Pulse energy boost method of self-starting figure-9 passively mode-locked fiber laser

Abstract

The invention discloses a pulse energy boosting method of a self-starting Figure-9 passive mode-locked fiber laser, which is applied to the Figure-9 passive mode-locked optical fiber composed of an equivalent NALM ring cavity, a linear arm, a rotating motor and a pump source In the laser; and include the following steps: 1 obtain the linear phase shift amount of the non-reciprocal phase shifter; 2 obtain the splitting ratio of the equivalent NALM ring cavity; 3 set the pump source output power and the non-reciprocal phase shifter parameters, and Repeat until the output pulse energy of the passively mode-locked fiber laser shown in Figure-9 is increased. The present invention can realize greater nonlinear phase shift tolerance during single-pulse mode-locking operation of the Figure-9 passive mode-locked fiber laser with self-starting function, thereby greatly increasing the output single-pulse energy, thereby obtaining long-term stability of self-starting The low-noise and high-energy femtosecond fiber laser in operation makes the laser have a wider application prospect in the field of femtosecond laser pulses.

Description

technical field [0001] The invention relates to the fields of laser precision machining, laser precision measurement, etc., and in particular to a method for increasing the pulse energy of a self-starting Figure-9 fiber laser. Background technique [0002] Femtosecond laser pulses have important applications in strong field physics, attosecond science, precision measurement, and nonlinear optics. Using Ti:Sapphire solid-state laser technology, it has been able to generate pulses with a peak power of up to PW and a pulse width as narrow as less than 15 fs. The fast-developing mode-locked fiber lasers in recent years show more colorful ultrashort pulse phenomena. Through nonlinear regulation of dispersion, femtosecond pulses of different formats can be generated, such as solitons, dispersion-managed solitons, self-similar pulses and dissipative solitons, etc. . With the continuous breakthrough of femtosecond pulse fiber amplification and coherent combination technology, the ...

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Problems solved by technology

However, this asymmetric cavity structure causes the nonlinear phase shift (NPS) experienced by the forward and reverse optical fields in the cavity to have different trends or slopes with the increase of pump power, and it is easy to break through the SA transmittance curve by increasing the pump power. Allowable Δφ for specified single pulse operation NL , restricting the improvement of the output pulse energy

And this kind of asymmetric cavity structure limited by self-starting requirements also limits the use of intracavity dispersion nonlinear control to increase the pulse energy

However, if the cavity asymmetry is reduced, in theory, Δφ can be allowed under extremely strong pumping NL While not breaking through the single-pulse operation range, the positive and negative light fields in the cavity can accumulate enough NPS to increase the pulse energy. The power of the light is extremely high, and the intracavity gain fiber is in a deep saturation state, but this deep saturation has a "self-healing" effect on the weak power fluctuations of continuous light, which is not conducive to amplifying such weak power fluctuations, resulting in a low asymmetry cavity. -9 Fiber lasers are difficult to achieve self-starting of mode locking

Although the pulse energy of the self-starting mode-locked fiber laser in Figure-9 has been improved to a certain extent by choosing a large-mode-field fiber to reduce the accumulation of NPS in the cavity and introducing the hybrid mode-locking of micro-nano material SA to help self-starting, but it has not In principle, it can solve the limitation of the output pulse energy caused by the introduction of linear phase shift and asymmetric cavity to ensure the self-starting function of this laser

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