Measurement of the anomalous phase velocity of ballistic light in a random medium by use of a novel interferometer

Ballistic light, i.e., radiation that propagates undeflected through a turbid medium, undergoes a small change in phase velocity and exhibits unusual dispersion because of its wave nature. We use a novel highly sensitive differential phase optical interferometer to study these previously unmeasurable phenomena. We find that ballistic propagation can be classified into three regimes based on the wavelength-to-size ratio. In the regime in which the scatterer size is comparable with the wavelength, there is an anomalous phase-velocity increase as a result of adding scatterers of higher refractive index. We also observe an anomaly in the relative phase velocity, where red light is slowed more than blue light even though the added scatterers are made of material with normal dispersion

Deterrence and Morale in Taxation: An Empirical Analysis

The standard model of tax evasion based on the subjective expected utility maximization does not perform particularly well in econometric analyses: it predicts too little evasion and produces unsatisfactory econometric parameter estimates. The model is extended by looking at how the tax authority deals with the taxpayers. Based on econometric estimates, it is shown that taxpayers’ tax morale is raised when the tax officials treat them with respect. In contrast, when tax officials solely rely on deterrence taxpayers tend to respond by actively trying to avoid taxation.

Illegal, Immoral, Fattening or What?: How Deterrence and Responsive Regulation Shape Tax Morale

The traditional economic approach to tax evasion does not appear to be particularly successful in explaining the extent of tax compliance. It is often argued that reciprocity norms which establish a fiscal exchange between the state and the citizens shape tax morale to a large extent. In that respect, a case study of Switzerland may be useful because the small size of the cantons and their direct democratic political systems procedurally establish a close exchange relationship between taxpayers and tax authorities. In this paper, evidence is discussed on how tax morale in Switzerland evolved over time. In addition, the impact of economic, legal, socio- demographic, psychological and institutional factors on Swiss tax evasion is analyzed. It can be concluded that Switzerland’s system of responsive regulation increases tax morale.Tax Evasion, Tax Morale, Deterrence, Responsive Regulation.

Trust Breeds Trust: How Taxpayers are Treated

Tax compliance has been studied in economics by analysing the individual decision of a representative person between paying and evading taxes. A neglected aspect of tax compliance is the interaction of taxpayers and tax authorities. The relationship between the two actors can be understood as an implicit or "psychological" contract. The more strongly the political participation rights are developed, the more important this contract is, and the higher tax morale is. In this paper, empirical evidence based on a survey of tax authorities of the 26 Swiss states (cantons) is presented, indicating that the differences in the treatment of taxpayers by tax authorities can be explained by differences in political participation rights.Tax evasion, tax authority, tax compliance, direct democracy

Cavity ring-down technique and its application to the measurement of ultraslow velocities

We have developed a new ring-down technique that does not require a shutter to turn a probe laser on and off. With a rapid cavity scan we can measure a simple exponential cavity decay from which a cavity finesse can be found. When the cavity is scanned slowly, the cavity decay exhibits an amplitude modulation, and an analytic expression is derived for this modulation. With this new technique we measured the ultraslow relative velocity of the mirrors (of the order of micrometers per second) as well as the linewidth (~100 kHz) of the probe laser

Phase-dispersion optical tomography

We report on phase-dispersion optical tomography, a new imaging technique based on phase measurements using low-coherence interferometry. The technique simultaneously probes the target with fundamental and second-harmonic light and interferometrically measures the relative phase shift of the backscattered light fields. This phase change can arise either from reflection at an interface within a sample or from bulk refraction. We show that this highly sensitive 5 phase technique can complement optical coherence tomography, which measures electric field amplitude, by revealing otherwise undetectable dispersive variations in the sample

Measurement of angular distributions by use of low-coherence interferometry for light-scattering spectroscopy

We present a novel interferometer for measuring angular distributions of backscattered light. The new system exploits a low-coherence source in a modified Michelson interferometer to provide depth resolution, as in optical coherence tomography, but includes an imaging system that permits the angle of the reference field to be varied in the detector plane by simple translation of an optical element. We employ this system to examine the angular distribution of light scattered by polystyrene microspheres. The measured data indicate that size information can be recovered from angular-scattering distributions and that the coherence length of the source influences the applicability of Mie theory

Phase-referenced interferometer with subwavelength and subhertz sensitivity applied to the study of cell membrane dynamics

We report a highly sensitive means of measuring cellular dynamics with a novel interferometer that can measure motional phase changes. The system is based on a modified Michelson interferometer with a composite laser beam of 1550-nm low-coherence light and 775-nm CW light. The sample is prepared on a coverslip that is highly reflective at 775nm. By referencing the heterodyne phase of the 1550-nm light reflected from the sample to that of the 775-nm light reflected from the coverslip, small motions in the sample are detected, and motional artifacts from vibrations in the interferometer are completely eliminated. We demonstrate that the system is sensitive to motions as small as 3.6nm and velocities as small as 1nm/s. Using the instrument, we study transient volume changes of a few (approximately three) cells in a monolayer immersed in weakly hypotonic and hypertonic solutions

Spatial coherence of forward-scattered light in a turbid medium

We study spatially coherent forward-scattered light propagating in a turbid medium of moderate optical depth (0-9 mean free paths). Coherent detection was achieved by using a tilted heterodyne geometry, which desensitizes coherent detection of the attenuated incident light. We show that the degree of spatial coherence is significantly higher for light scattered only once in comparison with that for multiply scattered light and that it approaches a small constant value for large numbers of scattering events