Increasing the repetition rate of high-energy Nd:Glass disk amplifiers

Abstract

Flash-lamp pumped disk amplifiers suffer from thermally-induced aberrations which greatly limits the repetition rate of the disk amplifiers. A comprehensive 3D, time-dependent mathematical model is presented which can successfully model the small signal gain, temperature, and the induced wave-front error. The key outputs of the model are verified using a Position Sensitive Detector wave-front sensor, a novel method of measuring the rise in thermal aberrations and small signal gain with a high temporal resolution. The experimental verification of the mathematical model is a critical contribution added to the existing body of knowledge. An alternative design, namely the Active-Mirror In a Cavity (AMIC) geometry based on active-mirrors is presented, which is shown to be three times more efficient (measured as Strehl efficiency) than the Vulcan’s 150 disk amplifier. The AMIC geometry consists of four active-mirrors pumped by two sets of flash-lamps. Furthermore, the maximum repetition rate of the AMIC geometry is derived by solving the time-dependent, three-dimensional heat equation using the Finite Element Method (FEM). The RMS wave front error due to thermally-induced aberrations are predicted to be much lower for the AMIC geometry operating at a repetition rate of one shot per 5 minutes, compared to the 150 disk amplifier operating at one shot per 20 minutes. The adaptability of the mathematical model described in the thesis, can be used to explore, and simulate the performance of any new flash-lamp pumped disk amplifier geometry.