Semiconductor laser array-pumped, neodymium glass, modelocked laser oscillator and regenerative amplifier

A semiconductor-laser-array-pumped cw modelocked Nd:glass laser oscillator and regenerative amplifier system is described. The difficulties associated with semiconductor laser pumping of Nd:glass are discussed. Pump beam shaping techniques are presented which reduce thermally induced distortions of the lasing mode within the Nd:glass gain medium. A resonator design is presented which allows the use of low f# pump beam focusing optics yet provides excellent immunity to thermal lensing within the Nd:glass. The effect of thermal lensing on the resonator mode is studied. The output versus input power relation for the oscillator is derived. From measurements of the laser threshold versus the output coupler reflectivity, the parasitic resonator loss, unsaturated gain as a function of pump power and the optimum output coupler reflectivity are determined. Measurements of the effect of intracavity etalons on the cw lasing spectrum as well as the absence of cavity beat notes over a wide frequency range indicate that gain broadening over the band widths considered is predominantly homogeneous. Good agreement is found between theory and experiment assuming a homogeneously broadened line. The cw modelocked Nd:glass laser oscillator produced optical pulses ranging from 20 to 90 ps in width at average powers of 20 to 50 mW.; The design and operation of the semiconductor laser array pumped Nd:glass regenerative amplifier is presented. Techniques for measurement of the time dependent resonator transmission as well as the output pulse energy are described. The amplifier's performance is consistent with predictions based on published theory and measured parameters. The regenerative amplifier, when used in conjunction with the modelocked oscillator, provided an energy amplification greater than 50 dB producing 4.7 {dollar}mu{dollar}J, 77 kW peak power pulses at a repetition rate of 355 Hz. This represents the largest peak power obtained to date from a semiconductor laser pumped laser system and was accomplished with an average electrical power consumption by the pump lasers of less than 8 W.; Several ideas are presented to enhance the systems performance including methods for compressing the pulse width and for increasing the amplified pulse energy.