High-performance ultra-short-cavity 1091nm single-frequency fiber laser based on Yb: YAG-SiO2 fiber

Abstract

The invention relates to a Yb: YAG-SiO2 optical fiber-based high-performance ultra-short cavity 1091nm single-frequency optical fiber laser, which belongs to the field of optical fiber lasers and comprises a laser pumping source, an optical fiber wavelength division multiplexer, a laser resonant cavity, an accurate temperature control system and an optical fiber isolator, the laser resonant cavity comprises a high-reflectivity fiber bragg grating, a Yb: YAG-SiO2 gain fiber and a low-reflectivity fiber bragg grating which are connected in sequence; pump light emitted by the laser pumping source is injected into the laser resonant cavity through the optical fiber wavelength division multiplexer, single-frequency laser of 1091 nm is generated under the action of the optical fiber grating, and the single-frequency laser enters the optical fiber isolator through the signal end of the optical fiber wavelength division multiplexer and is output. By using the advantages of high rare earth doping concentration, large gain, high mechanical strength, easy welding with commercial silica fibers and the like of the Yb: YAG-SiO2 fiber, high-efficiency, high-stability and narrow-linewidth 1091 nm single-frequency laser output is realized in a centimeter-level laser cavity.

Description

Technical Field

[0001] The present invention relates to a high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, belonging to the technical field of fiber lasers. Background Art

[0002] Single-frequency lasers (SFLs) have the advantages of narrow linewidth, low noise, long coherence length, etc., and are widely used in fields such as coherent beam combining, high-resolution spectroscopy, gravitational wave detection, and lidar. In particular, 1091 nm SFLs have attracted much attention due to their great application potential in fields such as astronomy, semiconductor industry, and biomedicine. Among them, the 545.5 nm laser directly generated by its second harmonic generation can be used to excite a continuous-wave Lyman-α source based on four-wave mixing in mercury vapor, and the 363.8 nm laser generated after third harmonic generation can be used to detect defects in semiconductor wafers and excite Raman spectra. In addition, it can also be used as the pump light of cascaded Raman lasers and amplifiers to obtain lasers with special wavelengths.

[0003] Although traditional 1091 nm SFLs can be realized by distributed feedback (DFB) laser diodes (LDs), their relatively wide linewidth and low signal-to-noise ratio limit their further applications. In contrast, single-frequency fiber lasers (SFFLs) are more promising due to their lower linewidth, smaller noise, and better beam quality. Currently, the laser in this band is mainly generated by Yb 3+ doped fiber. However, 1091 nm is almost at the edge of the emission spectrum of Yb 3+ doped fiber, with a small emission cross-section, and will face serious challenges of spontaneous emission (ASE) / parasitic laser during the generation of signal laser. However, high-performance 1091 nm SFFLs are also urgently needed and have not been reported yet.

[0004] For the implementation methods of 1091 nm SFFLs, they can be divided into ring cavity structure, DFB structure, and distributed Bragg reflector (DBR) structure. The ring cavity structure usually has a relatively long laser cavity length. To ensure single-frequency output, filtering devices often need to be inserted into the cavity, which will introduce additional insertion losses, and its structure is complex and the single-frequency stability is poor. Compared with the ring cavity, DFB and DBR cavities are easier to realize stable SFFLs due to their short cavity structures and large longitudinal mode spacing of the laser. However, the short cavity structure severely limits the length of the gain fiber. Especially for the DBR structure, combined with the bandwidth of commercial gratings, the length of the gain fiber is limited within a few centimeters. Therefore, a gain fiber with a high doping concentration is required to provide sufficient gain. Unfortunately, for traditional silica fibers, the rare earth doping level is low, and it is difficult to realize efficient SFFLs in this band. Although doped with Yb 3+Phosphate optical fibers can achieve high doping of rare earth ions. However, due to the introduction of P elements, the radiation spectral intensity in the long-wave band decreases sharply. In addition, such optical fibers have a low softening point, poor mechanical properties and thermal stability, and it is difficult to achieve high-strength fusion splicing with traditional quartz fiber devices, which is not conducive to the stable output of single-frequency lasers and difficult to adapt to harsh working environments. Summary of the Invention

[0005] In view of the above problems, the present invention provides a high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber. This 1091 nm single-frequency laser has the advantages of compact structure, high conversion efficiency, good stability, easy operation, etc. The output single-frequency laser wavelength is 1091.4 nm, the maximum output power is adjustable in the range of 0 mW to 500 mW, the laser slope efficiency is greater than 35%, the long-term power fluctuation is less than 0.35% (RMS), and the laser linewidth is less than 50 kHz.

[0006] The technical solution of the present invention is as follows:

[0007] A high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, including a laser pump source, an optical fiber wavelength division multiplexer, a laser resonator, a precise temperature control system and an optical fiber isolator. The laser resonator includes a high-reflectivity fiber grating, a gain fiber and a low-reflectivity fiber grating connected in sequence. The optical fiber wavelength division multiplexer has a total of three ports, where the common port is connected to the low-reflectivity fiber grating, the reflection port is connected to the laser pump source, and the signal port is connected to the optical fiber isolator; among them, the gain fiber is a Yb:YAG-SiO2 gain fiber;

[0008] The pump light emitted by the laser pump source is injected into the laser resonator through the optical fiber wavelength division multiplexer, and 109-nm single-frequency laser is generated under the action of the fiber grating, and then enters the optical fiber isolator from the signal port of the optical fiber wavelength division multiplexer and is output from the output port of the optical fiber isolator.

[0009] Preferably, for the Yb:YAG-SiO2 gain fiber, its cladding is made of high-purity quartz glass, and the core is a mixed vitreous body of Yb 3+ doped yttrium aluminum garnet and SiO2, and Yb 3+ is uniformly doped in the core, and the doping concentration is 1 wt.% to 50 wt.%.

[0010] Preferably, for the Yb:YAG-SiO2 gain fiber, its cladding diameter is 125 μm, and the core diameter is 3 to 25 μm.

[0011] Preferably, for the Yb:YAG-SiO2 gain fiber, its gain coefficient at 1091 nm is greater than 1.45 dB / cm, but not limited to this value.

[0012] Preferably, for the high-reflectivity fiber grating, its reflectivity at 1091 nm is greater than 99.5%, the reflection bandwidth is 0.15 - 0.5 nm, and the grating length is less than 20 mm.

[0013] Preferably, for the low-reflectivity fiber grating, its reflectivity is 40 - 95%, the reflection bandwidth is less than 0.08 nm, and the fiber grating length is less than 35 mm.

[0014] Preferably, the low-reflectivity fiber grating group is a non-polarization-maintaining fiber grating or a polarization-maintaining fiber grating.

[0015] More preferably, the laser pump source is a semiconductor laser, a fiber laser or a solid-state laser, and the central wavelength of the pump source is between 905 - 990 nm.

[0016] More preferably, the length of the gain fiber is 2 - 15 mm.

[0017] More preferably, the entire laser resonator is fixed in an accurate temperature control system to keep the temperature of the resonator of the laser at a constant temperature value, realizing stable single-frequency laser output. The temperature control accuracy of the accurate temperature control system is 0.01 °C.

[0018] For details not elaborated in the present invention, reference can be made to the prior art.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The present invention provides a high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, which has a compact structure, high conversion efficiency, good stability, and narrow output linewidth, and has broad application prospects. For example, it can be used as the seed source of a 1091 nm fiber amplifier, and the 363.8 nm laser generated by frequency tripling can be used for the detection of semiconductor wafers and the excitation of Raman spectra, etc.

[0021] (2) The present invention selects Yb:YAG-SiO2 fiber as the gain medium. This fiber has a high content of Y2O3 and Al2O3, which can effectively suppress the concentration quenching effect, increase the solubility of rare earth ions, so as to provide a sufficiently high gain (unit gain > 1.45 dB / cm). An ideal laser conversion efficiency can be achieved with a short fiber of centimeter magnitude; in addition, this kind of fiber also has the advantages of high mechanical strength and easy high-strength fusion splicing with quartz fiber, etc., to ensure stable and efficient single-frequency laser output.

[0022] (3) The 1091nm single-frequency fiber laser of the present invention adopts a DBR ultra-short cavity structure. The output single-frequency laser wavelength is 1091.4nm, and the maximum output power is adjustable within the range of 0mW to 500mW (by controlling the pump power, and then controlling the output power, that is, the output power increases linearly with the increase of the pump power). The laser slope efficiency is greater than 35%, the long-term power fluctuation is less than 0.35% (RMS), and the laser linewidth is less than 50kHz.

[0023] (4) The present invention provides a new feasible technical solution for the development of single-frequency fiber lasers in other special wavelength bands, that is, by utilizing the high gain, high mechanical strength and high compatibility with silica fiber of Re:YAG-SiO2 fiber, it may be possible to realize single-frequency lasers in some wavelength bands that are difficult to achieve with existing fibers at present, where Re includes Nd, Yb, Er, Tm, Ho, etc. Description of the Drawings

[0024] The specification drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application.

[0025] Figure 1 It is a schematic structural diagram of a high-performance, ultra-short cavity 1091nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber of the present invention;

[0026] Figure 2 It is the output spectrum diagram of Embodiment 1 of the present invention, where the abscissa in the figure is the wavelength, the ordinate is the laser intensity, and the OSNR is the optical signal-to-noise ratio of the laser;

[0027] In the figure, 1, laser pump source; 2, fiber wavelength division multiplexer; 3, low-reflectivity fiber grating; 4, Yb:YAG-SiO2 gain fiber; 5, high-reflectivity fiber grating; 6, laser resonator; 7, fiber isolator; 8, precise temperature control system. Detailed Embodiments

[0028] The present invention lists the following embodiments to further illustrate the present invention in detail, but the embodiments of the present invention are not limited thereto. For researchers in this field, the present invention can have various modifications and changes. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0029] In the present invention, unless otherwise specified, the raw materials used are all well-known commercially available products in this field.

[0030] Embodiment 1

[0031] A high-performance, ultra-short cavity 1091nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, as Figure 1 shown, includes a laser pump source 1, an optical fiber wavelength division multiplexer 2, a laser resonator 6, a precise temperature control system 8 and an optical fiber isolator 7. The laser resonator 6 includes a high-reflectivity fiber grating 5, a gain fiber and a low-reflectivity fiber grating 3 connected in sequence. The optical fiber wavelength division multiplexer 2 has a total of three ports, where the common port is connected to the low-reflectivity fiber grating 3, the reflection port is connected to the laser pump source, and the signal port is connected to the optical fiber isolator 7. Among them, the gain fiber is a Yb:YAG-SiO2 gain fiber 4;

[0032] The pump light emitted by the laser pump source 1 is injected into the laser resonator through the optical fiber wavelength division multiplexer 2, and single-frequency laser of 1091nm is generated under the action of the fiber grating, and then enters the optical fiber isolator 7 from the signal port of the optical fiber wavelength division multiplexer 2 and is output from the output port of the optical fiber isolator 7.

[0033] In this embodiment, the Yb:YAG-SiO2 gain fiber has a cladding made of high-purity fused silica and a core made of a mixed vitreous body of Yb 3+ doped yttrium aluminum garnet and SiO2, and Yb 3+ is uniformly doped in the core, and the doping concentration is 1wt.% to 20wt.%.

[0034] In this embodiment, the Yb:YAG-SiO2 gain fiber has a cladding diameter of 125μm and a core diameter of 3 to 25μm.

[0035] In this embodiment, the Yb:YAG-SiO2 gain fiber has a fiber length of 2 to 15mm, its gain coefficient at 1091nm is greater than 1.45dB / cm, and its transmission loss at 1550nm is less than 0.006dB / cm.

[0036] In this embodiment, the high-reflectivity fiber grating 5 has a reflectivity greater than 99.5% at 1091nm, a reflection bandwidth of 0.15 to 0.5nm, and a grating length less than 20mm.

[0037] In this embodiment, the low-reflectivity fiber grating 3 has a reflectivity of 40 - 95%, a reflection bandwidth less than 0.08nm, a fiber grating length less than 35mm, and the grating type is a non-polarization-maintaining fiber grating.

[0038] In this embodiment, the laser pump source 1 is a semiconductor laser, the fiber type is Hi1060 fiber, and the center wavelength is 976nm.

[0039] The entire laser resonator is fixed within an accurate temperature control system to maintain the temperature of the laser resonator at a constant temperature value, achieving stable single-frequency laser output. The temperature control accuracy of the accurate temperature control system is 0.01 °C.

[0040] The above-mentioned laser realizes continuous single-frequency laser output with a wavelength of 1091.4 nm. The maximum output power is adjustable from 0 to 500 mW, the slope efficiency is greater than 35%, the power fluctuation is less than 0.35%, and the laser linewidth is less than 50 kHz. The laser spectrum is as Figure 2 shown.

[0041] Example 2

[0042] A high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, as Figure 1 shown, includes a laser pump source 1, an optical fiber wavelength division multiplexer 2, a laser resonator 6, an accurate temperature control system 8, and an optical fiber isolator 7. The laser resonator 6 includes a high-reflectivity fiber grating 5, a gain fiber, and a low-reflectivity fiber grating 3 connected in sequence. The optical fiber wavelength division multiplexer 2 has a total of three ports, where the common port is connected to the low-reflectivity fiber grating 3, the reflection port is connected to the laser pump source, and the signal port is connected to the optical fiber isolator 7; among them, the gain fiber is a Yb:YAG-SiO2 gain fiber 4;

[0043] The pump light emitted by the laser pump source 1 is injected into the laser resonator through the optical fiber wavelength division multiplexer 2, generates single-frequency laser with a wavelength of 1091 nm under the action of the fiber grating, and then enters the optical fiber isolator 7 from the signal port of the optical fiber wavelength division multiplexer 2 and is output from the output port of the optical fiber isolator 7.

[0044] In this embodiment, the Yb:YAG-SiO2 gain fiber has a cladding made of high-purity quartz glass and a core made of a mixed vitreous body of Yb 3+ doped yttrium aluminum garnet and SiO2. Yb 3+ is uniformly doped in the core, and the doping concentration is 1 wt.% to 20 wt.%.

[0045] In this embodiment, the Yb:YAG-SiO2 gain fiber has a cladding diameter of 125 μm and a core diameter of 3 to 18 μm.

[0046] In this embodiment, the Yb:YAG-SiO2 gain fiber has a fiber length of 2 to 15 mm, its gain coefficient at 1091 nm is greater than 1.45 dB / cm, and its transmission loss at 1550 nm is less than 0.006 dB / cm.

[0047] In this embodiment, the high-reflectivity fiber grating 5 has a reflectivity greater than 99.5% at 1091 nm, a reflection bandwidth of 0.15 - 0.5 nm, and a grating length less than 20 mm.

[0048] In this embodiment, the low-reflectivity fiber grating 3 has a reflectivity of 40 - 95%, a reflection bandwidth less than 0.08 nm, a fiber grating length less than 35 mm, and the fiber type is polarization-maintaining fiber. The slow-axis reflection peak falls within the reflection bandwidth of the high-reflectivity grating, and the fast-axis reflection peak falls outside the reflection bandwidth of the high-reflectivity grating to ensure that the output is linearly polarized light.

[0049] In this embodiment, the laser pump source 1 is a semiconductor laser, the fiber type is Hi1060 fiber, and the central wavelength is 976 nm.

[0050] The entire laser resonator is fixed in an accurate temperature control system to keep the temperature of the laser resonator at a constant temperature value, realizing stable single-frequency laser output. The temperature control accuracy of the accurate temperature control system is 0.01 °C.

[0051] The above-mentioned laser realizes linearly polarized continuous single-frequency laser output with a wavelength of 1091.4 nm, a polarization extinction ratio greater than 30 dB, an adjustable maximum output power of 0 - 300 mW, a slope efficiency greater than 25%, a power fluctuation less than 0.35%, and a laser linewidth less than 30 kHz.

[0052] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber, characterized in that, It includes a laser pumping source, an optical fiber wavelength division multiplexer, a laser resonator, a precise temperature control system, and an optical fiber isolator. The laser resonator includes a high-reflectivity fiber grating, a gain fiber, and a low-reflectivity fiber grating that are connected in sequence. The optical fiber wavelength division multiplexer has a total of three ports. Among them, the common port is connected to the low-reflectivity fiber grating, the reflection port is connected to the laser pumping source, and the signal port is connected to the optical fiber isolator. Among them, the gain fiber is a Yb:YAG-SiO2 gain fiber; The pumping light emitted by the laser pumping source is injected into the laser resonator through the optical fiber wavelength division multiplexer, and single-frequency laser at 1091 nm is generated under the action of the fiber grating, and then enters the optical fiber isolator from the signal port of the optical fiber wavelength division multiplexer and is output from the output port of the optical fiber isolator.

2. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 1, characterized in that, The Yb:YAG-SiO2 gain fiber has a cladding made of high-purity silica glass and a core made of a mixed vitreous body of Yb 3+ -doped yttrium aluminum garnet and SiO2, with Yb 3+ uniformly doped in the core at a doping concentration of 1 wt.% to 50 wt.%.

3. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 2, wherein For the Yb:YAG-SiO2 gain fiber, its cladding diameter is 125 μm, and its core diameter is 3 - 25 μm.

4. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 3, characterized in that, For the Yb:YAG-SiO2 gain fiber, its gain coefficient at 1091 nm is greater than 1.45 dB / cm, but not limited to this value.

5. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 4, characterized in that, The high-reflectivity fiber grating has a reflectivity greater than 99.5% at 1091 nm, a reflection bandwidth of 0.15 - 0.5 nm, and a grating length less than 20 mm.

6. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 5, characterized in that, The reflectivity of the low-reflectivity fiber grating is 40 - 95%, the reflection bandwidth is less than 0.08 nm, and the fiber grating length is less than 35 mm.

7. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 6, characterized in that, The low-reflectivity fiber grating group is a non-polarization-maintaining fiber grating or a polarization-maintaining fiber grating.

8. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 7, characterized in that, The laser pumping source is a semiconductor laser, an optical fiber laser, or a solid-state laser, and the central wavelength of the pumping laser is between 905 - 990 nm.

9. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 8, characterized in that, The length of the gain fiber is 2 - 15 mm.

10. The high-performance, ultra-short cavity 1091 nm single-frequency fiber laser based on Yb:YAG-SiO2 fiber according to claim 9, characterized in that, The entire laser resonator is fixed inside the precise temperature control system, and the temperature control accuracy of the precise temperature control system is 0.01 °C.

Images