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V. Spassov

Publications and source records attributed to V. Spassov.

2 recordsLinked to original sources

Observation of enhanced transmission for s-polarized light through a subwavelength slit

Enhanced optical transmission (EOT) through subwavelength apertures is usually obtained for p-polarized light. The present study experimentally investigates EOT for s-polarized light. A subwavelength slit surrounded on each side by periodic grooves has been fabricated in a gold film and covered by a thin dielectric layer. The excitation of s-polarized dielectric waveguide modes inside the dielectric film strongly increases the s-polarized transmission. Transmission measurements are compared with a coupled mode model and show good qualitative agreement. Adding a waveguide can improve light transmission through subwavelength apertures, as both s and p-polarization can be efficiently transmitted.

cond-mat.mes-hall

Application of avalanche photodiodes as a readout for scintillator tile-fiber systems

The application of reach-through avalanche photodiodes (R'APD) as a photodetector for scintillator tiles has been investigated. The light collected by WLS fibers (0.84mm and 1mm diameter) embedded in the scintillator has been transmited to the 0.5mm2 active surface of APD by clear optical fibers and optical connectors. A low noise charge sensitive preamplifier (approximately 400 electrons equivalent noise charge) has been used to gain the photodiode signal. Various configurations of tile-fibre systems, suitable for CMS and LHCb experiments at LHC have been studied using cosmic muons and muon beam at SPS at CERN. In order to optimize the performance of APD, measurments in the temperature range from -10C to +25C have been done. The MIP detection efficiency and electron/MIP separation have been estimated in order to determine applicability of the readout for LHCb preshower.

physics.ins-det