Complex Optical Index Research Articles

Temperature effect (300–1500 K) on the infrared photon transport inside an X-ray microtomographic reconstructed porous silica glass

A Monte Carlo Ray Tracing program has been developed to predict the thermal radiative properties of an X-ray microtomographic reconstructed silica glass containing gas bubbles, for a large domain of wavelength (1–25 μm) and for a large domain of temperature (300–1500 K). The main input of the program is the complex optical index of the corresponding homogeneous silica glass. Validity of the model is checked by comparing a simulated normal spectral emittance, obtained on the reconstructed glass, with the experimental one recorded at T = 1300 K .

Study of strong coupling between surface plasmon and exciton in an organic semiconductor

In this paper the optical properties of thin films comprising J-aggregated dyes (TDBC) in a polymeric matrix (PVA) deposited on a metallic (silver) layer are studied. Angular reflectometry experiments are conducted in order to obtain the dispersion energy curve of the Surface Plasmon (SP) in relation with the exciton mode. It exhibits an anticrossing behavior characteristic of the strong coupling regime. Simulations using a transfer matrix method with complex optical indices are applied and discussed. They show a roughly good agreement with the experimental results and allow us to estimate the value of the oscillator strength of organic J-aggregate semi conductors used in our experimental studies.

Dielectric characterization of [Fe(NH2−trz)3]Br2•H2O thermal spin crossover compound by terahertz time domain spectroscopy

The complex optical index refraction of an iron (II) spin-crossover coordination polymer is measured in the Terahertz frequency range by Terahertz time-domain spectroscopy (THz-TDS). By scanning the temperature from 288 to 333 K, we have recorded the evolution of the THz spectrum within the low spin - high spin thermal hysteresis loop. We were able to simultaneously infer the refractive index and absorption variations. The low spin-high spin transition has a marked spectral signature in the millimeter wavelength. In the 0.1–0.6 THz frequency range, the variation of real and imaginary part of the index of refraction is 6% and 20%, respectively. A marked absorption is observed above 500 GHz. The THz-TDS provides a clear direct fingerprint of this class of materials, which are interestingly potential candidates for optical data storage and processing devices.

Propagation characteristics of single-mode optical fibers with arbitrary complex index profiles

A rapidly converging numerical technique for the evaluation mode characteristics of circularly symmetric optical fibers with an arbitrary complex refractive index profile is presented. This method is based on transmission-line principles. From Maxwell's equations, we derive a transmission-line equivalent circuit for the optical fiber refractive index profile and we demonstrate how it can be used to determine the mode effective index (normalized propagation constant) of cylindrical dielectric waveguides. To illustrate the effectiveness of the procedure, we have applied it to circularly symmetric fibers with complex step, parabolic, and segmented optical refractive index profiles. We have used this method to evaluate and manipulate the gain in a typical 980-nm pumped erbium-doped fiber as well as for calculating attenuation of optical fibers when radial loss factors are present.

Large optical Kerr effect in matrix-embedded metal nanoparticles

We report an experimental and theoretical study on the third-order nonlinear optical properties of gold particles embedded in a dielectric host. Thin films of various metal concentrations are elaborated by the sputtering technique. Several complementary techniques provide information about the metal concentration, the film thickness and the size of the particles. The effective complex optical index of the film is determined by spectrophotometry and ellipsometry. The third-order nonlinear susceptibility, χ (3), is measured using the z-scan technique in the nanosecond regime. Experimental results reveal very large nonlinearities, increasing with the metal concentration. Theoretical calculations of the amplification factor, based on a recursive transfer method, allow a better understanding of these results.

Optical Refractive Index and Thermal Coefficient Measurements of Yb-Doped Laser Glass with White Light Interferometer.

Optical refractive index of Yb-doped laser glass was measured with white light interferometer in which output beam was dispersed using a monochromater. The measured fringe spectrum was analyzed with compensating the amplitude modulation by the absorption. The estimated complex optical refractive index is better than 2×10-4 accuracy in absolute value and better than 2×10-5 in relative value in the wavelength range between 550 nm and 1160 nm. The feature of the anomalous dispersion due to Yb doped ion was clarified, quantitatively. This analysis denoted that in the case of Yb doped system, the contribution of the doped ions becomes dominant in the higher-order dispersion of refractive index. Thermal coefficient of this laser glass was also estimated from temperature dependence of refractive index from 293 K to 373 K. It was concluded that the excellent thermal stability of this laser glass was supported from the balance between negative thermo-optical coefficient and positive thermal expansion.

Optical properties of nickel thin films deposited by electroless plating

A nickel thin film is deposited onto a float glass substrate by means of an autocatalytic reducing reaction in a metallizing solution. The growth of this film is monitored in situ using an ellipsometer. By analysing the ellipsometric measurements, the changes in the complex optical index and the thickness of the film over time can be determined. A comparison of the complex optical index obtained from analysis of the experimental results and those predicted by various effective medium theories indicates that the Maxwell-Garnett theory is the best for modelling the optical properties of the nickel layer.

Electronic structure characterization of ion beam modified polyimide by optical absorption and reflection

Optical absorption and specular reflection spectrophotometries have been used to determine the optical constants of PMDA-ODA polyimide films irradiated with 2 MeV Kr + at different increasing ion fluences. The optical data are discussed in terms of interband transitions. The real and imaginary part of the complex optical index are calculated as a function of the wavelength in the energy range 500–2500 nm. Their comparison with the optical index of diamond and graphite shows diamondlike properties of the irradiated film at low fluences whereas graphitelike properties appear at the insulator-metal transition in correlation with the bandgap closing.

Stratified media theory interpretation of measurements of the spectral polarized directional emissivity of some oxidized metals

The emissivities of metals are strongly affected by the growth of oxide films. For small film thicknesses, perturbations are limited to the visible range. As thicknesses increase, they spread to the infrared range. Various samples of optically polished metals (Fe, Ni, Cr) and stainless steels (ELI.T 1803 MoT and AISI 304 or 316) have been oxidized at temperatures ranging from 400 to 800‡C. Their spectral polarized directional emissivities, e′λ‖ and e′λ⊥, have been measured with two experimental techniques. The spectral range studied extends from 0.4 to 14 Μm; the measurement directions vary between 0 and 80‡ from the normal to the sample. After measurement, each sample was analyzed by glowdischarge optical spectroscopy (GDOS). From the results of the analysis and from the survey of bibliographical data, we characterized the structure of the oxide films, i.e., their approximate thicknesses and compositions. If the complex optical indices of the metals and oxides are known, the stratified media theory enables the computation of the emissivities e′λ‖ and e′λ⊥. Computed and measured values have been compared. It appears that the theory accounts well for experimental data when the thicknesses of the oxides are small as in stainless steels. But for thicker oxide films, discrepancies are ascribed to several reasons.

Optical Properties Of Tellurium Films Used For Data Recording

The complex optical index of refraction for evaporated films of tellurium has been measured using ellipsometry over the wavelength range 439 to 633 nm. Values of n and k as a function of wavelength and as a function of thickness are presented. The transmittance and reflectance of single layers of tellurium, as well as multilayer structures to be used for optical data recording media, are shown as a function of wavelength. Oxide formation of these films has also been measured, and a model for the role of oxides in altering adhesion of the films is presented.