We describe a diode-pumped Yb:YAG laser that produces 1080 W of power cw with 27.5% optical optical efficiency and 532 W Q-switched with M(2)=2.2 and 17% optical-optical efficiency. The laser uses two composite Yb:YAG rods separated by a 90 degrees quartz rotator for bifocusing compensation. A microlensed diode array end pumps each rod, using a hollow lens duct for pump delivery. By changing resonator parameters we can adjust the fundamental mode size and the output beam quality. Using a flattened Gaussian intensity profile to calculate the mode-fill efficiency and clipping losses, we compare experimental data with modeled output power versus beam quality.
Experimental measurements of the energy contributed by one or more ruby amplifier rods driven by a ``Q-switched'' (pulse length of 10−7 sec) ruby oscillator are correlated to theoretical equations describing amplifier action. The equations describe amplification in all energy gain regimes, i.e., exponential, nonlinear, and saturated. The necessary requirements for the use of these equations are the prior knowledge of energy stored in the R1 level just before lasing, the energy input from an oscillator, and a ``nonsaturable loss coefficient'' (loss term) for the particular laser rod. Agreement between theory and experiment is demonstrated in all amplifier gain regimes. Energies of over 50 J in single submicrosecond pulses have been observed. No pulse narrowing has been noticed, but appreciable ruby damage occurs at these energy and power levels.
Using Fresnel diffraction integrals, calculations have been made of the irradiance and power distributions in the near field and in the vicinity of the focus for Gaussian beams focused through annular apertures. Universal curves have been plotted which display the calculations in terms of dimensionless parameters. For very large focal length infrared systems it has been found that the irradiance distribution is not symmetrical about the geometrical focal plane as is commonly assumed. Gaussian and sinusoidal phase aberrations in the aperture field have been included.
Optical phase reversal has been demonstrated using type-II phase matching in lithium formate operated as a degenerate optical parametric amplifier with pump peak powers as low as 103 W. The amplifier was driven in a collimated geometry.
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