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A new technique for determining the optical properties of organic thin films is presented. A detailed evaluation of the accuracy of the determined optical constants has been performed, and the best combination of measured values yielding the smallest errors in the index of refraction for realistic experimental uncertainties has been found. The proposed method utilizes the fact that optical constants are smooth continuous functions, which reduces the possibility of encountering multiple solutions. The method consists of two steps. In the first step the optical constants at all wavelengths and the film thickness are determined. In the second step the thickness and the imaginary part of the index of refraction are kept fixed while we reevaluate the real part of the index of refraction by using a different objective function with improved sensitivity to the refractive index. After verifying that the proposed method is capable of an accurate estimation of optical constants, we determine the index of refraction data of vanadyl-phthalocyanine in the visible spectral range.

The optical properties of diamonds are modeled over a wide spectral range with the modified Adachi's model. Model parameters were estimated by use of the acceptance-probability-controlled simulated annealing algorithm. The employed model is quite flexible, as it uses an adjustable broadening function at each critical point. The broadening function can vary over a range of functions with similar kernels but different wings, so that extended absorption tails inherent to the conventional Lorentzian broadening can be eliminated. Good agreement with the experimental data is obtained in the entire investigated range. The obtained relative rms error for the real part of the index of refraction equals 4.7%, whereas for the imaginary part of the index-of-refraction relative rms error is 3.6%.

A modification of the Lorentz oscillator model for optical constants is proposed in an effort to achieve better agreement with experimental data while keeping the calculation simple. Improvement in agreement between theoretical and experimental data obtained with a variable line shape (frequency-dependent damping constant) over a wide spectral range is demonstrated through modeling the index of refraction of Si(3)N(4) (1-24 eV), SiO (0.15-25 eV) and amorphous and crystalline SiO(2) (0.15-25 eV). Model parameters are estimated by acceptance-probability-controlled simulated annealing. Excellent agreement between the modified model and the experimental data is obtained for both real and imaginary parts of the index of refraction.

A paraboliclike quantum well structure can be used to produce polarization-insensitive waveguide type modulators. We propose the use of interdiffusion of AlGaAs/GaAs quantum wells to achieve the parabolic well shape. Criteria to achieve the paraboliclike quantum wells by interdiffusion are discussed. The theoretical results indicate that interdiffused quantum wells can produce equal eigenstate spacing, polarization insensitive Stark shifts, and modulation similar to an ideal parabolic quantum well. Three procedures are also proposed to develop polarization-insensitive on and off states in paraboliclike interdiffused quantum wells. The modulation depth is compatible with that of the measured parabolic quantum wells. For diffused quantum wells one can take advantage of using an as-grown rectangular quantum well with postgrowth thermal processing. These features demonstrate that an interdiffused quantum well structure can be used to produce a polarization-insensitive electroabsorptive modulator.