The use of lasers to drive inertial confinement fusion (ICF) has been under investigation since the advent of Q-switching with major program efforts over the past eight years. Critical factors which have emerged concerning the choice of a laser to drive a fusion power plant include the coupling of the laser light of the target, the cost, complexity, and reliability of the driver, and the driver efficiency.

The development of high-power glass lasers has stimulated interest in materials with low index nonlinearity. A number of authors have proposed empirical relations between the nonlinear index and linear dispersion parameters. We review these expressions and relate them to both classical and quantum theoretic derivations of the index nonlinearity. We show that the major differences arise in the trea...

For many laser applications, it is desired to focus a collimated beam with a specified transformation of the intensity distribution. The transformation properties of a lens or mirror system can be specified in terms of the principal surface r(alpha), which maps the height of the incident ray parallel to the optic axis onto a given angle at the focus. The intensity distribution at the focus is then given by the relation I(alpha) = I(r)r(dr/dalpha)/ sinalpha. One aspheric surface in an optical system is sufficient to yield diffraction limited focusing. By means of two aspheric surfaces, diffraction limited performance with a specified principal surface can be achieved. The problem of optical design is stated as follows: Given a principal surface r(alpha) and a maximum focal angle alpham, find the pair of optical surfaces for which diffraction limited focusing is achieved. It is shown that specification of r(alpha) and alpham uniquely determines the lens design to within a scale factor, given the refractive index of the lens. It is further shown that one straightforward Runge-Kutta integration routine generates both surfaces for either a lens or a pair of mirror surfaces. The complete family of aplanatic lenses will be described. Deviation from sphericity will be discussed, as will the possibility of realizing the specified lens designs. The family of lenses that map uniform incident intensity into uniform illumination about the focus will also be described. Extension of the method to off-axis aberrations will be considered.

In any laser fusion scheme dependent on adiabatic implosion of the fusion target, it is of the utmost importance to illuminate the target uniformly over its entire surface area. A convenient method of providing illumination over the entire spherical surface from two beams was proposed by Thomas.1 In this method, a catadioptric system is employed, involving a fast (NA 0.7) lens and a pair of ellipsoidal mirrors of eccentricity ⅓. Subsequent refinements of this scheme have been developed at the Lawrence Livermore Laboratory.2

The absorption of light and subsequent thermalisation of the absorbed energy can be significantly affected by the presence of non-equilibrium population distributions in gases. The phenomenon of thermal blooming in gases is discussed from this standpoint. It is shown that a transient phenomenon of “absorption cooling” can occur, leading to a focusing rather than defocusing of an incident laser beam. Flux densities causing saturation in air and pure CO2 are calculated. For vibrational saturation in air, I > 3.66 kw/cm2, for pure CO2, I > 4.58 kw/cm2. For rotational saturation, in either gas, I > 840 kw/cm2.

The steady-state performance of a Raman laser oscillator can be described by a simple standing-wave theory. This theory has been extended to take into account the time variation of the exciting laser pulse. The resulting differential equation is nonlinear, but analytic expressions can be obtained in the limiting cases of small-signal amplification and saturation. Experimental results in H2gas are ...

The Raman laser is potentially a device capable of converting laser output of poor spatial quality into a nearly diffraction-limited beam with high efficiency. A number of factors must be considered in the design of a Raman laser. To avoid beam trapping, gases are preferable as Raman media at high-power levels. For optimal mode control, an oscillator-amplifier combination is the most flexible conf...