Ultrabroad Band Collinear Mid-Infrared Optical Parametric Amplifier Driven by a Millijoule Femtosecond Tm:YAP Regenerative Amplifier

Abstract

We present a comprehensive study on the development and performance of an ultra-broadband mid-infrared (MIR) optical parametric amplifier (OPA) pumped by a home-built solid-state amplification system. The intricate design encompasses a thulium-doped fluoride (Tm:ZBLAN) fiber oscillator, a two-stage Tm:ZBLAN fiber preamplifier, and a regenerative amplifier featuring a thermoelectrically cooled thulium-doped yttrium aluminium perovskite crystal (Tm:YAP). The amplifier yields 265 fs 1 mJ pulses at 1940 nm. A portion of the pulse is directed into a polarization-maintaining ZBLAN fiber, generating a multi-octave MIR supercontinuum through self-phase modulation process. This supercontinuum is then collinearly combined with the regenerative amplifier’s output pulse and further amplified within a 1-mm thick gallium selenide crystal through an optical parametric process. The resulting spectra of the signal pulse and the idler pulse span from 2.5 to 4 µm and from 4 to 9 µm, respectively. The combined power of the signal and idler waves reaches 10 mW, with an overall efficiency of 4%. Remarkably, the transform-limited pulse durations for the signal and idler are 22 fs and 17 fs, respectively. This work underscores the successful realization of an advanced collinear MIR OPA system, offering unprecedented capabilities in terms of spectral coverage.