Experimental Demonstration of Spectral Intensity Optical Coherence Tomography

We demonstrate experimentally quantum-inspired, spectral-domain intensity optical coherence tomography. We show that the technique allows for both axial resolution improvement and dispersion cancellation compared to conventional optical coherence tomography. The method does not involve scanning and it works with classical light sources and standard photodetectors. The measurements are in excellent agreement with the theoretical predictions. We also propose an approach that enables the elimination of potential artifacts arising from multiple interfaces

Extinction correction and on-sky calibration of SCUBA-2

Commissioning of SCUBA-2 included a program of skydips and observations of calibration sources intended to be folded into regular observing as standard methods of source flux calibration and to monitor the atmospheric opacity and stability. During commissioning, it was found that these methods could also be utilised to characterise the fundamental instrument response to sky noise and astronomical signals. Novel techniques for analysing on-sky performance and atmospheric conditions are presented, along with results from the calibration observations and skydips.Comment: 10 pages, 7 figure

Decomposition of the point-dipole field into homogeneous and evanescent parts

In near-field optics the resolution and sensitivity of measurements depend on the abundance of evanescent waves in relation to propagating waves. The electromagnetic field propagator is related to the scalar spherical wave, for which the Weyl expansion is a half-space representation containing both evanescent and homogeneous plane waves. Making use of these results, we decompose the dyadic free-space Green function into its evanescent and homogeneous parts and show that some approaches put forward in the literature are inconsistent with this formulation. We express the results in a form that is suitable for numerical computation and illustrate the field decomposition for a point dipole in some typical cases.Peer reviewe

Degree of polarization in near fields of thermal sources: effects of surface waves

We introduce the concept of degree of polarization for electromagnetic near fields. The approach is based on the generalized Stokes parameters that appear as expansion coefficients of the 3×3 coherence matrix in terms of the Gell-Mann matrices. The formalism is applied to optical near fields of thermally fluctuating half-space sources with particular interest in fields that are strongly polarized owing to resonant surface plasmons or phonons. This novel method is particularly useful when assessing the full vectorial characteristics of random evanescent fields, e.g., for near-field spectroscopy and polarization microscopy.Peer reviewe

Cross-spectral purity of the Stokes parameters in random nonstationary electromagnetic beams

We consider cross-spectral purity in random nonstationary electromagnetic beams in terms of the Stokes parameters representing the spectral density and the spectral polarization state. We show that a Stokes parameter being cross-spectrally pure is consistent with the property that the corresponding normalized time-integrated coherence (two-point) Stokes parameter satisfies a certain reduction formula. The current analysis differs from the previous works on cross-spectral purity of nonstationary light beams such that the purity condition is in line with Mandel's original definition. In addition, in contrast to earlier works concerning the cross-spectral purity of the polarization-state Stokes parameters, intensity-normalized coherence Stokes parameters are applied. It is consequently found that in addition to separate spatial and temporal coherence factors the reduction formula contains a third factor that depends exclusively on the polarization properties. We further show that cross-spectral purity implies a specific structure for the electromagnetic spectral spatial correlations. The results of this work constitute foundational advances in the interference of random nonstationary vectorial light.Comment: 5 pages, 1 figur

Virtually isotropic transmission media with fiber Raman amplifier

We report a theoretical study and simulations of a novel fiber-spin tailoring technique to suppress the polarization impairments, namely polarization mode dispersion and polarization dependent gain (PDG), in fiber Raman amplifiers. Whereas use of depolarizer or multiplexing pump laser diodes with a final degree of pump polarization of 1% for periodically spun fiber results in PDG of about 0.3 dB, we demonstrate that application of just a two-section fiber (where the first part is short and has no spin, and the second one is periodically spun) can reduce the PDG to as low as below 0.1 dB

Effect of backscattering in phase conjugation with weak scatterers

An extension is presented of a recently developed theory (based on the first Born approximation) of cancellation of distortions by phase conjugation. The influence of backscattering of both the incident and the conjugate waves is considered. It is shown that, when backscattering is taken into account, distortions are not eliminated by phase conjugation, except when the conjugate wave is generated without a loss or a gain