阅读说明：本技术 锁波长97Xnm波段泵浦的线性腔全光纤激光振荡器 (Linear cavity all-fiber laser oscillator with 97Xnm wave band pump ) 是由 韩志刚 梁慧生 朱日宏 陈磊 沈华 于 2020-12-14 设计创作，主要内容包括：本发明公开了一种锁波长97Xnm波长泵浦的线性腔全光纤激光振荡器包括増益光纤、高反光纤光栅、低反光纤光栅、半导体激光器、泵浦信号合束器、信号传能光纤、泵浦传能光纤和光纤输出端帽；高反光纤光栅、增益光纤、低反光纤光栅通过信号传能光纤依次连接形成光纤激光谐振腔；半导体激光器输出泵浦光经泵浦传能光纤注入泵浦信号合束器,再经信号传能光纤注入到光纤激光谐振腔中；光纤激光谐振腔输出的激光经过与之连接的光纤输出端帽扩束输出。本发明吸收系数较低,可有效降低增益光纤的局部热负荷,提高非线性效应阈值,从而提高振荡器输出功率水平。锁波长泵浦源实现了一定温度范围内泵浦波长的稳定,使得激光器的输出功率稳定性大幅提高。(The invention discloses a linear cavity all-fiber laser oscillator of a wavelength-locked 97Xnm wavelength pump, which comprises an increasing fiber, a high-reflection fiber grating, a low-reflection fiber grating, a semiconductor laser, a pump signal beam combiner, a signal energy transmission fiber, a pump energy transmission fiber and a fiber output end cap; the high-reflection fiber grating, the gain fiber and the low-reflection fiber grating are sequentially connected through the signal energy transmission fiber to form a fiber laser resonant cavity; the output pump light of the semiconductor laser is injected into the pump signal beam combiner through the pump energy transmission optical fiber and then is injected into the optical fiber laser resonant cavity through the signal energy transmission optical fiber; and laser output by the fiber laser resonant cavity is expanded and output through the fiber output end cap connected with the fiber laser resonant cavity. The invention has lower absorption coefficient, can effectively reduce the local heat load of the gain optical fiber and improve the nonlinear effect threshold, thereby improving the output power level of the oscillator. The wavelength-locked pump source realizes the stability of the pump wavelength within a certain temperature range, so that the stability of the output power of the laser is greatly improved.)

1. The utility model provides a lock linear chamber all-fiber laser oscillator of 97Xnm wavelength pumping, includes increase optical fiber (4), high reflection of light fiber grating (3), low reflection of light fiber grating (5), forward pump closes and restraints ware (2), reverse pump closes and restraints ware (6), signal biography energy optic fibre, pump biography energy optic fibre, optic fibre output end cap (7) and 2 at least semiconductor laser (1), N is greater than or equal to 1, its characterized in that: the low-reflection fiber grating (5), the gain fiber (4) and the high-reflection fiber grating (3) are sequentially connected through signal energy transmission fibers to form a fiber laser resonant cavity, the forward pump combiner (2) is connected with the high-reflection fiber grating (3) through the signal energy transmission fibers, the reverse pump combiner (6) is connected with the low-reflection fiber grating (5) through the signal energy transmission fibers, the forward pump combiner (2) and the reverse pump combiner (6) are respectively connected with different semiconductor pump lasers (1) through the pump energy transmission fibers, pump lasers generated by the semiconductor pump lasers (1) are transmitted into an inner cladding of the gain fiber (4), a fiber output end cap (7) is welded at a high-power output end of the linear cavity all-fiber laser oscillator, the fiber output end cap (7) disperses the lasers, and the return light and the thermal damage of the end face of the fiber are prevented, and performing beveling processing on the signal input end of the forward pumping beam combiner (2).

2. The lock wavelength 97Xnm wavelength pumped linear cavity all fiber laser oscillator of claim 1, wherein: the working wavelength of the semiconductor laser (1) is 972-974 nm, and the output power is 330-350W.

3. The lock wavelength 97Xnm wavelength pumped linear cavity all fiber laser oscillator of claim 1 or 2, wherein: the semiconductor laser (1) adopts a VBG external cavity semiconductor laser.

4. The lock wavelength 97Xnm wavelength pumped linear cavity all fiber laser oscillator of claim 1, wherein: the peeling length of the optical fiber coating layers at the two ends of the fusion point of the signal transmission energy optical fiber for connecting the low-reflection optical fiber grating (5), the gain optical fiber (4) and the high-reflection optical fiber grating (3) is within 1cm, and the cutting angle of the signal transmission energy optical fiber is controlled within 0.3 degrees.

Technical Field

The invention belongs to the field of fiber lasers, and particularly relates to a linear cavity all-fiber laser oscillator with a pump locked with a wavelength of 97 Xnm.

Background

The fiber laser generally comprises a laser oscillator based on a single resonant cavity and a laser amplifier based on a main oscillation power amplification structure. Compared with the optical fiber amplifier with the main oscillation power amplification structure, the all-fiber laser oscillator has the advantages of low cost, compact structure, simple control logic, stable performance, strong anti-reflection light-returning capability and the like, and is widely applied to industrial processing.

Fiber laser oscillators have many different pumping configurations such as forward pumping, backward pumping, bi-directional pumping, and distributed pumping. The pumping light source is usually a semiconductor single-tube laser or a semiconductor multi-tube combined light source. The pump wavelength is 915 nm and 975 nm.

Heat dissipation and nonlinear effects are particularly problematic in these high power laser oscillators, particularly high power continuous and quasi-continuous laser oscillators. The 915 nm wavelength pump fiber laser oscillator is adopted, the quantum loss is large, the absorption coefficient is low, the required fiber length is long, and the stimulated Raman scattering effect is easy to cause. The 976nm wavelength pump fiber laser oscillator has the advantages of small quantum loss, high light-light conversion efficiency, high absorption coefficient and short required fiber length, but has obvious local thermal load, so that the mode instability phenomenon easily occurs in the fiber.

Disclosure of Invention

The invention aims to provide a linear cavity all-fiber laser oscillator with a pump locked with a wavelength of 97Xnm, wherein the pump is performed at a wavelength of 972-974 nm, and compared with the pump with a wavelength of 976nm, the local heating value of an optical fiber is reduced, and the problem of mode instability in a high-power optical fiber laser is effectively solved. The pump laser is a Volume Bragg Grating (VBG) external cavity semiconductor laser, and the wavelength-locked pump source realizes the stability of the pump wavelength within a certain temperature range, so that the stability of the output power of the laser is greatly improved.

The technical solution for realizing the purpose of the invention is as follows: a linear cavity all-fiber laser oscillator of a lock wavelength 97Xnm wavelength pump comprises a gain fiber, a high-reflection fiber grating, a low-reflection fiber grating, a forward pump beam combiner, a reverse pump beam combiner, a signal energy transmission fiber, a pump energy transmission fiber, a fiber output end cap and at least 2 semiconductor lasers. The low-reflection fiber grating, the gain fiber and the high-reflection fiber grating are sequentially connected through a signal energy transmission fiber to form a fiber laser resonant cavity, the forward pumping beam combiner is connected with the high-reflection fiber grating through the signal energy transmission fiber, the reverse pumping beam combiner is connected with the low-reflection fiber grating through the signal energy transmission fiber, the forward pumping beam combiner and the reverse pumping beam combiner are respectively connected with different semiconductor pumping lasers through the pumping energy transmission fiber to transmit pumping laser generated by the semiconductor pumping lasers to an inner cladding of the gain fiber, a fiber output end cap is welded at a high-power output end of the linear cavity all-fiber laser oscillator, the fiber output end cap disperses the laser to prevent return light and thermal damage of the end face of the fiber, and beveling processing is carried out at a signal input end of the forward pumping beam combiner.

Compared with the prior art, the invention has the remarkable advantages that: (1) compared with a 976nm wavelength, the absorption coefficient of the pump source with the lock wavelength of 97Xnm is lower, so that the local heat load of the gain fiber can be effectively reduced, the nonlinear effect threshold value is improved, and the output power level of the oscillator is improved.

(2) Compared with a non-wavelength-locked pump source, the wavelength-locked pump source realizes the stability of the pump wavelength within a certain temperature range, so that the stability of the output power of the laser is greatly improved.

(3) The fusion welding method of the optical fiber fusion welding point is improved, the problem of optical fiber heating near the optical fiber fusion welding point is reduced, and the fusion welding efficiency is improved.

Drawings

Fig. 1 is a schematic diagram of a linear cavity all-fiber laser oscillator with a lock wavelength of 97Xnm wavelength pump according to the present invention.

Fig. 2 is an absorption spectrum of ytterbium ion in quartz.

FIG. 3 is a graph of gain fiber temperature for a 976nm wavelength pumped linear cavity all-fiber laser oscillator.

Fig. 4 is a graph of the gain fiber temperature for a linear cavity all-fiber laser oscillator with lock wavelength 97Xnm wavelength pump.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings.

The invention utilizes a 97Xnm waveband semiconductor laser to pump a linear cavity all-fiber laser oscillator to obtain high-power and high-stability fiber laser output. The quantum loss is small, the absorption coefficient of the gain fiber is high, the required fiber length is short, and the suppression of nonlinear effect (especially stimulated Raman scattering effect) is facilitated

With reference to fig. 1, the linear cavity all-fiber laser oscillator with a locked wavelength of 97Xnm includes an enhancement fiber 4, a high-reflection fiber grating 3, a low-reflection fiber grating 5, a forward pump beam combiner 2, a backward pump beam combiner 6, a signal energy transmission fiber, a pump energy transmission fiber, a fiber output end cap 7, and at least 2 semiconductor lasers 1, where N is greater than or equal to 1. The backward fiber grating 5, the gain fiber 4 and the forward fiber grating 3 are connected in sequence through signal energy transfer fibers to form a fiber laser resonant cavity, the forward pumping beam combiner 2 is connected with the high-reflection fiber grating 3 through the signal energy transfer fibers, the backward pumping beam combiner 6 is connected with the low-reflection fiber grating 5 through the signal energy transfer fibers, the forward pumping beam combiner 2 and the backward pumping beam combiner 6 are respectively connected with different semiconductor pumping lasers 1 through pumping energy transfer fibers to transfer pumping laser generated by the semiconductor pumping lasers 1 into an inner cladding of the gain fiber 4, an optical fiber output end cap 7 is welded at the high-power output end of the linear cavity all-fiber laser oscillator, the optical fiber output end cap 7 diffuses laser, return light and thermal damage of the end face of the optical fiber are prevented, and beveling processing is carried out at the signal input end of the forward pumping beam combiner 2.

With reference to fig. 2, in order to increase the light-light conversion efficiency of the laser, improve the thermal effect of the laser, and increase the threshold of the nonlinear effect, the pumping wavelength needs to be selected reasonably. It can be seen from fig. 2 that there are two absorption peaks of 915 nm and 976nm in the spectrum, so that the pump wavelengths commonly used in the ytterbium-doped fiber laser are 915 nm and 976 nm. The 915 nm wavelength pumping scheme is adopted, the quantum loss is large, the absorption coefficient is low, the required optical fiber length is long, and the nonlinear effect is easy to cause. By adopting a 976nm wavelength pumping scheme, the quantum loss is small, the light-light conversion efficiency is high, the absorption coefficient is higher, the required optical fiber length is short, but the local thermal load is obvious, so that the mode instability phenomenon easily occurs in the optical fiber. Theoretically, compared with a pump with a wavelength of 976nm, the pump with the wavelength of 97Xnm (972-974 nm) is adopted, quantum loss is basically unchanged, the absorption coefficient of the gain fiber is small, and local heat load in the gain fiber can be reduced on the premise of ensuring the light-light conversion efficiency of a laser.

A cutting angle control that is used for connecting the signal transmission of low reflection of light fiber grating 5, increase benefit optic fibre 4, high reflection of light fiber grating 3 can the splice point both ends within 1cm the length of skinning of the optical fiber coating, signal transmission can the optic fibre within 0.3, has reduced the splice point department problem of generating heat, has improved the butt fusion efficiency.

The absorption coefficient of ytterbium ion in 97Xnm waveband is greatly influenced by temperature, the environmental sensitivity is poor under the condition of short optical fiber, the power is greatly influenced by the environmental temperature, and the fluctuation is large, the invention adopts the Volume Bragg Grating (VBG) as the outer cavity of the semiconductor laser, so that the on-line deviation of the semiconductor laser is greatly improved, and the semiconductor laser can stably work within the range of 5-10 ℃.

Examples

To verify the effectiveness of the inventive protocol, the following experiment was performed.

The backward fiber grating 5, the gain fiber 4 and the forward fiber grating 3 are sequentially connected through signal energy transmission fibers to form a fiber laser resonant cavity. The central wavelength of the fiber grating is 1080 nm, the reflectivities of the high-reflection grating and the low-reflection grating are respectively 99% and 10%, and the structural parameter of the gain fiber is 20/400 μm. A beam combiner is used to couple pump light into the resonant cavity. The laser output from the resonant cavity is output through an end cap (QBH). The thermal imager measures the temperature of the resonant cavity, the power meter measures the output power of the laser, and the spectrometer measures the spectrum of the output light by a method of measuring scattered light. The pump wavelengths studied experimentally were 976nm and 97Xnm, which have different absorption coefficients and different required gain fiber lengths. Analyzing the difference of laser light-light conversion efficiency under 915 nm, 976nm and 97Xnm wavelength pumping according to the output power measured by a power meter; analyzing the influences of 976nm and 97Xnm wavelengths on the local heat load of the gain optical fiber of the laser through the temperature of the gain optical fiber measured by a thermal imager; the effect of 976nm and 97Xnm wavelengths on the nonlinear effect of the laser was analyzed by spectroscopy.

With reference to fig. 3 and 4, when the pumping power is 700W after experimental tests, the maximum resonator temperature of the 976nm fiber laser oscillator is 34 ℃ and the maximum resonator temperature of the 97Xnm fiber laser oscillator is 31 ℃. The method can effectively reduce the local heat load of the gain optical fiber and improve the nonlinear effect threshold, thereby improving the output power level of the oscillator.