Study of the optical features of YBa2Cu3O7-x films by SEW spectroscopy

The results of YBa₂Cu₃O_7-x films on SrTiO₃ investigation by far infrared surface electromagnetic waves (SEW) amplitude and phase spectroscopy at temperatures 80–350 K are presented. Strong SEW absorption at frequency 142 cm^–1 has been observed. The origin of the observed absorbtion is proposed to be concerned with slab- phonons in YBa₂Cu₃O_7-x. The optical constants of the films have been obtained. Also has been determined, that only the imaginary part of the SEW refraction index changes when the film transits into superconducting state, while the real part remains unchanged.     

The ellipticity introduced by interferential mirrors on a linearly polarized light beam orthogonally reflected

Modifications of the state of polarization of a light beam trapped in a multipass cavity formed by interferential mirrors were studied. It was found that the mirrors analysed introduced ellipticities ranging from 3×10^–5 to 2×10^–4 per reflection.     

Broadband surface electromagnetic wave spectroscopy

Broadband generation and spectroscopic detection of infrared surface electromagnetic waves (SEW's) are reported from 600 to 1800 cm^?1. For KReO₄ coated metal samples a sharp absorption line near 1000 cm^?1 is used to compare the SEW and surface reflection spectroscopy (SRS) techniques. The integrated optical density of the absorption line is an order of magnitude larger with SEW spectroscopy than with SRS.     

Far infrared surface electromagnetic waves propagation on A3B5 semiconductors

The real and imaginary parts of surface electromagnetic waves (SEW) refraction index n_ef in n-type InSb, GaAs and InP have been measured in FIR region (=85–142 cm^–1). The n_ef measurements allowed to determine plasma frequency _p and plasmon damping . The obtained nonlinear SEW propagation distance L dependence on Te impurity concentration in GaAs (N=10¹⁷–10¹⁹ cm^–3) was explained taking into account the conduction band nonparabolity as well as the presence of isostructural phase transition at N=2×10¹⁰ cm^–3.     

Formation,reflection, and refraction of magnetostatic wave beams

Excitation of a magnetostatic surface wave beam in a thin magnetic film is studied theoretically and experimentally. Unique features in the propagation of such a beam are found, and the laws of beam reflection and refraction are studied. It is shown that there are significant features from Snell's and Euclid's law for such beams.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 67–75, November, 1988.     

A wave-beam shift on reflection from a plane screen in an isotropic chiral medium

The paper considers reflections of a wave beam of circular polarization from a plane, perfectly conducting screen restricting an isotropic chiral-medium half-space. Lateral and transverse shifts of the reflected beam resulting from fulfilment of the total reflection condition are calculated using a modified energy method.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 11–15, December, 2004.     

Millimeter wave beams diffracted from reflecting gratings

According to the angular-spectrum method, a radiation beam of an antenna horn in the Fresnal region is decomposed into the plane waves with the fast Fourier transform algorithm and the waves diffracted from a reflection grating are superposed as a diffracted beam. Compared with the reflected beam from the same size mirror, the radiation half width of the diffracted beam from a grating is narrower and its lateral shape is shift. These performances have been experimentally verified at Ka-band by: (1). The relative diffraction efficiencies in the first order with two triangular gratings which is put along propagating direction of a beam produced by a conical lens-horn. (2). H-plane lateral width with power—3dB lapsed of the focus beam from a grating and a mirror in a grating spectrometer for millimeter waves (25–100 GHz).     

铌酸锶钡光折变表面电磁波实验

在实验中观察到扩散和漂移机理下在光折变晶体铌酸锶钡（SBN）与空气的界面形成的光折变表面电磁波. 这种表面电磁波形成的条件是：入射光束与界面成55°角入射，信号光与背景光比值越大越有利于形成表面电磁波，外加电场越大表面电磁波就越强. 关键词： 表面电磁波 扩散和漂移机制 SBN     

Interference wedge properties relevant to laser applications: transmission and reflection of restricted light beams

The optical properties of the interference wedge are analysed for the case of restricted laser beam illumination. By further development of Brossel's method, equations describing this case are derived and used to calculate the reflected and transmitted beam profiles for typical intracavity laser beam diameters (0.2–0.6 mm) for Gaussian and uniform intensity distributions. In particular, the experimentally observed formation of bright fringes outside the beam impact area at resonant wavelengths is explained. some useful dependencies concerning the wedge reflection and transmission for laser applications are obtained and experimentally demonstrated.     

Accurate heterodyne interferometric ellipsometer

We describe a heterodyne interferometric ellipsometer which requires only a single reflection from the sample surface. A simple arrangement is described that enables a reference beam to be created in one arm of a modified Mach–Zehnder interferometer such that the p- and s-polarisations in this arm have a common phase and fixed relative amplitude, irrespective of the sample. When this beam is recombined interferometrically with the measurement beam, the spatially separated p and s fringes have an amplitude ratio and relative phase that are directly proportional to tanψ and Δ, respectively. Adjusting the azimuthal angle of the input linear polarisation allows both ψ-tracking to be implemented and error reduction through averaging. Measurements made with this instrument of a native oxide layer on a silicon substrate are in excellent agreement with those obtained using a commercial ellipsometer.     

Reflection and transmission of the unequal mirrors interference wedge

Some interesting features of the interference wedge of thickness 5–200 m are found which characterize its reflection and transmission when it is constructed of unequal-reflectivity mirrors. The analysis of the wedge's behaviour is made using equations derived by us for restricted laser beam illumination on the assumption of truncated Gaussian amplitude distribution and uniform phase distribution. It is shown that at resonant wavelengths the unequal-reflectivity mirrors interference wedge has a property of optical asymmetry in reflection for both contraincidences and that the earlier-reported phenomenon of spectrally controlled resurgence of light outside the nonresonantly reflected beam increases drastically to reach at resonance 60–70% of the reflected power. We ascertained that the wedge spectral selectivity is a function of the product of the reflectivities of its mirrors. Keeping one of them fixed and increasing the other, a higher wedge transmission may be obtained, but for a constant value of their product a maximum in transmission is achieved at equal reflectivities. Some of the dependences obtained have been checked experimentally.     

Skew-grid dichroic plate with rectangular apertures for use on a Ka-Band beam waveguide antenna

The first Ka-Band Deep Space Network downlink demonstration was recently carried out by the Ka-Band Link Experiment (KABLE) in association with the Mars Observer spacecraft. In order to support the mission, a dichroic plate was required in the DSS-13 beam waveguide antenna to allow simultaneous X- and Ka-Band dual-frequency operation. AnX/Ka/KABLE dichroic plate was designed to transmit a future Ka-Band downlink (31.8–32.3 GHz), future Ka-Band uplink (34.2–34.7 GHz), and KABLE downlink frequency (33.6–33.8 GHz), while reflecting X-band (7.1–8.6 GHz). A computer program was developed for the analysis of a dichroic plate with rectangular apertures using the mode-matching method. The plate was then fabricated and tested. The reflection, group delay, and noise temperature in the antenna system due to the dichroic plate were measured. The experimental results show good agreement with theoretical predictions.     

Reflection of a focused light beam in a medium with Kerr nonlinearity. I. Estimates in the paraxial-beam approximation

The reflection intensity in a nonlinear dielectric layer is calculated in the approximation of paraxial incident and reflected light beams. It is shown that reflection is mainly determined by discontinuities of the refractive-index on the boundaries. Unlike reflection by a linear dielectric layer, reflection by a nonlinear layer occurs with a three-time decrease in the effective reflection area and the corresponding broadening of the angular spectrum. The intensity of the reflected wave is comparable to that of an incident wave with nearly critical beam power.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 7, pp. 867–875, July, 1996.This work was supported by the International Science Foundation and the Russian Federation Government (projects MR1000 and MR1300).     

Short wave pass and long wave pass dichroic coating at 45° on zinc selenide substrate for dual band thermal imager

In dual band thermal imager dichroic coating plays a vital role in separating 3–5 μm and 7.5–10.5 μm wavelength region for observing better image quality from two different channels. In this work a study has been carried out on the design and fabrication of short and long wave pass dichroic coating at 45° on zinc selenide flat substrate. These dichroic coated optics can be used to separate 3–5 μm (in reflection or transmission channel) and 7.5–10.5 μm (in transmission or reflection channel) wavelength region. An inhomogeneous refractive index profile which is a polynomial of 5th order was considered to design the high and low wave pass dichroic coating on zinc selenide substrate. The inhomogeneous profile was then approximated with five steps from substrate to air medium. These steps were then converted in terms of durable coating materials of six and seven layer stack for short and long wave pass dichroic coating respectively. The coating material combination used was germanium as high index material and IR-F625 as low index material. Result achieved for short wave pass dichroic filter was 94% average transmission in 3–5 μm region and 95% average reflection in 7.5–10.5 μm region. Similarly, result achieved for long wave pass dichroic filter was 95% average reflection in 3–5 μm region and 94% average transmission in 7.5–10.5 μm.     

Elastic and inelastic scattering of slow positrons from a LiF(100) surface

The intensity profile for the elastic specular reflection of 5–100 eV positrons from a LiF(100) surface (ang1e of incidence 45°) has been measured using a simple time-of-flight spectrometer. The profile exhibits strong maxima below 25 eV and a smaller peak at 57 eV. Positron energy loss spectra have also been measured for a range of incident energies by retarding field analysis of the scattered beam. The mean energy loss appears to increase with increasing incident beam energy. Both the elastic and inelastic results are compared with similar data for slow-electron scattering obtained with the same apparatus.     

A photometer to measure light scattering in optical glass

A photometer is described for the measurement of light-scattering in high-quality, optical bulk glass. The photometer operates continuously over the wavelength range 0.5 to 1m and can measure scattering coefficients down to a level of 5×10^–7 cm^–1. A photon counting technique is used for light measurement and calibration is by reflection of the incident beam from an ideal diffusing screen. Measurements with high-purity benzene are in good agreement with computed and previous experimental values. Results of scattering from two samples of optical glass are given.     

High speed tunable thermic modulation of far infrared waves

This paper proposes a new method for the high speed temporal modulation of infrared wave beams reflected from thin films of semiconductor plasma containing free carriers. The physical foundations of such a method, based on the non-linear and bi-stable properties of free carriers in these films, show possibilities of the elaboration of high-speed tunable modulators and polarizers. The bi-stable conditions are tunable by means of a magnetic field. The reflection of a continuous wave beam from the film with a tunable reflection coefficient leads to pulse shaping, pulse duration being as small as 10^–9 s.     

Thermally induced optical bistability in a new polymeric blend at room temperature

The transition from the transmission to the reflection regime for an Ar⁺-laser beam propagating in the new polymeric blend PMMA-EVA at a nonlinear interface has been observed. A comparison between the experimental data and a calculation of the input optical intensity at which this transition should occur (1.45×10⁷ W m^–2) is presented using Kaplan's theory. The results suggest the presence of thermally induced optical bistability in PMMA-EVA.     

General intense electron beams by means of a contracted arc discharge

Two types of contracted arc discharge are investigated with a view to generating intense electron beams over a wide pressure range (1–10^–3 Pa). For an arc discharge with a hollow cathode and anode, an electron beam corresponding to a current of up to 300 A and a pulse length of 25 µsec is obtained at a pressure of 1–10^–1 Pa in the accelerating gap with an accelerating voltage of up to 15 kV. At pressures of 10^–2–10^–3 Pa, emitting plasma is created by a low-pressure arc discharge on the basis of a Penning cell. Three discharge systems operating in parallel are used to increase the working life of the cathode and improve the current density distribution of the beam. An electron beam of diameter 200 mm with a current of up to 125 A and a pulse length of 50 µsec is obtained.Institute of High-Power Electronics, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshkikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 76–82, March, 1994.