Fiber-amplifier-pumped, 1-MHz, 1-µJ, 2.1-µm, femtosecond OPA with chirped-pulse DFG front-end.

High-repetition-rate, high-power, few-cycle mid-infrared lasers with carrier envelope phase (CEP) stabilization are ideal driving sources for studying strong-field nonlinear processes, such as strong-field driven electron emission solid-state high-harmonic generation and nonlinear microscopy. Here, we report on a 1-MHz, 1-mu J, femtosecond. 2.1 mu m optical parametric amplifier (OPA), pumped by a Yb-doped fiber chirped-pulse amplifier (CPA) and seeded by a chirped-pulse difference-frequency generation (DFG) front-end providing positively chirped 2.1-mu m signal pulses. The home-built multi-stage 1030-nm Yb-doped fiber CPA pump laser generates >55-mu J near-transform-limited (245-fs) pulses at 1 MHz repetition rate using a novel 4-pass all-fiber stretcher/front-end for careful dispersion/spectral management. The chirped-pulse DFG scheme is achieved by wave-mixing the 1030 nm pump pulse with a dispersive wave at 645-735 nm generated in a photonic crystal fiber, allowing passive CEP stability of the 2.1-mu m pulses. The 2.1-mu m pulse is amplified to 1 mu J in a two-stage dispersion-managed optical parametric amplifier (OPA) with a pump energy of similar to 21 mu J resulting in 95-fs pulses with nice beam profile without additional pulse compression. Multi-mu J, sub-30 fs pulses can be obtained at full pump energy and additional dispersion compensation. The fiber-amplifier-based mid-infrared OPA can be directly applied to high-harmonic generation in solids and optical-field-driven nanophotonic devices and is a compact front-end for a future high-power, high-repetition-, long wavelengths CEP-stabilized source for gas-phase high-order harmonic generation. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement