail bracket by laser welding or UV adhesive curing. The bracket has a pre-set adjustment gap, allowing the output pigtail to be adjusted in three dimensions during coupling.

[0017] The beneficial effects of this invention are: the coupling tolerance is significantly increased, the output pigtail is set independently relative to the focusing lens, and the small angular deviation of the focusing lens can be compensated by three-dimensional adjustment of the output pigtail, which effectively increases the focal point deviation tolerance, increases the angular deviation, reduces the high assembly precision requirements of the preceding components, and reduces the debugging difficulty.

[0018] The coupling efficiency is significantly improved by adopting a dual-lens coupling structure consisting of a collimating lens and a focusing lens to form a low-loss parallel light transmission path. This not only greatly improves the coupling efficiency but also effectively increases the output optical power in narrow linewidth applications, meeting the needs of high-power application scenarios.

[0019] In addition, the spacing between the collimating lens and the focusing lens in the parallel light transmission path can be flexibly adjusted, allowing devices such as isolators and beam splitters to be easily embedded in the middle of the optical path, reserving ample space for subsequent expansion of functions such as monitoring wavelength, and significantly enhancing the scalability and practicality of the system.

[0020] The debugging efficiency and yield rate are improved. There is no need to manually adjust the tilt angle of the output pigtail. Efficient coupling can be achieved simply by translating and adjusting the output pigtail. The debugging time per unit is short. With the positioning design of the tube shell structure, the production yield rate is effectively improved, making it suitable for automated large-scale production. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser according to the present invention; Figure 2 This is a schematic diagram of an integrated lens coupling structure.

[0023] In the diagram: 1. Tube shell, 2. TEC, 3. Heat sink, 4. Substrate, 5. RSOA, 6. Single lens, 7. External cavity grating, 8. Collimating lens, 9. Isolator, 10. Focusing lens, 11. Tube shell output hole, 12. Pigtail bracket, 13. Output pigtail, 14. Fiber core. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1, as Figure 1 , Figure 2 As shown, a lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser includes a housing 1 and an output pigtail 13. Optical components are housed within the housing 1, including a collimating lens 8 and a focusing lens 10. The focusing lens 10 is integrated into the housing's output aperture 11. An isolator 9 is provided between the collimating lens 8 and the focusing lens 10. The collimating lens 8, isolator 9, and focusing lens 10 are coupled together to form an integrated lens. The output pigtail 13 is coupled and fixed to the housing 1, and is aligned with the output focused spot of the integrated lens. This dual-lens coupling structure, consisting of the collimating lens 8 and the focusing lens 10, significantly improves coupling efficiency and effectively increases the narrow linewidth output power. Furthermore, the output pigtail 13 is independently positioned relative to the focusing lens 10, allowing for three-dimensional adjustment of the output pigtail 13 to compensate for minor angular deviations in the focusing lens 10. This effectively increases the focal point deviation tolerance, reduces the high assembly precision requirements of preceding components, and lowers the debugging difficulty.

[0026] In addition, the spacing between the collimating lens 8 and the focusing lens 10 of the parallel light transmission path can be flexibly adjusted, which allows devices such as the isolator 9 to be easily embedded in the middle of the optical path, leaving ample space for subsequent expansion of functions such as monitoring wavelength, and significantly enhancing the scalability and practicality of the system.

[0027] Furthermore, the center of the focusing lens 10 is coaxially arranged with the output hole 11 of the housing. In this embodiment, the housing 1 is made of Kovar alloy or ceramic material; the focusing lens 10 is fixed to the output hole 11 of the housing through precision injection molding, laser welding or glass sintering process to form an integrated structure, ensuring the optical axis alignment accuracy.

[0028] Furthermore, a groove is provided on the inner side of the tube shell 1, and the isolator 9 is disposed in the groove. The optical axis of the isolator 9 is aligned with the output optical axis of the external cavity grating 7. The isolator 9 is used to suppress backlight interference and prevent backlight from affecting the stability of laser resonance; the groove positions and fixes the isolator 9 to ensure that the isolator 9 is accurately installed in the tube shell 1.

[0029] Example 2, based on Example 1, provides a lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser. The optical components further include RSOA5 and an external cavity grating 7. The output light from RSOA5 is coupled to the external cavity grating 7, and the output light from the external cavity grating 7 is transmitted sequentially through a collimating lens 8 and an isolator 9 to a focusing lens 10 located at the output aperture 11 of the housing. RSOA5 serves as a gain medium, and its output light coupled to the external cavity grating 7 constitutes the gain source for laser resonance. The external cavity grating 7 reflects and feedbacks light of a specific wavelength, forming a narrow linewidth laser resonance.

[0030] Furthermore, the focal length of the focusing lens 10 is matched with the divergence angle of the output light from the external cavity grating 7. The focusing lens 10 adopts an aberration-free design; the focusing lens 10 is made of optical glass or high-transmittance plastic, and the divergence angle matching can ensure that the light field is efficiently focused onto the output pigtail 13.

[0031] Furthermore, the optical assembly also includes a single lens 6, which is located between the RSOA5 and the external cavity grating 7. The output light from the RSOA5 is coupled to the external cavity grating 7 via the single lens 6.

[0032] Furthermore, a TEC2 is provided inside the housing 1, and a heat sink 3 is mounted on the TEC2 to support the single lens 6, the external cavity grating 7, and the collimating lens 8. The TEC2 enables temperature control of the optical components, ensuring the operational stability of the laser. A substrate 4 is mounted on the heat sink 3, and the RSOA5 is disposed on the substrate 4. The substrate 4 is a COC substrate, and the substrate 4 is bonded to the heat sink 3 to achieve stable mounting and heat dissipation of the RSOA5.

[0033] Furthermore, the output pigtail 13 is coupled to the output port 11 of the housing via the pigtail bracket 12. The output pigtail 13 is aligned with the output focused spot of the integrated lens. The output pigtail 13 is fixed to the pigtail bracket 12 by laser welding or UV adhesive curing. The pigtail bracket 12 has a pre-reserved fine-tuning gap, allowing the output pigtail 13 to be adjusted in three dimensions during coupling.

[0034] The assembly process of the lens-integrated coupling structure is as follows: 1. Optical component assembly: The RSOA5 is fixed on the substrate 4 and then glued to the heat sink 3. The single lens 6 is installed between the RSOA5 and the external cavity grating 7 through the precision adjustment frame, so that the output light of the RSOA5 is incident on the external cavity grating 7 after passing through the single lens 6. After coupling the external cavity grating 7, the collimating lens 8 at the output end of the external cavity grating 7 is coupled. A standard non-integrated focusing lens 10 and the collimating lens 8 are used to adjust the light field. A single-mode grating is used to receive the light after the focusing lens 10. The relative positions of the focusing lens, the collimating lens 8 and the optical fiber are adjusted to maximize the output power of the optical fiber. At this time, the collimating lens 8 is fixed to the heat sink 3 with glue.

[0035] 2. Pre-assembly of isolator 9 and housing 1: The assembled optical components are installed into housing 1. The optical components are installed into the housing 1 through TEC2, so that the output optical axis of the external cavity grating 7 corresponds to the position of the groove inside the housing 1. Then, the isolator 9 is fixed in the preset groove inside the housing 1, so that its optical axis is aligned with the output optical axis of the external cavity grating 7. The quartz focusing lens 10 is fixed at the output hole 11 of the housing by laser welding or glue process, ensuring that the center of the focusing lens 10 is coaxial with the output hole 11 of the housing.

[0036] 3. Fiber Coupling and Fixing: The output fiber 13 (9μm core, 0.14 numerical aperture) is passed through the fiber optic bracket 12 of the tube shell 1. The position of the output fiber 13 is adjusted by a six-dimensional fine-tuning stage: the output fiber 13 is moved along the axial direction to the position with the smallest focused spot. The core 14 of the output fiber 13 is radially fine-tuned to make the optical power coupling efficiency ≥90%. Then, the fiber optic bracket 12 is fixed to the tube shell 1 by laser welding. The welding points are located on both sides of the output fiber 13 to avoid thermal stress affecting the coupling area.

[0037] 4. Overall encapsulation: Cover the tube shell 1, and laser seal the edge of the tube shell 1 to complete the laser encapsulation.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lens-integrated coupling structure for a semiconductor external cavity narrow linewidth laser, characterized in that, The device includes a housing (1) and an output pigtail (13). The housing (1) contains an optical assembly, which includes a collimating lens (8) and a focusing lens (10). The focusing lens (10) is integrated at the housing output hole (11) of the housing (1). An isolator (9) is provided between the collimating lens (8) and the focusing lens (10). The collimating lens (8), the isolator (9) and the focusing lens (10) are coupled together to form an integrated lens. The output pigtail (13) is coupled and fixed to the housing (1). The output pigtail (13) is aligned with the output focused spot of the integrated lens.

2. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 1, characterized in that, The center of the focusing lens (10) is coaxially set with the output hole (11) of the tube shell.

3. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 1, characterized in that, The inner side of the tube shell (1) is provided with a groove, and the isolator (9) is set in the groove. The optical axis of the isolator (9) is aligned with the output optical axis of the outer cavity grating (7).

4. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to any one of claims 1 to 3, characterized in that, The optical components also include RSOA (5) and external cavity grating (7). The output light of RSOA (5) is coupled to external cavity grating (7). The output light of external cavity grating (7) is transmitted sequentially through collimating lens (8) and isolator (9) to focusing lens (10) at tube output hole (11).

5. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 4, characterized in that, The focal length of the focusing lens (10) is matched with the divergence angle of the output light of the external cavity grating (7).

6. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 5, characterized in that, The optical components also include a single lens (6) located between the RSOA (5) and the external cavity grating (7).

7. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to any one of claims 1 to 3, 5, and 6, characterized in that, The tube shell (1) is equipped with a TEC (2), and the TEC (2) is equipped with a heat sink (3) for carrying the single lens (6), the external cavity grating (7) and the collimating lens (8).

8. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 7, characterized in that, A substrate (4) is provided on the heat sink (3), and RSOA (5) is disposed on the substrate (4).

9. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 8, characterized in that, The output pigtail (13) is coupled to the tube shell output hole (11) through the pigtail bracket (12).

10. The lens-integrated coupling structure of the semiconductor external cavity narrow linewidth laser according to claim 9, characterized in that, The output pigtail (13) is fixed to the pigtail bracket (12) by laser welding or UV adhesive curing.

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