Femtosecond optical parametric chirped-pulse amplification in birefringent step-index fiber.

We demonstrate an optical parametric chirped-pulse amplifier (OPCPA) that uses birefringence phase matching in a step-index single-mode optical fiber. The OPCPA is pumped with chirped pulses that can be compressed to sub-30-fs duration. The signal (idler) pulses are generated at 905 nm (1270 nm), have 26 nJ (20 nJ) pulse energy, and are compressible to 70 fs duration. The short compressed signal and idler pulse durations are enabled by the broad bandwidth of the pump pulses. Numerical simulations guiding the design are consistent with the experimental results and predict that scaling to higher pulse energies will be possible. Forgoing a photonic crystal fiber for phase-matching offers practical advantages, including allowing energy scaling with mode area.