Absorption spectra of benzene-isooctane mixtures in the wavelength range 1620–1820 nm

Experimental absorption spectra of benzene, isooctane, and their mixtures are obtained in the wavelength range λ = 1620–1820 nm in which the first overtones of vibrational frequencies of CH, CH₂, and CH₃ hydrocarbon groups are located. Positions of fundamental absorption bands of benzene are refined. Absorption spectra of benzene-isooctane mixtures are shown to intersect in a narrow area near λ ≈ 1695 nm. The main maximum of benzene absorption at λ = 1671.5 ± 0.5 nm, where the influence of isooctane absorption is practically absent, is proposed for determining the content of benzene in benzene-isooctane mixtures. A linear calibration curve for λ = 1671.5 nm that encompasses the full range of benzene concentrations (0–100%) is presented. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 631–634, September–October, 2008.     

Investigation of the optical constants of arsenic chalcogenide films in the wavelength range 0.5–2.5 μm

Thin films of chalcogenide glasses deposited on quartz glass substrates by thermal evaporation in vacuum have been investigated. The dependences n(λ) and k(λ) for films of different composition have been determined from the transmission spectra. Expressions of the n = A + BL + CL ² + Dλ ² + Eλ ⁴ type (L = (λ ² ? 0.028)^?1 and A, B, C, D, and E are constants) for calculating the refractive indices of As₂Se₃, AsSe₄, AsS₄, and AsS_16.2Se_16.2 films in the wavelength range from 0.5 to 2.5 μm are reported.     

Performance of a polarizer using synthetic mica crystal in the 12–25 nm wavelength range

To develop polarizer functioning in the extreme ultraviolet (EUV) and soft X-ray region, the polarization performance of synthetic mica has been investigated theoretically with a simulation code using Fresnel equations and optical constants from the Henke database. The reflectance of synthetic mica crystal for s and p polarization was measured to investigate its polarization performance in a home-made synchrotron radiation soft X-ray polarimeter at beamline 3W1B, Beijing Synchrotron Radiation Facility (BSRF...     

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 to 100 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.     

An efficient algorithm for optimal allocation of wavelength converters in wavelength routing optical network

In a wavelength routing optical network (WRON), the optimal allocation of wavelength converters (WCs) is very important to minimize the number of WCs, enhance the fiber utilization, reduce the blocking probability, etc.. In this paper, a novel simplified network model with shared WCs has been proposed. An effective algorithm for optimal allocation of shared WCs has been presented by using a revised Dijkstra algorithm and genetic algorithm (GA). The effectiveness of the revised algorithm was verified through the simulation on Nature and Science Foundation (NSF) net of USA. This revised algorithm can achieve blocking probability 36% less than the algorithm in previous work, and the calculating time of the minimum blocking probability can be reduced dramatically.     

Injection lasers in the 1.3–1.8 μm wavelength range

Conclusion There are developed techniques for the preparation of diode lasers in the 1.3 to 1.8 m range on the basis of quaternary epitaxial heterostructure. Devices for a particular wavelength of 1.3 m are now commercially available. The state of art in the laser studies with connection to lower room-temperature threshold and to higher operation temperature is illustrated in fig. 9. We feel that the laser system of InGaAsP, which is known since 1974 [1, 2], may be elaborated further for higher laser characteristics in spite of the fact that present state is quite acceptable for different applications. There are many fibre-optics projects based on the conception of laser optical communication with the use of diodes in the range of 1.3–1.8 m.Invited talk at the International Conference on Radiative Recombination and Related Phenomena in III–V Compound Semiconductors, Prague, 4–7 October, 1983.The author is indebted to Dr. L. M. Dolginov, B. N. Sverdlov, A. E. Drakin, P. A. Louk, E. G. Shevchenko for the help in this work.     

Attaining the wavelength range 189–197 nm by frequency mixing inβ-BaB2O4

Wavelengths in the range from 188.9 to 197 nm have been obtained by type-I sum frequency generation (SFG) in -BaB₂O₄. The fundamental beams were supplied by pulsed dye lasers one of which tuned between 780 and 950 nm and the other frequency-doubled at 497 nm. The possibility of shifting the excimer wavelength 248.5 nm to the excimer wavelength 193 nm has been demonstrated, replacing the frequency-doubled dye laser by KrF excimer lasers of different beam properties.     

New self-developing photopolymers for holographic recording in the 500–700 nm range

The methods of sensitization in the visible spectral region of self-developing photopolymeric materials on the basis of oligoether- and oligourethane acrylates have been investigated. As a result of the choice of the initiating system and modification of the monomer component of the base FPK-488, new FPK-520 and FPK-650 compositions have been obtained that provide holographic recording in the 500–700 nm range. The compositions developed can be used to record holographic optical elements (gratings, lenses) as well as for holographic interferometry and in pattern recognition systems. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 29–33, January–February, 2000.     

Performance of a polarizer using synthetic mica crystal in the 12——25 nm wavelength range

To develop polarizer functioning in the extreme ultraviolet (EUV) and soft X-ray region, the polarization performance of synthetic mica has been investigated theoretically with a simulation code using Fresnel equations and optical constants from the Henke database. The reflectance of synthetic mica crystal for s and p polarization was measured to investigate its polarization performance in a home-made synchrotron radiation soft X-ray polarimeter at beamline 3W1B, Beijing Synchrotron Radiation Facility (BSRF). The reflectivity of the synthetic mica crystal at an angle of grazing incidence of 48° was obtained from the experimental data, which is about 4.8 × 10^-3 at 25 nm and 6.0 × 10^-4 at 12 nm, and the linear polarizance of the X-ray reflected by the synthetic mica crystal that we measured using an analyzer-rotating method increases from 80% to 96.6% in this EUV region, while higher than 98.2% in the simulation. The result indicates that this synthetic mica crystal works as a practical polarizer in this EUV region of 12--25 nm, and also in an extensive wavelength region higher than 25 nm.     

Setup for studying quasi-free neutron-neutron scattering in the energy range of 20–60 MeV

A setup installed on the RADEX neutron beam channel (Institute for Nuclear Research, Russian Academy of Sciences) and designed to study quasi-free nn scattering in the n + d → p + n + n reaction is described. The setup is a two-arm time-of-flight spectrometer composed of scintillation neutron hodoscope (in the left arm), a scintillation neutron detector (in the right arm), and an active scintillation deuterated target for detecting protons. Secondary neutrons are detected at angles corresponding to the kinematic conditions of quasi-free nn scattering. Events are selected at low energies of the outgoing proton spectator. It is shown that data on neutron-neutron quasi-free scattering can be obtained in a wide range of primary-neutron energies.     

Measurement of complex dielectric constant of inhomogeneous materials in the range 102–107 Hz

A method of measuring the complex dielectric constant of a mixture composed of a disperse substance and water by insertion of dielectric spacers between the electrodes and the investigated substance is discussed. This system exhibits relaxation of the Maxwell-Wagner type in the conductivity range 10^–8–10^{–2 –1}·m^–1. By constructing and analyzing Cole-Cole diagrams it is possible to determine the complex dielectric constant of mixtures with a water content of 1–100 wt.% in the frequency range 10²–10⁷ Hz.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 40–46, September, 1978.     

Analysis of optical properties of bio-smoke materials in the 0.25–14 μm band

At present, research into optical properties of bio-smoke materials mostly concentrates on single band or single germplasm. Herein, we measured the spectral reflectance of three eukaryotic bio-smoke materials and three prokaryotic bio-smoke materials in the waveband from 0.25 μm to 14μm. Based on the Kramers-Kroning algorithm, the complex refractive index m(λ) was calculated and the Fourier-transform infrared(FTIR) spectra of materials were analyzed. The results show that n(λ) of bio-smoke materials varies between 1.1-2, and n(λ) values in the visible light to near-infrared wavebands are significantly larger than those in other wavebands. The k(λ) of bio-smoke materials varies between 0-0.4.At 6-6.5 μm, k(λ) of prokaryotic materials is 3 times that of eukaryotic materials, which is caused by C=O stretching vibration of amide I and C-N stretching vibration of amide Ⅱ in proteins. At 2.5-3 μm and 9.75 μm, k(λ) values of eukaryotic bio-smoke materials are nearly 2 times that of prokaryotic ones. The absorption peak at 2.5-3 μm is mainly triggered by C-H stretching vibration in lipid and O-H stretching vibration in bound water. The absorption peak at 9.75 μm is mainly caused by symmetric stretching vibration of PO2-in nucleic acids.     

Femtosecond optical parametric converter in the 168–182-nm range

Femtosecond pulses continuously tunable in the vacuum ultraviolet (VUV) spectral range between 168 and 182 nm were generated using four-wave frequency mixing in an argon-filled capillary. The pulse energy reached 200 nJ at a pump-to-VUV conversion efficiency of 1%. The bandwidth at 181 nm was up to 27 THz corresponding to a transform limited duration of 17 fs. The upper limit in the shortest measured pulse duration was 75 fs.     

Anomalous properties of crystalline methane in the range of 60–70 K

Mechanical, structural, thermal, and spectral properties of solid methane in the temperature range 0.5T _tr-T _tr (T _tr is the triple point) at the equilibrium vapor pressure have been analyzed. It has been shown that the totality of observed anomalies in the temperature range of 60–70 K can be explained by the existence of collective rotational degrees of freedom in solid methane.     

Fiber parametric oscillator for the 2 μm wavelength range based on narrowband optical parametric amplification

We describe a widely tunable synchronously pumped coherent source based on the process of narrowband parametric amplification in a dispersion-shifted fiber. Using an experimental fiber with a zero-dispersion wavelength of 1590 nm and pump wavelengths of 1530 to 1570 nm yields oscillations at 1970 to 2140 nm-the longest reported wavelength for a fiber parametric oscillator. The long-wavelength oscillations are accompanied by simultaneous short-wavelength oscillations at 1200 to 1290 nm. The parametric gain is coupled to stimulated Raman scattering. For parametric oscillations close to the Raman gain peak, the two gain processes must be discriminated from each other. We devised two configurations that achieve this discrimination: one is based on the exploitation of the difference in group delay between the wavelengths where Raman and parametric gain peak, and the other uses intracavity polarization tuning.     

Characteristics of microwave photoconductivity of natural diamond in the spectral range 200–250 nm

Mechanically polished plates of natural diamond of the IIa and Ia types were investigated by the microwave photoconductivity (MW PC), conventional (direct-current or, more precisely, low-frequency) photoconductivity (LF PC), and optical-absorption techniques. It is shown that the polycrystalline structure of the samples and high spatial inhomogeneity of the impurity defect distribution provide differences in MW PC and LF PC spectra. It is assumed that nonequilibrium holes in the illuminated diamond are trapped by the crystallite boundaries, while free electrons “oscillate” within the crystallites during their lifetime. The influence of chemical and mechanical treatment on the LF and MW PC is demonstrated.     

Photofission of americium isotopes in the energy range 6–12 MeV

By means of the reference method, the cross sections for the fission of the ²⁴¹Am, ^242m Am, and ²⁴³Am isotopes were measured at the microtron of the Institute of Physics and Power Engineering (Obninsk). These measurements, which employed the cross section for ²³⁸U photofission as a reference, covered the energy range 6–12 MeV scanned with a variable step of 50 to 200 keV. Data on ^242m Am photofission in the energy range 6–12 MeV and ²⁴³Am photofission in the region between 6 and 7 MeV were obtained for the first time. New results for ²⁴¹Am reveal that the cross sections for ²⁴¹Am photofission from previous studies of the present author were exaggerated. The new results for this isotope comply well with data of other authors. It is not confirmed that the fissility of ²⁴¹Am is less than the fissility of ²⁴³Am. The energy dependences of the fissilities of the americium isotopes from photofission data are compared with those that were obtained for these fissilities from data on direct reactions like ²⁴⁰Pu(³He, df)²⁴¹Am. The results of this comparison show that the observed fission thresholds and the plateaulike dependences at energies above 7.5 MeV from the two types of studies comply well. The present data show evidence that, in the energy region around 6 MeV, the photofission cross section has a maximum, which is associated, in all probability, with the low-energy resonance structure in the cross section for dipole photoabsorption.     

Kramers–Kronig analysis of the optical constants of magnetite,pyrite, and chalcopyrite in the microwave range

The optical constants of a series of ore minerals (pyrite, magnetite, and chalcopyrite) have been analyzed in the microwave range using the Kramers–Kronig method. The spectral dependences of the reflectance of these minerals in a wide frequency range (from deep UV to microwave) have been plotted based on numerous experimental data from different sources. These dependences made it possible to calculate the optical constants of the minerals under study in a frequency range of 12–145 GHz and compare them with the results of the theoretical and laboratory studies published in different sources.     

Investigation of ultrafast processes in photoexcited bismuth by broadband probing in the wavelength range 0.4–0.9 μm

The decay of the photoexcited state of a bismuth single crystal is investigated in the wavelength range from 400 to 900 nm by means of femtosecond laser reflection spectroscopy. Oscillations produced by coherent fully symmetric A _1g phonons have been detected in the photoinduced response, along with a relaxation component. The dynamics of the electronic subsystem of the crystal is shown to be characterized by three values of the decay time: 1 ps, 7 ps, and ∼1 ns. The spectral dependence of the reflectivity oscillation amplitude has been measured; the possible cause of the shape of the derived curve is described.