Abstract

The master oscillator is a frequency tunable TEA CO₂ laser with a grating in Littrow setup producing pulses in the lowest order transverse mode of up to 400 mJ with a total pulse duration of 3 μs at a wavelength of 10.49 μm.¹ As a power amplifier an e-beam sustained system with large gain volume (125 • 10 • 10 cm³) is used in a multipass geometry. The experiment will be carried out with the scheme depicted in Fig. 1. An optical isolator (OI) consisting of a polarizer and a Faraday rotator will prevent backcoupling of radiation into the master oscillator. The diameter of the output radiation will be enlarged with a telescope (T) and subsequently focused down to transfer the laser beam into the smaller diameter required for the four-wave mixing (4WM) cell. A beamsplitter (BSj) separates the signal beam from the forward propagating pump beam. The signal beam transits a stack of attenuators A, is reflected off a low reflectivity beamsplitter BS2, and will be amplified in the aforementioned power amplifier. Using a lens L (f = 4 m), the beam is focused into the 4WM cell for phase conjugation. SF6, the nonlinear medium, is kept in a pressure cell with AR/AR windows. The backward travelling phase conjugate signal beam should saturate the amplifying medium and will be coupled out via the beamsplitter BS2. A delay line is necessary to reduce pathlength differences between the pump and signal beam.

© 1994 Optical Society of America