Multiphoton Effects Enhanced Due to Ultrafast Photon-Number Fluctuations

Multi-photon processes are the essence of nonlinear optics. Optical harmonics generation and multi-photon absorption, ionization, polymerization or spectroscopy are widely used in practical applications. Generally, the rate of an n-photon effect scales as the n-th order autocorrelation function of the incident light, which is high for light with strong photon-number fluctuations. Therefore `noisy' light sources are much more efficient for multi-photon effects than coherent sources with the same mean power, pulse duration and repetition rate. Here we generate optical harmonics of order 2-4 from bright squeezed vacuum (BSV), a state of light consisting of only quantum noise with no coherent component. We observe up to two orders of magnitude enhancement in the generation of optical harmonics due to ultrafast photon-number fluctuations. This feature is especially important for the nonlinear optics of fragile structures where the use of a `noisy' pump can considerably increase the effect without overcoming the damage threshold

Deciphering nonfemtoscopic two-pion correlations in p+pp+p collisions with simple analytical models

A simple model of nonfemtoscopic particle correlations in proton-proton collisions is proposed. The model takes into account correlations induced by the conservation laws as well as correlations induced by minijets. It reproduces well the two-pion nonfemtoscopic correlations of like-sign and unlike-sign pions in proton-proton collision events at $\sqrt{s} = 900$ GeV analyzed by the ALICE Collaboration. We also argue that similar nonfemtoscopic correlations can appear in the hydrodynamic picture with event-by-event fluctuating nonsymmetric initial conditions that are typically associated with nonzero higher-order flow harmonics.Comment: 21 pages, 10 figures, misprints correcte

Optical morphology of distant RATAN-600 radio galaxies from subarcsecond resolution NOT images

We present direct imaging data of 22 ultra steep spectrum radio sources obtained at (or near) a subarcsecond seeing. The basic sample of 40 double radio sources was selected from the RATAN-600 catalogue. The FRII-structure has been confirmed with VLA and preliminary optical identifications which come from the 6 m-telescope. As the RATAN-600 flux limit at 3.9 GHz ($\approx$ 10mJy) is fainter than that of major surveys, the sample may have high-$z$ contents. This is also suggested by the faint magnitudes in the Hubble diagram. The final aim is to create a homogeneous sample of high-$z$ radio galaxies in a well defined strip around the sky, with faint radio limit and subarcsecond morphology down to $m_{R}=24$. We could confirm 16 identifications down to $m_{R}\sim$24. Most of the extended objects have multicomponent structures as expected from other surveys of high-redshift radio galaxies. We found five unresolved objects even with a subarcsecond seeing. Of the remaining six objects, three are extremely faint and the other three have such a complex environment that further observations are needed to confirm the optical identification.Comment: A&AS in pres

Fabrication of YAG:RE (RE = Yb, Nd, Cr) Ceramics Using Divalent Sintering Aids

High-quality YAG:RE (Yb, Nd, Cr) ceramics with CaO and MgO as sintering aids were manufactured by solid state reactive sintering method in vacuum. Influence of annealing temperature on optical properties was studied. This combination of sintering aids requires annealing temperatures at least 1300∘C to fully eliminate oxygen vacancies and at least 1400∘C to convert Cr3+ to Cr4+. It was found that annealing in oxidizing atmosphere creates strong changes in short wavelength transmittance.     Keywords: laser ceramics, Yttrium aluminium garnet, sintering aid

Investigations of parameters of image quality for adaptive optical systems of BSVT

The criteria image qualities based on wave front aberration caused by atmospheric turbulence using in adaptive optics are summarized. Atmospheric turbulence profile for Big Solar Vacuum Telescope (BSVT) observatory is obtained based on satellite date. On this based the development of adaptive optics systems of BSVT are discussed

The KHOLOD Experiment: A Search for a New Population of Radio Sources

Published data from long-term observations of a strip of sky at declination +5 degrees carried out at 7.6 cm on the RATAN-600 radio telescope are used to estimate some statistical properties of radio sources. Limits on the sensitivity of the survey due to noise imposed by background sources, which dominates the radiometer sensitivity, are refined. The vast majority of noise due to background sources is associated with known radio sources (for example, from the NVSS with a detection threshold of 2.3 mJy) with normal steep spectra ({\alpha} = 0.7-0.8, S \propto {\nu}^{- \alpha}), which have also been detected in new deep surveys at decimeter wavelengths. When all such objects are removed from the observational data, this leaves another noise component that is observed to be roughly identical in independent groups of observations. We suggest this represents a new population of radio sources that are not present in known catalogs at the 0.6 mJy level at 7.6 cm. The studied redshift dependence of the number of steep-spectrum objects shows that the sensitivity of our survey is sufficient to detect powerful FRII radio sources at any redshift, right to the epoch of formation of the first galaxies. The inferred new population is most likely associated with low-luminosity objects at redshifts z < 1. In spite of the appearance of new means of carrying out direct studies of distant galaxies, searches for objects with very high redshifts among steep and ultra-steep spectrum radio sources remains an effective method for studying the early Universe.Comment: 13 pages, 10 figure

Problems of High-quality Doped Y2O3-ceramics Fabrication

Tm:Y2O3 , Ho:Y2O3 and Yb:Y2O3 ceramic samples were fabricated using different heat treatments modes. La2O3 (0.5 mol.%) and ZrO2 (1.5 mol.%) were used as sintering additives. Based on the investigation of structural properties of obtained samples, annealing mode was adjusted, and another set of samples with better optical quality was fabricated. In-line transmittance of the latter samples is 70% at 400nm and 75.6% at 600nm. &nbsp; &nbsp; Keywords: Y2O3 , laser ceramic

Astrophysical and Astrobiological Implications of Gamma-Ray Burst Properties

Combining results for the local cosmic rate and mean peak luminosity of GRBs with the cosmic history of the star formation rate, we provide estimates for the local GRB rate per unit blue luminosity in galaxies. We find a typical GRB rate per unit B luminosity of 2.4x10^-17 h_{70}^2/Lsun/yr. The corresponding mean rate in the Milky Way is 5.5x10^-7 h_{70}^2/yr. We conclude: 1) the ratio of supernova rate to isotropic equivalent GRB rate is large: more than 6000 SNIbc per GRB or 30,000 SNII per GRB. GRBs could arise in a large fraction of black hole-forming events only with collimation in the range 0.01 - 0.001 and a steep enough slope of the IMF; 2) GRBs cannot account for the majority of large HI holes observed in galaxies; 3) the probability that the solar system was exposed to a fluence large enough to melt the chondrules during the first 10^7 yr of solar system history is negligibly small; 4) Even for very opaque atmospheres, a significant fraction of the GRB energy is transmitted as UV lines due to excitation by secondary electrons. For eukaryotic-like organisms in thin atmospheres (e.g. contemporary Mars), or for UV line exposure in thick atmospheres (e.g. Earth), biologically significant events occur at a rate of about 100--500 /Gyr. The direct contribution of these "jolts" to mutational evolution may, however, be negligible because of the short duration of the GRBs. Evolutionary effects due to partial sterilizations and to longer-lived disruptions of atmospheric chemistry should be more important. (Abridged)Comment: 36 pages, no figures Accepted by Astrophysical Journal Oct. 2001. First submitted December,1999. Substantially rewritten discussion of burst source count distributions and of biological implication

Suppression of surface barrier in superconductors by columnar defects

We investigate the influence of columnar defects in layered superconductors on the thermally activated penetration of pancake vortices through the surface barrier. Columnar defects, located near the surface, facilitate penetration of vortices through the surface barrier, by creating ``weak spots'', through which pancakes can penetrate into the superconductor. Penetration of a pancake mediated by an isolated column, located near the surface, is a two-stage process involving hopping from the surface to the column and the detachment from the column into the bulk; each stage is controlled by its own activation barrier. The resulting effective energy is equal to the maximum of those two barriers. For a given external field there exists an optimum location of the column for which the barriers for the both processes are equal and the reduction of the effective penetration barrier is maximal. At high fields the effective penetration field is approximately two times smaller than in unirradiated samples. We also estimate the suppression of the effective penetration field by column clusters. This mechanism provides further reduction of the penetration field at low temperatures.Comment: 8 pages, 9 figures, submitted to Phys. Rev.

RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514

A strong emission line at 6703A has been detected in the optical spectrum for the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850 MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of the identification of this line with Ly\alpha at redshift z=4.514. In this case, the object belongs to the group of extremely distant radio galaxies of ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a time less than the age of the Universe at the observed z(1.3 Gyr) or had a primordial origin.Comment: 8 pages, 3 figure