A Frequency-stabilized, Diode-pumped Ytterbium:KYW Optical Frequency Comb for Metrology
There has been a wealth of research into applying optical frequency combs to a variety of scientific and technological problems in the last decade. Thus there is much interest in the development of new frequency comb sources to fulfill the requirements of these applications. In this thesis I will present the first frequency-stabilized, diode-pumped Yb3+-crystal frequency comb. The comb is based on a 180 MHz mode-locked Yb:Tungstate (Yb:KYW) fs-laser. The fs-laser output was amplified, temporally compressed and broadened to an octave-spanning spectrum in microstructured fiber. The offset frequency was then detected using an f–2f interferometer and locked using a phase-locked loop. The repetition rate was locked to a cavity-stabilized laser. The frequency-locked Yb:KYW comb was compared to a Ti:Sapphire comb locked to a different CW reference laser. Each comb was photodetected and the resulting microwave harmonics of the repetition rates were mixed. The phase noise of the mixed-down signal was measured to verify the generation of very stable microwave signals from the Yb:KYW comb. This result demonstrated the potential of Yb:KYW combs for low noise applications. With that established, routes towards the GHz repetition rates that are desirable for many comb applications will be presented. These include a Kerr-lens mode-locked 800 MHz Yb:KYW fs-laser and a combination of amplification and cavity filtration. My results demonstrate that such a Yb-doped tungstate laser can provide an efficient, compact, high-repetition-rate optical frequency comb with coverage from 650-1450 nm. Finally, in the process of the laser development, the pump-dependent Yb:KYW resonant dispersion was measured, which will also be presented.