External Multipass Optical Ring Cavity for Counterpropagating Pulsed Laser Applications.

摘要

With the intent of increasing the efficiency of laser-gas interactions, an external bidirectional multipass optical cavity has been developed for use with counterpropagating high energy pulsed lasers. By exploiting the closed-path recirculation of two counterpropagating laser pulses, obtained through polarization-dependent trapping of the pulses inside the cavity via a Pockels cell, such an optical cavity allows the counterpropagating pulses to repeatedly and concurrently interact within a specific region in space. This cavity allows the setup to exhibit an effective pulse repetition frequency much higher than the loading laser. This increased repetition frequency permits greater sensitivity in probing a medium or increased energy deposition, depending on application, over the single pass case. Pulses from a 12 mJ, frequency doubled, 5 ns FWHM, pulsed Nd:YAG laser were split and injected into opposing sides of a symmetric multipass 2.44 m (96 in) optical ring cavity. Using a Pockels cell, the counterpropagating pulses were 'locked' into the cavity for cavity round trips. This represents an 8 fold increase in the interacting laser energy over the single pass case. This cavity concept suggests a variety of potential applications ranging from established cavity processes, e.g. laser-based absorption spectroscopy studies and x-ray production, to new processes which can benefit from the counterpropagating feature of this design, such as non-resonant optical lattice gas heating and time-resolved coherent Rayleigh-Brillouin scattering diagnostic studies of a rapidly evolving flow.