Fiber laser amplifier
By combining bidirectional pumping and fiber optics, along with an auxiliary resonant cavity and a high-reflectivity chirped fiber grating, the problem of system instability under high power in erbium-ytterbium co-doped gain fiber was solved, achieving efficient laser conversion and high-quality output.
Patent Information
- Application Number
- CN202423317392.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2034-12-31
AI Technical Summary
In existing technologies, erbium-ytterbium co-doped gain fibers are prone to parasitic oscillations at high power, leading to system instability. Furthermore, high thermal load affects laser conversion efficiency, resulting in poor output laser beam quality and high requirements for input signal optical power.
A bidirectional pumping method is used to combine erbium-doped gain fiber and erbium-ytterbium co-doped gain fiber, which are connected through a mode field adapter. Laser amplification is achieved by combining an auxiliary resonant cavity and a high-reflectivity chirped fiber grating, thus realizing dual-pass amplification and dispersion compensation.
Achieving high laser conversion efficiency and high output power under low power input, suppressing parasitic oscillations, improving beam quality, reducing thermal effects, and enhancing system stability and signal-to-noise ratio.
Smart Images
Figure CN223625403U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of laser technology, and specifically relates to a fiber laser amplifier. Background Technology
[0002] The 1.5μm wavelength laser lies within the low-loss window of optical fiber communication, holding a crucial position not only in this field but also demonstrating strong application potential and commercial value in precision machining, spectroscopy, and medicine. Erbium-doped gain fiber is the primary method for achieving 1.5μm wavelength laser output; however, high concentrations of erbium ions can lead to concentration quenching, resulting in reduced pump efficiency. Research indicates that incorporating ytterbium ions as an activator into erbium-doped fiber can solve this problem. Erbium-ytterbium co-doped fiber can achieve high laser conversion efficiency, but at high power, Yb-ASE (Yb-band amplified spontaneous emission) is very pronounced and prone to parasitic oscillations, affecting system stability. Furthermore, high conversion efficiency places high demands on the power of the input signal light. In addition, strong absorption during high-power pumping leads to high thermal loads on the fiber, impacting both pump light power and laser conversion efficiency.
[0003] Currently, the main solution to the low laser conversion efficiency problem is the use of erbium-ytterbium co-doped gain fiber. However, erbium-ytterbium co-doped gain fiber has high requirements for the input signal light, and high energy conversion efficiency can only be achieved at high input signal power (W level). Currently, a combination of erbium-doped gain fiber and erbium-ytterbium co-doped gain fiber has been used to achieve high laser energy conversion efficiency at low output power, but this uses unidirectional pumping, and strong absorption leads to high thermal load on the fiber, thus limiting the pump light power and its conversion efficiency. Furthermore, at high power, Yb-ASE in erbium-ytterbium co-doped fiber is very pronounced and prone to parasitic oscillations, affecting system stability. In addition, high-power laser output amplifiers generally use large-mode-field gain fiber, but their output laser beam quality is generally poor. Utility Model Content
[0004] Based on this, this utility model proposes a fiber laser amplifier to solve the problems of low laser energy conversion efficiency, low output power, and poor pulse output quality.
[0005] The fiber laser amplifier provided by this utility model comprises, along the optical path direction, the following components in sequence:
[0006] A circulator is used to receive signal light and output the signal light to a forward coupler;
[0007] A forward coupler is used to couple signal light and forward pump light, outputting forward coupled light;
[0008] Erbium-doped gain fiber is used to pre-amplify the forward-coupled light and output pre-amplified laser light;
[0009] Erbium-ytterbium co-doped gain fiber is used to perform main amplification on the pre-amplified laser and output the main amplified laser.
[0010] A reverse coupler is used to couple reverse pump light into an erbium-ytterbium co-doped gain fiber.
[0011] A chirped fiber grating (CFBG) is used to reflect the main amplified laser back to its original path, and the laser is output from the circulator after secondary amplification.
[0012] Furthermore, the erbium-doped gain fiber and the erbium-ytterbium co-doped gain fiber are connected via a mode field adapter.
[0013] Furthermore, the fiber laser amplifier also includes two fiber high-reflection mirrors disposed before and after the erbium-ytterbium co-doped gain fiber along the optical path direction.
[0014] Furthermore, the circulator includes a first end, a second end, and a third end. The first end of the circulator is used to connect to the signal light optical fiber, the second end of the circulator is used to output the signal light, and the third end of the circulator is used to output the laser light after secondary amplification.
[0015] Furthermore, the fiber laser amplifier also includes a single-mode fiber connected to the circulator for optimizing the beam quality of the output laser after secondary amplification.
[0016] Furthermore, the fiber laser amplifier also includes a fiber end cap connected to the single-mode fiber to prevent Fresnel reflection at the fiber end.
[0017] Furthermore, the chirped fiber grating (CFBG) is a 1560nm high-reflectivity CFBG.
[0018] Furthermore, the fiber high-reflection mirror is a 1010nm-1060nm fiber high-reflection mirror.
[0019] Furthermore, the fiber laser amplifier includes a first pump source and a second pump source, wherein the first pump source is used to generate forward pump light and the second pump source is used to generate reverse pump light.
[0020] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0021] 1. This invention employs a combination of bidirectional pumped erbium-doped gain fiber and erbium-ytterbium co-doped gain fiber, achieving high laser conversion power and high-power output laser even with low-power input laser. The bidirectional pumping method provides higher slope efficiency and signal-to-noise ratio, reduces thermal effects, and effectively increases the pump light power that the amplification system can withstand.
[0022] 2. Directly connecting erbium-doped gain fiber and erbium-ytterbium co-doped gain fiber places high demands on the core diameter matching of the fiber. This utility model uses a mode adapter for connection, which can increase the types of gain fiber that can be used.
[0023] 3. This invention uses fiber optic mirrors to form an auxiliary resonant cavity. 10××nm high-reflectivity fiber mirrors are inserted before and after the erbium-ytterbium co-doped gain fiber to form an auxiliary resonant cavity. This auxiliary resonant cavity can effectively suppress the Yb-ASE effect, and the Yb band oscillation within the auxiliary resonant cavity can perform secondary pumping, thereby improving the pump conversion efficiency (PCE).
[0024] 4. After single-pass amplification, the laser light is reflected back to the original path by a 1560nm high-reflectivity CFBG. After a second amplification, the laser light is output from the circulator (completing two-pass amplification). Dual-pass amplification can improve amplification efficiency. The 1560nm high-reflectivity CFBG can also compensate for higher-order dispersion and further filter out Yb-ASE, thereby improving the output light signal-to-noise ratio and improving the output laser performance. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a schematic diagram of the structure of a fiber laser amplifier provided in an embodiment of the present invention.
[0027] The meanings of the labels in the attached diagram are as follows:
[0028] 1-Signal light, 2-Circulator, 3-Forward pump light, 4-Forward coupler, 5-Erbium-doped gain fiber, 6-Mode field adapter, 7-First 1040nm high-reflectivity mirror, 8-Erbium-ytterbium co-doped gain fiber, 9-Second 1040nm high-reflectivity mirror, 10-Reverse coupler, 11-Reverse pump light, 12-1560nm high-reflectivity CFBG, 13-Single-mode fiber, 14-Fiber end cap. Detailed Implementation
[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0030] Please see Figure 1 The fiber laser amplifier provided in this embodiment includes, in sequence along the optical path, a circulator 2, a forward coupler 4, an erbium-doped gain fiber 5, a mode field adapter 6, an erbium-ytterbium co-doped gain fiber 8, a reverse coupler 10, and a 1560nm high-reflectivity CFBG 12, and requires a signal light 1, a forward pump light 3, and a reverse pump light 11.
[0031] Circulator 2 includes a first end 21, a second end 22, and a third end 23; wherein the first end 21 of the circulator is connected to the signal light fiber and is used to receive the signal light; the second end 22 of the circulator outputs the signal light to the forward coupler; and the third end 23 of the circulator outputs the laser light after secondary amplification. The signal light is the laser light to be amplified. As an example, a 1.5μm pulsed laser with a power of approximately 100mW is selected as the signal light to be amplified.
[0032] The main function of a circulator in an optical path is to separate forward and reverse transmitted light, enabling bidirectional optical signal transmission on a single optical fiber. A circulator is non-reciprocal, meaning that the signal transmission direction is irreversible; it can only guide an optical signal from one port to another in one direction at a time.
[0033] Both the forward pump light 3 and the reverse pump light 11 are generated by pump sources, which can be integrated inside the fiber laser amplifier. These pump sources include a first pump source and a second pump source. The first pump source generates the forward pump light, and the second pump source generates the reverse pump light. Bidirectional pumping offers higher slope efficiency and signal-to-noise ratio, reduces thermal effects, and effectively increases the pump light power that the amplification system can withstand.
[0034] Forward coupler 4 is used to couple signal light 1 and forward pump light 3, and outputs forward coupled light.
[0035] The reverse coupler 10 is used to couple the reverse pump light 11 into the erbium-ytterbium co-doped gain fiber 8.
[0036] This invention employs a combination of erbium-doped gain fiber (EDF) and erbium-ytterbium co-doped gain fiber (EYDF) to improve PCE at low input, reduce the number of amplifier stages, and achieve high energy conversion efficiency with low input power. The erbium-doped gain fiber (EDF) is used to pre-amplify the forward-coupled light, outputting pre-amplified laser light. The erbium-ytterbium co-doped gain fiber (EYDF) is used to primarily amplify the pre-amplified laser light, outputting the primarily amplified laser light.
[0037] In this embodiment, the erbium-doped gain fiber 5 and the erbium-ytterbium co-doped gain fiber 8 are connected via a mode field adapter 6. If the size difference between the two fiber segments of the erbium-doped gain fiber 5 and the erbium-ytterbium co-doped gain fiber 8 is not significant, the two fiber segments can be directly connected without the need for the mode field adapter 6.
[0038] Preferably, fiber mirrors are inserted before and after the erbium-ytterbium co-doped gain fiber 8 along the optical path to form an auxiliary resonant cavity. This invention uses 1010nm-1060nm high-reflectivity fiber mirrors as the fiber mirrors. In this embodiment, 1040nm high-reflectivity fiber mirrors are used as an example, namely, a first 1040nm high-reflectivity mirror 7 and a second 1040nm high-reflectivity mirror 9 located before and after the erbium-ytterbium co-doped gain fiber 8 along the optical path. The auxiliary resonant cavity can effectively suppress the Yb-ASE effect, and the Yb-band oscillation within the auxiliary resonant cavity can perform secondary pumping, thereby improving the PCE (pump conversion efficiency).
[0039] It should be noted that the high-reflectivity mirror mentioned in this embodiment of the invention refers to a mirror with a reflectivity exceeding 99%.
[0040] After single-pass amplification, the laser beam is output to the 1560nm high-reflectivity CFBG12. The 1560nm high-reflectivity CFBG is used to reflect the laser back to the original path. After a second amplification, the laser beam is output from the third terminal 23 of the circulator (completing two-pass amplification).
[0041] A high-reflectivity chirped fiber grating (CFBG) is a chirped fiber grating (CFBG) with high reflectivity and an ultra-flat reflection spectrum etched into an optical fiber. In this embodiment, a chirped fiber grating with a reflectivity exceeding 99% can be called a high-reflectivity CFBG, and a 1560nm high-reflectivity CFBG is preferred in this embodiment.
[0042] Dual-pass amplification using a high-reflectivity CFBG improves amplification efficiency and reduces the length of the gain fiber; the optical path structure designed in this invention achieves high integration. Furthermore, the high-reflectivity CFBG can compensate for higher-order dispersion and further filter Yb-ASE, thereby improving the output light signal-to-noise ratio and enhancing the output laser performance.
[0043] Furthermore, the fiber laser amplifier also includes a single-mode fiber 13 connected to the third end 23 of the circulator, for optimizing the beam quality of the output laser after secondary amplification.
[0044] Furthermore, the fiber laser amplifier also includes a fiber end cap 14 connected to the single-mode fiber 13, used to reduce the output optical power density and prevent Fresnel reflection at the output fiber end.
[0045] When the fiber laser amplifier is working, both the erbium-doped gain fiber 5 and the erbium-ytterbium co-doped gain fiber 8 are placed on a water-cooled plate for heat dissipation.
[0046] In a preferred embodiment of this invention, the fiber laser amplifier employs a combination of erbium-doped gain fiber (EDF) and erbium-ytterbium co-doped gain fiber (EYDF), combined with auxiliary resonant cavity pumping to suppress Yb-ASE, and uses a high-reflectivity CFBG to reflect the beam back to the original path for dual-pass amplification. This achieves improved PCE at low input, reduced amplifier stages, increased amplification efficiency, reduced gain fiber length, compensation for higher-order dispersion, and improved output light signal-to-noise ratio. Ultimately, it achieves high energy conversion efficiency, high output power, and high-quality laser pulse output.
[0047] High-reflectivity CFBG can achieve dual-pass amplification to improve amplification efficiency, compensate for higher-order dispersion introduced during amplification, and further filter out Yb-ASE, thereby improving the output light signal-to-noise ratio and output laser performance.
[0048] The fiber laser amplifier disclosed in the embodiments of this utility model has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the core idea of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.
Claims
1. A fiber laser amplifier, characterized in that, The fiber laser amplifier comprises, along the optical path direction, the following components in sequence: A circulator is used to receive signal light and output the signal light to a forward coupler; A forward coupler is used to couple signal light and forward pump light, outputting forward coupled light; Erbium-doped gain fiber is used to pre-amplify the forward-coupled light and output pre-amplified laser light; Erbium-ytterbium co-doped gain fiber is used to perform main amplification on the pre-amplified laser and output the main amplified laser. A reverse coupler is used to couple reverse pump light into an erbium-ytterbium co-doped gain fiber. A chirped fiber grating (CFBG) is used to reflect the main amplified laser back to its original path, and the laser is output from the circulator after secondary amplification.
2. The fiber laser amplifier according to claim 1, characterized in that, The erbium-doped gain fiber and the erbium-ytterbium co-doped gain fiber are connected via a mode field adapter.
3. The fiber laser amplifier according to claim 2, characterized in that, The fiber laser amplifier also includes two fiber high-reflection mirrors arranged along the optical path direction before and after the erbium-ytterbium co-doped gain fiber.
4. The fiber laser amplifier according to claim 1, characterized in that, The circulator includes a first end, a second end, and a third end. The first end of the circulator is used to connect to the signal light fiber, the second end of the circulator is used to output the signal light, and the third end of the circulator is used to output the laser light after secondary amplification.
5. The fiber laser amplifier according to claim 1, characterized in that, The fiber laser amplifier also includes a single-mode fiber connected to the circulator for optimizing the beam quality of the output laser after secondary amplification.
6. The fiber laser amplifier according to claim 5, characterized in that, The fiber laser amplifier also includes a fiber end cap connected to the single-mode fiber to prevent Fresnel reflection at the fiber end.
7. The fiber laser amplifier according to claim 1, characterized in that, The chirped fiber grating (CFBG) is a 1560nm high-reflectivity CFBG.
8. The fiber laser amplifier according to claim 3, characterized in that, The fiber optic high-reflection mirror is a 1010nm-1060nm fiber optic high-reflection mirror.
9. The fiber laser amplifier according to claim 1, characterized in that, The fiber laser amplifier includes a first pump source and a second pump source, wherein the first pump source is used to generate forward pump light and the second pump source is used to generate reverse pump light.