Optimization of pulsed fiber lasers, nonlinear pulse combining and optical frequency conversion

The research described in this doctoral thesis was aimed at optimization of pulse characteristics achievable from fiber lasers and amplifiers. Pulse generation and amplification in ytterbium doped fused silica fibers is investigated. Also, optical frequency conversion and combining of pulsed beams in quadratic susceptibility crystal is investigated. The thesis consists of literature review chapter and four research chapters. The first research chapter is dedicated to investigation of the novel ultrashort pulse generation in fiber method, which allows for operation without using conventional saturable absorbers. In the second chapter, pulse amplification in fibers is studied. Nonlinear fiber chirped pulse amplification system, in which self-phase modulation is utilized both in pulse stretching and amplification stages, is investigated and optimized. In the third chapter, second harmonic generation of broadband pulsed radiation from fiber lasers is considered. Promising method for efficient second harmonic generation by inducing temperature gradient along a nonlinear crystal is investigated. In the fourth chapter, two methods for combining of pulsed radiation in quadratic susceptibility crystal are presented. In one case, pulsed beams from four fiber amplifiers are combined into single sum-frequency beam, in which pulses are multiplexed in time. In the other case, two separated in time pulses are combined into single sum-frequency pulse.