High pulse energy near-infrared ultrafast optical parametric oscillators

Abstract

A source-demand in the near- and mid-IR wavelength spectrum exists for various applications such as waveguide inscription, multiphoton imaging, and nonlinear spectroscopy. All of the applications seek for higher repetitions rates for faster processing speed, better signal to noise ratios or to improve the results for applications like laser waveguide inscription. This is in contrast to the high pulse energies, required to drive the nonlinear processes involved with these applications. Available systems are either based on low-energy, high-repetition-rate optical parametric oscillators or high-energy, low-repetition-rate optical parametric amplifiers. In this thesis a sources was developed that can bridge the wide gap between these two extremes, providing sufficient energy to drive nonlinear processes, with repetition rates in the MHz domain. This was achieved by introducing three techniques previously employed for energy scaling in laser cavities. Firstly an exchange from the conventionally used Ti:sapphire pump to a commercial high power Yb:fibre laser system readily scaled the usable pump energy. This was combined with a technique known as cavity-length extension, which allows a lowering of the cavity roundtrip time offering the build-up of pulses with increased energy. In a final stage, cavity-dumping on basis of an acousto-optic modulator was introduced into the a redesigned cavity. The combination of these three techniques, novel to synchronously pumped optical parametric oscillators, enabled the extraction of record-high pulse energies and peak powers