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Browsing by Author "Aggarwal, I. D."

Now showing 1 - 4 of 4
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    Characterization And Modeling Of Drift Noise in Fourier Transform Spectroscopy: Implications For Signal Processing And Detection Limits
    Hazel, G.; Bucholtz, F.; Aggarwal, I. D. (Optical Society of America, 1997-05-01)
    A theoretical analysis of long-term drift noise in Fourier transform spectroscopy is presented. Theoretical predictions are confirmed by experiment. Fractional Brownian motion is employed as a stochastic process model for drift noise. A formulation of minimum detectable signal is given that properly accounts for drift noise. The spectral exponent of the low-frequency drift noise is calculated from experimental data. A frequency-dependent optimal spectrum averaging time is found to exist beyond which the minimum detectable signal increases indefinitely. It is also shown that the minimum detectable signal in an absorbance or transmission measurement degrades indefinitely with the time elapsed since background spectrum acquisition. (C) 1997 Optical Society of America.
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    Effect Of Temperature on The Absorption Loss Of Chalcogenide Glass Fibers
    Nguyen, V. Q.; Sanghera, J. S.; Kung, F. H.; Aggarwal, I. D.; Lloyd, I. K. (Optical Society of America, 1999)
    The change in the absorption loss of IR-transmitting chalcogenide glass fibers in the temperature range? of -90 degrees C less than or equal to T less than or equal to 70 degrees C was investigated. For sulfur-based glass fibers the change in loss relative to room temperature was slightly affected by the temperature in the wavelength region of 1-5 mu m. For lambda greater than or equal to 6 mu m the change in loss was mainly due to multiphonon absorption. The change in loss for tellurium-based glass fibers increased significantly at T = 60 degrees C. The increase in the loss at short wavelengths (lambda less than or equal to 4.1 mu m) was due to electronic excitations in the tail states. Between 5 and 9 mu m there was noticeable free-carrier absorption. Beyond lambda greater than or equal to 9 mu m, multiphonon absorption dominated the loss spectrum. (C) 1999 Optical Society of America.
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    Infrared Evanescent-Absorption Spectroscopy with Chalcogenide Glass-Fibers
    Sanghera, J. S.; Kung, F. H.; Pureza, P. C.; Nguyen, V. Q.; Miklos, R. E.; Aggarwal, I. D. (Optical Society of America, 1994-01-01)
    We have used telluride glass fibers fabricated in house to measure the evanescent-absorption spectra of water, methanol, ethanol, isopropanol, acetone, ethanoic acid, hexane, and chloroform. Furthermore, detection limits of less than 2 vol. % solute were obtained for mixtures of water and methanol, ethanol, isopropanol, acetone, and ethanoic acid. Techniques to reduce the detection limits are discussed.
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    Separation of Intrinsic and extrinsic Optical-Absorption in a Fluoride Glass
    Jewell, J. M.; Williams, Glen M.; Jaganathan, J.; Aggarwal, I. D.; Greason, P. (AIP Publishing, 1991-07-01)
    The contribution of impurity ions to the total optical absorption of a heavy metal fluoride glass has been determined at 532 and 1064 nm. Four ZrF4-BaF2-LaF3-AlF3-NaF glasses were prepared from various purity raw materials. The absorption coefficients of these glasses range from 0.92 to 45.4 x 10(-4) cm-1 at 1064 nm and from 7.43 to 11.1 X 10(-4) cm-1 at 532 nm as determined by laser calorimetry. The concentrations of Fe, Ni, Cu, and Co ions in each glass were determined by graphite furnace atomic absorption spectroscopy. These two measurements enable the absorption, due to transition metal ions to be differentiated from the intrinsic absorption of the glass. At 1064 nm, the absorption coefficient of these glasses is controlled entirely by the transition metal ion content. However, at 532 nm, the absorption by the transition metal ions accounts for 4-42% of the total absorption depending on impurity concentration. The intrinsic absorption of this fluoride glass calculated from these data at 532 nm is (7.69 +/- 0.99) X 10(-4) cm-1.