A method for stable autogeneration of ultrashort laser pulses in a polarization maintaining optical fiber ring resonator and the laser based upon

A method for generating ultrashort laser pulses with passive mode locking, based on the non-linear birefringence effect in a polarization-maintaining fiber (PM-fiber) light guide of a ring resonator, comprising generation of unidirectional polarized radiation in a ring resonator after passing through an active fiber section for optical amplification of pre-polarized radiation, optical filtering of pulses after removal from the resonator of a part of the amplified radiation, which leads to excitation of pulses in the ring resonator in dissipative soliton mode, wherein non-linear birefringence (non-linear evolution of polarization) is achieved in the combined fiber non-linear optical element (NOE), consisting of two segments of optical fiber L1 and L2, equal in length and joined to each other by splicing with an orthogonal orientation of the polarization axes and having spliced joints with an external fiber/loop of the ring resonator at input and output mismatched according to the angle of polarization axes orientation at an acute angle of less than 40 degrees, wherein at the input of the non-linear optical element a band-pass optical filtering is carried out and, at its output, a polarization of the output radiation along a slow axis of the light guide is carried out, characterized in that a self-excitation and a temperature stable autogeneration of pulsed radiation in the PM-fiber ring resonator are provided by an optimal matching and stabilization of the phase shift of the polarization components of the optical wave, its linear and non-linear phase components at the output of the non-linear optical element (NOE), creating in particular:

• preliminary selection and fixing of temperatures T1 and T2 (and these selected values do not require re-selection at later generation start-ups) for the two fiber loops of the NOE, respectively, wherein a stable mode of self-excitation and autogeneration of ultrashort pulses at a given level of optical amplification in the fiber active section, which determines energy parameters of the generated ultrashort pulse, is ensured;
• thermostatically controlling at fixed temperatures T1 and T2 of each fiber loop of the NOE, including the joints of segments L1 and L2 inside and outside at the input and output of the NOE, in order to eliminate the temperature drift of the phase mismatch of the polarization components of optical waves along the two polarization axes of the PM-fiber at the NOE output, wherein one of the loops contains an orthogonally oriented joint of unequal parts of the segments L1 and L2 of the PM-fibers, and the other loop contains remaining parts and their external connections (NOE input and output) with the PM-fiber ring resonator, wherein by selecting and fixing the temperatures of these loops a non-zero value for the linear component of the phase difference of the radiation along the two polarization axes in the PM-fiber at the NOE output is achieved and, at the same time, by means of placing together the fiber sections of segments L1 and L2 in the two thermostatically controlled loops, additional partial temperature compensation for the inhomogeneity of birefringence and phase drift of polarization components in the equal sections of segments L1 and L2 in each loop and in the gap between the loops is achieved.