No abstract

To achieve high output energy by generating a large gain mode volume, a Nd:phosphate glass ring regenerative amplifier with a built-in 1:1 telescope was proposed as a part of a terawatt chirped-pulse amplification Nd:glass laser, and its performance was characterized. In this ring regenerative amplifier, an input energy of 80 pJ could be amplified up to 33 mJ, and the output beam size was 2.3 mm in width and 2.0 mm in height. The amplified spectrum showed that high amplification could be obtained without a noticeable gain narrowing from the injected spectrum of 6 Å bandwidth.

Fig.1 scheme of the experimental setup Fig.2 Energy level relevant to the process of stimulated Raman scattering in Pb.

A split-disk geometry amplifier is reported, which uses several highly doped thin phosphate glasses instead of a single thick plate in such an ordinary disk amplifier to improve cooling efficiency. A simulation code was developed for the potential extrapolation of the experimental results under more severe pumping conditions to design the specifications of electrical parameters, disk glass thickness, Nd doping rate, and pumping cavity geometry and also to evaluate the gain coefficient of the amplifier. A gain coefficient of 0.027 cm-1 calculated in active media volume of 300 cm3 with a pumping efficiency of 0.92 % at 4 kJ pump energy agrees with the experimental value within errors of less than 10 %.