2.76–3.98 μm picosecond mid-infrared optical parametric generation in a muti-grating MgO: PPLN

Abstract

The high repetition rate, widely tunable, picosecond mid-infrared laser plays an important role in various fields. In this paper, the single-pass optical parametric generator (OPG) pumped by Yb-fiber laser based on MgO: PPLN is proposed. The Yb-fiber laser is mode locked by a nonlinear amplifying loop mirror (NALM) with an all-polarization-maintaining (PM) structure. A maximum power of 6.2 W was obtained with a repetition rate of 15.8 MHz and pulse duration of 18 ps after amplification by cascaded fiber. Based on the principle of nonlinear frequency down-conversion, the tunable mid-infrared output wavelength of 2.76–3.98 μm was realized by varying the crystal grating periods and temperature. The maximum power was 500 mW at 3.22 μm, corresponding to a quantum conversion efficiency of 25%, and the relative power fluctuation was measured as 0.37% over 30 min.

2.79-μm high peak power LiNbO3 acousto-optic Q-switched Er,Cr:YSGG laser with thermal lensing effect compensation

“…Where, K is the thermal conductivity, A is the cross section area of the laser rod, dn/dT is the temperature gradient of the refractive index, α is the coefficient of thermal expansion, P a is the heat absorbed by the laser crystal. To compensate the thermal lensing effect effectively, the thermal focal length of Er,Cr:YSGG laser crystals was calculated theoretically according to formula (1).…”

“…Currently, mid-infrared laser with narrow pulse duration, high peak power and good stability has wide range of scientific research and practical application value [1,2]. The free electron laser can obtain the mid-infrared laser of peak power with adjustable wavelength, but the opto-electromechanical structure of this system is very complex, large size and high investment cost.…”