Spectral Shaping by Phase-Modulated, Picosecond-Pumped, Optical Parametric Chirped-Pulse Amplification

Project Overview

Aggressive advanced spectral shaping is required in frontends of high-power laser systems to compensate for spectral gain narrowing in subsequent power amplifiers. This feasibility study pioneers a new technique for spectral shaping, employing phase-modulated picosecond-pumped optical parametric chirped pulse amplification (OPCPA). Prior to injection into a nonlinear crystal, the seed pulse is phase-modulated, resulting in subsequent spectrally-dependent gain modulation.

To demonstrate this method, we built an OPCPA testbed, which consists of one OPCPA stage operated at degeneracy. Both the seed and pump pulse are derived from a multi-mJ Ti:sapphire system to ensure passive temporal synchronization between the pulses. The seed is phase-modulated using an acousto-optic programmable dispersion filter (Dazzler, Fastlite) and amplified in 2 mm BBO crystal. To compare the experiments to calculations, a spectrally resolved one-dimensional model has been developed to support this study. Experimentally, we have achieved a spectrum shaping with a contrast of 10x. This result has been replicated numerically, and the model suggests that the main mechanism responsible for the spectrum shaping is the gain saturation of the phase-modulated signal.

Mission Impact

This work advances the Laboratory's core competency in lasers and optical science and technology and supports the LLNL's work in high-energy and high-average-power laser technologies. Advances in spectral-shaping techniques are expected to inform the design of high-energy, high-peak-power laser systems that are being developed for basic science, accelerator technology, and industrial uses.