Generation of femtosecond pulses with an energy of ~10 μJ at a wavelength of 1.56 μM and nonlinear conversion of their frequency in a hollow revolver fiber

Abstract

A fiber source of ultrashort pulses (USPs) with a powerful hybrid amplifier based on erbium and erbium-ytterbium fibers connected in series with a double cladding and an increased mode diameter, pumped by multimode laser diodes at a wavelength of 976 nm, was created and studied. Pulses from the output of a powerful amplifier at a central wavelength of about 1.56 μm with a duration of ~200 ps and an energy of up to 21.9 μJ, following with a frequency of 198.5 kHz, were compressed using a compressor based on a pair of volumetric polarization-independent diffraction gratings operating at transmission, with an efficiency of ≈73%. A minimum duration of compressed pulses of 742 fs was achieved, while their maximum energy and peak power were 15.8 μJ and ≈13 MW, respectively (maximum average power - 3.14 W) at a central wavelength of 1.56 μm in a beam with a Gaussian profile and measured quality parameters = 1.58 and = 1.38. When pumped by pulses from an erbium fiber source of various durations, the SRS transformation of 1.56 μm → 1.71 μm was realized in a hollow revolver light guide with a core of 75 μm in diameter filled with molecular hydrogen. Pulses with a maximum energy of about 200 nJ at a wavelength of 1.71 μm were obtained. The developed ultrashort pulse source can be useful in creating advanced systems for precision processing of transparent materials, especially silicon, as well as for other applications that require high energy and peak power of ultrashort pulses.