Abstract

We present a novel grazing incidence multipass amplifier exhibiting a gain medium with low thermo-optical aberrations. The amplifier consists of a 260 µm thin Nd:YVO₄ plate that is diffusion-bonded to an undoped YVO₄ slab. The plate is cooled at just one side, suppressing temperature gradients that would induce wavefront distortions to the laser beam. The pump light of a non-collimated diode laser bar is directly coupled into the undoped YVO₄ slab and guided by total internal reflection to the attached Nd:YVO₄ plate. Since no pump beam shaping optics is required, the amplifier is simple and efficient. We obtained 5.4 W of single-frequency radiation with a beam quality factor M² of 1.4 by means of an 18-pass, prism-folded amplification of a 50-mW nonplanar ring oscillator. The optical-to-optical conversion efficiency is 22 %, whereas the optical amplification is 20 dB. The amplifier excess noise is less than 10^-5 Hz^−1/2.

© 2005 Optical Society of America