A small-size narrow-linewidth laser with wavelength tunability

Abstract

The utility model provides a kind of wavelength adjustable small size narrow line width laser, the output light path of the laser includes for facula beam expander and wavelength selection beam expander device (3), laser is with laser gain chip (1) as light source, the diffraction light generated at beam expander and wavelength selection device of light source output is reflected back to the active region of laser gain chip by reflector (4) as feedback signal;When laser needs to promote laser line width, by adding folding optical path in output light path to reduce the module size of output light path and increase the external cavity optical length of output light path, folding optical path includes free space ring, triangular reflector or right-angle prism;The utility model can be wavelength tunable while making laser output line width narrow, and miniaturization.

Description

Technical Field

[0001] This utility model relates to the fields of optical communication and optical sensing technology, and in particular to a small-sized, narrow-linewidth laser with tunable wavelength. Background Technology

[0002] Narrow-linewidth semiconductor lasers, with their single longitudinal mode, narrow linewidth, low noise, and high side-mode suppression ratio, are widely used in fiber optic hydrophones, B-OTDRs, lidar, coherent optical communication, and seismic sensing. With the rapid development of optical communication technology and lidar, higher demands are being placed on the spectral coordination range and linewidth of semiconductor lasers. As the core light source for these applications, narrow-linewidth lasers must not only possess a single longitudinal mode and narrow linewidth, but also support tunable output wavelength and small size. Linear width narrowing technology for semiconductor lasers mainly involves two methods: internal cavity and external cavity. Traditional internal cavity feedback, such as DFB / DBR, suffers from linewidth expansion due to inherent large cavity losses and spontaneous emission of the gain medium, which is difficult to eliminate and limits its linewidth characteristics. Furthermore, electrical tuning based on carrier dispersion or thermal tuning based on thermo-optical effects restricts the wavelength tuning range, typically only a few nm. To obtain lasers with a wider tuning range and narrower linewidth, researchers have introduced external cavity semiconductor lasers. External cavity lasers mainly include FBG schemes, diffraction grating schemes, and etalon filtering schemes. Both FBG and etalon schemes have the problem of fixed wavelength output and limited tuning range. Grating schemes can achieve wavelength tuning, but existing grating schemes, whether Littrow or Littman, are relatively large in size.

[0003] Existing grating-based spatial cavity structures include Littrow and Littman. The Littrow structure typically consists of a gain chip, a coupling lens, and a diffraction grating. The diffraction grating acts as a feedback element, supporting wavelength tuning, mode selection, and linewidth compression. The Littman structure adds a mirror to the Littrow structure, allowing wavelength tuning to be achieved by rotating or rotating the mirror. Commonly used gratings in both Littrow and Littman structures include reflective, transmissive, and blazed gratings. These technologies suffer from the problem of requiring high linewidth compression or beam expansion to achieve high resolution, resulting in relatively large module sizes. Furthermore, high-line-density gratings are difficult to fabricate and costly.

[0004] To address the aforementioned issues, this invention proposes a structure and implementation method for a small-size, narrow-linewidth tunable laser. This allows for both narrowing the linewidth and achieving wavelength tunability and miniaturization. The invention utilizes prisms or prism pairs to expand the beam, and uses circulators or right-angle prisms to fold the optical path, thereby reducing the module size while increasing the external cavity optical length and improving the laser linewidth. Utility Model Content

[0005] This invention proposes a small-sized, narrow-linewidth laser with tunable wavelength, which can achieve both wavelength tunability and miniaturization while narrowing the laser output linewidth.

[0006] The present invention adopts the following technical solution.

[0007] A small-size, narrow-linewidth laser with tunable wavelength, wherein the output optical path of the laser includes a beam-expanding and wavelength-selecting device (3) for beam expansion and wavelength selection, the laser uses a laser gain chip (1) as a light source, and the diffracted light generated by the light source at the beam-expanding and wavelength-selecting device is reflected back to the active region of the laser gain chip as a feedback signal by a reflector (4).

[0008] When a laser needs to increase its linewidth, the module size of the output optical path can be reduced and the external cavity optical length of the output optical path can be increased by adding a folded optical path. The folded optical path includes a free-space circulator, a triangular mirror, or a right-angle prism.

[0009] The beam expander and selector includes a prism, a prism, or a transmission grating.

[0010] The reflector is a mirror or a MEMS.

[0011] The laser gain chip is a single longitudinal mode output laser gain chip. Its reflective end face, grating and reflector / MEMS form a resonant cavity. The diffracted light reflected back to the laser gain chip is transmitted to the isolator FSI (6) through the aspherical lens (5).

[0012] The laser's output optical path is provided with an aspherical lens collimator (2).

[0013] When the beam expander and wave selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator (2) and is incident on the prism grating or transmission grating. The light generated by the prism grating or transmission grating is diffracted to the reflector (4). After the reflector is rotated and adjusted, the light passes through the grating of the beam expander and wave selector again and returns to the laser chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

[0014] When the folded optical path does not contain a circulator, the triangular mirrors in the folded optical path are arranged in pairs. If the beam expander and wave selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator (2), enters the triangular mirror (7), and is reflected onto the prism grating of the beam expander and wave selector. Then, it is diffracted through the grating of the beam expander and wave selector to the reflector (4). After the reflector is rotated and adjusted, it passes through the grating of the beam expander and wave selector again and returns to the laser gain chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

[0015] When the folded optical path includes a free-space circulator (9) and a filter mirror (8), the light output from the laser gain chip passes through the first aspherical transmission collimator, enters port 2 of the free-space circulator, is reflected by the triangular mirror (7), and then enters the prism of the beam expander and wave selector device. After being diffracted by the grating, it reaches the filter mirror, undergoes frequency selection filtering and reflection by the filter mirror, and then passes through port 1 of the free-space circulator to port 2. Finally, it returns to the laser gain chip through the first aspherical transmission collimator to form external cavity feedback.

[0016] When the laser is outputting a single longitudinal mode, if the beam expander and selection device includes a prism grating or a transmission grating, the laser can select different wavelengths of the output laser by selecting the grating specifications of the beam expander and selection device, and achieve filtering and frequency selection through the transmission grating of the beam expander and selection device and the reflector of the reflector.

[0017] When a laser outputs a single longitudinal mode, different output spots are achieved based on the resolution of the grating, and the grating bandwidth is inversely proportional to the spot size.

[0018] The grating uses a reflective grating, which is a cemented composite of a prism and a grating. The prism expands the light spot, thus narrowing the grating's filtering bandwidth.

[0019] At the same time, prism pairs or multiple prisms can be added to expand the spot size, further narrowing the laser linewidth.

[0020] The laser proposed in this invention features tunable wavelength, small size, and narrow linewidth. As shown in Embodiment 1, filtering and frequency selection are achieved through a transmissive grating and a reflector. Based on the grating resolution, the grating bandwidth and the spot size are inversely proportional. This invention proposes a prism grating, which is a composite of a prism and a grating. After passing through the prism, the spot size is further expanded, and the grating filtering bandwidth can be further narrowed. At the same time, prism pairs or multiple prisms can be added to expand the spot size, thereby further narrowing the laser linewidth.

[0021] This invention employs optical element bonding integration or optical path folding, which can effectively reduce the size and even achieve a standard butterfly package size, thus narrowing the linewidth while enabling wavelength tuning.

[0022] This invention proposes a structure and implementation method for a small-size, narrow-linewidth tunable laser, which enables wavelength tunability and miniaturization while narrowing the linewidth. This invention expands the beam by using a prism grid or adding prism pairs, and folds the optical path by using a circulator or right-angle prism, thereby reducing the module size while increasing the external cavity optical length and improving the laser linewidth. Attached Figure Description

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0024] Appendix Figure 1 This is a schematic diagram of an embodiment of the present invention without a folded optical path;

[0025] Appendix Figure 2 This is a schematic diagram of an embodiment of the present invention that uses a folded optical path but does not employ a circulator;

[0026] Appendix Figure 3 This is a schematic diagram of an embodiment of the present invention that uses a folded optical path and a circulator;

[0027] Appendix Figure 4 This is a schematic diagram illustrating the principle of this utility model;

[0028] In the diagram: 1-Laser gain chip; 2-Aspherical lens collimator; 3-Beam expander and wave selector; 4-Reflector; 5-Aspherical lens; 6-Isolator FSI. Detailed Implementation

[0029] As shown in the figure, a small-sized narrow-linewidth laser with tunable wavelength is provided. The output optical path of the laser includes a beam-expanding and wavelength-selecting device 3 for beam expansion and wavelength selection. The laser uses a laser gain chip 1 as a light source. The diffracted light generated by the light source at the beam-expanding and wavelength-selecting device is reflected back to the active region of the laser gain chip by a reflector 4 as a feedback signal.

[0030] When a laser needs to increase its linewidth, the module size of the output optical path can be reduced and the external cavity optical length of the output optical path can be increased by adding a folded optical path. The folded optical path includes a free-space circulator, a triangular mirror, or a right-angle prism.

[0031] The beam expander and selector includes a prism, a prism, or a transmission grating.

[0032] The reflector is a mirror or a MEMS.

[0033] The laser gain chip is a single-longitudinal-mode output laser gain chip. Its reflective end face, grating and reflector / MEMS form a resonant cavity. The diffracted light reflected back to the laser gain chip is transmitted to the isolator FSI6 through the aspherical lens 5.

[0034] The laser's output optical path is provided with an aspherical lens collimator 2 at the beginning.

[0035] When the beam expander and wave selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator 2 and is incident on the prism grating or transmission grating. The light generated by the prism grating or transmission grating is diffracted to the reflector 4. After the reflector is rotated and adjusted, the light passes through the grating of the beam expander and wave selector again and returns to the laser chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

[0036] When the folded optical path does not contain a circulator, the triangular mirrors in the folded optical path are arranged in pairs. If the beam expander and selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator 2, enters the triangular mirror 7, and is then reflected onto the prism grating of the beam expander and selector. After being diffracted by the grating of the beam expander and selector to the reflector 4, the light is adjusted by rotating the reflector and then passes through the grating of the beam expander and selector again, returning to the laser gain chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

[0037] When the folded optical path includes a free-space circulator 9 and a filter mirror 8, the light output from the laser gain chip passes through the first aspherical transmission collimator, enters port 2 of the free-space circulator, is reflected by the triangular mirror 7, and then enters the prism of the beam expander and selector device. After being diffracted by the grating, it reaches the filter mirror, undergoes frequency selection filtering and reflection by the filter mirror, and then passes through port 1 of the free-space circulator to port 2. Finally, it returns to the laser gain chip through the first aspherical transmission collimator to form external cavity feedback.

[0038] When the laser is outputting a single longitudinal mode, if the beam expander and selection device includes a prism grating or a transmission grating, the laser can select different wavelengths of the output laser by selecting the grating specifications of the beam expander and selection device, and achieve filtering and frequency selection through the transmission grating of the beam expander and selection device and the reflector of the reflector.

[0039] When a laser outputs a single longitudinal mode, different output spots are achieved based on the resolution of the grating, and the grating bandwidth is inversely proportional to the spot size.

[0040] The grating uses a reflective grating, which is a cemented composite of a prism and a grating. The prism expands the light spot, thus narrowing the grating's filtering bandwidth.

[0041] At the same time, prism pairs or multiple prisms can be added to expand the spot size, further narrowing the laser linewidth.

[0042] Example:

[0043] like Figure 1 As shown, a transmissive grating scheme is adopted. The light emitted from the gain chip 1 is collimated by the aspherical lens 2 and incident on the prism grating or transmissive grating 3. After being diffracted by the prism grating or transmissive grating, it is projected onto the reflector or MEMS 4. The reflector or MEMS rotating mirror 4 is rotated and adjusted, and the light passes through the grating again, returning to the laser chip along the original path to form external cavity feedback, realizing single longitudinal mode output. Different wavelengths can be selected through the grating. Alternatively, a reflective prism grating can be used.

[0044] like Figure 2 As shown, the embodiment Figure 2 In the embodiments Figure 1Based on this, a triangular reflector is added to fold the optical path, further increasing the optical length of the external cavity and reducing the linewidth. Specifically, the light emitted from the optical path gain chip 1 passes through the aspherical transmission collimator 2, enters the reflector 7, is folded by the reflector, and then enters the grating 3. After being diffracted by the grating, it enters the reflector or MEMS 4. After being adjusted by the rotation of the reflector or MEMS 4, it passes through the grating again and returns to the gain chip to form external cavity feedback, realizing single-mode output.

[0045] like Figure 3 As shown, the embodiment Figure 3 In the embodiments Figure 2 Based on this, a free-space circulator and a triangular reflector are added to fold the optical path, further increasing the external cavity length and optimizing the linewidth to make it narrower. Specifically: Light from gain chip 1 passes through aspherical transmission collimator 2, enters free-space circulator port 2, is folded by reflector 7, and then enters prism grating 3. After diffraction by the grating, it is reflected onto the reflector, undergoes frequency selection filtering by reflector 8, and then passes through port 1 to port 2 to form external cavity feedback.

[0046] like Figure 2 The scheme shown uses a mirror to fold the optical path. The optical path is folded using mirror 7 and mirror 4, which increases the external cavity length, narrows the linewidth, and further reduces the size of the laser, thus achieving miniaturization.

[0047] like Figure 3 As shown, further, a free-space circulator and a mirror can be used to fold the external cavity optical path, further increasing the external cavity optical length, shortening the device size, and achieving wavelength tunability, narrow linewidth, and small size.

Claims

1. A wavelength-tunable, small-size, narrow-linewidth laser, characterized in that: The output optical path of the laser includes a beam-expanding and wavelength-selecting device (3) for beam expansion and wavelength selection. The laser uses a laser gain chip (1) as a light source. The diffracted light generated by the light source at the beam-expanding and wavelength-selecting device is reflected back to the active region of the laser gain chip by a reflector (4) as a feedback signal. When a laser needs to increase its linewidth, the module size of the output optical path can be reduced and the external cavity optical length of the output optical path can be increased by adding a folded optical path. The folded optical path includes a free-space circulator, a triangular mirror, or a right-angle prism.

2. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 1, characterized in that: The beam expander and selector includes a prism, a prism, or a transmission grating.

3. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 2, characterized in that: The reflector is a mirror or a MEMS.

4. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 3, characterized in that: The laser gain chip is a single longitudinal mode output laser gain chip. Its reflective end face, grating and reflector / MEMS form a resonant cavity. The diffracted light reflected back to the laser gain chip is transmitted to the isolator FSI (6) through the aspherical lens (5).

5. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 3, characterized in that: The laser's output optical path is provided with an aspherical lens collimator (2).

6. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 3, characterized in that: When the beam expander and wave selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator (2) and is incident on the prism grating or transmission grating. The light generated by the prism grating or transmission grating is diffracted to the reflector (4). After the reflector is rotated and adjusted, the light passes through the grating of the beam expander and wave selector again and returns to the laser chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

7. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 3, characterized in that: When the folded optical path does not contain a circulator, the triangular mirrors in the folded optical path are arranged in pairs. If the beam expander and wave selector is a prism grating or a transmission grating, the light from the output optical path passes through the aspherical lens collimator (2), enters the triangular mirror (7), and is reflected onto the prism grating of the beam expander and wave selector. Then, it is diffracted through the grating of the beam expander and wave selector to the reflector (4). After the reflector is rotated and adjusted, it passes through the grating of the beam expander and wave selector again and returns to the laser gain chip to form external cavity feedback, thereby realizing the single longitudinal mode output of the laser.

8. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 3, characterized in that: When the folded optical path includes a free-space circulator (9) and a filter mirror (8), the light output from the laser gain chip passes through the first aspherical transmission collimator, enters port 2 of the free-space circulator, is reflected by the triangular mirror (7), and then enters the prism of the beam expander and wave selector device. After being diffracted by the grating, it reaches the filter mirror, undergoes frequency selection filtering and reflection by the filter mirror, and then passes through port 1 of the free-space circulator to port 2. Finally, it returns to the laser gain chip through the first aspherical transmission collimator to form external cavity feedback.

9. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 2, characterized in that: The prism is a reflective prism.

10. A wavelength-tunable, small-size, narrow-linewidth laser according to claim 9, characterized in that: A reflective grating is a composite of a prism and a grating. The prism expands the light spot, thus narrowing the grating's filtering bandwidth.

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