Optical parametric amplifier test for optical stochastic cooling of RHIC

Optical Stochastic Cooling (OSC) of gold ions in the Relativistic Heavy Ion Collider (RHIC) operating on wavelength ~12 mum has been proposed by Ilan Ben-Zvi and use of Optical Parametric Amplifier (OPA) for OSC was suggested by Max Zolotorev [1, 2]. We have tested the performance of the OPA suggested to be used in OSC for RHIC. Our OPA is based on a single CdGeAs₂ crystal that has been pumped by a second harmonic of pulsed CO₂ laser system. Particle emission was emulated by output of another hybrid CO₂ laser operating in single longitudinal mode regime at wavelength 9.552 mum. The maximum amplification was achieved at a pump intensity value of 9.2times10⁶ W/cm². Further increase of the pump intensity caused amplification quenching which we attribute to nonlinear multiphoton absorption of the pump beam. We also performed interferometric measurements that demonstrate that amplification of the radiation in OPA preserves its coherence.