Highly efficient Yb-ion-doped lasers pumped at 946 nm by a compact Nd:YAG laser

The development of efficient ultrafast laser sources based on Yb-doped crystals is very important for a variety of optical applications such as nonlinear spectroscopy, nonlinear microscopy, telecommunications etc. A powerful and high beam quality (near diffraction limited: M2~1) pump laser is desirable to mitigate the effect of reabsorption loss that Yb-doped crystals exhibit and realize highly efficient operation in both continuous-wave (CW) and pulsed domains. Unfortunately, there are no commercially available laser diodes that can provide both high beam quality and high output power (>1 W) simultaneously. This thesis presents the development of a powerful and high beam quality pump laser and then utilizes this pump laser to demonstrate the efficient operation of Yb:YAG laser in CW domain and Yb:KGW laser in both the CW and pulsed domains. In the first part of the thesis, a high-power compact CW Nd:YAG laser was built with greatly improved beam quality operating at 946 nm. A maximum output power of 9.98 W with beam quality factor M2 ~ 5 was obtained. I also demonstrated a highly efficient and tunable CW Yb:YAG laser pumped by the developed Nd:YAG laser. The maximum CW output power of 4.37 W was obtained at 1030 nm with optical-to-optical efficiency of 70% with respect to the absorbed pump power. Wavelength tuning of Yb:YAG laser was then explored due to metrological applications such as references for high-resolution spectroscopy or dimensional metrology. The laser produced a continuously tunable operation over 100 nm from 1000 nm to 1100 nm. This is the most tunable laser among bulk crystalline Yb:YAG solid-state lasers. Due to the increasing interest in dual-wavelength (DW) operation for the use as an optical source for terahertz (THz) radiation, this thesis also gave a demonstration of DW Yb:YAG laser operation. This is the first demonstration of DW operation of Yb:YAG laser pumped by a Nd:YAG laser at 946 nm. The latter part of the thesis concentrated on developing a highly efficient ultrashort pulse Yb:KGW laser oscillator pumped by the Nd:YAG laser. In the mode-locked regime, 175 fs duration pulses centered around 1025 nm were generated at a repetition rate of 54.6 MHz with a total average output power of up to 1.1 W, corresponding to optical-to-optical efficiency of 34.8% with respect to the absorbed pump power. In the CW regime, the maximum output power of 3.7 W was obtained for an absorbed power of 5.13 W that represents optical-to-optical efficiency of 72.12%. Furthermore, the tunability of Yb:KGW laser was studied and the laser produced a continuously tunable operation of 90 nm from 990 nm to 1080 nm. This is the most tunable and efficient laser in the CW regime among bulk crystalline Yb:KGW solid-state lasers.

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