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Shamirzaev T.S.,RAS Semiconductor Physics Institute
Semiconductors | Year: 2011

In spite of a great number of publications concerned with studies of semiconductor heterostructures, the type-I semiconductor heterostructures, in which the ground electron state belongs to the indirect-gap (X and L) minimums of the conduction band, have remained poorly understood until recently. In this paper, the possibility is discussed of using III-V semiconductor compounds to create type-I semiconductor heterostructures with electron states belonging to the indirect-gap minimums of the conduction band. © 2011 Pleiades Publishing, Ltd. Source

Tsarev A.V.,RAS Semiconductor Physics Institute
Optics Letters | Year: 2010

This Letter presents a beam splitter in a silicon-on-insulator (SOI) ridge waveguide loaded by a photonic crystal row of holes close to the Brewster angle. The propagation of the fundamental guided mode in this structure has been examined by the three-dimensional finite-difference time-domain method. It is shown that a TE-polarized optical beam exhibits the Brewster effect at an incident angle of about 39°, giving a small splitting ratio (<0.04) in a wide spectral range for silica-filled holes with a typical diameter of 200 nm and a spacing of 300 nm. The row of holes close to the Brewster angle is the perspective to be used in developing complementary metal-oxide semiconductor-compatible tunable devices based on multireflector filtering technology. © 2010 Optical Society of America. Source

Tsarev A.V.,RAS Semiconductor Physics Institute
Optics Letters | Year: 2010

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO3 waveguide has been proposed and numerically studied by the two-dimensional finitedifference- time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μ m × 150 μ m, with an FWHM bandwidth of 4:4 nm, a tuning range of 110 nm, internal loss of-3 dB, and sidelobes of-20 dB, thus providing a unique value of 0:6 μ m2 for the productFWHMbandwidth by an AO length. It is intended for use in fiber optics telecommunications and sensing. © 2010 Optical Society of America. Source

Tsarev A.,RAS Semiconductor Physics Institute
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Paper present results of numerical investigation by finite difference time domain (FDTD) method of new tunable optical filter which utilized multiple coupled silicon wire waveguides on SOI structures. In order to improve simulation accuracy we introduce modified effective index method (MEIM) which correctly describes in 2d case both the phase and the group indexes in 3d strip waveguide, typically used in silicon photonics in thin SOI structures. MEIM utilizes the combined index profile containing two spatial parameters as in actual 3d waveguide. Namely, the central part with refractive index of Si has the width w around waveguide height h and it is mainly responsible for the group index. The base part has the same width W as in 3d waveguide and refractive index Nb which is mainly responsible for the phase index. As a results, MEIM provides typical error about 1%-2% for the filter free spectral range (FSR) instead of about 30% for EIM. Numerical simulation of novel filter proves its general conception and demonstrates that a short 360 mkm structure with 32 couplers has spectral resolutions 1.5 nm, loss -1 dB and sidelobes below -26 dB. It provides wavelength tuning (without Vernier principle) within total FSR 36 nm at central optical wavelength 1.55 mkm by temperature change up to 100 C in four sets of thermo optic phase shifters. Device of 1 cm size provides 0.05 nm filter linewidth. Filter can be manufactured by CMOS compatible technology and very promising for applications in photonics. Source

The intermediate stages of the formation of a Ge wetting layer on Si(111) and Si(100) surfaces under quasiequilibrium grow conditions have been studied by means of scanning tunneling microscopy. The redistribution of Ge atoms and relaxation of mismatch stresses through the formation of surface structures of decreased density and faces different from the substrate orientation have been revealed. The sites of the nucleation of new three-dimensional Ge islands after the formation of the wetting layer have been analyzed. Both fundamental differences and common tendencies of atomic processes at the formation of wetting layers on Si(111) and Si(100) surfaces have been demonstrated. The density of three-dimensional nuclei on the Si(111) surface is determined by changed conditions for the surface diffusion of Ge adatoms after change in the surface structure. Transition to three-dimensional growth on the Si(100) surface is determined by the nucleation of single {105} faces on the rough Ge(100) surface. © 2012 Pleiades Publishing, Ltd. Source

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