Infrared Transmission Spectra Research Articles

Structure and nonvolatile holographic recording of Mg:Ce:Cu:LiNbO3 crystals

A series of Mg:Ce:Cu:LiNbO3 crystals has been grown by Czochralski method. Their infrared transmittance spectra and ultraviolet–visible absorption spectra were measured and discussed to investigate their defect structure. The nonvolatile holographic recording of Mg:Ce:Cu:LiNbO3 crystals was characterized by the two-photon fixed method. We found that the recording time of Mg:Ce:Cu:LiNbO3 crystals became shorter and nonvolatile diffraction efficiency decreases with the increase of Mg doping concentration, especially doping with Mg approaches and exceeds the so-called threshold. And the nonvolatility vanishes when the concentration of MgO exceeds 4mol%. The intrinsic and extrinsic defects were discussed to explain the nonvolatile holographic properties in the Mg:Ce:Cu:LiNbO3 crystals.

Coherent thermal radiation in thin films and its application in the emissivity design of multilayer films

The infrared transmission spectra of a 0.54-μm-thick Ge film and a 20-μm-thick Si film were experimentally measured. As the incident radiation was in the wavelength range from 1.5 μm to 10 μm, the Ge film demonstrated a strongly spectral coherence. However, thermal radiation of the Ge film was found to be spatially incoherent due to its extreme thinness. The Si film exhibited significantly spectral and spatial coherence. The results confirmed that thermal radiation of a monolayer film could be coherent spectrally and spatially if the film thickness was comparable with the wavelength. The optical characteristic matrix method was applied to calculate the transmission spectra of the Si and Ge film, and the results agreed well with the measurements. This method was further used to analyze two multilayer films composed of five low emissive layers. Their emissivities were found to be highly emissive at a certain zenith angle, and the emissive peak could be controlled by careful selection of film thickness.

Effects of Ge addition on the optical and electrical properties of eutectic Sb 70Te 30 films

The aim of this work is to study the influence of Ge addition on the optical and electrical properties in eutectic SbTe thin films (with the compositions: Sb 70Te 30, Ge 2Sb 70Te 28, Ge 5Sb 70Te 25 and Ge 10Sb 65Te 25) using visible optical reflectance, ellipsometry measurements, near infrared transmittance spectra, and four probe electrical resistivity measurements. From near infrared transmittance measurements the optical band gap was determined using Tauc’s expression for amorphous materials, a value of about 0.47 eV was obtained without any clear dependence on the Ge content. All amorphous films have approximately the same reflectance value, however the contrast ratio between the crystalline and amorphous phases decrease with increase of Ge. Using in situ four probe measurements versus temperature the dependence of the activation energy of conductance and the onset of the crystallization temperature have been determined for different materials. Four probe measurements have shown that the resistivity of amorphous films increases with increase of Ge. The results obtained have shown that optical and electrical properties of SbTe films with near eutectic composition change with the Ge content and depending on the application, in either optical or electrical memory devices, the most suitable composition needs to be determined.

Correlation between infrared transmission spectra and the interface trap density of SiO 2 films

This work is an attempt to estimate the electrical properties of SiO 2 thin films by recording and analyzing their infrared transmission spectra. In order to study a big variety of films having different infrared and electrical properties, we studied SiO 2 films prepared by low pressure chemical vapor deposition (LPCVD) from SiH 4 + O 2 mixtures at 425 °C and annealed at 750 °C and 950 °C for 30 min. In addition thermally grown gate quality SiO 2 films of similar thickness were studied in order to compare their infrared and electrical properties with the LPCVD oxides. It was found that all studied SiO 2 films have two groups of Si–O–Si bridges. The first group corresponds to bridges located in the bulk of the film and far away from the interfaces, the grain boundaries and defects and the second group corresponds to all other bridges located near the interfaces, the grain boundaries and defects. The relative population of the bulk over the boundary bridges was found equal to 0.60 for the LPCVD film after deposition and increased to 4.0 for the LPCVD films after annealing at 950 °C. Thermally grown SiO 2 films at 950 °C were found to have a relative population of Si–O–Si bridges equal to 3.9. The interface trap density of the LPCVD film after deposition was found equal to 5.47 × 10 12 eV −1 cm −2 and decreases to 6.50 × 10 10 eV −1 cm −2 after annealing at 950 °C for 30 min. The interface trap density of the thermally grown film was found equal to 1.27 × 10 11 eV −1 cm −2 showing that films with similar Si–O–Si bridge populations calculated from the FTIR analysis have similar interface trap densities.

INFLUENCE OF POST-TREATMENT ON OPTICAL PROPERTIES OF Sc:Ce:Cu:LiNbO3 CRYSTALS

The congruent Sc(3 mol%):Ce:Cu:LiNbO 3 single crystals were grown by the Czochralski method and three kinds of different samples were prepared by proper reduction or oxidation post-treatment processes. The extrinsic defect structures of samples were determined by infrared transmittance spectra. Two-wave coupling and light induced scattering experiments were used to measure the photorefractive properties. It is found that the reduction treatment made erasure time and diffraction efficiency decrease, but light-induced scattering resistance increase; the inverse case occurred with oxidation treatment. Analysis indicated that photoconductivity change was responsible for photorefractive properties.

Texture evolution and infrared optical properties of praseodymium fluoride films

Praseodymium fluoride (PrF3) thin films were deposited on Ge(111) and zinc selenide substrates by molybdenum boat evaporation method. The crystal structures of thin film were characterized using XRD technique and the texture coefficients were calculated. The texture of praseodymium fluoride films changes from (302) to (110) texture when the temperature increases from 100°C to 250°C. Drastic tensile stress makes all the films covered by a network of fine cracks with width of nanometer-scale. The infrared transmission spectrum was measured to investigate the optical properties for all the films. The optical constants of praseodymium fluoride film were determined by using Lorentz oscillator model in the range from 8000cm−1 to 500cm−1.

Growth and holographic storage properties of In:Ce:Cu:LiNbO 3 crystal

A series of In:Ce:Cu:LiNbO 3 crystals with different concentration of In 2O 3 were grown by the Czochralski method. The infrared transmission spectra and the photo-damage resistant ability of the crystals were measured. The OH − absorption peak of In(3 mol%):Ce:Cu:LiNbO 3 crystal shifts to ultraviolet. The photo-damage resistant ability of In(3 mol%):Ce:Cu:LiNbO 3 crystal is about two orders of magnitude higher than those of pure LiNbO 3 and Ce:Cu:LiNbO 3 crystals. The diffraction efficiency, response time of In:Ce:Cu:LiNbO 3 crystals were tested by two-wave coupling experiment. The response time of In(3 mol%):Ce:Cu:LiNbO 3 crystal only one fourth of that of Ce:Cu:LiNbO 3. The mechanism of OH − absorption peak shifting and photo-damage resistant ability enhancement were discussed.

Electromagnons in MultiferroicYMn2O5andTbMn2O5

Based on temperature dependent far infrared transmission spectra of YMn2O5 and TbMn2O5 single crystals, we report the observation of electric dipole-active magnetic excitations, or electromagnons, in these multiferroics. Electromagnons are found to be directly responsible for the step-like anomaly of the static dielectric constant at the commensurate--incommensurate magnetic transition and are the origin of the colossal magneto-dielectric effect reported in these multiferroics.

Visible and Near Infrared Spectroscopy for Rapid Analysis of the Sugar Composition of Raw Ume Juice

Visible and near infrared spectroscopy was investigated as a method for rapid analysis of the sugar compositions of raw ume juice. In total, 314 raw ume juice samples were collected over a long growth period and visible and near infrared transmittance spectra between 400 and 1850nm were acquired using a spectrophotometer with a quartz cuvette with 1-mm thickness. The partial least squares (PLS) calibration models for the total sugar content of ume fruit juice were developed using original spectra and pretreated spectra (normalization, first derivative, second derivative and multiplicative scatter correction) in five different wavelength ranges. The best models used the second derivative spectral data in the wavelength ranges of 1100-1850nm with the lowest standard error of prediction (0.133%). Moreover, good calibration models for sugar compositions (fructose, glucose, sorbitol, sucrose) of ume juice were obtained using the same second derivative spectral data in the wavelength range of 1100-1850nm, and gave relatively good predictions with high value of R2 and low value of SEP : fructose, 0.96 and 0.062% ; glucose, 0.94 and 0.068%, sucrose, 0.92 and 0.065%, sorbitol, 0.87 and 0.046, respectively. Results indicated that near infrared spectroscopy provided useful method to rapidly analyze the total sugar content and the sugar composition of raw Ume fruit juice.

A study on proton-exchanged and heat-treated LiNbO 3 crystals by means of Raman and infrared spectrum

A study on LiNbO 3 single-crystal samples obtained by different treatments has been performed by means of Raman and Infrared spectra. Raman scattering spectra show that some modes not only couple each other but also exchange intensities. Two characteristic absorption peaks at 2840 and 2920 cm −1 in Infrared transmission spectra have been found. The results may be attributed to the changes of LiNbO 3 microstructure and the coexistence of two possible phases formed by proton exchange and quick heat treatments, and to the existence of an internal strain induced by the nonuniform thermal expansion during the heat treatment process at high temperature.

The relation between crystal structure and infrared optical properties of ErF3 film

In this article, thermal evaporation technology was employed to deposit erbium fluoride films on germanium(111) substrates. XRD diffraction pattern shows that films turn from amorphous to crystalline with the increase of substrate temperature. Correspondingly, the morphology and infrared optical properties change obviously. The infrared transmission spectrum of the partially crystalline film is homologous to the totally amorphous film but not the crystalline films. Crystal lattice parameters calculation indicates that there is great compression thermal stress in the erbium fluoride film deposited at high deposition temperature. The refractive indices and extinction coefficients of the films were calculated by fitting the infrared transmission spectrum using Lorentz oscillator model. The refractive index and extinction coefficients at 10μm for the amorphous erbium fluoride film are n=1.38 and k=0.01, and for crystalline films are n=1.32 and k=0.006, respectively.

High quality factor Er3+-activated dielectric microcavity fabricated by rf sputtering

The authors report on one-dimensional dielectric photonic crystals activated by Er3+ ion and fabricated by rf-sputtering deposition. The cavity was constituted by an Er3+-doped SiO2 active layer inserted between two Bragg reflectors consisting of six pairs of SiO2∕TiO2 layers. Near infrared transmittance spectra evidence the presence of a stop band from 1350to1850nm and a cavity resonance centered at 1537nm. Intensity enhancement and narrowing of the I13∕24→I15∕24 emission band of Er3+ ion, due to the cavity effect, were observed. A cavity quality factor of 171 was achieved.

Self-modulation of infrared waves in rutile

Abstract Electromagnetic waves carry angular and linear momentums and exert torques on anisotropic dielectrics, arising from the fact of the tensor property of the dielectric constant, that is, the direction of electric displacement is not parallel to the electric field vector of the incident light. The torque per unit volume exerted on a wave plate is given by P × E , where P is the polarization and E is the electric field, which induces the rotations of eigenvibration direction in the crystals. The rotation angles increase with the intensity of the incident light and the dielectric constant of the crystals. Because of the large dielectric constants, self-modulation of the incident light in the infrared frequency region was clearly demonstrated in the infrared transmission spectra of ferroelectric and piezoelectric crystals. Rutile (TiO2) is a non-ferroelectric and non-piezoelectric crystal, but it also has the large dielectric constants. Rotations of the vibration direction of the ordinary (o-ray) and the extraordinary (e-ray) waves were shown in the infrared transmission spectra recorded by incidence of the plane-polarized light and transmission through a rutile plate. Interference of the o-ray and the e-ray waves transmitted through the crystals confirms the rotations of eigenvibration direction, a self-modulation effect of light in the crystal of large dielectric constants and large birefringence in the infrared range.

Proper Light Array Design for the Optimum Nondestructive Evaluation of Fruit’s Internal Quality

This study was conducted to develop an accurate quality evaluation system based on optimized factors such as light source array and light power, which are used in non-destructive fruit sorter to obtain the internal quality information of fruits using the near infrared transmittance spectra. It is necessary to provide the proper design guide for the light source part in the existing non-destructive fruit sorters for apples and pears, and to measure the real-time near infrared transmittance spectrum without the leakage of light. The near infrared transmittance spectrum detection system was developed with the light source part which has the power-controllable 12 halogen lamps (100W/12V) with gold coating, light detection part, and transfer line. By using the accurate control of the voltage and current (maximum power is 1.2kW) in light power control part, it is concluded that the minimum power for the internal quality evaluation of apples and pears was over 0.5 kW. To prevent the leakage of light, the array of light source was rearranged and tested. Without changing the tray structure, it is concluded that the leakage of light can be prevented by the proper array of light source and power. For the irradiation for the moving apples and pears, 2 upper lamps and 4 lower lamps combination did not have leakage of light and the correlation coefficient of this combination shows the 0.90 for apples and 0.96 for pears.

Thermal conductivity and infrared spectra study of polycrystalline La0.67Ca0.33MnO3

Abstract The thermal conductivity and infrared transmission spectra of La 0.67 Ca 0.33 MnO 3 are investigated systematically. The thermal conductivity increases abruptly as the temperature is decreased through the Curie temperature. The effective charge carriers number and the frequency of transverse optic phonon corresponding to the stretching mode also increase dramatically along with decreasing temperature near Curie temperature. Combining our observation with previous reported results, we ascribe the abrupt change of thermal conductivity to the itinerating of the charge carriers due to the remarkable reduction of Jahn–Teller distortion below the Curie temperature.

Spectroscopic properties of fluorophosphate glass with high Er3+ concentration

Fluorophosphate glass with 4 mol. % ErF3 content was prepared. The different scanning calorimetry was conducted. Raman spectrum, infrared transmission spectrum, absorption spectrum were measured. Fluorescence spectrum and lifetime of emission around 1.53 μm were measured under 970 nm laser diode excitation. The metaphosphate content in the composition is limited, but the maximum phonon energy of glass amounts to 1290 cm-1, and is comparatively high. The full width at half maximum is about 56 nm, and is wider than for most of the materials investigated. The measured lifetime of 4 I 13/2→4 I 15/2 transition, contributed by the high phonon energy, inefficient interaction of Er3+ ions, and low water content, amounts to no less than 7.36 ms though the Er3+ concentration is high. This work might provide useful information for the development of compact optical devices.

Origin of a localized vibrational mode in a GaSb substrate with a MBE-grown ZnTe epilayer

A localized vibrational mode (LVM) with a remarkable fine structure is observed in the infrared transmission spectrum of a ZnTe epilayer grown with molecular beam epitaxy (MBE) on a GaSb substrate. On the basis of the Zn and Te deposited on the GaSb substrate during the MBE growth of ZnTe, and assuming diffusion of Zn and Te into GaSb, the LVM is attributed to Zn, substitutionally replacing either the cation, Ga (ZnGa), or the anion, Sb (ZnSb). The frequency of the LVM and its fine structure can then be interpreted in terms of the infrared active modes of 64Zn substituting for Sb as an anti-site impurity and treating the centre as an XY4 quasimolecule. With X≡64Zn and Y≡69Ga and 71Ga, occupying the nearest-neighbour sites reflecting all the possible combinations and permutations as well as the natural isotopic abundance of Ga, the fine structure of the LVM can be accounted for quantitatively.

Optical and structural properties of copper oxide thin films grown by oxidation of metal layers

Copper oxide films were grown by oxidation of vacuum evaporated copper layers on silicon substrates. Oxidations were performed at atmospheric pressure, in a nitrogen–oxygen mixture 10% in oxygen and at temperatures varying between 185 and 450 °C. X-ray diffraction (XRD) patterns showed that, dependent on oxidation temperature, films were composed either of Cu2O at 225 °C, or of CuO above 350 °C. Films obtained at 185 °C were composed of copper silicide, formed near the interface with the substrate and Cu2O. At 280 °C films were composed of copper silicide, Cu2O and CuO. Fourier transform infrared transmittance spectra confirmed the results obtained from the XRD. The optical properties of films were studied with spectroscopic ellipsometry measurements within the energy range 1 to 3.5 eV. These measurements were analysed using the Tauc–Lorentz (TL) model to simulate the dispersion of the complex refractive index of disordered films. It was shown that the TL model describes satisfactorily the refractive index dispersion of these copper oxide films. The band gap, as defined by the TL model, was found equal to 2.3 eV for Cu2O and between 1.05 and 1.2 eV for CuO. It was shown that the gap of the Cu2O films was free of localized states, which was not the case for the gap of CuO.

Experimental and theoretical investigation of lattice defect structures in a series of Zn, Fe-doped nonstoichiometric lithium niobate

A series of the double doped lithium niobate (LiNbO 3, LN) single crystals had been grown by Czochralski method. The Curie temperatures of various concentrations doped or [Li]/[Nb] ratio LN crystals measured by differential thermal analysis (DTA) were discussed to investigate their defect structures with Safaryan et al. new approach about LN lattice defect structure using Curie temperatures calculated. Infrared transmission spectra of various concentrations doped were used to compare the investigation above. The results show that the lithium vacancy model is the more probable to describe the lattice defect structure of the doped LN single crystal.

Simulations of the accuracy in retrieving stratospheric aerosol effective radius, composition, and loading from infrared spectral transmission measurements

We examine the extent to which three physical aerosol parameters--effective radius, composition (sulfate weight percent), and total volume-can be determined from infrared transmission spectra. Using simulated transmission data over the range 800-4750 cm(-1) (12.5-2.1 microm) and errors taken from the infrared spectral measurements of the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument, we use optimal estimation to recover these aerosol parameters. Uncertainties in these are examined as a function of the size, composition, and loading of stratospheric aerosols and of the spectral range employed. Using the entire spectral range above, we retrieve all three parameters with a precision to within 3% if the size distribution form is known. Additional errors result, however, from an uncertainty in the size distribution width. These are small (only a few percent) for composition and total volume but are substantial (as much as 50%) for effective radius. Errors also increase substantially when the spectral range is reduced. The retrieved effective radius can have an error of 100% or greater for typical stratospheric aerosol sizes when the spectral range is restricted to the lower wavenumber part of the range. For good accuracy in effective radius, the spectral range must extend beyond approximately 3000 cm(-1). Composition and total volume are less sensitive to the spectral range than effective radius. These simulations were carried out with modeled data to test the potential accuracy of stratospheric sulfate aerosol retrievals from the Atmospheric Chemistry Experiment (ACE). Because of the limitations that result from the use of simulated data, we have tested our retrieval algorithm using ATMOS spectra in different filter regions and present here the aerosol parameters obtained.