Values Of Optical Parameters Research Articles

Efficient approach to designing a Schmidt-Cassegrain objective for a remote sensing satellite

This paper presents an efficient approach to designing a Schmidt-Cassegrain objective for a remote sensing satellite. The objective is required to have multispectral operational bands, with three spectral channels distributed along the range (0.5 to 0.9 mum), as well as a panchromatic channel; 4 degrees field of view; distortion smaller than 0.3%; and a modulation transfer function, at 50 lines/mm spatial frequency, better than 0.5 and 0.35 at the center and edge of the field of view. The proposed design approach is based on Slyusarev's theory of aberrations and optical design. An image quality index is formulated as a function of optical system component powers and axial distances. For each combination of parameters, there exists a possible solution that can be realized into a thin lens system by solving Seidel sum equations. The final design is then reached by a simple and quick optimization step. The best three designs are compared in terms of initial values of optical system parameters and final design specifications. The best system image quality is thoroughly analyzed. All three presented designs meet and exceed the required design specifications.

The Settlement and Remote - Measured Spectra of Absorption of V3 Bands of Methane and Their Analysis

It is lead settlement works and remote research of a spectrum of absorption of ν3 bands of methane in a range of lengths of waves 3.25–3.45 microns. Time forms and intensity of separate lines P- and R-branches are calculated. Comparison of experimentally measured and settlement spectral width and intensity separate lines of ν3 strips of methane is lead. The received results allow finding optimum values of optical parameters of probing tunable parametrical laser radiation. Settlement values of spectral width and intensity separate lines of ν3 bands of methane it will well be coordinated with the measured experimental sizes.

A study of optical properties of hydrogenated microcrystalline silicon films prepared by plasma enhanced chemical vapor deposition technique at different conditions of excited power and pressure

Two sets of hydrogenated microcrystalline silicon thin-film samples were prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique at different deposition conditions of excited power and pressure. The correlation between the crystalline volume fraction for the samples determined from Raman spectra and the excited power, pressure, absorption coefficient, refractive index and optical energy gap was discussed. The values of optical parameters (refractive index and absorption coefficient), were calculated from the transmission spectra in the range 400–2500 nm. The optical band energy gap and Urbach energy were obtained using the calculated values of absorption coefficients

Comment on “Local Lattice Structure Study of the Octahedral (CrO6)9− Clusters for Cr3+ Ion Doping in a Variety of Oxide Crystals by Simulating the Corresponding EPR and Optical Spectra”

(and also of the smalldistortion undergone by the oxygen octahedron), can be obtainedfrom an analysis of experimental values of optical transitionsand EPR parameters through a parametrized crystal-field model.In essence such an analysis is founded on two main assumptions:(1) Electronic properties due to Cr

Hydrography, currents and distribution of suspended matter during a dumping experiment in the western Baltic Sea at a site near Warnemünde

During a dumping experiment on 20/21 June 2001, an extensive data record was collected to understand the dynamical processes in the water column of the investigation area and to validate model results. Weak westerly winds with strongly changing cloud coverage characterized the meteorological situation. During the second day the wind calmed down and moved shortly to easterly directions. The water column was characterized by a strong vertical stratification with discontinuity layers in temperature and salinity in 12 and 16 m. The current regime was dominated by outflow at the water surface and inflow along the German coast, with strong current shearing in the dumping area. The suspended matter clouds could be identified by optical methods and ADCP (Acoustic Doppler Current Profiler) scattering intensity. During the experiment the suspended matter plumes were only visible at the surface up to 1 h after the dumping. The aerial photographs document that the particle clouds at the surface drifted to the west and, after approximately 40 min, they were only weakly visible. The fine material was concentrated in the discontinuity layer leading to substantially higher values of optical parameters and suspended matter concentration than measured in the surface clouds. Due to the vertical current shears the material was transported in the water column in different directions. At the first day the maximum of the suspended matter in the discontinuity layer was in the north-western corner and in the bottom layer in the northeast corner of the dumping area. Strong wind conditions after the dumping led to periodical resuspension processes.

Dental biothermophotonics: How photothermal methods are winning the race with X-rays for dental caries diagnostic needs of clinical dentistry

Recent trends in biothermophotonics of teeth are presented. The presentation is centered on the development of clinical-level frequency-domain photothermal radiometry and modulated luminescence to address issues associated with the early diagnosis of demineralization caries in human teeth. Biothermophotonic principles and applications to the detection of the carious state in human teeth as embodied by laser photothermal radiometry are presented and further supported by modulated luminescence. The emphasis is on recent developments with regard to abilities of these techniques to diagnose interproximal lesions between teeth, etching with phosphoric acid and with an artificial demineralization gel in order to simulate early demineralization, as well as demineralization and remineralization of dental crown enamel and root dentin. These are lesions which normally go undetected by X-ray radiographs. Comparisons with X rays, Micro-Computed Tomography (μ-CT) and Transverse Micro-Radiography (TMR) are discussed. A theoretical model involving coupled diffuse photon density and thermal-wave fields is developed and applied to frequency scans from demineralized artificial lesions to produce quantitative values for optical and thermophysical parameters of teeth as well as the thickness of the induced lesion.

Optical properties of GexSb20−xTe80 thin films and their changes by light illumination

The influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge x Sb 20-x Te 80 (x = 15, 17, 19) composition is studied by spectral ellipsometry in the visible range of light. The films were deposited onto glass substrates by vacuum thermal evaporation of parent glasses and were subjected to an 1-h illumination with a 500 W HBO mercury lamp. It has been established that illumination of the films leads to a decrease of the refractive index, n, in the whole spectral region studied and to an increase of the extinction coefficient, k, in the range of 600-800 nm. The optical bandgap energy Eg values are within 0.55-0.76 eV with a tendency to increase with increasing the Ge content. Illumination resulted in a sharp decrease of the Eg values indicating structural change in the films. Leaving the films at atmospheric conditions the optical parameters values change toward their initial values of unilluminated state.

Influence of pulsed and cw pumping on optical nonlinear parameters of laser dyes probed by a closed-aperture Z-scan technique

Two dye pairs suitable for energy transfer along with a photostable dye have been studied by using the closed-aperture (CA) Z-scan technique under pulsed and cw pumping. Here we use a theoretical model to elucidate the refractive and absorptive nonlinearity present simultaneously in the CA Z-scan profile. A separate open-aperture (OA) Z-scan study has been carried out to compare the nonlinear absorption parameters obtained from the CA Z-scan technique. At a fixed pumping wavelength, values of optical nonlinear parameters increase with the absorbance of dyes. It is found that the sign of refractive nonlinearity is dependent on the irradiance and the pulse width of the pump beam. In addition to the contribution of the third-order optical nonlinearity, various other mechanisms such as fifth-order nonlinearity, population relaxation to triplet states, and thermal effects are discussed here.

Preparation of selective absorbers based on CuMn spinels by dip-coating method

CuMn-spinel thin films were prepared on aluminum substrates by the so-called dip-coating method. The layers were deposited from alcoholic solutions based on nitrate precursors and subsequently sintered in air at 500 °C. Reflectance spectra in the NIR–vis–UV interval were measured for samples with different composition and thickness. The absorber quality of the films was checked by calculating the solar absorptance. The films displaying the best reflectance spectra and the highest solar absorptances (αs>0.87) were deposited from solutions containing molar ratio Cu/Mn=1. The analysis of composition showed that Cu/Mn ratio in the film was very close to the ratio in the dip-in solution and supported the formation of a spinel-like material of stoichiometry Cu1.5Mn1.5O4. Solar absorptance was dramatically improved when a SiO2 antireflective layer was deposited onto the spinel. By optimizing film thickness of both CuMn-spinel and SiO2 layers optical parameter values as good as αs=0.94 and εT(1 0 0)=0.06 were achieved.

γ-Irradiation effects on the thermal and optical properties of undoped and eosin doped 70/30 (wt/wt%) PVA/glycogen films

Abstract Differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), UV/visible spectra and colour detection of pristine and γ-irradiated undoped and eosin-doped 70/30 (wt/wt%) PVA/glycogen has been measured. The kinetic parameters such as the activation energy, entropy, enthalpy and free energy for all investigated samples were determined using Coats–Redfern relation. The shift of T g position towards lower temperatures with increasing γ-doses reflect that the degradation process is the predominant one. The values of absorbance and optical parameters in UV/visible range for γ-irradiated blend sample doped with eosin showed no significant variation with increasing γ-doses. This reflects that the addition of eosin to 70/30 (wt/wt%) PVA/glycogen makes it more resistant to γ-radiolysis. The calculated colour parameters such as L ∗ , U ∗ , V ∗ , C ∗ , hue and Y e were found to be dependent on addition of eosin and γ-irradiation.

Effect of Killer Impurities on Optical Properties of ZnO at Low Temperature

Optical characterizations for ZnO doped with killer impurities (Co or Fe or Ni) having doping concentrations 0.05–1.00% by weight have been carried out at 77 K. Optical properties such as excited state lifetime, trap-depth and decay constant values have been measured using the pulse excitation method. The effect of killer dopants, concentration of killer ions as well as the effect of temperature on various optical parameters values has been observed. Multi-exponential decay curves have been observed. Lifetime values are found to be in the micro- and nano-second time domain and a reverse trend is obtained with increase in concentration of killer impurities. With decreases in temperature from 300 to 77 K, lifetime shortening takes place. The effect of killer impurities is more prominent at higher concentrations. A mixed trend in decay constant values is observed with the increase proportional to the concentration of killer impurities. The values of the decay constant show a mixed effect with change in impurity concentrations. The value of the decay constant 0.76, corresponding to ZnO: Ni (0.7%) is the highest among all the doped ZnO phosphors.

Investigation of dispersion characteristic in MI- and MII-type single mode optical fibers

Abstract Dispersion characteristic of MI and MII type single mode optical fibers is analytically investigated. For this purpose modal analysis of these fibers to obtain possible wave vectors for given system parameters are done. Then using numerical evaluation of the presented analytical relations, chromatic and waveguide dispersions are calculated. The effects of geometrical and optical parameters of the fibers on dispersion characteristics are investigated. In this analysis, we show that with increase of Δ (optical parameter) for MI structure the slope of dispersion curve is decreased and the case is reversed for MII structure. Also, with rising of Q (geometric parameter) for MI structure the slope of dispersion curve is decreased and the situation is reversed for MII structure. Finally, we show that with boosting of R 2 for MII structure the slope of dispersion is increased. As a final result, our simulations show that small values for optical parameters are better in MII structure for multi-channel optical communications. In MI structure to obtain small dispersion slope, Q can be increased that is easy for fabrication in practice. Finally, Q and R 2 are suitable parameters for control of dispersion in the proposed structures.

High optical quality IZO (In 2Zn 2O 5) thin films by PLD – A novel development for III–V opto-electronic devices

Abstract Extrinsic zinc oxide (heavily indium oxide doped), i.e., indium zinc oxide (In 2 Zn 2 O 5 ) (IZO) as novel transparent conducting oxide (TCO) thin films were grown by pulsed laser deposition (PLD) technique using Johnson Matthey “specpure” – grade 90% In 2 O 3 mixed 10% ZnO (as commercial indium tin oxide (ITO) composition) pellets. The effects of substrate temperatures and heavy indium oxide incorporation on IZO thin film growth, optical transmission, absorption, reflection and photoluminescence were studied. As well as the feasibility of developing a novel high quality transparent oxide thin films was also studied simultaneously. Also, as a novelty merit we want to emphasize as a interesting physical effect that the average optical transmittance T % (max) ⩾95% of IZO thin films is rivals that of the most TCO films for this conductivity level (of the order of 10 3 Ω −1 cm −1 ). This is the first time that we have applied these PLD prepared IZO thin films to iso and hetero semiconductor–insulator–semiconductor (SIS) type solar cells as TCO coatings. The optical parameter values were calculated, diagrammatically enumerated and tabulated. From optical studies, we have observed that the films were act as highly anti-reflective (AR) coatings. From PL study, we have confirmed the purity and high electrical conductivity of the deposited thin films. Supplementary studies on surface, electrical, structural and internal morphology of thin film growth correlated with optical transmission, absorption, reflection and photoluminescence gives added advantages to this work.

Reply: Analysis of cellular structure by light scattering measurements in a new cytometer design based on a liquid-core waveguide

The results of applying a novel microfluidic optical cytometer to generate and observe the light scattered from biological cells over a wide range of angles are presented. This cytometer incorporates a waveguide that increases the intensity of the scattered light to the extent that an inexpensive digital camera can be used to detect the light over a large solid angle. This device was applied to yeast cells and latex beads and experimental data were compared with the results of a finite difference time-domain (FDTD) method of simulation. The simulated scattering patterns were calculated from reported values of optical parameters and are in good qualitative agreement with experiment. It is demonstrated that this system could be used to acquire information on the microstructure and potentially the nanostructure of cells.

Brain tissue phantoms for optical near infrared imaging

In this study, solid, stable, and cost-effective optical phantoms of scalp-skull, white matter and grey matter are developed by inverse method. To begin with, to obtain a range of optical parameters, absorption and reduced scattering coefficients (mu(a) and mu(s)', respectively), 20 homogeneous phantoms were made of paraffin wax by using optically contrast black and highly scattering white colouring materials in different combination. By comparing the measured reflectance values for each phantom got from the four channel reflectometer with that obtained from steady-state diffusion equation, the values of mu(a) and mu(s)' were determined. Next, phantoms which exhibit specific optical properties of scalp-skull, white and grey matter are developed iteratively by comparing actual reflectance measurements got by adjusting the colour concentration with the predicted reflectance values from the diffusion equation. This is done as follows: to obtain mu(a) of 0.04 mm(-1) for scalp-skull, 9.5 mg of black dye per 100 ml of wax added since more attenuation of light occurs in bone tissue. To obtain a mu(s)' 6.0 mm(-1) for white matter in brain tissue, 190 mg of white dye per 100 ml of wax was used to facilitate more scatter of light. The colour concentrations of phantoms were then adjusted to obtain the predetermined values of optical parameters for scalp-skull, grey and white matter.

Effect of the optical characteristics of semiconductor resonator structures on the amplitudes of their thermal radiation lines

Abstract We investigated, both theoretically and experimentally, the dependence of the intensity of spectral lines of thermal radiation from plane-parallel semiconductor resonator structures on their optical parameters (volume absorption and coefficients of reflection from surfaces). The investigations were performed in the spectral region of absorption by free charge carriers ( λ = 3–17 μm). It is shown for such structures that the amplitudes of thermal radiation lines depend non-monotonically on the transmission factor. We determined the optical parameter values for a resonator structure that are optimal when forming comb radiation spectrum. The conditions are found under which the intensity of lines of thermal radiation from a semiconductor plane-parallel layer approaches that of thermal radiation from a blackbody.

DETERMINATION OF THE OPTICAL CONSTANTS AND THICKNESS OF SEMITRANSPARENT THIN FILMS USING SUCCESSIVE INTERFERENCE FRINGES OF TRANSMISSION SPECTRA

A simple method for determination of optical constants and thickness of semitransparent thin films deposited onto a transparent finite substrate has been developed. The method is based on the analysis of successive interference fringes of transmission spectra created by the films. It is essentially not necessary to obtain the envelope of transmission spectra in this method. The determined values of optical parameters are in good agreement with their true values used to generate transmission data. The accuracy of method in determining refractive index and thickness of the films is better than 1%.

Light emission efficiency and imaging performance of Y3Al5O12: Ce (YAG: Ce) powder screens under diagnostic radiology conditions

In this study Y3Al5O12: Ce powder scintillator was evaluated for use in X-ray imaging detectors. This phosphor, also known as YAG: Ce scintillator or P-46 phosphor, is a non-hygroscopic, emitting green light with very short decay time. These properties are very attractive for X-ray imaging. Y3Al5O12: Ce powder was used to prepare various test screens (33–166 mg/cm2). Absolute luminescence efficiency measurements were performed for various X-ray tube voltages (50–130 kVp). In addition parameters related to image quality such as the modulation transfer function and the detective quantum efficiency were examined. A theoretical model, describing radiation and light transfer, was employed to fit experimental data and to estimate values of optical parameters. Absolute efficiency was found to decrease with X-ray tube voltage. Highest efficiency was obtained for the 107 mg/cm2 screen. Light attenuation coefficients were close to those of green emitting rare earth scintillators. At low spatial frequencies the detective quantum efficiency was high for the 107–166 mg/cm2 screens. The light emission efficiency and imaging performance of Y3Al5O12: Ce was not better than currently employed scintillators. However due to its very fast response and high spectral compatibility to optical sensors it may be considered for use in digital imaging detectors.

Development of a novel high optical quality ZnO thin films by PLD for III–V opto-electronic devices

Abstract A novel highly transparent intrinsic zinc oxide (ZnO) thin films (without adding any dopants and annealing) were grown by pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”- grade ZnO pellets. The effects of substrate temperatures on zinc oxide thin film growth, optical transmission, absorption, reflection and photoluminescence properties were studied. As well as the feasibility of developing high quality transparent oxide thin films was also studied simultaneously. The optical transmission window of such obtained films, i.e., T % (max) ⩾ 95% is broader than those of other transparent conducting oxides such as indium tin oxide (ITO) and absolute rivals that of the most transparent conducting oxides (TCOs). Also as a novelty merit, we want to emphasize as a interesting, significant and novel physical effect that the average optical transmittance of ZnO thin films rivals that of the most transmittive TCO films reported to date for this conductivity level (of the order of 10 3 Ω −1 cm −1 ). Also this is the first time that we have applied these PLD prepared ZnO thin films to iso and hetero semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) coatings. From optical studies, we know that the films were act as highly anti-reflective coatings. From photoluminescence study, we confirmed the purity and high electrical conductivity of the deposited thin films of ZnO. The optical parameter values for the films were calculated, tabulated and graphically emphasized. Supplementary studies on surface, electrical, structural and internal morphological properties of zinc oxide thin film growth correlated with optical transmission, absorption, reflection and photoluminescence properties gives added advantages to this work. We hope that surely these data should be helpful either as a scientific or technical basis in the semiconductor processing and technology.

Study of optical properties of skin tissues from ultraviolet to short-wave infrared

Accurate knowledge of optical properties of skin tissues is fundamental to the study of tissue optics and development of optical instrumentation in clinics. The goal of research described in this dissertation is to develop a system of experimental methods and theoretical models for the inverse determination of optical parameters of mammalian tissues and various tissue phantoms. Based on the integrating sphere and spatial filtering techniques, various experimental systems have been constructed and improved to measure the diffuse reflectance, the diffuse transmittance, and the collimated transmission of turbid samples from the spectral region of ultraviolet to short-wave infrared. Different Monte Carlo based algorithms have been developed to simulate photon transportation under different experimental configurations based on the radiation transfer theory. The corresponding procedures for inverse determination of optical parameters from the experimental data have been established. We have determined the complex refractive index of polystyrene microspheres as a function of wavelength from using a Monte Carlo model in combination with the Mie phase function. The optical parameters of porcine skin dermis tissues have also been determined by assuming the surface of the dermis samples were flat and smooth. The effect of surface roughness on the inverse determination of bulk optical parameters of a turbid sample has been investigated. We found that the condition of the sample surface plays an important role in determining the light distribution in a turbid sample. Numerical simulations have shown that the surface roughness on scales close to the wavelength of light can significantly affect the values of bulk tissue optical parameters inversely determined from in vitro measurements even for a moderate index mismatch. As a result, we have developed a confocal imaging method to measure the surface profile of slab samples of fresh porcine skin dermis and extracted the profile parameters. With this knowledge, the surface roughness corrected optical parameters of porcine dermis tissue have been determined at the wavelengths of 325, 442, 532, 632.8, 850, 1064, 1330, and .