Browsing by Author "Sudarshanam, V. S."

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    Fiberoptic Polarization And Phase Modulator Utilizing Transparent Piezofilm with Indium Tin Oxide Electrodes
    Sudarshanam, V. S.; Desu, Seshu B. (Optical Society of America, 1995-06-01)
    A highly efficient optical polarization and phase modulator formed by the placement of a thin transparent piezofilm with indium tin oxide electrodes directly in the path of the output from an optical fiber is presented. Various configurations that differ in the clamping conditions, utilization of epoxy, and optical arrangement are presented. For a film thickness of 63.9 mu m, a linear phase-shifting coefficient of 0.131 rad/voltage peak (Vp) at 2 kHz and of 0.508 rad/Vp at 7.4 kHz is demonstrated. An intrinsic birefringence of 0.0328 between the directions along the stretch and its perpendicular in the plane of the film has been measured. The polarization modulation coefficient was determined to be 0.323 rad/Vp at 8.423 kHz, corresponding to a half-wave voltage of 8.353 Vp. Applications of the device involving concurrent spatiotemporal polarization and phase modulation are indicated.
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    Measurement Of Dynamic Polarization Modulation Depth Utilizing The J(1)-J(4) Method Of Spectrum Analysis
    Sudarshanam, V. S.; Desu, Seshu B. (AIP Publishing, 1994-07-01)
    A spectrum analysis method for the linear, direct, and self-consistent measurement of dynamic modulation depth of polarization modulators is presented. This method utilizes the Bessel recurrence relation to determine the modulation depth from the photodetector voltage amplitudes at the fundamental frequency and its next three harmonics. Based on the existing J1-J4 method of dynamic phase-shift measurement in homodyne interferometry, this method is useful for calibration of polarization modulated ellipsometers. The method is demonstrated through the use of a highly birefringent transparent thin film of piezoelectric polyvinylidene fluoride with indium tin oxide electrodes. The theoretical analysis of the measured noise factor for the particular system configuration predicted a minimum detectable polarization modulation depth of 0.2 rad, and was experimentally verified.
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    Minimum Detectable Phase-Shift in Spectrum-Analysis Techniques Of Optical Interferometric Vibration Detection
    Sudarshanam, V. S. (Optical Society of America, 1992-11-01)
    The minimum detectable phase shift indicated in recent experimental reports of new linear spectrum-analysis techniques of optical interferometric vibration detection is established as the direct consequence of the 1/f noise voltage in the system components. The dynamic range and in accuracy predicted by the simple theoretical model presented is in good agreement with experimental measurements. The conclusions of the analysis are compared with experimental reports of heterodyne shot-noise-limited optical systems. With this effective tool the generic class of spectrum-analysis techniques can be analyzed and relatively weighed to assess the effect of noise. This analysis is applicable to optical interferometry in general, although the experiments specifically involved fiber-optic modulators.