ABSTRACT
Excimer-laser microetching of a variety of materials is applied to the fabrication of surface-relief optical microstructures of arbitrary morphology, with particular emphasis on computer-generated holographic structures. High-definition, high-radiation-intensity selective laser ablative etching in conjunction with step-and-repeat (period) replication or raster (pixel) scanning is used. To support such developments, the characteristic etching properties of a wide range of solid materials, from metals to semiconductors and polymers, are studied. Optical-interconnect and generic object holograms are produced by means of this alternative one-step holographic information-recording method.
ABSTRACT
A theoretical analysis is presented of two-wave mixing in photorefractive materials in which the complex amplitude of a weak signal beam has slowly varying but otherwise arbitrary spatial dependence and arbitrary time variation. The set of coupled partial differential equations that couple the dynamics of the optical fields to the photorefractive medium is solved analytically to give the complex amplitude of the transmitted signal in the undepleted pump regime. The results are compared with known results for the transient two-wave mixing of plane waves.
ABSTRACT
Photorefractively induced index-of-refraction phase gratings are shown to combine coherently the optical fields of a strong pump and a suitably amplitude- or phase-modulated signal beam in such a way that an apparent amplification of the modulating waveform appears as intensity modulation of the transmitted signal and pump beam intensities. The source of the signal gain is shown to be the square-law (intensity) detection of the coherently combined pump and modulated signal beams, just as in coherent optical communication systems in which a strong local-oscillator field is coherently added with a weak optical signal field by a beam splitter.
