Plasmonic generation of sound by counterpropagating light beams in semiconductors

The possibility of generating longitudinal sound waves on a deformation potential in a semiconductor medium has been investigated. This generation is due to the excitation of internal longitudinal electric field in the plasma electron subsystem of semiconductor by external counterpropagating light beams.     

Squeezed light goes flexible

Since its first experimental demonstration,squeezed light has been the driving force to push forward the frontier of quantum optics[1].Recently,with the rapid d...     

Squeezed light from spin-squeezed atoms

We propose to transfer quantum correlations from atoms to light by Raman scattering of a strong laser pulse on a spin-squeezed atomic sample. We prove that the emission is restricted to a single field mode which perfectly inherits the quantum correlations of the atomic system.     

Second-harmonic generation in centro-symmetric semiconductors

Summary The crystallographic dependence of optical-second-harmonic generation (SHG) in Si and Ge single crystals is obtained with 10 ps pulses at 527 nm and at incident fluences above the threshold for laser melting of the crystal lattice. We find that the experimentally observed dependence of SHG on crystal orientation remains unchanged up to the damage limit. Observed selection rules are analysed in terms of various possible contributions.

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Riassunto Generazione della seconda armonica ottica è ottenuta nei monocristalli di Si e Ge con impulsi laser di 10 ps, a 527 nm, e con densità di energia inpingente superiore all soglia per la fuzione del reticolo cristallino. Si osserva che la seconda armonica mantiene la propria dipendenza dall' orientazione cristallografica, indipendente dal valore della densità di energia che è incidente sulla superficie cristallina, fino alla soglia del danno. Il mutamento d'intensità di generazione a secondo orientazione cristallografica e piano di polarizzazione è stato analizzato in funzione di vari contributi probabili.

     

Second harmonic generation in centro-symmetric semiconductors

Second harmonic generation is observed in Si and Ge at electron-hole plasma densities of 10²¹-10²² cm^?3 and found to depend strongly on crystal orientation. We suggest that a lower crystal symmetry within the absorption volume is consistent with a model in which depletion of covalent bond charge, and subsequent lattice softening, is brought about by laser excitation of a high density of electrons into antibonding states.     

Squeezed states of light as self-similar structures

A new approach to investigating a broad class of dynamic states for a quantum oscillator is suggested. It is based on an invariant transformation of the equation to a new time determined by the quantum dispersion of the corresponding state. The squeezed states of a quantum system generated by the ground-state wave function are constructed. In coordinate representation, these states are described by a self-similar wave function localized near a classical trajectory. The statistics of the squeezed state of light is analyzed in the single-mode approximation. The parametric excitation of squeezed states for a quantum harmonic oscillator is considered.     

Squeezed field generation by nonlinear bounded quantum oscillators

A new, effective method of squeezing is presented, based on the parametric resonance excitation of nonlinear bounded oscillators as vibration modes of multiatomic molecules.Presented at the International Workshop on Squeezed and Correlated States in Quantum Optics, Moscow, December 3–7, 1990.     

Electron-hole plasma generation and evolution in semiconductors

We discuss various physical problems related to dense electron-hole (e-h) plasmas in silicon-like semiconductors such as: the e-h plasma energy in the quantum and classical limits including the actual band structure; the dielectric constant using the appropriate plasma frequency mass and the variation of the plasma relaxation time due to e-h collisions; the plasma generation including its nonlinear aspect when the e-h density passes the plasma frequency density of the pump beam; the e-h plasma evolution due to Auger recombination and impact ionization as well as the e-h plasma hydrodynamics; finally, we will discuss also the possibility of a very fascinating melting at T=0.     

Infrared radiation harmonic generation in degenerate semiconductors

The basic properties of infrared laser radiation odd harmonic generation due to electron-charged impurity collisions in degenerate semiconductors are investigated. It is found that in the case of relatively weak fields, the electron Fermi distribution is the cause of an anomalous suppression of harmonic radiation. In the case of strong fields, the effect of the selective suppression of single harmonics is established.Received: 22 May 2004, Published online: 26 November 2004PACS: 78.20.-e Optical properties of bulk materials and thin films     

Stress-tuned stimulated light scattering in p-type semiconductors

We propose a new mechanism for generating tunable high power coherent radiation in the wavelength range 10micro–25micro from a single laser system. The proposed device is based on stimulated light scattering continuously tuned by stress in p-type semiconductors. The conditions and feasibility for such Raman laser operation are discussed in detail.     

Optimum acoustic wave second-harmonic generation in piezoelectric semiconductors

The phenomenological approach has been used to study analytically the acoustic wave second harmonic generation in piezoelectric semiconductors in the presence of the d.c. electric and an oscillating electromagnetic field (OEF). It has been suggested that the second harmonic acoustic flux (SHAF) can be enhanced considerably by the application of an OEF polarized in the direction of the propagating acoustic wave. The SHAF exhibits a maximum at Ω = ω, where Ω is the frequency of the OEF and ω is the frequency of the acoustic wave. The SHAF also shows a maximum at d.c. electric fields for which the average drift velocity of the carriers is equal to the velocity of sound. It is found that for a typical case of n-type nondegenerate InSb (77°K, n = 2·5 × 10¹⁴ cm^?3) that the SHAF is enhanced by a factor of 10³ over its value in the absence of OEF. The present analysis is valid in the low frequency region only (i.e. ql ? 1).     

Nonlinear induced reflection of light waves in semiconductors

A scheme of nonlinear optical four-wave mixing of two counterpropagating laser beams on the surface of a semiconductor is proposed and analyzed. It is shown that the density modulation of the electron-hole plasma current carriers in the light-induced grating manifests itself in the probe beam depolarization signal after the reflection from the surface, which is sensitive to the state of the surface and presence of complex molecules on it.     

Defect generation during plasma treatment of semiconductors

Defect generation during various dry etching processes is studied and the important parameters for the formation of point defects are discussed. The role of intrinsic defects and the fast diffusion of defects during the plasma treatment is considered. Special emphasis is devoted to the influence of hydrogen on the defect generation in plasma etching techniques. The evidence for optical recombination at hydrogen stabilized platelets in Si, as reported previously in the literature, is critically reviewed.     

Squeezed light from microstructured fibres: towards free-space quantum cryptography

Amplitude-squeezed pulsed light has been produced using a microstructured silica fibre. By spectrally filtering after the non-linear propagation in the fibre a squeezing value of -1.7 dB has been measured. A quantum key distribution scheme based on squeezed light from such microstructured fibres is proposed. Received: 9 July 2001 / Published online: 23 November 2001     

Magnetotrasmission and magnetoreflection of unpolarized light in magnetic semiconductors

Conventional magneto-optical Kerr and Faraday effects are widely used to solve many urgent problems in various fields of physics and technique. However, in view of the small magnitude of these effects (related to their relativistic origin), it is necessary to search for ways to enhance known magneto-optical effects and materials, as well as to reveal new (stronger) ones. In this study, we consider the effects of magnetotransmission and magnetoreflection of unpolarized light (of large magnitude), which were revealed in single crystals, films, and structures based on magnetic semiconductors. Some physical problems, calling for further study, are discussed, and a possibility of applying these effects to design different magneto-optical devices is demonstrated.