An ultrafast optical parametric laser for driving high energy density science

• Main Author: Mecseki, Katalin
• Other Authors: Smith, Roland; Rose, Steven
• Published: Imperial College London 2013
• Subjects: 530
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.650620

This thesis describes the development of a multi-mJ, few-cycle, absolute-phase controlled laser system based on optical parametric chirped pulse amplification (OPCPA) operating at a kHz repetition rate. A laser system with these specifications will provide a table-top platform to enable a broad range of experiments in demanding research areas, including laser electron acceleration and the creation of exotic highenergy density plasmas from solid targets. The approach of the work is a combination of both experimental effort and numerical simulations used to guide and aid interpretation of laboratory studies. The non-collinear parametric gain stages of the laser have been optimised using detailed numerical simulations. A comparison is given on phase matching conditions in BBO and LBO crystals along with a novel nonlinear material BiBO. The production of 600 μJ pulses with a bandwidth that supports a transform limited temporal duration of 8.5 fs is presented in a three stage BBO based design. An all optical, low-jitter synchronisation scheme for the OPCPA pump and signal pulses has been designed and implemented by use of solitonic wavelength shifting in a photonic crystal fiber (PCF). Commercially available fibers with various core sizes have been assessed. The propagation of few-cycle pulses in the PCF has been studied by numerically solving the generalised Schrödinger equation with the splitstep Fourier method. An OPA pump laser with excellent spatial and temporal qualities has been developed. Amplification of the PCF output at 1053 nm is achieved in a regenerative diode pumped Nd:YLF amplifier and a multipass power amplifier. Self-phase modulation and gain narrowing is greatly reduced using a customised 500 μm low-finesse etalon in the regenerative amplifier cavity. Spectral modulation was found to increase both frequency doubling and parametric amplification efficiency and stability. The construction of an alternative 10 Hz, high-energy pump beam line is also presented.