Acousto-optic intensity modification of a gaussian laser beam

Gaussian-beam profile shaping by acousto-optic Bragg diffraction

“…For a typical rectangular sound column with plane-wave incidence, as shown in Fig. 1, the general multiple-scattering theory can be reduced to the following infinite coupled equations: (1) with the boundary condition En = incbnO at z < 0, where 8nO is the Kronecker delta and En is the complex amplitude of the nth-order plane wave of light in the direction (,, = ()ine + 2nB.…”

“…'-' 2 Using the acousto-optic effect, Ohtsuka et al1 2 have been able to produce a uniform far-field distribution with the sound cell operating in the Raman-Nath regime.' 3 Most recently, Tervonen et al have improved the acousto-optic approach by utilizing the methods of synthetic diffractive optics.1 2 In this paper we employ a multiple-plane-wave theory for strong acoustooptic interaction 3 " 4 together with a newly developed transfer-function formalism 5 " 6 to investigate how Gaussian intensity profiles can be transformed into either near-field or far-field flattop profiles by use of Bragg diffraction. Section 2 presents the multipleplane-wave theory in terms of a set of infinite coupled differential equations and reviews the transferfunction formalism.…”

High-performance laser beam shaping and homogenization system for semiconductor processing

“…In the literature, various methods have been proposed for beam shaping and homogenization: intensity modification of Gaussian laser beams by phase filtering or diffraction gratings (Veldkamp 1981, Katti and Mehta 1976, Lee 1981) acousto-optical effects (Ohtsuka and Tanone 1981), aspherical lenses (Shafer 1982), particular absorption elements (Penzkofer andFrohlich 1979, Greenaway andSteinle 1979), beam splitting/ superimposing techniques (Pera et al 1985, Latta and Jain 1984, Jain and Latta 1985, Pressley 1984, Kawamura et a1 1983 and others. However, serious drawbacks prevent these methods from being applied for semiconductor treatment: an exact flat-top intensity profile possessing sharp edges cannot be generated; the residual deviation of the actual profile from the ideal form is not acceptable, 0 the optical-geometrical parameters of the resulting profile (flatness, cross section, position on the target) remain sensitive to the parameters of the incoming beam in a certain degree, such as position, aperture, divergence, intensity distribution.…”