Annular aperture arrays: study in the visible region of the electromagnetic spectrum

Baida and Van Labeke recently proposed a structure that exhibits a supertransmission of light through an array of nanometric coaxial apertures in a metallic film that has been named an annular aperture array (AAA) [Opt. Commun. 209, 17 (2002); Phys. Rev. B 67, 155314 (2003); J. Microsc. 213, 140 (2003)]. We present the first experimental study, to our knowledge, of an AAA structure in the visible region. For technological reasons, the structure under study does not produce a supertransmission of 80% as in Baida and Van Labeke [Opt. Commun. 209, 17 (2002)]. We built the nanostructure and experimentally recorded its far-field spectral response. This transmission shows only one broad band with a maximum around lambda = 700 nm, giving a maximum efficiency around 17%. A finite-difference time-domain simulation reproduces quite well the obtained transmission spectrum.     

Electroluminescence of gallium phosphide in the visible spectrum region

The effect of doping impurities and the container material on the color and intensity of electroluminescence (EL) of gallium phosphide crystals grown from the melt in gallium is considered. It is found that the maximum efficiency of red EL is observed in crystals grown in quartz containers, and of green EL — in crystals produced in alundum containers having aluminum nitride coatings. The optimal doping-impurity concentrations are determined for producing diodes with red, yellow, and green radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 12–16, April, 1973.     

Broadband polarization-converting mirror for the visible region of the spectrum

A mirror structure that enables the polarization of linearly polarized light to be rotated by 90 degrees over the entire visible region of the spectrum is presented. Theoretical modeling is used to show that this phenomenon occurs for light that is normally incident upon a metal grating consisting of a series of high and narrow ridges that are oriented at 45 degrees to the polarization angle. This broad polarization-conversion band is shown to arise from mode mixing of surface plasmon polariton-mediated polarization-conversion bands and interference-mediated polarization-conversion bands.     

Optimized equivalent layers for a wide region of the spectrum

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 284–290, August, 1989.     

Nanoscale synthesis and optical features of nickel nanoparticles

Nickel nanoparticles have been synthesized by chemical reduction method. By the analysis of X-ray diffraction, the resultant particles are characterized and found to be pure crystalline nickel with a face-centered cubic (FCC) structure. The morphology and size of the nanoparticles are studied by scanning electron microscopy (SEM) and micrographs reveal that the nanoparticles are mostly spherical. The compositional analysis has been carried out by using EDAX. The quantum size confinement of the crystallites is evident from the blue-shift of the absorption edge in the UV–vis absorption spectrum.     

Band spectrum of the molecule germanium monoxide (GeO) in the visible region

Thermal emission spectrum of the molecule GeO has been recorded in the visible region λλ 5100-4600 for the first time, using a high temperature vacuum graphite furnace. Bands observed are red-degraded and constitute a new system which appears to be an analog of the B systems observed in the case of PbO and SnO.     

Generation of a wide discrete visible spectrum in a frequency-doubling optical fiber

We describe some special features of frequency doubling in a Ge-doped SiO₂ optical fiber. The generation of a multi-frequency visible spectrum in a single short fiber pumped with 1.06 µm radiation is demonstrated. This effect is the result of an interplay between the processes of frequency doubling and third-order nonlinear frequency mixing. Most of the new components coincide with the characteristic stimulated four-wave-mixing spectrum of the fiber, although the power of the internally generated 0.532 µm pump was more than an order of magnitude below the respective thresholds.     

Temperature dependence of optical absorption for the visible region in transparent conducting oxides

We study theoretically the temperature dependence of the optical-absorption coefficient, for the visible region, in thin films of transparent conducting oxides by using the well-known Varshni approach relative to optical band-gap energy. Zero absorption is considered and an approximate formula for the coefficient of visible absorption is derived when photon energy is near the band-gap energy, that is, when absorption is negligible.     

An optical method for wavelength fine-selection in optical spectrum analysers

This letter describes a novel optical method for wavelength fine-selection in the optical spectrum analysers(OSAs) for dense wavelength division multiplexing (DWDM) applications. The proposed new method employs a 'refractive optical lever'system consisting of a rotating optical wedge prism.A new OSA system based on Littman-type monochromator is proposed and the wavelength selection accuracy and resolution of OSA that has included such an optical lever system have been improved by a factor of 20 to100 depending on the wedge angle and offset orientation angle of the optical wedge prism. This proposed 'refractive optical lever' may also simplify the rotation mechanism of the mirror in the commercially available OSAs.     

Density functional study of optical properties of beryllium chalcogenides compounds in nickel arsenide B8 structure

The structural, electronic and optical properties of beryllium chalcogenides BeS, BeSe and BeTe using the full-potential linear augmented plane wave (FP-LAPW) method are investigated. The exchange-correlation energy within the local density approximation (LDA) and the generalized gradient approximation (GGA) are described. The Engel-Vosko (EVGGA) formalism is applied for electronic and optical properties. The structural parameters of our model and the transition pressure from zinc-blende (B3) to the NiAs (B8) phase are confirmed. It is found that these compounds have indirect band gaps except for BeTe in NiAs (B8) phase. The results of reflectivity, refractive index and optical dielectric functions of Be compounds are investigated. An agreement is found between our results and those of other theoretical calculations and the experimental data.     

Modeling of the optical properties of porous silicon photonic crystals in the visible spectral range

Optical devices based on photonic crystals are of great interest because they can be efficiently used in laser physics and biosensing. Photonic crystals allow one to control the propagation of electromagnetic waves and to change the emission characteristics of luminophores embedded into photonic structures. One of the most interesting materials for developing one-dimensional photonic crystals is porous silicon. However, an important problem in application of this material is the control of the refractive index of layers by changing their porosity, as well as the refractive index dispersion. In addition, it is important to have the possibility of modeling the optical properties of structures to choose precisely select the fabrication parameters and produce one-dimensional photonic crystals with prescribed properties. In order to solve these problems, we used a mathematical model based on the transfer matrix method, using the Bruggeman model, and on the dispersion of silicon refractive index. We fabricated microcavities by electrochemical etching of silicon, with parameters determined by the proposed model, and measured their reflection spectra. The calculated results showed good agreement with experimental data. The model proposed allowed us to achieve a microcavity Q-factor of 160 in the visible region.     

Spectral and concentration dependences of the optical properties of thin layers of oxidized amorphous copper and nickel nanoparticles in the infrared spectral region

Optics and Spectroscopy - The optical properties of thin layers of nanostructures based on oxidized amorphous copper and nickel granules are studied in the IR spectral region. The absorption...     

Optical properties of AgI/Ag infrared hollow fiber in the visible wavelength region

We report on AgI/Ag infrared hollow fiber with low-loss in visible region. Improved methods of silver plating and iodination were proposed to fabricate the hollow fiber. The surface roughness of the silver layer and the silver iodide layer was reduced by the pretreatment with an SnCl2 solution and low iodination temperature. Losses for the Er:YAG and green laser light were 0.4 and 7dB/m. The loss property of green laser beam was low to deliver a pilot beam for the invisible infrared laser light. Owing to the smooth and uniform AgI film, the loss spectrum of the hollow fiber showed clear interference peaks in the visible region. An empirical formula for AgI material dispersion was derived, which is of special importance for the design of high-performance AgI/Ag hollow fiber.     

A method for measuring the phase of the reflection coefficient in the visible range of the spectrum

A method for measuring the phase of the reflection coefficient in the optical wavelength range is proposed. The method is simple in experimental implementation and is based on measuring the energyreflection coefficients of a sample in two media with different refractive indices. Analytical and numerical estimates show that the measurement accuracy of the phase is on the order of 1°. The possibilities of using the results of the phase measurement in practice for a more complete characterization of materials and structures under investigation are considered.     

Unravelling the visible spectrum of strontium monomethoxide

The bands of the A²E–X²A₁ and B²A₁–X²A₁ electronic transitions of SrO¹²CH₃ and the B²A₁–X²A₁ transition of SrO¹³CH₃ have been recorded at high resolution using a laser ablation jet source. The optical–optical double resonance population depletion technique was used to facilitate the assignment of the spectra. Rotational levels with K = 0, ±1 in the X²A₁ and B²A₁ states and K = 0, 1 and 2 in the A²E state have all been characterised. A perturbation affecting the B²A₁ state caused a reversal of the ordering of the spin-rotation components, F₁ and F₂, in the SrO¹²CH₃ isotopologue. This required the introduction of a modified rotational constant B_mod, affecting only the K = 1, F₂ component of the B²A₁ state, in order to model the SrO¹²CH₃ data in a global fit of the A²E–X²A₁ and B²A₁–X²A₁ transitions.