Optical properties of ion-modified metal surface in the infrared range

The results of study of ion-cleaned and -implanted surfaces of polycrystalline Be, Al, Ti, Fe, Cu, Mo, Zr, and W using optical and infrared (IR) spectroscopy are presented. It is shown that major changes in the optical reflectance spectra are observed in the range of 190–250 nm and are associated with both the formation of scattering centers and features of the chemical state of near-surface layers of materials. It is established using IR spectroscopy that treatment by Ar⁺ ion beam with a broad energy spectrum increases the reflection coefficient of the modified surface and additional resonance lines related to the formation of oxides themselves and hydroxyl groups are revealed in the reflectance spectrum in the case of formation of oxide film on the surface.     

Light emission properties of sapphire under shock loading in the stress range of 40-120 GPa

The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40-120 GPa.The results showed that the spectral distribution with wavelength clearly fit well with the grey-body spectrum.We have analyzed the emissions and discovered they mostly came from the shear banding,which is a typical thermal radiation.The radiance intensity changing linearly with time revealed it was a volume effect.All of the data from pyrometer can be explained by the model of Boslough’s study,especially for pressures over megabar.The color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the different phase structures of sapphire.     

冲击压缩下蓝宝石单晶散射消光的理论计算

考虑局部温升会引起折射率的变化,对蓝宝石体材及其内部绝热剪切带的折射率进行了理论计算。计算结果表明,绝热剪切带以及周围体材的折射率均随波长的增加而减小,并且二者之差在80GPa、99GPa、132GPa、183GPa和255GPa五个压力点处均高于0.02。在此基础上,本文提出并建立了冲击绝热剪切带散射消光的物理模型,并采用离散偶极子近似方法计算了蓝宝石在上述五个压力点处的散射消光谱。计算的散射截面随波长和压力的增加而减小;在计算出剪切带数密度后,所得散射系数与实验数据定性相符。本文研究取得的蓝宝石散射消光认识对于理解脆性材料动态变形的微细观机理及其冲击透明性变化具有一定的参照价值。     

Optical properties of mucous membrane in the spectral range 350–2000 nm

The optical characteristics of the mucous membrane from the human maxillary sinus are studied experimentally. The experiments were carried out in vitro in the spectral range 350–2000 nm. On the basis of the measured total transmittance and diffuse reflectance spectra, the absorption and transport scattering coefficients are calculated in the entire range in terms of the inverse adding-doubling method.     

冲击压缩下蓝宝石单晶散射消光的理论计算

考虑局部温升会引起折射率的变化,对蓝宝石体材及其内部绝热剪切带的折射率进行了理论计算。计算结果表明,绝热剪切带以及周围体材的折射率均随波长的增加而减小,并且二者之差在80GPa、99GPa、132GPa、183GPa和255GPa五个压力点处均高于0.02。在此基础上,本文提出并建立了冲击绝热剪切带散射消光的物理模型,并采用离散偶极子近似方法计算了蓝宝石在上述五个压力点处的散射消光谱。计算的散射截面随波长和压力的增加而减小;在计算出剪切带数密度后,所得散射系数与实验数据定性相符。本文研究取得的蓝宝石散射消光认识对于理解脆性材料动态变形的微细观机理及其冲击透明性变化具有一定的参照价值。     

Optical amplifying module and its optoelectronic properties

Conclusion We have constructed miniature optical amplifying modules based on buried stripe heterostructures emitting in the 1.2 m band. The modules have single-mode fiberoptics lead-ins; the hermetically sealed housing contains also a Peltier refrigerator and a temperature sensor. The gain characteristics of the module were investigated and show that it can be used for information access (including spectrally selective access) by using the optoelectronic signal produced in the pump electric circuit by passage of an amplified optical signal.Quantum Electronics Laboratory, Lebedev Physics Institute. Translated from Preprint No. 47 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

Optical vibronic absorption spectra in 14.8 MeV neutron damaged sapphire

Preliminary observations of several anisotropic optical absorption bands are reported for high-purity sapphire following exposure to a pure 14.8 MeV neutron beam. These bands are compared with and found to be similar to those reported following fission-spectrum exposure, and are associated with lattice displacement damage. Two of these bands at 3.47 and 4.09 eV show similar sharpline features at low temperature; this ≈200 cm^?1 vibronic progression it tentatively associated with a local mode.     

Ti:sapphire second-harmonic-pumped visible range femtosecond optical parametric oscillator

A β-barium borate (BBO) femtosecond optical parametric oscillator (OPO) pumped by the second-harmonic of a modelocked 82 MHz Ti:sapphire laser is described. With intracavity dispersion compensation, pulse durations down to 30 fs are obtained with a total average power up to 100 mW. The current wavelength range, with a 400 nm pump, is from 566 nm to 676 nm. Unusual tuning characteristics, including bichromatic emission, are presented in detail and explained theoretically.     

Optical properties of the subcutaneous adipose tissue in the spectral range 400–2500 nm

The optical characteristics of subcutaneous adipose tissue are studied in the wavelength range 400–2500 nm. The experiments are conducted in vitro using a Cary 2415 spectrophotometer. Based on the measured diffuse reflectance and total transmittance spectra, the spectra of the absorption and transport scattering coefficients are calculated in terms of the inverse adding-doubling method.     

Optical anisotropy of ZnO nanocrystals on sapphire by thermoreflectance spectroscopy

The band-edge excitonic transitions of vertically aligned and tilted ZnO nanorods on sapphire have been characterized using thermoreflectance (TR) measurements in the temperature range between 30 and 300 K. The TR spectra of the nanorods with largely {0001} planes show considerable difference in energy and line shape with respect to those of the other sample with largely side planes of {1010}. The TR result at each temperature clearly indicates the band-edge excitons (A, B, and C) measured from the largely {0001} planes of the rods are lower in energy with respect to those obtained from the other sample dominated by the side planes of {1010}. Optical anisotropy in the transition amplitudes of the TR spectra for the vertically aligned and tilted ZnO nanorods is observed. The TR is shown to be very sensitive to the detection of the ZnO nanorods' alignment.     

Optical anomalies and residual stresses in basal-plane-faceted ribbons of Stepanov-grown sapphire crystals

The effects of an anomalous biaxiality and a residual-stress field in basal-plane-faceted single-crystal sapphire ribbons were studied by an optical polarization method using a conoscopic light beam. Formulas that relate the difference between the principal stresses to the angle of optical-axis divergence are obtained. It is shown that the central regions of the ribbons undergo compressive stresses whereas their edges undergo tensile stresses. As compared to block-free ribbons, the stresses in block-containing ribbons increase more intensely with distance from the seed.     

Optical properties of Nd3+ pairs in LiYF4-existence of a short range interaction

Optical studies of Bridgman grown LiYF₄ crystals weakly doped with Nd³⁺ have been made in the vicinity of the ⁴I_9/2→⁴G_5/2 transition. By selective excitation with a narrow pulsed laser or with a CW monomode laser, excitation spectra and dynamical characteristics of infrared and ultraviolet (up-converted) fluorescences produced by satellites associated with Nd³⁺ pairs have been obtained. From the results, an assignment of the satellites to the various classes of pairs has been possible. The existence of a short range interaction, probably superexchange, has been proved which confirms previous observations in another fluoride compound, LaF₃.     

Optical nutation in the exciton range of spectrum

Optical nutation in the exciton range of spectrum is studied in the mean field approximation taking into account exciton-photon and elastic exciton-exciton interactions. It is shown that the features of nutation development are determined by the initial exciton and photon densities, the resonance detuning, the nonlinearity parameter, and the initial phase difference. For nonzero initial exciton and photon concentrations, three regimes of temporal evolution of excitons and photons exist: periodic conversion of excitons to photons and vice versa, aperiodic conversion of photons to excitons, and the rest regime. In the rest regime, the initial exciton and photon densities are nonzero and do not change with time. The oscillation amplitudes and periods of particle densities determined by the system parameters are found. The exciton self-trapping and photon trapping appearing in the system at threshold values of the nonlinearity parameter were predicted. As this parameter increases, the oscillation amplitudes of the exciton and photon densities sharply change at the critical value of the nonlinearity parameter. These two phenomena are shown to be caused by the elastic exciton-exciton interaction, resulting in the dynamic concentration shift of the exciton level.     

Optical properties and structural characteristics of ZnO thin films grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy

We investigated structural and optical properties of ZnO thin films grown on (112?0) a-plane sapphire substrates using plasma-assisted molecular beam epitaxy. Negligible biaxial stress in ZnO thin films is due to the use of (112?0) a-plane sapphire substrates and slow substrate cooling. The 14 K photoluminescence spectrum shows a blueshift of energy positions compared with ZnO single crystal. A donor with binding energy of 43 meV and an acceptor with binding energy of ～170 meV are identified by well-resolved photoluminescence spectra. A characteristic emission band at 3.320 eV (so-called A-line) is studied. Based on analysis from photoluminescence spectra, the origin of the A-line, it seems, is more likely an (e, A°) transition, in which defect behaves as an acceptor. The room-temperature photoluminescence is dominated by the FX at 3.307 eV, which is an indication of strongly reduced defect density in ZnO thin films.     

Optical property measurements of 235 mm large-scale Ti:sapphire crystal

A Ti:sapphire crystal with a diameter of 235 mm and thickness of 72 mm was grown by the heat exchange method(HEM). The absorption intensity of the crystal at 532 nm averaged at 91%. The figures of merit(FOMs)at different positions of the crystal were measured and the FOM value in the central region was found to reach 90.The transmittance laser beam was intact with no obvious distortions and had only a small deformation compared with the incident laser beam. A small-signal amplification experiment was performed on the Ti:sapphire crystal and a gain of more than 6 times was achieved with a pump energy density of 1.98 J∕cm~2. These tests indicate that the 235 mm Ti:sapphire crystal has excellent optical qualities and will further improve the energy output of a 10 PW laser system.