2μm mode-locked fiber laser based on smf-simf-gimf-smf fiber structure

Abstract

The invention discloses a 2 [mu] m mode-locked fiber laser based on an SMF-SIMF-GIMF-SMF fiber structure. The laser is of an annular cavity structure and comprises a pumping source, a wavelength division multiplexer, a gain fiber, a non-polarization-maintaining isolator and a polarization controller, an all-fiber saturable absorption device serving as a mode locking device and a coupler serving as an output; the all-fiber saturable absorption device is composed of an input single-mode fiber, a step multimode fiber, a gradient multimode fiber and an output single-mode fiber. The laser mode locking mechanism disclosed by the invention adopts the nonlinear multimode interference effect in the multimode fiber, has the advantages of all-fiber structure, high damage threshold, self starting of model locking, high stability and compact structure, and has a wide application prospect.

Description

technical field

[0001] The invention relates to a fiber laser, in particular to a 2 μm mode-locked fiber laser based on an SMF-SIMF-GIMF-SMF (single-mode-step multimode-gradient multimode-single-mode) fiber structure. Background technique

[0002] 2μm mode-locked fiber lasers have broad application prospects in the fields of eye safety radar, laser medical treatment, photoelectric countermeasures, and special material processing. Saturable absorber (SA) is the key device for passively mode-locked fiber laser to achieve mode-locked pulse output, which has saturable or saturable-like absorption effect. There are mainly the following schemes to achieve passive mode locking: carbon nanotubes, semiconductor saturable absorber mirrors, nonlinear polarization rotation and nonlinear fiber loop mirrors. The damage threshold of the first two structures is relatively low, and the latter two structures are more sensitive to environmental factors, so these mode-locking mechanisms have c...

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