Distributed feedback laser array line width narrowing device and method based on self-injection feedback

Abstract

The invention discloses a distributed feedback laser array line width narrowing device and method based on self-injection feedback, and the device is characterized in that a laser array is connected with an array waveguide grating, the array waveguide grating is connected with an optical fiber circulator, and the optical fiber circulator is connected with an optical fiber coupler; the output of the laser array is combined through the array waveguide grating and then input into the optical fiber circulator, part of laser entering the optical fiber coupler from the optical fiber circulator passes through the optical fiber circulator and the array waveguide grating again and is injected into the laser array in the form of optical feedback, and the working state of the laser array is influenced by the optical feedback. And the line width of the laser array is narrowed. Through the synergistic effect of the laser array, the array waveguide grating, the optical fiber circulator and the optical fiber coupler, a self-injection feedback loop is constructed, part of output laser is re-injected into the laser unit after wave combination and light splitting, and phase noise is suppressed through optical feedback, so that the linewidth is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic chips, and in particular to a device and method for narrowing the line width of a distributed feedback laser array based on self-injection feedback. Background Art

[0002] Semiconductor lasers have become core components in the field of optical fiber communication and sensing due to their advantages such as small size, low cost and good single-mode characteristics. However, with the development of coherent optical communication and high-precision measurement systems, the MHz-level linewidth and single-channel design of traditional distributed feedback lasers can no longer meet the requirements of multi-wavelength and narrow linewidth. Although the reconstruction of equivalent chirp technology can realize low-cost multi-wavelength laser arrays, the Y-branch waveguide coupling device it relies on still has the problems of high power consumption and output power decreasing with the number of channels. Although small-sized combiners (such as multi-mode interferometers) have been proposed, their process is complex and the wavelength sensitivity is insufficient. Although waveguide array gratings have the advantages of low loss and high wavelength selectivity, the difficulty of traditional coupling methods increases significantly with the increase in the number of channels. Summary of the Invention

[0003] The purpose of the present invention is to provide a device and method for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback, which uses the self-injection feedback mechanism of an optical fiber circulator to compress the linewidth of the distributed feedback laser from the MHz level to the kHz level.

[0004] To achieve the above object, the technical solution provided by the present invention is:

[0005] The first aspect of the present application provides a device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback, comprising: a laser array, an arrayed waveguide grating, a fiber circulator, and a fiber coupler;

[0006] The laser array is connected to an arrayed waveguide grating, which is connected to a fiber circulator, which is connected to a fiber coupler. The output of the laser array is combined by the arrayed waveguide grating and then input into the fiber circulator. Part of the laser light that enters the fiber coupler from the fiber circulator passes through the fiber circulator and the arrayed waveguide grating again and is injected into the laser array in the form of optical feedback. The optical feedback is used to influence the working state of the laser array, thereby narrowing the line width of the laser array.

[0007] To optimize the above technical solutions, specific measures taken also include:

[0008] The optical fiber circulator has port 1, port 2, and port 3; the laser propagation routes between port 1, port 2, and port 3 of the optical fiber circulator are: the laser propagates unidirectionally from port 2 to port 3, and propagates unidirectionally from port 1 to port 2;

[0009] The output of the laser array is combined by an arrayed waveguide grating and then input into port 2 of the fiber circulator. The laser propagates along port 2 to port 3. Port 3 of the fiber circulator is connected to the input end of the fiber coupler. The other end of the fiber coupler is the splitter end, one of which is connected to port 1 of the fiber circulator.

[0010] After the laser light propagates from port 3 to the fiber coupler and is split, part of it is transmitted from port 1 to port 2, and then injected from port 2 into each laser unit of the laser array through the arrayed waveguide grating, forming optical feedback.

[0011] Furthermore, the optical fiber coupler is a 1×2 splitter coupler with a splitting ratio of 10:90. A single port on one side is an input end, which is connected to the three ports of the optical fiber circulator. The other side includes a first splitter end with a splitting ratio of 10% connected to the one port of the optical fiber circulator and a second splitter end with a splitting ratio of 90% as an output end.

[0012] Furthermore, the laser array is a distributed feedback laser array chip; and the arrayed waveguide grating is an arrayed waveguide grating based on silicon-on-insulator.

[0013] Furthermore, the laser array includes a multi-quantum well layer and a grating layer. The grating layer is an array structure composed of multiple gratings with different sampling periods, which respectively correspond to each laser unit in the laser array.

[0014] Furthermore, the grating layer is designed and manufactured using a reconstruction equivalent chirp technology, and after holographic exposure and ultraviolet lithography, a sampling grating with different periods is formed, and an equivalent π phase shift structure exists at the central position of the grating.

[0015] Furthermore, in the laser array, each laser unit has a different period, and is respectively provided with an equivalent π phase shift structure, the corresponding grating Bragg wavelength interval is fixed, and the length of the equivalent π phase shift structure is half of the corresponding sampling period.

[0016] Furthermore, the arrayed waveguide grating has 7 to 10 channels, and the channel spacing is 1.6 nm.

[0017] Furthermore, the laser array and the arrayed waveguide grating are connected via photon wire bonding; and the arrayed waveguide grating is connected to the fiber circulator via a single-mode optical fiber.

[0018] Furthermore, the laser array and arrayed waveguide grating are arranged on a carrier, and the carrier is a silicon photonic integrated platform. The laser array and arrayed waveguide grating are interconnected through on-chip waveguides.

[0019] In a second aspect of the present application, a method for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback is disclosed. The output of the laser array is combined by an array waveguide grating and then input into a fiber circulator. Part of the laser light that enters the fiber coupler from the fiber circulator passes through the fiber circulator and the array waveguide grating again and is injected into the laser array in the form of optical feedback. The optical feedback is used to influence the working state of the laser array, thereby narrowing the linewidth of the laser array.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a device and method for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback. Through the synergistic effect of a laser array, an arrayed waveguide grating, an optical fiber circulator, and an optical fiber coupler, a self-injection feedback loop is constructed. Part of the output laser is re-injected into the laser unit after combining and splitting, and optical feedback is used to suppress phase noise, thereby significantly narrowing the linewidth.

[0022] This method uses heterogeneous integration technology to bond the laser array and arrayed waveguide grating to a silicon photonic platform, combines the reconstruction of equivalent chirp technology to design a multi-wavelength grating structure, and cooperates with the directional transmission characteristics of the fiber circulator to achieve multi-wavelength linewidth synchronous compression. At the same time, it avoids the traditional external cavity solution's dependence on long optical fibers, and has the advantages of high wavelength selectivity, low loss and process compatibility, providing a low-cost, highly stable multi-wavelength narrow-linewidth light source solution for dense wavelength division multiplexing communications and high-precision sensing systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the line width narrowing of the distributed feedback laser array based on self-injection feedback of the present invention.

[0024] Figure 2 It is a schematic diagram of the laser linewidth testing system of the present invention.

[0025] Figure 3 This is a schematic diagram of the line width of each channel in the laser array before line width narrowing.

[0026] Figure 4 It is a schematic diagram of the line width of each channel in the laser array after the line width is narrowed.

[0027] Figure 5 Schematic diagram of the linewidth of a single channel in a laser array at different injection intensities.

[0028] The figures are marked as follows: 101-laser array, 102-arrayed waveguide grating, 103-carrier, 104-single-mode optical fiber, 105-optical fiber circulator, 106-optical fiber coupler, 107-polarization controller, 201-first optical fiber coupler, 202-test system single-mode optical fiber, 203-delay optical fiber, 204-acousto-optic modulator, 205-polarization controller, 206-second optical fiber coupler, 207-photodetector, 208-spectrometer. DETAILED DESCRIPTION

[0029] The above contents of the present invention are further described in detail below in the form of specific implementation methods, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0030] The orientation or position relationship is based on the relationship shown in the drawings and is only for the convenience of describing the present invention and simplifying the description. It does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0031] This application provides a device and method for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback, such as Figure 1 As shown, it includes: a laser array 101, an arrayed waveguide grating 102, a fiber circulator 105 and a fiber coupler 106;

[0032] The laser array 101 is connected to the arrayed waveguide grating 102, the arrayed waveguide grating 102 is connected to the fiber circulator 105, and the fiber circulator 105 is connected to the fiber coupler 106. The output of the laser array 101 is combined by the arrayed waveguide grating 102 and then input into the fiber circulator 105. Part of the laser light that enters the fiber coupler 106 from the fiber circulator 105 passes through the fiber circulator 105 and the arrayed waveguide grating 102 again and is injected into the laser array 101 in the form of optical feedback. The optical feedback is used to influence the working state of the laser array 101, thereby narrowing the line width of the laser array 101.

[0033] The optical fiber circulator 105 has port 1, port 2, and port 3. The laser propagation routes between port 1, port 2, and port 3 of the optical fiber circulator 105 are: the laser propagates unidirectionally from port 2 to port 3 and from port 1 to port 2.

[0034] The output of the laser array 101 is combined by the arrayed waveguide grating 102 and input into port 2 of the fiber circulator 105. The laser propagates along port 2 to port 3. Port 3 of the fiber circulator 105 is connected to the input end of the fiber coupler 106. The other end of the fiber coupler 106 is a splitter end, one of which is connected to port 1 of the fiber circulator 105.

[0035] After the laser light propagates from port 3 to the fiber coupler 106 and is split, part of it is transmitted from port 1 to port 2, and then injected from port 2 into each laser unit of the laser array 101 through the arrayed waveguide grating 102, forming optical feedback.

[0036] Preferably, the laser array 101 is a distributed feedback DFB laser array chip; and the arrayed waveguide grating 102 is an arrayed waveguide grating AWG based on silicon-on-insulator (SOI).

[0037] The present invention uses the self-injection feedback mechanism of the optical fiber circulator 105 to compress the linewidth of the distributed feedback laser from the MHz level to the kHz level, reducing it by an average of about 200 times. This solution overcomes the wavelength sensitivity and bandwidth limitations of traditional external cavities such as Fabry-Perot cavities, and can achieve synchronous narrowing of multi-wavelength linewidths without relying on high-cost long single-mode optical fibers.

[0038] In some embodiments, the fiber optic coupler 106 is a 1×2 splitter coupler with a splitting ratio of 10:90, wherein a single port on one side is an input end connected to port 3 of the fiber optic circulator 105, and the other side includes a first splitter end with a splitting ratio of 10% connected to port 1 of the fiber optic circulator 105 and a second splitter end with a splitting ratio of 90% as an output end.

[0039] The laser array 101 includes a multi-quantum well layer and a grating layer. The grating layer is an array structure composed of multiple gratings with different sampling periods, which respectively correspond to each laser unit in the laser array 101.

[0040] The grating layer is designed and manufactured using the reconstructed equivalent chirp technology to achieve precise control of the wavelength; after holographic exposure and ultraviolet lithography, sampling gratings with different periods are formed, and an equivalent π phase shift structure exists in the central position of the grating to ensure that the laser operates at a single wavelength, thereby realizing the manufacture of a multi-wavelength laser array.

[0041] In the laser array 101 , each laser unit has a different period and is respectively provided with an equivalent π phase-shift structure, the corresponding grating Bragg wavelength interval of which is fixed, and the length of the equivalent π phase-shift structure is half of the corresponding sampling period.

[0042] In some embodiments, the arrayed waveguide grating 102 has 8 channels with a channel spacing of 1.6 nm.

[0043] The laser array 101 and the arrayed waveguide grating 102 are connected via photon wire bonding; the arrayed waveguide grating 102 is connected to the fiber circulator 105 via a single-mode optical fiber 104 .

[0044] The present invention uses photonic wire bonding technology to heterogeneously integrate the laser array 101 with the passive waveguide array waveguide grating 102, reducing alignment accuracy requirements and improving stability. The array waveguide grating 102 acts as a wavelength selective router and combiner to eliminate injection crosstalk between wavelengths of multiple laser units.

[0045] In some embodiments, the laser array 101 and the arrayed waveguide grating 102 are disposed on a carrier 103 , which is a silicon photonics integration platform. The laser array 101 and the arrayed waveguide grating 102 are interconnected via on-chip waveguides.

[0046] In some embodiments, the distributed feedback laser array chip of the present invention is formed by stacking a multi-layer structure, including a substrate layer, a buffer layer, an upper confinement layer, a lower confinement layer, a corrosion barrier layer, a waveguide layer, and a contact layer.

[0047] The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback described in this embodiment uses the characteristics of self-injection feedback to achieve laser linewidth narrowing, utilizes the reconstruction equivalent chirp technology to prepare a sampled grating to control the wavelength of the laser array, uses photonic wire bonding technology to achieve low-loss connection between the laser chip and the passive array waveguide grating, and utilizes a fiber circulator and a fiber coupler to achieve self-injection feedback, thereby achieving highly integrated multi-channel laser linewidth narrowing.

[0048] The eight channels in this embodiment's distributed feedback laser array are fabricated using reconstructed equivalent chirp technology. Holographic exposure and UV lithography are used to fabricate each laser grating layer. Different lasers correspond to different sampling grating periods, which in turn correspond to different lasing wavelengths. By properly designing the position of the +1-order sub-grating and the gain region of the active region, effective lasing of the +1 sub-grating and suppression of the 0th-order grating are achieved. A π-phase shift structure is placed at the center of each laser grating layer to ensure stable single-wavelength operation of the laser.

[0049] Reference Figure 2 In this embodiment, the line width of the laser is measured by the self-heterodyne method, and the characteristics of the arrayed waveguide grating are used to achieve the coupling of multi-wavelength light waves of the light source and the wave splitting during self-injection, thereby achieving the narrowing of the line width of each laser.

[0050] Effect test:

[0051] (1) Line width narrowing test method:

[0052] Use as Figure 2 The linewidth test device based on the self-heterodyne method is shown in FIG. 1 to test the initial linewidth of a laser array without self-injection feedback at a current of 120 mA. During the test, the connection between the 10% splitting port of the fiber coupler 106 and the polarization controller is disconnected. At this time, the laser array has no self-injection feedback, and the 90% splitting port of the fiber coupler is connected to the left input port of the first fiber coupler 201 in the test device. The test results are shown in FIG. Figure 3 As shown by Figure 3 It can be seen that in the absence of self-injection feedback, the initial linewidths of the eight channels of the laser array are 8.9 (CH1), 4.8 (CH2), 17.8 (CH3), 3.5 (CH4), 7.7 (CH5), 6.2 (CH6), 4.1 (CH7) and 11.8 (CH8) MHz, respectively.

[0053] use Figure 2 The device shown in the present invention proposes the following Figure 1 The self-injection scheme shown in the figure was tested, and the test results were as follows Figure 4 As shown, the initial linewidths of the eight channels of the laser array are 29.2 (CH1), 80.2 (CH2), 107 (CH3), 16.5 (CH4), 50.1 (CH5), 20.6 (CH6), 16.9 (CH7) and 63.7 (CH8) kHz, respectively, indicating that the method proposed in the invention can achieve significant narrowing of the linewidth.

[0054] (2) Effect of self-injection intensity on line width

[0055] By connecting a tunable optical attenuator to the 10% splitting end of the fiber coupler to control the intensity of the feedback light, adjusting the loss of the tunable optical attenuator, and measuring the attenuated power value with a power meter before injecting it into the 1st port of the fiber circulator, the actual power of the injected laser is obtained by subtracting the insertion loss of the arrayed waveguide grating and the coupling loss of the photon wire bonding. Figure 5 As shown in the figure, the line width of CH4 is evaluated under various feedback power conditions. Figure 5 It can be seen that by increasing the feedback power, the 3.5MHz linewidth of the DFB laser in the free-running state can be reduced to 16.5kHz. At the same time, from this evolution process, it can be seen that as the feedback intensity increases, the laser linewidth narrows, which is consistent with theoretical expectations.

[0056] The present invention adopts photon wire bonding and arrayed waveguide grating technology to increase the coupling efficiency and system integration of array lasers. The wave splitting and combining characteristics of the arrayed waveguide grating are used to realize simultaneous self-injection of multiple lasers, thereby achieving simultaneous narrowing of the linewidth of the laser array. This solution eliminates the wavelength dependence of traditional external cavities, reduces the linewidth of multi-wavelength sources, and meets the application requirements of coherent optical communication systems and high-precision detection.

[0057] The present invention eliminates the wavelength dependence of the traditional external cavity and reduces the linewidth of the multi-wavelength source. It has broad application prospects in fields such as coherent optical communication systems and high-precision detection. It provides a high-performance multi-wavelength light source for high-capacity coherent optical communication systems and high-precision optical detection, and has important application value.

[0058] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement and improvement made by any technician familiar with the profession to the above embodiment without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback, characterized in that: include: Laser array (101), arrayed waveguide grating (102), fiber circulator (105) and fiber coupler (106); The laser array (101) is connected to an arrayed waveguide grating (102), the arrayed waveguide grating (102) is connected to an optical fiber circulator (105), and the optical fiber circulator (105) is connected to an optical fiber coupler (106); the output of the laser array (101) is combined by the arrayed waveguide grating (102) and then input into the optical fiber circulator (105); part of the laser light entering the optical fiber coupler (106) from the optical fiber circulator (105) passes through the optical fiber circulator (105) and the arrayed waveguide grating (102) again and is injected into the laser array (101) in the form of optical feedback, and the optical feedback is used to influence the working state of the laser array (101), so that the line width of the laser array (101) is narrowed.

2. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The optical fiber circulator (105) has port 1, port 2, and port 3; the laser propagation routes between port 1, port 2, and port 3 of the optical fiber circulator (105) are: the laser propagates unidirectionally from port 2 to port 3, and propagates unidirectionally from port 1 to port 2; The output of the laser array (101) is combined by the arrayed waveguide grating (102) and then input into port 2 of the optical fiber circulator (105). The laser propagates along port 2 to port 3. Port 3 of the optical fiber circulator (105) is connected to the input end of the optical fiber coupler (106). The other end of the optical fiber coupler (106) is a splitting end, and one of the splitting ends is connected to port 1 of the optical fiber circulator (105). After the laser light propagates from port 3 to the optical fiber coupler (106), part of it is transmitted from port 1 to port 2, and then injected from port 2 into each laser unit of the laser array (101) through the arrayed waveguide grating (102), thereby forming optical feedback.

3. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 2, characterized in that: The optical fiber coupler (106) is a 1×2 splitting coupler with a splitting ratio of 10:

90. A single port on one side is an input end connected to the three ports of the optical fiber circulator (105), and the other side includes a first splitting end with a splitting ratio of 10% connected to the one port of the optical fiber circulator (105) and a second splitting end with a splitting ratio of 90% as an output end.

4. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The laser array (101) is a distributed feedback laser array chip; the arrayed waveguide grating (102) is an arrayed waveguide grating based on insulating silicon.

5. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The laser array (101) comprises a multi-quantum well layer and a grating layer. The grating layer is an array structure composed of a plurality of gratings with different sampling periods, which respectively correspond to the laser units in the laser array (101).

6. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 5, characterized in that: The grating layer is designed and manufactured using a reconstruction equivalent chirp technology, and is subjected to holographic exposure and ultraviolet lithography to form sampling gratings with different periods, and an equivalent π phase shift structure is present at the center of the grating. In the laser array (101), each laser unit has a different period and is provided with an equivalent π phase shift structure, the corresponding grating Bragg wavelength interval of which is fixed, and the length of the equivalent π phase shift structure is half of the corresponding sampling period.

7. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The arrayed waveguide grating (102) has 7 to 10 channels, and the channel interval is 1.6 nm.

8. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The laser array (101) and the arrayed waveguide grating (102) are connected via photon wire bonding; The arrayed waveguide grating (102) is connected to the optical fiber circulator (105) via a single-mode optical fiber (104).

9. The device for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback according to claim 1, characterized in that: The laser array (101) and the arrayed waveguide grating (102) are arranged on a carrier (103), and the carrier (103) is a silicon photonic integrated platform. The laser array (101) and the arrayed waveguide grating (102) are interconnected via an on-chip waveguide.

10. A method for narrowing the linewidth of a distributed feedback laser array based on self-injection feedback, characterized by: The output of the laser array (101) is combined by an arrayed waveguide grating (102) and then input into a fiber circulator (105). Part of the laser light that enters the fiber coupler (106) from the fiber circulator (105) passes through the fiber circulator (105) and the arrayed waveguide grating (102) again and is injected into the laser array (101) in the form of optical feedback. The optical feedback is used to influence the working state of the laser array (101), so that the line width of the laser array (101) is narrowed.

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