High-power regenerative Nd:phosphate glass amplifier.
A compact high-power regenerative Nd:phosphate glass amplifier is described which incorporates spatial filtering and full image relay techniques. Output energies up to 1.2 J at a pulse duration of 140 ± 10 psec (FWHM) and 3 J at 900 ± 70 psec (FWHM) are achieved in a smooth nearly flattop beam intensity profile. Even with present-day technology, this system could be scaled into a terawatt regime.
Short pulse injection seeding of Q-switched Nd:glass laser oscillators-theory and experiment
A 0.5-GW-peak-power solid-state laser source that is based on injection seeding a Q-switched Nd:Glass laser is discussed. In the first experimental demonstration, a Q-switched oscillator producing 101 mJ was seeded by a train of 11-ps pulses from a CW (continuous-wave) mode-locked laser to produce injection-mode-locked pulses under a 91-ns envelope. A theoretical analysis of injection seeding of a high-gain Q-switched oscillator by the output of a mode-locked oscillator is presented. The numerical analysis predicts the minimum signal power required for injection mode locking and the temporal shape of the output pulse. The experimental results agree well with the theoretical predictions. The amplification demonstrated by this technique is 104.4 dB, which is much greater than that demonstrated by a multipass or regenerative amplifier. The experimental advantages of injection mode locking include greater than 100 dB of effective amplification and noncritical cavity length adjustment of the seed resonator. >
Fresnel diffraction effects in the design of high‐power laser systems
Fresnel diffraction by circular apertures for beams commonly encountered in high‐power laser systems is investigated. Striking agreement is demonstrated between experimental results and theoretical calculations for beams with uniform and Gaussian intensity profiles. It is pointed out that Fresnel diffraction patterns produced by circular apertures depend only on the incident wave front and the Fresnel number corrected for curvature of the incident beam, F = a2/λL + a2/λR. This also gives an excellent experimental method for measuring divergence. Methods are discussed for minimizing the occurrence of severe intensity variations and resulting self‐focusing problems in high‐power laser amplifiers.