Device for improving pulse contrast based on nonlinear amplification loop mirror principle

Abstract

The invention provides a device for improving pulse contrast based on a nonlinear amplification loop mirror principle. The device is based on a non-linear amplification loop mirror, precise control of non-linear phase shift is realized by adjusting pulse gain, so that time domain narrowing of optical pulses and effective filtering of small sidelobe pulses are realized, and the pulse contrast can be remarkably improved finally by combining an external cavity multi-pass control technology. The pulse time domain shaping technology can be used for generating high-contrast light pulses and has the advantages of being good in light beam space mode, wide in pulse width application range, simple in overall system structure and the like.

Description

technical field [0001] The invention relates to the field of ultrafast lasers, in particular to a device for improving pulse contrast based on the principle of a nonlinear magnifying ring mirror. Background technique [0002] Ultrashort pulse laser has the characteristics of high peak power and narrow pulse width, and has been widely used in many fields, such as high-speed optical communication, ultra-fine cold processing, micro-nano device manufacturing, biological tissue cutting, etc. In specific application scenarios, pulse contrast is particularly important as a key laser parameter. For example, in the experiment of laser hitting a solid target, even a small sidelobe pre-pulse relative to the main pulse may cause target rupture and pre-ionization before the main pulse arrives, so the lack of pulse contrast will have a serious impact on the experimental results. Another example, in femtosecond laser micromachining, the pulse contrast will directly affect the processing q...

AI Technical Summary

Problems solved by technology

1. The pulse time-domain shaping technology based on saturable absorbers has high requirements for peak power, which will exceed the energy required by most media to generate self-focusing, resulting in distortion of the spatial profile of the beam

2. The nonlinear polarization rotation method can adopt an all-fiber structure, which has the advantages of simple structure, low cost, and low loss, but it is sensitive to parameters such as incident light power and fiber length, and the process of optimizing the contrast is relatively cumbersome.

3. The scanning filtering method, whose gating principle is based on the frequency of light rather than intensity, cannot effectively filter out the noise of fs-level light pulses

4. Cross-polarization filtering technology, its contrast enhancement effect is limited by the polarization extinction ratio. When the peak power density is high, its conversion efficiency tends to be saturated, and the nonlinear crystal is easily damaged when working at high power density, which affects the system. long-term job stability

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