Precision Spectral Sculpting of Broadband FM Pulses Amplified in a Narrowband Medium

LLE Review, Volume 90 79 Solid-state laser systems envisioned for inertial fusion energy (IFE) applications will require both high efficiency and high single-beam, on-target uniformity. High efficiency is achieved by diode pumping, and on-target uniformity is achieved by beam-smoothing techniques. One of the most-promising gain media for these high-efficiency lasers is ytterbium-doped strontium fluorapatite (Yb+3:SFAP).1 While this material is ideal for efficient diode pumping, its gain bandwidth is relatively narrow. This has implications for the amount of on-target beam smoothing that can be achieved with techniques such as smoothing by spectral dispersion (SSD),2 which requires bandwidths of the order of 1 THz in the ultraviolet3 or roughly 0.333 THz (330 GHz) in the infrared part of the system.4 Since this bandwidth is comparable to the gain bandwidth of Yb+3:SFAP, significant gain narrowing can be expected in the laser system.