We investigated the spatial confinement oflaser beams focused through human cornea and sciera using long near infrared wavelengths. Using a 0.4 numerical aperture lens, we measured the spatial transmission ofthe smallest emergent beam on the back surface ofthe tissue. We found that standard axia' transmission measurements over estimate the amount of unscattered light for the sciera and that 1600 run to 1700 nm had the maximum unscattered transmission through cornea and sciera. The light confinement may be useful in producing localized subsurface linear and nonlinear optical processes.
Very high-speed MSM photodiodes have been fabricated on Er-doped GaAs over a doping range of 1018-1020 cmP3. The impulse response (characterized by photoconductive sampling) of these diodes, with finger widthdspacings of 2 pm, has been found to be tunable over a range of about 3 ps-22 ps. Electro-optic sampling was used to characterize MSM diodes with finger widthdspacings of 0.5 pm and 1 pm on a sample with [Er] = lo1' ~m -~, resulting in 3-dB bandwidths of 160 GHz and 140 GHz, respectively, corresponding to pulse widths of 2.7 ps and 3.3 ps. Correlation measurements were also done on the GaAs:Er samples, using an all-electronic Sampling Optical Temporal Analyzer (SOTA) structure. HE use of Metal-Semiconductor-Metal (MSM) photode-
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