Reeta Vyas

Pulsed photothermal deflection spectroscopy in a flowing medium: a quantitative investigation

A comprehensive investigation of pulsed photothermal deflection spectroscopy in a flowing medium has been carried out. A rigorous solution of the appropriate diffusion equation has been obtained, and experiments have been conducted to verify the theoretical predictions. Absolute measurements of the photothermal deflection were made and no adjustable parameters were used in the theory. Very good agreement between the theory and the experiment was obtained.

Ringing revivals in the interaction of a two-level atom with squeezed light

The Jaynes–Cummings interaction of a two-level atom with the radiation field is studied when the radiation is initially in a strongly squeezed coherent state. The dynamic response of the atomic inversion shows echoes after each revival when the squeezed coherent state exhibits an oscillatory photon-counting distribution due to the phase-space interference effect. The sensitivity of the dynamic behavior to approximations used in computing the atomic inversion is discussed. Comparison is made with the intensity-dependent interaction model of Buck and Sukumar [ Phys. Lett.81A, 132 ( 1981)]; this model does not exhibit echoes. The mean, variance, and entropy for the photon-number distribution are calculated and found to show behavior similar to that of the atomic inversion.

Photothermal lensing spectroscopy in a flowing medium: theory

A complete and general theoretical description of dual-beam photothermal lensing spectroscopy is given. The results are valid for the most general conditions, that is, for flowing as well as stationary media, and for cw as well as pulsed excitation. For pulsed excitation, the results are valid for arbitrary pulse length. The cw results apply to both modulated as well as unmodulated excitation. Both transverse and collinear geometries are considered.

Green's function solution to the tissue bioheat equation.

A Greens function solution to the tissue bioheat equation including blood flow in cylindrical geometry is obtained. Numerical results for temperature variation in the bovine muscle are reported when the tissue is exposed to neodymium-yttrium-aluminum garnett (Nd:YAG) lasers with Gaussian profile and a comparison with recent measurements is made. A strong dependence of the tissue temperature on the beam radius and pulse time is found.

Phase and interference properties of optical vortex beams

Laguerre-Gauss vortex beams carrying different topological charges are generated from Hermite-Gauss laser beams emitted by a gas laser, and their phase properties are explored by studying their interference with a plane wave. Interference of two Laguerre-Gauss vortex beams carrying equal but opposite topological charge is also studied by using a modified Mach-Zehnder interferometer. Experimentally recorded intensity profiles are in good agreement with the theoretically expected profiles.

Higher-order sub-Poissonian photon statistics in terms of factorial moments

We introduce the concept of higher-order super-Poissonian and sub-Poissonian statistics and show that higher-order sub-Poissonian statistics is a signature of a nonclassical field. Fields generated in intracavity second-harmonic generation and single-atom resonance fluorescence are shown to exhibit higher-order sub-Poissonian statistics.

Photothermal lensing detection: theory and experiment

Photothermal lensing signal shapes are experimentally investigated and compared with those predicted theoretically in our earlier paper. The investigation included flowing and stationary media and pulsed and cw excitations. Good qualitative agreement between theory and experiment is found. Since the lensing signal is almost always accompanied by a deflection signal, the influence of the deflection signal on the detection of lensing signal is investigated. For a perfectly aligned detection geometry the influence of the deflection signal on the lensing signal is negligible, but in the presence of misalignments a significant amount of deflection signal could be superimposed on the lensing signal. The effect of lensing on the deflection signal is also been considered. The effect of the finite size of the probe beam on the lensing signals is also investigated.

Continuous wave photothermal deflection spectroscopy in a flowing medium

A complete and rigorous theoretical treatment of the continuous wave photothermal deflection spectroscopy in a flowing medium is given. The theoretical results have been verified experimentally.

Scattering of atoms by light: probing a quantum state and the variance of the phase operator

Abstract An experiment is proposed to study the quantum state and the variance of the phase operator by measuring the momentum distribution of the atoms resulting from the interaction of an atomic beam with a single mode electromagnetic field via a two-photon interaction. A comparison of the results with those obtained for a one-photon interaction is made. Advantages in using the two-photon interaction are pointed out.

Pulsed and cw photothermal phase shift spectroscopy in a fluid medium: theory.

A theoretical treatment of photothermal phase shift spectroscopy in a fluid medium for the most general conditions is given. The medium is assumed to be flowing. Results for a stationary medium appear as a special case. Both pulsed and cw excitation are considered. For pulsed excitation, the results are valid for excitation pulses of arbitrary length. For the cw case, modulated excitation is explicitly considered, and the results for unmodulated excitation appear as a special case.