Raman shifter optimized for lidar at a 1.5 μm wavelength

Abstract

A Raman shifter is optimized for generating high-energy laser pulses at a $1.54\mu \text{m}$ wavelength. A forward-scattering design is described, including details of the multiple pass and nonfocused optical design, Stokes injection seeding, and internal gas recirculation. First-Stokes conversion efficiencies up to 43%—equivalent to 62% photon conversion efficiency—were measured. Experimental results show output average power in excess of 17.5 W, pulse energies of $350\text{\hspace{0.17em} mJ}$ at $50\text{\hspace{0.17em} Hz}$, with good beam quality $\left(M^2<6\right)$. Narrow bandwidth and tunable output is produced when pumping with a single longitudinal mode Nd:YAG laser and seeding the process with a Stokes wavelength narrowband laser diode.

© 2007 Optical Society of America