Imaginary part of the refractive index of sulfates and nitrates in the 0.7-2.6-microm spectral region

We have carried out the transmission spectroscopy and obtained the imaginary part of the refractive index k of sulfate and nitrate aqueous solutions in the spectral range between 0.7 and 2.6 microm for several concentrations at temperatures of T = 24 degrees C and T = -24 degrees C. A linear interpolation with volume fraction is found to reproduce the measured k spectra of the ammonium solutions.     

Application of antimonide lasers for gas sensing in the 3-4-microm range

Antimonide semiconductor laser devices designed for continuous-wave emission in the 3-4-mum spectral range have been investigated with respect to spectroscopic applications. Representative data on the mode structure, output power, noise characteristics, far-field pattern, and modulation response are presented. Selected laser devices have been applied for methane (CH(4)) and formaldehyde (HCHO) measurements by use of a high-frequency modulated diode laser spectrometer. From an Allan variance analysis of experimental data a detection limit for HCHO of 120 pptv (where 1 pptv = 10(-12) volume mixing ratio) with a 40-s integration time and for CH(4) of 2 ppbv (where 1 ppbv = 10(-9) volume mixing ratio) with 20-s integration time were determined. The results show that, for selected gases, InAsSb lasers can be an alternative to lead-salt diode lasers.     

Complex optical index of single wall carbon nanotube films from the near-infrared to the terahertz spectral range

We retrieve the complex optical index of single-walled carbon nanotube (CNT) films in the 0.6-800 μm spectral range. Results are obtained from a complete set of optical measurements, reflection and transmission, of free-standing CNT films using time domain spectroscopy in the terahertz (THz) and Fourier transform infrared (IR) spectroscopy in the visible-IR. Based on a Drude-Lorentz model, our results reveal a global metallic behavior of the films in the IR, and confirm their high optical index in the THz range.     

High-accuracy calculations of the refractive indices of optical materials in a wide spectral range

The interaction between light and matter is studied thoroughly by means of the quantum theory. On the basis of it, the refractive indices of types of optical materials are calculated by several formerly experienced formulas. Finally,anew, tested approximate formula with the highest calculated accuracy is obtained, and some groups of valuable parameters are given.     

Model function to calculate the refractive index of native hemoglobin in the wavelength range of 250-1100 nm dependent on concentration

The real part of the complex refractive index of oxygenated native hemoglobin solutions dependent on concentration was determined in the wavelength range 250 to 1100 nm by Fresnel reflectance measurements. The hemoglobin solution was produced by physical hemolysis of human erythrocytes followed by ultracentrifugation and filtration. A model function is presented for calculating the refractive index of hemoglobin solutions depending on concentration in the wavelength range 250 to 1100 nm.     

Development of a detector-based absolute spectral irradiance scale in the 380-900-nm spectral range

A detector-based absolute scale for spectral irradiance in the 380-900-nm wavelength region has been developed and tested at the Helsinki University of Technology (HUT). Derivation of the scale and its use for photometric and colorimetric measurements are described. A thorough characterization of a filter radiometer, constructed from a reflection trap detector, a precision aperture, and a set of seven temperature-controlled bandpass filters, is presented. A detailed uncertainty analysis of the scale indicates a relative standard uncertainty of approximately 0.2% throughout most of the wavelength region. The standard uncertainties obtained in measurements of correlated color temperature and luminous intensity of three Osram Wi41/G tungsten-halogen lamps are 2 K and 0.3%, respectively. The spectral irradiance scale is compared with the HUT luminous intensity scale. The agreement of the results at the 0.1% level is well within the combined standard uncertainty of the two scales.     

TiO2-SiO2系统凝胶玻璃薄膜折射率的研究

应用光度法研究了溶胶－凝胶系统组成、热处理温度对iO2-SiO2系统凝胶玻璃薄膜折射率的影响规律。随薄膜中TiO2含量的增加以及热处理温度的升高，薄膜的折射率逐渐增大。通过调整TiO2-SiO2系统的组成及适当的热处理温度，可实现TiO2-SiO2系统薄膜折射率在1．5－2．4之间的连续变化。     

Picosecond measurement of the nonlinear refractive index of new salts of carboxylate anions with chiral ammonium cations

The third order nonlinear optical properties of novel carboxylate anions with chiral amines and ammonium cations have been studied by a new alternative of the classical z-scan technique with picosecond laser pulses (pulse duration of 30 ps at 1064 nm wavelength). The materials do not present linear and nonlinear (two-photon) absorptions at the wavelength and the intensities used for the experiments. The non-resonant molecular second order hyperpolarizability γ obtained can reach 4.4 × 10⁻⁴⁸ SI. These values are two and three orders of magnitude larger than those CS₂ and of C₆H₆ respectively.     

Mid-infrared (5-12-microm) and limited (5.5-8.5-microm) single-knob tuning generated by difference-frequency mixing in single-crystal AgGaS2

We describe tunable 5-12-mum mid-infrared generation in single-crystal silver gallium sulfide (AgGaS(2)), from nonlinear optical difference-frequency generation. Signal and idler waves obtained from a Nd:YAG laser-pumped LiNbO(3) optical parametric oscillator (OPO) were mixed in AgGaS(2) crystal to yield difference-frequency waves. For the efficient generation of difference frequency, an unstable resonator was employed as the OPO to reduce output beam divergence. A maximum difference-frequency power of 95 muJ/pulse was obtained near 7.5 mum for a 1-cm-long AgGaS(2) crystal. Spectral noncritical phase matching within a specific tuning range was also investigated that permitted limited single-knob tuning (5.5-8.5 mum) of the difference-frequency generator.     

Measurements of the refractive index of yttrium in the 50-1300-eV energy region

The first experimental results to our knowledge on the refractive index n = 1 - delta + ibeta of yttrium in the extreme-ultraviolet and soft x-ray energy ranges are discussed. To determine the absorptive part beta, transmittance measurements were performed on pure yttrium films in the 50-1300-eV energy region at beamline 6.3.2 of the Advanced Light Source. The dispersive part delta was then calculated from the absorption results by means of the Kramers-Kronig transformation. Compared with prior tabulated values, the new wet of data for the refractive index of yttrium is in better agreement with the sum rules and contains previously unresolved fine structure information in the regions of the M2,3 and M4,5 absorption edges, where yttrium-based multilayer mirrors operate.     

The effect of different power spectral densities of refractive index on the propagation of coherently combined beams

Using the expansion of the mutual coherence function in the Taylor series, the analytically approximate expression for the average intensity of a general combined beam in turbulence is derived. Comparison with numerical calculation shows that the expression not only provides a reasonable approximate approach to study the propagation of a combined beam in non-Obukhov–Kolmogorov turbulence, but also provides a much more precise method to study the propagation of a combined beam in Obukhov–Kolmogorov turbulence. As an example, the effect of different power spectral densities of refractive index on the beam-spreading of seven laser arrays arranged in a circular plate are investigated and discussed in detail.     

On the refractive index dispersions of ion-beam-synthesized β-FeSi2 layers

Continuous layers and precipitates of the β-FeSi₂ phase were formed by ion-beam synthesis followed by rapid thermal annealing. Two steps of Fe⁺ ion implantation in Si, at energies of 20 and 60 keV, were performed, using three different doses – 5×10¹⁵, 5×10¹⁶, and 10¹⁷ cm^?2. The infrared spectra were used as a criterion for the formation of the β-FeSi₂ phase. The refractive-index-energy dependences were calculated from the transmittance and reflectance spectra, using the general matrix method. From these dependences, the energy band gap and the energies of the higher-energy transitions in the vicinity of the gap were determined.     

Analysis of particle sizes, concentration, and refractive index in measurement of light transmittance in the forward-scattering-angle range

A simple method for determining the mean size, the concentration, and the refractive index of the monodispersion and the polydispersion of particles has been presented. The method is based on the empirical inversion of measurements of forward-angle light-scattering transmittance. The effects of particle size distribution and optical constants on forward-angle-scattering transmittance have been considered by using Mie theory. The proposed method has been used successfully for single latex spheres in water and polydispersed weakly absorbing particles of Al(2) O(3) and SiO(2) in the flow of the propane-air flame combustion products.     

Preparation of wide range refractive index diamond-like carbon films by means of plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition technology has been elaborated for obtaining diamond-like carbon (DLC) coatings of a wide range of properties. Alternative and direct bias voltages have been applied on the substrate, and refractive index dependencies upon various deposition technological parameters have been investigated. The frequency of the bias voltage has been varied in the region of 150-450 kHz. The maximum refractive index range that has been achieved is 1.46-3.2. Thin DLC films have been prepared on crystalline silicon substrates. Because of the wide range of physical, optical, and mechanical properties of the obtained films, they can successfully be applied in different fields of nano-optics.     

Anatase-brookite mixed phase nano TiO2 catalyzed homolytic decomposition of ammonium nitrate

Compared to the conventional ammonium perchlorate based solid rocket propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. Application of AN as propellant oxidizer is restricted due to low reactivity and low energetics besides its near room temperature polymorphic phase transition. In the present study, anatase-brookite mixed phase TiO₂ nanoparticles (∼10 nm) are synthesized and used as catalyst to enhance the reactivity of the environmental friendly propellant oxidizer ammonium nitrate. The activation energy required for the decomposition reactions, computed by differential and non-linear integral isoconversional methods are used to establish the catalytic activity. Presumably, the removal of NH₃ and H₂O, known inhibitors of ammonium nitrate decomposition reaction, due to the surface reactions on active surface of TiO₂ changes the decomposition pathway and thereby the reactivity.     

Determination of optical constants of scandium films in the 20-1000 eV range

The transmittance of thin films of Sc deposited by evaporation in ultrahigh vacuum conditions has been investigated in the 20-1000 eV spectral range. Transmittance measurements were performed in situ on Sc layers that were deposited over grids coated with a C support film. Transmittance measurements were used to obtain the extinction coefficient of Sc films at each individual photon energy investigated. These data, along with the data available in the literature for the rest of the spectrum, were used to obtain the refractive index of Sc by means of the Kramers-Kr?nig analysis. Sum-rule tests indicated an acceptable consistency of the data.     

Transmittance and optical constants of erbium films in the 3.25-1580 eV spectral range

The optical constants of erbium (Er) films were obtained in the 3.25-1580 eV range from transmittance measurements performed at room temperature. Thin films of Er were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Substrates consisted of a thin C film supported on a grid. Transmittance measurements were used to obtain the extinction coefficient k of the Er films. The refractive index n of Er was calculated using the Kramers-Kr?nig analysis. k data were extrapolated both on the high- and low-energy parts of the spectrum by using experimental data and calculated k values available in the literature. Er, similar to other lanthanides, has a low-absorption band below the O(2,3) edge onset; the smallest absorption was measured at ~22.5 eV. Therefore, Er is a promising material for filters and multilayer coatings in the energy range below the O(2,3) edge, in which materials typically have an absorption stronger than at other energies. Good consistency of the data resulted from the application of f and inertial sum rules.     

Luminescence dynamics of terbium monodipicolinate in ethyl ammonium nitrate

Energy level dynamics are experimentally examined for terbium monodipicolinate dissolved in ethyl ammonium nitrate (EAN). The luminescence lifetime, the luminescence risetime, and the absorption spectrum of terbium monodipicolinate in EAN are measured. The risetime of luminescence in terbium dipicolinate is experimentally shown to be nonzero and measurable. A dynamic model is presented that describes the evolution of terbium dipicolinate luminescence in EAN. The long risetime in the model is caused by a resonance between the 5E6 state in the terbium cation and the lowest triplet state (T1) in the dipicolinate anion. Bacterial endospore components dissolved in EAN are used to check the time resolution of the experimental apparatus. EAN is discussed partly because it is a room-temperature ionic liquid (RTIL), which is a class of solvents that may be useful for detecting bacterial endospores in the atmosphere.