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The paper includes two contributions. First, it proves that the series and shunt radiation components, corresponding to longitudinal and transversal electric fields, respectively, are always in phase quadrature in axially asymmetric periodic leaky-wave antennas (LWAs), so that these antennas are inherently elliptically polarized. This fact is theoretically proven and experimentally illustrated by two case-study examples, a composite right/left-handed (CRLH) LWA and a series-fed patch (SFP) LWA. Second, it shows (for the case of the SFP LWA) that the axial ratio is controlled and minimized by the degree of axial asymmetry., Comment: IEEE Transactions on Antennas and Propagation, Vol. 62, No. 4, April 2014

The shape of the photoluminescence line excited at an edge face of InP wafer and recorded from the broadside is used to investigate the intrinsic emission spectrum. The procedure is much less sensitive to the surface properties and the carrier kinetics than the conventional methods used with the reflection or transmission geometry of photoluminescence. Our method provides a tool for studying the effects of non-equilibrium distribution of minority carriers in doped direct-band semiconductors., Comment: 6 pages, 4 figures

We study the spatial distribution of minority carriers arising from their anomalous photon-assisted diffusion upon photo-excitation at an edge of n-InP slab for temperatures ranging from 300 K to 78 K. The experiment provides a realization of the "L\'evy flight" random walk of holes, in which the L\'evy distribution index gamma is controlled by the temperature. We show that the variation \gamma(T) is close to that predicted earlier on the basis of the assumed quasi-equilibrium (van Roosbroek-Shockley) intrinsic emission spectrum, \gamma=1-\Delta /kT, where \Delta(T) is the Urbach tailing parameter of the absorption spectra. The decreasing \gamma at lower temperatures results in a giant enhancement in the spread of holes -- over distances exceeding 1 cm from the region of photo-excitation., Comment: 4 pages, 3 figures

We study the photoluminescence spectra excited at an edge side of n-InP slabs and observed from the broadside. In a moderately doped sample the intensity drops off as a power-law function of the distance from the excitation - up to several millimeters - with no change in the spectral shape.The hole distribution is described by a stationary Levy-flight process over more than two orders of magnitude in both the distance and hole concentration. For heavily-doped samples, the power law is truncated by free-carrier absorption. Our experiments are near-perfectly described by the Biberman-Holstein transport equation with parameters found from independent optical experiments., Comment: 4 pages, 3 figures

We study the photoluminescence spectra of n-doped InP bulk wafers, both in the reflection and the transmission geometries relative to the excitation beam. From the observed spectra we estimate the spatial distribution of minority carriers allowing for the spectral filtering due to re-absorption of luminescence in the wafer. This distribution unambiguously demonstrates a non-exponential drop-off with distance from the excitation region. Such a behavior evidences an anomalous photon-assisted transport of minority carriers enhanced owing to the high quantum efficiency of emission. It is shown that the transport conforms very well to the so-called Levy-flights process corresponding to a peculiar random walk that does not reduce to diffusion. The index gamma of the Levy flights distribution is found to be in the range gamma = 0.64 to 0.79, depending on the doping. Thus, we propose the high-efficiency direct-gap semiconductors as a remarkable laboratory system for studying the anomalous transport., Comment: 12 pages, 9 figures

We observed and studied strong reduction of optical reflection from the surface of InP wafers after high-temperature annealing. The effect is observed over a wide range of the incident wavelengths, and in the transparency band of the material it is accompanied by increasing transmission. The spectral position of a minimum (almost zero) of the reflection coefficient can be tuned, by varying the temperature and the time of annealing, in the spectral range between 0.5 and 6 eV. The effect is explained by the formation of a uniform oxide layer, whose parameters (thicknesses and average index) are estimated by detailed modeling., Comment: 20 pages, 11 figures, submitted to Journal of Applied physics

Implementation of a semiconductor as a scintillator with a lattice-matched surface photo-diode for radiation detection requires efficient luminescence collection. Low and heavily doped bulk n-InP has been studied to optimize luminescence transmission via photon recycling., Comment: 2 pages, 2 figures, Frontiers in Optics, JTuA33, Rochester, NY, September 24-28, 2010

Operation of semiconductor scintillators requires optically-tight integration of the photoreceiver system on the surface of the scintillator slab. We have implemented an efficient and fast quaternary InGaAsP pin photodiode, epitaxially grown upon the surface of an InP scintillator wafer and sensitive to InP luminescence. The diode is characterized by an extremely low room-temperature dark current, about 1 nA/cm2 at the reverse bias of 2 V. The low leakage makes possible a sensitive readout circuitry even though the diode has a large area (1 mm/times1 mm) and therefore large capacitance (50 pF). Results of electrical, optical and radiation testing of the diodes are presented. Detection of individual \alpha-particles and \gamma-photons is demonstrated., Comment: 16 pages, 11 figures