Fiber laser system with mode instability effect suppression function

Abstract

The invention provides a fiber laser system with a mode instability effect suppression function. A high-reflection grating and a low-reflection grating in the laser system are both few-mode fiber bragg gratings, and the few-mode fiber bragg gratings are circular refractive index modulation areas concentric with fiber cores and arranged in the fiber cores of few-mode fibers, and the radius of the refractive index modulation area is less than that of the fiber core. The high-order mode filter is etched on the doped optical fiber, so the high-order mode in the fiber core can be converted into thecladding waveguide, the high-order mode in the fiber core is prevented from being amplified, and the threshold value of the mode instability effect is further improved. Moreover, the wavelength of the pump light is changed, and the proportion of backward pump light energy is properly increased, so the unstable power threshold of the laser mode is improved, and the output power is improved. Starting from a device and a pumping mode, the mode instability effect is suppressed from the perspective of thermal load and the perspective of particle number inversion, the mode instability threshold value is greatly reduced, and the output power of the oscillator is higher.

Description

technical field [0001] The invention relates to the technical field of fiber lasers, in particular to a fiber laser system with mode instability effect suppression function. Background technique [0002] The mode instability effect is the main obstacle to further increase the power of large-core fiber lasers. After the output power of the fiber laser reaches a certain threshold, the beam quality drops significantly, and the power is difficult to further increase, and the power is very unstable. The earliest experimental observations on the mode instability phenomenon came from large-core fiber amplifiers. After that, the mode instability phenomenon in the amplifier has been deeply studied experimentally and theoretically. In amplifiers, the threshold of mode instability and other nonlinear effects is usually low, which limits the further increase of the output power of the amplifier. [0003] In recent years, fiber optic oscillators have been extensively studied, and the th...

AI Technical Summary

Problems solved by technology

[0004] Experimental studies have shown that both the transverse mode competition caused by particle number inversion and thermally induced transverse mode competition can cause mode instability in the oscillator, and the effect of mode competition caused by particle number inversion is particularly obvious. Boost, the oscillation frequency of the mode competition caused by the inversion of the number of particles coincides with the longitudinal mode frequency of the oscillator, and the two effects resonate, resulting in extreme confusion in the output power

In the amplifier, due to the photothermal effect, the interference field of the two modes forms a refractive index grating that is periodically distributed along the fiber axis. In the case of external disturbances, the interference field and the refractive index grating are no longer synchronized, so that the fiber core Alternate energy conversion occurs between the two modes, the output power is extremely unstable, and the beam quality decreases

Images