Efficient Frequency Doubling of an Nd:YLF Amplifier System Using an LBO Crystal

Abstract

Ultrafast laser amplifiers based on Titanium-doped Sapphire (Ti:Sa) laser crystals togenerate multi-Joule femtosecond pulses have grown in popularity, and the pumping architectures used for these amplifiers are of paramount importance. This thesis describes the design and implementation of an efficient frequency doubling setup to be used to upgrade the Advanced Lasers for Extreme Photonics (ALEPH) Ti:Sa laser at the Advanced Beam Laboratory (ABL) at Colorado State University (CSU). It includes substituting the front end of the pump laser of ALEPH, which is based on a flashlamp-pumped Q-switch oscillator, to a diode-pumped regenerative amplifier which is capable of generating a square temporal profile with a supergaussian spatial profile. The upgraded front-end design produces 527nm pulses with 0.32J of energy and a 10ns square temporal profile, at repetition rates up to 20Hz. This output is produced from a Neodymium-doped Yttrium Lithium Fluoride (Nd:YLF) regenerative amplifier and Nd:YLF double-pass amplifier producing 400mJ pulses of 1053nm radiation, which are subsequently frequency doubled using Lithium Triborate (LBO) as the frequency doubling medium. The design was tested to produce 527nm pulses with 0.32J of energy and a 10ns square temporal profile with a doubling efficiency of 79%. Details about the basic concepts and design of this laser, including the regenerative amplifier, injection seeder, double-pass amplifier, and frequency doubling setup are presented here, along with the recorded data from the measurements conducted to evaluate the system’s performance.