Method for filtering ASE noise of ultrafast fiber laser amplifier and filter

Abstract

The invention relates to the field of ultrafast fiber laser, in particular to a method and a filter for filtering ASE noise of an ultrafast fiber laser amplifier, and the method comprises the following steps: 1) welding a section of filtering fiber with the same parameters as a gain fiber at the tail end of the gain fiber of the fiber amplifier, or welding a section of filtering optical fiber of which the core diameter and the numerical aperture difference with the gain optical fiber are both less than 50%; (2) coating high-refractive-index glue capable of filtering pump light at a welding point; 3) enabling the signal output by the optical fiber amplifier to pass through a filtering optical fiber, and filtering ASE noise. The filter comprises a filtering optical fiber welded with the tailend of a gain optical fiber of an optical fiber amplifier; the filtering optical fiber and the gain optical fiber have the same parameters or are close to the gain optical fiber core diameter and numerical aperture; the welding point of the filtering optical fiber and the gain optical fiber is coated with high-refractive-index glue used for filtering pump light. According to the method and the filter, ASE noise can be effectively filtered, and an all-fiber structure of the ultrafast fiber laser is maintained.

Description

technical field [0001] The invention relates to the field of ultrafast fiber lasers, in particular to a method and filter for filtering ASE noise of an ultrafast fiber laser amplifier. Background technique [0002] With the development of ultrafast fiber laser technology and the wide application of high-energy ultrafast fiber lasers in the field of industrial micromachining, the demand for high-performance ultrafast fiber laser sources in the ultrafast laser micromachining market is increasing day by day. The signal-to-noise ratio of the light source is crucial to the process effect of micromachining. Excessive amplified spontaneous emission (ASE) noise in the beam will cause thermal effects in the processing process, resulting in thermal damage to the processed material. Therefore, the ASE noise is suppressed and the light source is improved. The signal-to-noise ratio is of great significance for improving the effect of ultrafast lasers in industrial micromachining applicat...

AI Technical Summary

Problems solved by technology

The structure of an ultrafast fiber laser generally consists of a low-power, high-repetition-frequency mode-locked fiber oscillator (with a power of a few milliwatts to tens of milliwatts and a repetition rate of tens of megahertz) and a multi-stage fiber amplifier. It needs to be amplified to several watts to tens of watts, and the repetition frequency needs to be greatly reduced (hundreds of times) to hundreds of kilohertz during the amplification process. Therefore, several small-signal high-gain fiber amplifiers are required to achieve effective signal amplification. In the small-signal high-gain fiber amplifier, because there is no strong enough signal to evacuate the excess reverse ions excited by the pump light in time, strong ASE radiation is inevitably generated, and these ASE radiation will be in the subsequent amplifier Further amplification and enhancement in the middle, and finally make the output laser include relatively strong noise

Usually, the spatial bandpass filter can filter out the ASE noise outside the signal wavelength range, but it will destroy the all-fiber structure of the laser, and increase the structural complexity of the ultrafast fiber laser, resulting in a decrease in the stability of the laser.

At the same time, the spatial filter cannot filter out the ASE noise that overlaps with the signal wavelength

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