The development of high-peak-power and average-power ytterbium-doped chirped-pulse amplifiers.

摘要

This thesis will investigate ytterbium-doped laser materials and new techniques to produce simpler and more compact chirped-pulse amplification (CPA) laser systems. Yb:glass is a promising directly diode-pumped material as a result of several attractive properties. The 2-ms upper-state lifetime, broad fluorescence spectrum, 15-wt% doping concentration, greater than 40-J/cm 2 saturation fluence, and 7% quantum defect of Yb:glass distinguish it as a material which can amplify short pulses, can be pumped easily by free-running lasers or laser diodes, and can store an extremely high energy density for CPA.; The two difficulties of Yb:glass are its relatively low emission cross-section and poor thermal conductivity. The former problem is addressed by using a low-gain low-loss regenerative amplifier to efficiently extract the stored energy. Spectroscopic measurements and simulations of the quasi-3-level CPA process are performed to optimize the extraction efficiency and amplified bandwidth. Based on these simulations, a Yb:glass regnerative amplifier was constructed producing 150 mJ, the highest energy obtained from a short-pulse regenerative amplifier. This regenerative amplifier pumped by a free-running high-energy pump source in combination with a diode-pumped Yb:glass oscillator demonstrate a compact terawatt laser system with excellent beam quality defined by the regenerative cavity.; One solution for the thermal problem is introduced and demonstrated through the use of a moving gain medium. The laser medium is pumped with a uniform transverse spatial profile and is lased during the resulting transient uniform temperature profile. This simple technique for the removal of thermal problems is well-suited for long pulse energy extraction from Yb:glass, in which the high saturation fluence can be fully taken advantage.; A technique for the precise control of the gain spectrum by spatially dispersing an injected pulse in a regenerative amplifier is discussed. This technique results in numerous advantages, including increasing the mode size using the bandwidth of the laser. Broadening the spectrum by greater than a factor of five in a spatially-dispersed Yb:YAG laser demonstrates the feasibility for a truly directly-diode-pumped high-average-power 100-fs source.