Active cooling of pulse compression diffraction gratings for high energy, high average power ultrafast lasers.

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation.

Precise diffraction efficiency measurements of large-area greater-than-99%-efficient dielectric gratings at the Littrow angle.

We have developed improved cavity-finesse methods for characterizing the diffraction efficiencies of large gratings at the Littrow angle. These methods include measuring cavity length with optical techniques, using a Michelson interferometer to calibrate piezoelectric transducer nonlinearities and angle-tuning procedures to confirm optimal alignment. We used these methods to characterize two 20 cm scale dielectric gratings.

Wet-etch figuring for precision optical contouring.

Wet-etch figuring utilizes free surface flows driven by surface tension gradients (the Marangoni effect) to confine and stabilize the size and shape of an etchant droplet attached to the underside of a glass surface. This droplet, or wetted zone, is translated on the surface, etching where it contacts and leaving behind no residue, to facilitate an etching-based small-tool figuring process that is free of mechanical and thermal stresses. The optic needs no backing plate, and its back side is free for inspection by optical means.