Fizeau wedge with unequal mirrors for spectral control and coupling in a linear laser oscillator-amplifier system

We propose a new tunable linear laser oscillator-amplifier system that incorporates a Fizeau wedge with unequal mirrors as the coupler. Because of asymmetry in reflection and wedge focusing in unequal mirrors, our system acts as a highly efficient selector in the oscillator and practically eliminates reinjection of spontaneous emission in the amplifier. We studied the wedge action by developing a procedure for the calculation of reflected interference patterns at a distance from the wedge. Using this procedure we found the feedback factors for both the oscillator and the amplifier. Background emission levels of less than 1% of the peak intensity in the emitted line were experimentally obtained.