A high-power, narrow-linewidth external cavity laser based on weak feedback

Abstract

This invention relates to a high-power narrow-linewidth laser with weak feedback in an external cavity, comprising: a sub-source output section for outputting a sub-source; a laser output section for outputting narrow-linewidth laser light; an isolator disposed between the sub-source output section and the laser output section; a multilayer reflective film assembly deposited on the input end of the isolator or on the output end of the sub-source output section for filtering the sub-source to form transmitted light and feedback light; the rear end of the isolator outputs the transmitted light to the laser output section as narrow-linewidth laser output; the sub-source output section also receives the feedback light to achieve self-injection locking, possessing the advantages of high-power narrow-linewidth laser output, simple structure, low cost, simple process, relatively small packaging size, and ease of laser packaging.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a high-power, narrow-linewidth external cavity laser based on weak feedback. Background Technology

[0002] Lasers have broad application prospects in fields such as communications, military, medical and optical information processing. With the development of Internet communications, people’s demand for communication capacity has increased dramatically, which puts forward more stringent requirements on the linewidth and frequency stability of lasers.

[0003] Currently, there are two main methods for achieving linewidth narrowing: the internal cavity method and the external cavity method. The internal cavity method mainly achieves linewidth narrowing by designing the structure of the internal resonant cavity of the semiconductor laser, such as a laser diode (DFB). However, its narrowing effect is limited, and its linewidth is generally still in the hundreds of kHz range. The external cavity method mainly utilizes the high quality factor of the external cavity, such as by setting grating reflectors or multiple grating structures in the external cavity of the laser. However, its disadvantages are also obvious: the structure is relatively complex, which increases the difficulty of processing and packaging to a certain extent, and the processing technology requirements are high, resulting in high costs.

[0004] Therefore, it is urgent for those skilled in the art to develop a high-power narrow-linewidth external cavity laser based on weak feedback, which combines the advantages of high-power narrow-linewidth laser output with simple structure, low cost, simple process, relatively small packaging size, and easy laser packaging. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a high-power narrow-linewidth external cavity laser based on weak feedback.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-power, narrow-linewidth external cavity laser based on weak feedback, comprising:

[0008] Sub-light source output section, used to output sub-light sources;

[0009] The laser output section is used to output narrow linewidth lasers;

[0010] An isolator is disposed between the sub-light source output section and the laser output section;

[0011] A multilayer reflective film assembly is deposited on the input end of the isolator or on the output end of the sub-light source output section, for filtering the sub-light source to form transmitted light and feedback light;

[0012] The isolator outputs the transmitted light to the laser output section at its rear end to serve as a narrow linewidth laser output.

[0013] The sub-light source output unit is also used to receive the feedback light in order to achieve self-injection locking.

[0014] Preferably, the multilayer reflective film assembly includes a spacer layer and two reflective films;

[0015] Along the optical path, the spacer layer is located between two reflective films, and the reflectivity of the two reflective films is equal.

[0016] Preferably, the optical thickness of the reflective film is 1 / 4 of the center wavelength.

[0017] Preferably, the reflective film comprises a plurality of alternately stacked first dielectric films and second dielectric films;

[0018] The first dielectric film and the second dielectric film have different refractive indices;

[0019] The first dielectric film and the second dielectric film are made from a substrate, and the refractive index of the substrate ranges from 1.38 to 2.6.

[0020] Preferably, the reflectivity of the multilayer reflective film assembly is less than 5%.

[0021] Preferably, the spacer layer is a single-layer thin film, or the spacer layer is two-layer thin films with the same refractive index.

[0022] Preferably, the sub-light source output section includes a laser diode and an output collimating lens;

[0023] The output collimating lens is disposed between the laser diode and the isolator, forming the output end of the sub-light source output section, and is used to collimate the output light of the laser diode.

[0024] The multilayer reflective film assembly is deposited on the front or rear surface of the output collimating mirror;

[0025] The laser diode is positioned on the effective focal plane of the output collimating lens.

[0026] Preferably, the laser diode is configured as a distributed feedback semiconductor laser;

[0027] The front end of the distributed feedback semiconductor laser is coated with an AR antireflection film, and the rear end is coated with a high reflectivity film.

[0028] Preferably, the laser output section includes a focusing lens and an output optical fiber;

[0029] The focusing lens is used to focus the transmitted light onto the output optical fiber;

[0030] The output optical fiber is used to output narrow linewidth laser light.

[0031] Preferably, it also includes a base, an aluminum nitride heat sink, a thermoelectric cooler, and a thermistor;

[0032] The laser output unit, the isolator, and the aluminum nitride heat sink are all fixedly mounted on the base.

[0033] The sub-light source output section includes a laser diode, which is mounted on the aluminum nitride heat sink.

[0034] The thermistor is disposed on one side of the laser diode to detect the real-time temperature of the laser diode;

[0035] The thermoelectric cooler is used to regulate the laser temperature based on the real-time temperature detected by the thermistor.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The aforementioned technical solution provides a high-power, narrow-linewidth external cavity laser based on weak feedback. By depositing a multi-layer reflective film assembly at the input of the isolator or the output of the sub-source light source, a FP filtering function is achieved. This allows the output light from the sub-source light source to achieve weak feedback self-injection locking after filtering by the multi-layer reflective film assembly, further enabling the laser output section to output high-power, narrow-linewidth laser light. Furthermore, by depositing a multi-layer reflective film at the input of the isolator or the output of the sub-source light source, a high degree of matching with the commonly used butterfly package form of lasers can be achieved. This allows weak feedback self-injection locking to be achieved without increasing the size of the laser diode butterfly package or the number of components, further enabling the laser output section to output high-power, narrow-linewidth laser light. Compared to other existing types of narrow-linewidth semiconductor lasers (such as those with grating structures within the external cavity), the laser in this solution combines the advantages of achieving high-power, narrow-linewidth laser output with simple structure, low cost, simple manufacturing process, and ease of laser packaging. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 A schematic diagram of one example of a laser provided by the present invention.

[0040] Figure 2 for Figure 1A schematic diagram of one example of a multilayer reflective film assembly.

[0041] Figure 3 A schematic diagram of another example of a laser provided by the present invention.

[0042] Figure 4 This is a schematic diagram of a second example of a laser provided by the present invention.

[0043] Figure 5 This is a schematic diagram of a third example of a laser provided by the present invention.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1. Sub-light source output section; 11. Laser diode; 12. Output collimating lens; 2. Laser output section; 21. Focusing lens; 22. Output optical fiber; 3. Isolator; 4. Multilayer reflective film assembly; 41. Spacer layer; 42. Reflective film; 421. First dielectric film; 422. Second dielectric film; 5. Base; 6. Aluminum nitride heat sink; 7. Thermoelectric cooler; 8. Thermistor. Detailed Implementation

[0046] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0047] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] Example 1

[0050] See Figures 1 to 3 This invention provides a high-power, narrow-linewidth external cavity laser based on weak feedback, comprising a sub-source output section 1, a laser output section 2, an isolator 3, and a multilayer reflective film assembly 4. The sub-source output section 1 outputs a sub-source; the laser output section 2 outputs a narrow-linewidth laser; the isolator 3 is disposed between the sub-source output section 1 and the laser output section 2; the multilayer reflective film assembly 4 is deposited at the input end of the isolator 3 or at the output end of the sub-source output section 1, and is used to filter the sub-source to form transmitted light and feedback light. The rear end of the isolator 3 outputs the transmitted light to the laser output section 2 as the narrow-linewidth laser output; the sub-source output section 1 also receives the feedback light to achieve self-injection locking. When the laser is in use, the sub-source output unit 1 outputs a sub-source, which is then sent to the multilayer reflective film assembly 4 and the isolator 3. The multilayer reflective film assembly 4 filters and selects the frequency of the sub-source. Part of the sub-source passes through the multilayer reflective film assembly 4 to form transmitted light. The transmitted light passes through the rear end of the isolator 3 and is output to the laser output unit 2 as a narrow linewidth laser output. Part of the sub-source is reflected by the multilayer reflective film assembly 4 to form reflected light. The reflected light is reflected back to the sub-source output unit 1 to achieve self-injection locking.

[0051] By depositing a multilayer reflective film assembly 4 at the input end of the isolator 3 or the output end of the sub-light source output section 1, a FP filtering function is achieved. This allows the output light from the sub-light source output section 1 to achieve weak feedback self-injection locking after being filtered by the multilayer reflective film assembly 4, further enabling the laser output section 2 to output high-power, narrow-linewidth laser. Furthermore, by setting a multilayer reflective film 42 at the input end of the isolator 3 or the output end of the sub-light source output section 1, a high degree of matching with the commonly used butterfly package form of lasers can be achieved. This allows weak feedback self-injection locking to be achieved without increasing the size of the laser diode butterfly package or the number of components, further enabling the laser output section 2 to output high-power, narrow-linewidth laser. Compared to other existing types of narrow-linewidth semiconductor lasers (such as those with grating structures in the external cavity), the laser in this solution combines the advantages of achieving high-power, narrow-linewidth laser output with simple structure, low cost, simple process, and easy laser packaging.

[0052] Specifically, in this embodiment, the multilayer reflective film assembly 4 can be directly deposited on the front end surface of the isolator 3, that is, deposited on the output end of the isolator 3. This makes the solution perfectly compatible with the existing laser butterfly packaging structure, thus eliminating the need for the alignment step between the outer cavity and the laser during the packaging process.

[0053] To achieve weak feedback, in this embodiment, the reflectivity of the multilayer reflective film assembly 4 is less than 5%.

[0054] See Figure 2 In this embodiment, the multilayer reflective film assembly 4 includes a spacer layer 41 and two reflective films 42; along the optical path direction, the spacer layer 41 is located between the two reflective films 42, and the reflectivity of the two reflective films 42 is equal.

[0055] Specifically, the reflective film 42 includes several alternately stacked first dielectric films 421 and second dielectric films 422; the first dielectric films 421 and second dielectric films 422 have different refractive indices; the first dielectric films 421 and second dielectric films 422 are made of a substrate, and the refractive index of the substrate ranges from 1.38 to 2.6; thus, the overall reflectivity of the reflective film 42 can be changed by changing the refractive index of the first dielectric films 421 and second dielectric films 422.

[0056] Of course, in other embodiments, the reflective film 42 may also be configured as a non-uniform film in which the refractive index changes continuously with the increase of thickness.

[0057] Furthermore, the optical thickness of the reflective film 42 is 1 / 4 of the center wavelength.

[0058] Furthermore, in this embodiment, the spacer layer 41 is configured as a single-layer thin film. Of course, in other embodiments, the spacer layer 41 may also be configured as two-layer thin films with the same refractive index.

[0059] See Figure 1 and Figure 3 In this embodiment, the sub-light source output unit 1 includes a laser diode 11 and an output collimating lens 12. The output collimating lens 12 is disposed between the laser diode 11 and the isolator 3, forming the output end of the sub-light source output unit 1, and is used to collimate the output light of the laser diode 11. Of course, in other embodiments, the sub-light source output unit 1 can also be configured as a combination structure of SOA and output collimating lens 12.

[0060] Specifically, the output collimating lens 12 is configured as an aspherical lens, and the laser diode 11 is disposed on the effective focal plane of the output collimating lens 12.

[0061] Furthermore, the laser diode 11 is configured as a distributed feedback semiconductor laser; along the optical path direction, the front end face of the distributed feedback semiconductor laser is coated with an AR antireflection film, and the rear end face is coated with a high reflectivity film.

[0062] See Figure 1 and Figure 3 In this embodiment, the laser output unit 2 includes a focusing lens 21 and an output optical fiber 22; the focusing lens 21 is used to focus the transmitted light onto the output optical fiber 22; the output optical fiber 22 is used to output a narrow linewidth laser.

[0063] In order to achieve the stability of the entire laser and ensure that the position of the optical components is not affected by vibration and other factors, thereby improving the stability of the output narrow linewidth laser, this embodiment also includes a base 5, on which the sub-light source output unit 1, the laser output unit 2, and the isolator 3 are all fixed.

[0064] Specifically, the laser diode 11 of the sub-light source output unit 1 is fixed to the base 5 via an aluminum nitride heat sink 6. The laser diode 11 is fixedly mounted to the aluminum nitride heat sink 6 using a eutectic bonding process, and the light-emitting surface of the laser diode 11 is flush with one side (one end face along the optical path) of the aluminum nitride heat sink 6. The aluminum nitride heat sink 6 is fixed to the base 5 by gold soldering. The output collimating lens 12 of the sub-light source output unit 1, the focusing lens 21 of the laser output unit 2, and the isolator 3 can all be fixed to the base 5 via corresponding mounting brackets. The mounting brackets and the base 5 can also be fixed together by laser welding.

[0065] It can be known that along the direction of the light path (i.e. Figure 1 As shown in the L direction, the laser diode 11, output collimating lens 12, multilayer reflective film assembly 4, isolator 3, focusing lens 21, and output fiber 22 are arranged in sequence.

[0066] See Figure 3 In order to reduce the deformation of the laser chip (such as laser diode 11 or SOA) caused by temperature changes, and thus the resulting laser power jitter, this embodiment also includes a thermoelectric cooler 7 and a thermistor 8. The active and tight temperature control of the laser chip (such as laser diode 11 or SOA) is achieved through the thermistor 8 and the thermoelectric cooler 7.

[0067] Specifically, the thermistor 8 is positioned on one side of the laser diode 11 to detect the real-time temperature of the laser diode 11; the thermoelectric cooler 7 is placed below the base 5 to regulate the temperature of the entire laser based on the real-time temperature detected by the thermistor 8. In other words, the real-time temperature detected by the thermistor 8 is fed back to the thermoelectric cooler 7, which then controls the overall temperature of the laser in real time.

[0068] Example 2

[0069] See Figure 4 Based on the above embodiment one, the difference in this embodiment is that the multilayer reflective film assembly 4 is deposited on the output end of the sub-light source output section 1. Specifically, in this embodiment, the multilayer reflective film assembly 4 is deposited on the front end surface of the output collimating lens 12.

[0070] Example 3

[0071] See Figure 5Based on the above embodiment one, the difference in this embodiment is that the multilayer reflective film assembly 4 is deposited on the output end of the sub-light source output section 1. Specifically, in this embodiment, the multilayer reflective film assembly 4 is deposited on the rear end surface of the output collimating lens 12.

[0072] It is worth noting that although the multilayer reflective film assembly 4 is shown in the illustration, it is only for schematic purposes. The specific coating method and coating thickness can be set according to actual needs.

[0073] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A high-power, narrow-linewidth external cavity laser based on weak feedback, characterized in that, include: Sub-light source output section (1) is used to output sub-light sources; Laser output section (2) is used to output narrow linewidth laser; An isolator (3) is disposed between the sub-light source output section (1) and the laser output section (2); A multilayer reflective film assembly (4) is deposited on the input end of the isolator (3) or on the output end of the sub-light source output section (1) to filter the sub-light source in order to form transmitted light and feedback light. The isolator (3) outputs the transmitted light to the laser output section (2) at its rear end as a narrow linewidth laser output. The sub-light source output unit (1) is also used to receive the feedback light in order to achieve self-injection locking; The multilayer reflective film assembly (4) includes a spacer layer (41) and two reflective films (42). Along the optical path, the spacer layer (41) is located between two reflective films (42), and the reflectivity of the two reflective films (42) is equal; The spacer layer (41) is configured as a single-layer thin film, or the spacer layer (41) is configured as two-layer thin films with the same refractive index.

2. The external cavity high-power narrow-linewidth laser based on weak feedback according to claim 1, characterized in that, The optical thickness of the reflective film (42) is 1 / 4 times the center wavelength.

3. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 1, characterized in that, The reflective film (42) includes a plurality of alternately stacked first dielectric films (421) and second dielectric films (422). The first dielectric film (421) and the second dielectric film (422) have different refractive indices; The first dielectric film (421) and the second dielectric film (422) are made from a substrate, and the refractive index of the substrate ranges from 1.38 to 2.

6.

4. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 1, characterized in that, The reflectivity of the multilayer reflective film assembly (4) is less than 5%.

5. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 1, characterized in that, The sub-light source output section (1) includes a laser diode (11) and an output collimating lens (12). The output collimating lens (12) is disposed between the laser diode (11) and the isolator (3) to form the output end of the sub-light source output section (1) and is used to collimate the output light of the laser diode (11); The multilayer reflective film assembly (4) is deposited on the front or rear surface of the output collimating mirror (12); The laser diode (11) is disposed on the effective focal plane of the output collimating lens (12).

6. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 5, characterized in that, The laser diode (11) is configured as a distributed feedback semiconductor laser; The front end of the distributed feedback semiconductor laser is coated with an AR antireflection film, and the rear end is coated with a high reflectivity film.

7. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 1, characterized in that, The laser output unit (2) includes a focusing lens (21) and an output optical fiber (22). The focusing lens (21) is used to focus the transmitted light onto the output optical fiber (22). The output optical fiber (22) is used to output narrow linewidth laser.

8. A high-power, narrow-linewidth external cavity laser based on weak feedback according to claim 1, characterized in that, It also includes a base (5), an aluminum nitride heat sink (6), a thermoelectric cooler (7) and a thermistor (8); The laser output unit (2), the isolator (3) and the aluminum nitride heat sink (6) are all fixed on the base (5); The sub-light source output section (1) includes a laser diode (11), which is mounted on the aluminum nitride heat sink (6); The thermistor (8) is disposed on one side of the laser diode (11) to detect the real-time temperature of the laser diode (11); The thermoelectric cooler (7) is used to regulate the laser temperature based on the real-time temperature detected by the thermistor (8).

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