Polarization-insensitive, high-gain parametric amplification of radially polarized femtosecond pulses

Abstract

Radially polarized lasers, in contrast to the conventional Gaussian laser mode, possess unique features such as sharp focusing and strong longitudinal fields. Thus far, radially polarized femtosecond pulses have been produced only by low-power devices such as mode-locked resonators and segmented half-wave plates. It is imperative to solve the bottleneck problem in generating higher powers and shorter durations. This paper reports on a polarization-insensitive, high-gain optical parametric amplifier for radially polarized femtosecond pulses, which works at type-II phase-matching and approximately degenerate wavelength. We experimentally demonstrate > --> 1000 -fold amplification of radially polarized ∼ 400 f s pulses at 1610 nm, via chirped ∼ 280 f s pumping at 800 nm, with the axially symmetric intensity profile and radial polarization state both being well-maintained within a 20 nm spectral range. With currently available high-energy picosecond pumping, the demonstrated amplification scheme will be promising to create radially polarized femtosecond pulses with ultrahigh powers and may facilitate future applications such as strong-field physics.