A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectance-versus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method’s validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering.
A new approach for the measurement of a refractive index is presented, following the introduction of a novel feature based on the selection of a large number of angles of incidence along a direction of symmetry at the prism-ambient interface, without moving the incident beam. This gives rise to very high sensitivities over a refractive index range determined by the divergence of this beam.
Various oxides have been reported to be sensitive to humidity of the environment. Recently ceramic type humidity sensors using aluminates and ferrates are widely reported as stable sensors. The change in electrical resistance due to change in humidity is considered due to adsorption of water molecule in the pores of material. If the material has more active centers, it will yield better results. It is suggested that the protonic conduction is possible due to pores where H3O+ and OH- ions are formed due to moisture adsorption. The formations of protonic ions are possible if electrically active centers are present which will help to increase the sensitivity. It αis expected that in porous structure/surface the presence of dangling bonds may act as electrically active centers and facilitate the increase in sensitivity of the humidity sensor. The present paper reports the measurement of spin density of ferrates fired at different temperatures and correlates its humidity sensitivity with spin density. This explains that dangling bonds act as active centers and if the process of fabrication of humidity sensor increases the dangling bonds, it is possible to increase the sensitivity of the sensor.
Phase-sensitive detection of resonance fluorescence, i.e., allowing the light emitted from an atom which is undergoing Rabi oscillations in free space to interfere with a coherent local oscillator (LO) beam, has drawn considerable attention throughout the history of quantum optics. Recently, phase-sensitive squeezing spectra for single-atom resonance fluorescence were observed for the first time using strongly-driven long-lived atoms. A measurement of phase-sensitive intensity correlations for this system will be presented. Using physical arguments I will construct the phase-sensitive two-time intensity autocorrelation function, and elucidate the role played by quantum fluctuations in phase-dependent resonance fluorescence.
We demonstrate the measurement of path-length-resolved optical phase space distributions as a new framework for exploring the evolution of optical coherence in a turbid medium. This method measures joint transverse position and momentum (i.e., angle) distributions of the optical field, resolved by optical path length in the medium. The measured distributions are related to the Wigner phase space distribution function of the optical field, and can provide complete characterization of the optical coherence in multiple scattering media. Optical phase space distributions are obtained as contour plots which enable a visual as well as quantitative method of characterizing the spatial coherence properties and wavefront curvature of the input and scattered fields. By using a broad-band source in a heterodyne detection scheme, we observe transmission and backscatter resolved by path length in the random medium, effectively providing timing resolution. New two-window heterodyne detection methods permit independent control of position and momentum resolution with a variance product that surpasses the uncertainty limit associated with Fourier transform pairs. Hence, high position and angular resolution can be simultaneously achieved. These techniques may provide new venues for using optical coherence in medical imaging.
We demonstrate the measurement of path-length-resolved optical phase space distributions as a new framework for exploring the evolution of optical coherence in a turbid medium. This method measures joint transverse position and momentum (i.e., angle) distributions of the optical field, resolved by optical path length in the medium. The measured distributions are related to the Wigner phase space distribution function of the optical field, and can provide complete characteristics of the optical coherence in multiple scattering media. Optical phase space distributions are obtained as contour plots which enable a visual as well as quantitative method of characterizing the spatial coherence properties and wavefront curvature of the input and scattered fields. By using a broad-band source in a heterodyne detection scheme, we observe transmission and backscatter resolved by path length in the random medium, effectively providing timing resolution. New two-window heterodyne detection methods permit independent control of position and momentum resolution with a variance product that surpasses the uncertainty limit associated with Fourier transform pairs. Hence, high position and angular resolution can be simultaneously achieved. These techniques may provide new venues for using optical coherence in medical imaging.
We explore enhanced backscatter from a random medium using time-resolved optical phase space measurement, i.e. measurement ofjoint position and momentum (x, p) distributions of the light field as a function of propagation time in the medium. Enhanced backscatter is a coherent effect and is not predicted by radiative transport theories. By using a low-coherence source in a heterodyne detection scheme, we observe enhanced backscattering resolved by path length in the random medium, effectively providing timing resolution. Such time-resolved studies are important for exploring the evolution of optical coherence as a function of penetration depth in the random medium. Optical phase space methods provide a visual as well as quantitative method of characterizing the spatial coherence properties and wavefront curvature of the input and scattered fields. These techniques may provide new venues for using optical coherence in medical imaging.
The newly designed prism based fiber optical refractometer sensor has been used to determine adulteration in petrol. A procedure for identification of the adulterant and determination of its concentration in a sample of petrol has been reported. Substances like kerosene, diesel, a mixture of these two or of aviation gasoline and kerosene have been used as adulterants.
The new design for the prism based refractometer sensor presented here is characterized by its high sensitivity over a wide range of refractive indices of the ambient. The refractometer is more robust and user friendly than other such refractometers reported in literature.
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