Passive mode-locking fiber laser based on graded-refractive index multimode fiber saturable absorber

Abstract

The invention discloses a passive mode-locking fiber laser based on a graded-refractive index multimode fiber saturable absorber, and relates to the field of fiber lasers. The passive mode-locking fiber laser adopts a ring cavity structure, and includes a semiconductor pumping source, and a wavelength division multiplexer, an erbium-doped fiber, a polarization-independent isolator, a graded-refractive index fiber saturable absorber device, and an output coupler which are successively form a beam loop. The graded-refractive index fiber saturable absorber device functions as a saturable absorberon the basis of the nonlinear multimode interference effect in the graded-refractive index fiber, and is composed of a two single-mode fibers intermediately fused with a graded-refractive index multimode fiber. Two ends of the saturable absorber device are fixed on a movable fiber clamp for changing the length of the fiber. The fiber laser realizes the full fiberization of mode-locking lasers, has the advantages of simple structure and high damage threshold, and greatly improves the stability and practicability of the mode-locking lasers.

Description

technical field [0001] The patent of the present invention relates to the field of fiber lasers, in particular to a mode-locked fiber laser based on a "graded-index multimode fiber saturable absorber", in particular to a saturable absorber for mode-locked and Q-switched fiber lasers. Background technique [0002] Ultrashort pulse laser with a pulse width of hundreds of femtoseconds has a wide range of applications in basic research, material fine processing, national defense, biotechnology, medical treatment, and other fields due to its narrow pulse width, high peak power, and wide spectral width. , its development enables us to directly observe many ultrafast reactions in chemistry, biology and other research, and has become one of the core technologies of national strategies and high-end industries. At present, ultrashort pulse lasers are usually obtained by passive mode-locking technology. Compared with active mode-locked fiber lasers, passive mode-locked fiber lasers ha...

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Problems solved by technology

Among them, the semiconductor saturable absorber mirror, as the most widely used saturable absorber material, still has some disadvantages. Its characteristics are determined by the design parameters during production, expensive, poor adjustability, and limited by materials, it is difficult to produce Pulses shorter than picoseconds

In addition to graphene, other two-dimensional materials including graphene oxide, topological insulators such as bismuth telluride and transition metal sulfides have also been observed to have good nonlinear saturable absorption effects, although they have been widely used in mode-locked fiber lasers However, the absorbing material is sensitive to external pollution and is easy to deteriorate; and the damage threshold of the absorbing material also greatly limits the output power of the laser

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