Waveguiding was used to measure the extinction coefficient of a thin film while it was being deposited in a vacuum
chamber. Experimental results are presented and compared to calculations and measurements by other techniques.
Experimental results are presented on using one or more additional windows to reduce the distortion from existing windows transmitting high average power laser beams. A concept is presented for a compound window that will neither distort nor depolarize a high power beam.
The advantages of backside irradiation and controlling the polarization and angle of incidence of laser beams used to conventionally clean surfaces have been described previously. This paper considers beams internally incident upon the surface of a transparent substrate at angles of incidence beyond the critical angle for total internal reflection. Attenuated total internal reflection provides an efficient means for both finding and removing absorbing contaminants. Beams may enter the substrate through an edge or a coupling prism. Erbium laser pulses were used to remove water from several dielectric and semiconductor materials. In some cases the water was explosively removed, with no sign of damage to the substrate. A 2.94 μm laser should be especially effective whenever water is present, either naturally from adsorption or capillary condensation or when added for steam laser cleaning. Unabsorbed light can be efficiently routed to clean adjacent areas through multiple total internal reflections. Thus some of the scanning is done at the speed of light. Theory indicates that ATR laser cleaning is effective for very small particles that cannot be removed by shock laser cleaning. This paper will describe attenuated total internal reflection laser cleaning and compare it to conventional laser cleaning techniques.
A number of concepts using the principle of the refraction of light have been developed to steer light beams. Refractive beam steering concepts involve the use of optical wedges in order to deviate a light beam. This principle is ideally suited for steering laser light since dispersion is minimal due to the monochromatic nature of the laser. The methods used to form the optical wedge and the means developed to adjust it are what distinguish the various concepts and have resulted in many patents over the years for their innovators. A new concept called a Lubricated Adjustable Optical Wedge (LAOW) has been recently developed that does not require complicated mechanical systems to form the wedge and provide the adjustment necessary to deviate the light beam. An optical wedge is formed using plano-convex and plano-concave lenses that are contacted together using a thin film of transparent index matching lubricant between the spherical surfaces. The forces of capillary action and surface tension provide the sole means of keeping the lens elements together. This technique has demonstrated a repeatability ≤±0.12 arc seconds in beam deviation angle.
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