Оценка потерь в оптических плёночных волноводах с шероховатыми границами и поглощением

The method of small indignations with use of the optics-geometrical approach solves a problem of light propagation in a film waveguide with rough surfaces and absorption. Experimental researches specified waveguide structures are carried out. Results of these researches substantially do not correspond to conclusions of the developed theory. As a result of the analysis of the revealed discrepancies and additional calculations more exact model of scattering process in film waveguides with rough surfaces is offered.Методом малых возмущений с использованием оптико-геометрического подхода решена задача о распространении света в плёночном волноводе с шероховатыми границами и поглощением. Выполнены экспериментальные исследования указанных волноводных структур. Результаты этих исследований несколько расходятся с выводами развитой теории. В итоге анализа выявленных несоответствий предложена более точная модель процесса рассеяния в плёночных волноводах с шероховатыми границами

Pulsar Wind Nebulae with Bow Shocks: Non-thermal Radiation and Cosmic Ray Leptons

Pulsars with high spin-down power produce relativistic winds radiating a non-negligible fraction of this power over the whole electromagnetic range from radio to gamma-rays in the pulsar wind nebulae (PWNe). The rest of the power is dissipated in the interactions of the PWNe with the ambient interstellar medium (ISM). Some of the PWNe are moving relative to the ambient ISM with supersonic speeds producing bow shocks. In this case, the ultrarelativistic particles accelerated at the termination surface of the pulsar wind may undergo reacceleration in the converging flow system formed by the plasma outflowing from the wind termination shock and the plasma inflowing from the bow shock. The presence of magnetic perturbations in the flow, produced by instabilities induced by the accelerated particles themselves, is essential for the process to work. A generic outcome of this type of reacceleration is the creation of particle distributions with very hard spectra, such as are indeed required to explain the observed spectra of synchrotron radiation with photon indices Γ≲ 1.5. The presence of this hard spectral component is specific to PWNe with bow shocks (BSPWNe). The accelerated particles, mainly electrons and positrons, may end up containing a substantial fraction of the shock ram pressure. In addition, for typical ISM and pulsar parameters, the e+ released by these systems in the Galaxy are numerous enough to contribute a substantial fraction of the positrons detected as cosmic ray (CR) particles above few tens of GeV and up to several hundred GeV. The escape of ultrarelativistic particles from a BSPWN—and hence, its appearance in the far-UV and X-ray bands—is determined by the relative directions of the interstellar magnetic field, the velocity of the astrosphere and the pulsar rotation axis. In this respect we review the observed appearance and multiwavelength spectra of three different types of BSPWNe: PSR J0437-4715, the Guitar and Lighthouse nebulae, and Vela-like objects. We argue that high resolution imaging of such objects provides unique information both on pulsar winds and on the ISM. We discuss the interpretation of imaging observations in the context of the model outlined above and estimate the BSPWN contribution to the positron flux observed at the Earth

The waveguide method for measuring parameters of the surface layers

A new method has been applied for determining the mean square deviation of surface roughness and the imaginary part of permittivity of the material near-surface region. The method is based on the scattering and absorption of light in waveguide systems of integrated optics. It has high sensitivity and ease of implementation. The advantages of the proposed method are confirmed experimentally

The waveguide method for measuring parameters of the surface layers

A new method has been applied for determining the mean square deviation of surface roughness and the imaginary part of permittivity of the material near-surface region. The method is based on the scattering and absorption of light in waveguide systems of integrated optics. It has high sensitivity and ease of implementation. The advantages of the proposed method are confirmed experimentally. © 2012 EDP Sciences

Effects of surface roughness and absorption on light propagation in graded-profile waveguides

This paper examines the effects of surface roughness and absorption on laser light propagation in graded-profile waveguiding structures. We derive analytical expressions for the scattering and absorption coefficients of guided waves and analyse these coefficients in relation to parameters of the waveguiding structure and the roughness of its boundary. A new approach is proposed to measuring roughness parameters of precision dielectric surfaces. Experi- mental evidence is presented which supports the main conclusions of the theory. © 2011 Kvantovaya Elektronika and Turpion Ltd

The waveguide method for measuring parameters of the surface layers

A new method has been applied for determining the mean square deviation of surface roughness and the imaginary part of permittivity of the material near-surface region. The method is based on the scattering and absorption of light in waveguide systems of integrated optics. It has high sensitivity and ease of implementation. The advantages of the proposed method are confirmed experimentally. © 2012 EDP Sciences

Effects of surface roughness and absorption on light propagation in graded-profile waveguides

This paper examines the effects of surface roughness and absorption on laser light propagation in graded-profile waveguiding structures. We derive analytical expressions for the scattering and absorption coefficients of guided waves and analyse these coefficients in relation to parameters of the waveguiding structure and the roughness of its boundary. A new approach is proposed to measuring roughness parameters of precision dielectric surfaces. Experi- mental evidence is presented which supports the main conclusions of the theory. © 2011 Kvantovaya Elektronika and Turpion Ltd

Pulsar Wind Nebulae with Bow Shocks: Non-thermal Radiation and Cosmic Ray Leptons

Pulsars with high spin-down power produce relativistic winds radiating a fraction of the power in the range from radio to gamma-rays in the pulsar wind nebulae (PWNe). The rest of the power is dissipated in the interactions of the PWNe with the interstellar medium (ISM). Some of the PWNe are moving relative to the ISM with supersonic speeds producing bow shocks. In this case, the ultrarelativistic particles accelerated at the termination surface of the pulsar wind may be reaccelerated in the converging flow system formed by the outflow from the wind termination shock and the inflow from the bow shock. An outcome of this reacceleration is the creation of particle distributions with hard spectra, such as required to explain the observed synchrotron spectra with photon indices Gamma <~ 1.5. The presence of this hard component is specific to PWNe with bow shocks (BSPWNe). The accelerated particles may end up containing a substantial fraction of the shock ram pressure. For typical ISM and pulsar parameters, the positrons released by these systems are numerous enough to contribute a substantial fraction of the positrons detected as galactic cosmic ray particles above few tens and up to several hundred GeV. The escape of ultrarelativistic particles from a BSPWN and its appearance in the far-UV and X-ray bands is determined by the directions of the interstellar magnetic field, the velocity of the astrosphere and the pulsar rotation axis. In this respect we review the observed appearance and multiwavelength spectra of three different types of BSPWNe: PSR J0437-4715, the Guitar and Lighthouse nebulae, and Vela-like objects. We argue that high resolution imaging of such objects provides unique information on pulsar winds and on the ISM. We discuss the interpretation of imaging observations and estimate the BSPWN contribution to the positron flux observed at the Earth. (ABRIDGED)Comment: 69 pages, 18 figures, Space Science Reviews (in press) 201