A. H. Kung

Generation of 1182‐Å radiation in phase‐matched mixtures of inert gases

Coherent radiation at 1182 A is obtained by third‐harmonic generation in a phase‐matched mixture of Xe and Ar. For generation from 3547 to 1182 A, Xe is negatively dispersive, and phase matching is obtained at a ratio of Xe:Ar=1:430. A conversion efficiency of 2.8% is obtained at an input power of 13 MW. As predicted by theory the conversion efficiency increases linearly to the limit of our available input power.

Generation of tunable picosecond VUV radiation

A coherent tunable vacuum ultraviolet picosecond source has been constructed by third‐order nonlinear mixing of a broadly tunable picosecond visible source and the fourth harmonic of a mode‐locked Nd : YAG laser in xenon. Tunable radiation in the VUV covering portions of the region from 1180 to 1470 A and continuously from 1631 to 1946 A is obtained.

Stimulated emission in multiple-photon-pumped xenon and argon excimers.

Multiple photon absorption of laser radiation at 2660 and 3547 A is used to pump excimers of Xe and Ar. Line narrowing is observed in bands ∼ 100 A wide, centered at 1730 and 1260 A, respectively.

Generation of ultraviolet and vacuum ultraviolet radiation

The paper describes the use of nonlinear optical techniques for the generation of coherent radiation at ultraviolet, vacuum ultraviolet, and soft x-ray wavelengths. Mixtures of metal vapors and inert gases, and other mixed gas systems, allow generation to regions of the spectrum where nonlinear optical crystals are opaque; and also allow generation at high incident power and energy densities. Progress is reported on programs aimed at efficient conversion from 1.064µ to 3547 A, and from 3547 A to 1182 A. To date, the shortest wavelength generated by this technique is 887 A. Theoretical considerations indicate that generation into the soft x-ray region should be possible. Using 1182 A radiation, a holographic grating with a fringe spacing of 836 A has been constructed and examined on an electron microscope.

1202.8-Å generation in Hg using a parametrically amplified dye laser

We have generated 1202.8-Å radiation, one-half the frequency of the1s^{1} S_{o}-2s^{1}S_{o}forbidden transition in He, using resonantly enhanced four-wave optical mixing in Hg vapor. Peak powers of 300 W in a ∼ 15-ps pulse have been achieved using a tunable narrow-band source consisting of a parametrically amplified commercial dye laser. The dependence of the conversion efficiency on the spectral properties of this source is described. Hg is shown to be negatively dispersive for this process, and thus phase matchable.