Femtosecond single-pass optical parametric generator (OPG) for 1.38-1.56 μm with 35 MHz repetition rate

Abstract

Optical parametric generation (OPG) in a single pass through a χ(2) nonlinear crystal is a simple way to generate ultrashort pulses which are tunable in a broad wavelength range. In contrast to an ultrafast optical parametric oscillator, OPG does not require an oscillator cavity which is synchronized to the laser. However, the required pump intensities are much higher. For this reason, so far OPG experiments with ultrashort pulses have always required amplified pump sources, e.g. based on a mode-locked oscillator and a high-gain amplifier operated at a repetition rate of typically far below 1 MHz [1, 2]. Such pump sources lead to quite complex systems, and low repetition rates very much limit the obtainable average output power. Recent progress on high-power passively mode-locked all-solid-state lasers has enabled us to pump a parametric generator directly with a mode-locked laser, not using any amplifier system. In this way we obtained up to 0.5 W of average power in femtosecond pulses at 35 MHz repetition rate in the wavelength range of 1.38-1.56 μm using a periodically poled LiNbO3 (PPLN) crystal. The corresponding range of the idler is 3.03-4.06 μm.