Values Of Complex Refractive Index Research Articles

Methodologies for determining thermoplastic films optical parameters at 10.6 μm laser wavelength

A set of simple methodologies is presented so that optical parameters relevant to 10.6 μm CO 2 laser radiation processing of thermoplastics films are obtained. These methodologies are applied to transparent and white polyethylene and transparent polypropylene samples, with thicknesses between 10 and 800 μm. Optical parameters like transmittance, reflectance and absorptance are measured directly with two simple experimental apparatus. With these values, two methodologies are developed in order to obtain the attenuation coefficients. One of the methods relies on curve fitting and shows low uncertainty. The other, based on calculations derived from the Beer–Lambert law, presents dependency on experimental errors for samples with lower thickness, needing further calculation in order to minimize it. The attenuation length and the complex refractive index values are also determined. The resulting data demonstrate the high transparency of thermoplastic samples to 10.6 μm radiation for thicknesses lower than 200 μm, which is significant information for modelling thermoplastics laser processing.

A theoretical investigation of the influence of optical constants and particle size on the radiative properties and heat transfer involving ash clouds and deposits

This paper presents an analysis of the influence of optical constants and particle size on the radiative properties and heat transfer involving ash clouds and deposits. Previous reported studies are mostly based on grey values of complex refractive index, which fails to reflect the true nature of the ash cloud and ash deposits. The analysis indicates that for radiative heat transfer calculations, information on size distribution of the ash cloud and wall emittance are more important than the radiative properties of ash cloud. For prediction of emittance of an opaque particulate ash deposit, careful estimation of absorption index is more important than the real index, which may be taken to be constant at 1.5, unless the deposit material is weakly absorbing and composed of fine particles. In such cases knowledge of spectral values of both real and absorption index appears to be necessary.

光散乱測定による,大気中および海洋中の浮遊粒子の複素屈折率と粒径分布の同時決定

To estimate the complex refractive indices and the size distributions of aerosols and hydrosols from light scattering measurements, we present a data processing technique using both inversion and library methods. Extensive numerical simulations have shown that the true values of complex refractive index and size distribution are retrieved fairly well when this method is applied to measurements of polarization components of scattered radiation parallel and perpendicular to the scattering plane.

Extinction cross-section measurements on single falling water drops at 100 GHz

An open resonator with 100 GHz source is used to determine the extinction cross-section of water drops falling freely through the atmosphere. Results show a very close agreement with the theoretical values computed using classical Mie scattering theory and values of complex refractive index from an empirical model.