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We investigate the systematic errors at the second order for a Mueller matrix ellipsometer in the dual rotating compensator configuration. Starting from a general formalism, we derive explicit second-order errors in the Mueller matrix coefficients of a given sample. We present the errors caused by the azimuthal inaccuracy of the optical components and their influences on the measurements. We demonstrate that the methods based on four-zone or two-zone averaging measurement are effective to vanish the errors due to the compensators. For the other elements, it is shown that the systematic errors at the second order can be canceled only for some coefficients of the Mueller matrix. The calibration step for the analyzer and the polarizer is developed. This important step is necessary to avoid the azimuthal inaccuracy in such elements. Numerical simulations and experimental measurements are presented and discussed. [c] 2010 Optical Society of America OCIS codes: 120.2130, 120.3940.

We present a spectroscopic, autocollimating ellipsometer capable of operating at arbitrary angles of incidence. Linearly polarized light incident on a sample is circularly polarized on reflection, ensuring that the retroreflected beam is orthogonal to the input polarization state. In order to achieve this at arbitrary angles of incidence, a Soleil--Babinet compensator (SBC) is introduced with its fast axis fixed horizontally. Nulling is achieved by varying the SBC delay and the azimuthal angle of the input linear polarization. A single calibration equation at a fixed wavelength and a knowledge of the wavelength dependence of the compensator birefringence enables the delay to be accurately calculated at any wavelength. Single-wavelength, variable angle of incidence measurements made on a thick gold film are in excellent agreement with those obtained with a traditional null ellipsometer. Spectroscopic measurements at a fixed angle of incidence of a silicon dioxide film on a silicon substrate yield thicknesses that are in excellent agreement with independent measurements made with a null ellipsometer and a commercial instrument. OCIS codes: 120.2130, 120.3940.

To apply reflection ellipsometry to determine the real and imaginary parts of the refractive index of biological tissues simultaneously, we combine reflection ellipsometry with total internal reflection to warrant minimal influences by the strong scattering and absorption of biological tissues. A K9 glass prism with refractive index 1.51468 at wavelength 632.8 nm and a Glan prism polarizer with an angular sampling interval of 0.1[degrees] were used in our experimental setup. Using the setup, the complex refractive indices of some typical mammalian tissues were measured under the wavelength of 632.8 nm. The results show that the indices of porcine muscle, liver, pancreas, and dermis tissues were 1.3713 + 0.062i, 1.3791 + 0.0087i, 1.3517 + 0.0113i, and 1.3818 + 0.0049i, respectively. OCIS codes: 120.3890, 170.0170, 170.3890.

The optical properties of AgGa[Te.sub.2] chalcopyrite semiconductor are studied by optical absorption, spectroscopic ellipsometry (SE), and thermoreflectance (TR) spectroscopy. Optical absorption spectra suggest that AgGa[Te.sub.2] is a direct-gap semiconductor having a bandgap of ~ 1.2 eV at T = 300 K. The pseudodielectric- function spectra of AgGa[Te.sub.2] are determined by SE in the range between E = 1.2 and 5.2 eV for both states of polarization. These spectra reveal distinct structures at energies of the critical points in the Brillouin zone. The TR spectra are also measured in the E = 1.0-5.3 eV ranges at T = 20 K-300 K. The spin--orbit and crystal-field splitting parameters of AgGa[Te.sub.2] are determined to be [[DELTA].sub.so] - 0.70 eV and [[DELTA].sub.cr] = -0.23 eV, respectively. OCIS codes: 160.4760, 300.6470.

The application of nonlinear optical Stokes ellipsometry (NOSE) coupled with principal component analysis (PCA) is demonstrated for the chemically selective analysis of molecular monolayers. NOSE allows for rapid polarization measurements of nonlinear optical materials and thin surface films, which in turn benefits from comparably fast data analysis approaches. PCA combined with linear curve fitting techniques greatly reduce the analysis time relative to nonlinear curve fitting. NOSE-PCA is first validated with studies of z-cut quartz, followed by analysis of four thin dye films with similar nonlinear optical properties. The high precision of NOSE measurements combined with the rapid analysis time enabled chemical discrimination between different dyes and the practical realization of NOSE microscopy. 10.1021/ac901832u

A new approach to automatic null ellipsometry is described in which the analyzer of a traditional polarizer compensator sample analyzer (PCSA) null ellipsometer is replaced with a heterodyne Michelson interferometer. One arm of this interferometer is modified such that it produces a fixed, linearly polarized reference beam, irrespective of the input polarization state. This beam is recombined interferometrically with the measurement beam and spatially separated into its p and s polarizations. The relative phase of the resulting temporal fringes is a linear function of the polarizer azimuthal angle P, and thus this component can be driven to its null position without iteration. Once at null, the azimuthal angle of the reflected, linearly polarized light is trivially determined from the relative amplitude of the fringes. Measurements made with this instrument on a native oxide film on a silicon wafer were in excellent agreement with those made with a traditional PCSA null ellipsometer. OCIS codes: 120.0120, 120.2130, 120.3180, 120.3930.

The reflection of s-and p-polarized electromagnetic plane waves from an anisotropic ultrathin dielectric film on transparent isotropic substrate is investigated in the long-wavelength limit. The analytical approximate formulas are obtained for the reflection coefficients and ellipsometric angles that agree with the exact computer solution of the reflection problem for anisotropic systems. The possibilities of using the obtained expressions for resolving the inverse problem for ultrathin anisotropic dielectric films upon isotropic dielectric substrates are discussed. It is shown that a promising technique for determining the optical constants of anisotropic dielectric films on transparent substrates is the integration of ellipsometry and differential reflectivity. OCIS codes: 260.2110, 240.0310, 310.6860, 260.2130, 120.4530.

A rigorous, much simplified, and accurate analysis of the modal field characteristics such as propagation constants, mode power confinement, delay and dispersion characteristics of a single-mode graded-index elliptical core fiber is presented applying a variational method and super-Gaussian approximation of the fundamental modal field. Normalized propagation constants, a fundamental parameter to evaluate other modal characteristics, obtained through this method showed a greater accuracy over the entire range of practical interest in comparison with other reported methods. The effects of various aspect ratios on these characteristics are analyzed. In addition, the effect of Kerr nonlinearity on these characteristics is investigated using the reported method, and a comparison is made with the linear results. OCIS codes: 060.2310, 060.2270, 060.2400.

Ellipsometry is an optical technique that is widely used for determining optical and geometrical properties of optical thin films. These properties are in general extracted from the ellipsometric measurement by solving an inverse problem. Classical methods like the Levenberg--Marquardt algorithm are generally too long, depending on direct calculation and are very sensitive to local minima. In this way, the neural network has proved to be an efficient tool for solving these kinds of problems in a very short time. Indeed, it is rapid and less sensitive to local minima than the classical inversion method. We suggest a complete neural ellipsometric characterization method for determining the index dispersion law and the thickness of a simple Si[O.sub.2] or photoresist thin layer on Si, Si[O.sub.2], and BK7 substrates. The influence of the training couples on the artificial neural network performance is also discussed. OCIS codes: 120.2130, 200.4260.

The two independent components of the gyration tensor of quartz, [g.sub.11] and [g.sub.33], have been spectroscopically measured using a transmission two-modulator generalized ellipsometer. The method is used to determine the optical activity in crystals in directions other than the optic axis, where the linear birefringence is much larger than the optical activity. OCIS codes: 260.1180, 260.1440, 160.1585, 240.2130.

Silicon nanotips fabricated by electron cyclotron resonance plasma etching of silicon wafers are studied by spectroscopic ellipsometry. The structure of the nanotips is composed of columns 100-140 nm wide and spaced by about 200 nm. Ellipsometry data covering a wide spectral range from the midinfrared to the visible are described by modeling the nanotip layer as a graded uniaxial film using the Bruggeman effective medium approximation. The ellipsometry data in the infrared range reveal two absorption bands at 754 and 955 cm-1, which cannot be resolved with transmittance measurements. These bands indicate that the etching process is accompanied with formation of carbonaceous SiC and CHn species that largely modify the composition of the original crystalline silicon material affecting the optical response of the nanotips. OCIS codes: 120.2130, 160.1245, 260.2065, 310.3840.

To be compared with the wavelength modulation technique for measuring two-dimensional (2D) cell parameters of a twisted nematic liquid crystal (TN-LC), we propose an amplitude-sensitive heterodyne ellipsometer (ASHE) of a single wavelength that is able to characterize TN-LC in 2D quantitatively. A quarter-wave plate (QWP) is rotated continuously in this setup to modulate the polarization state of the incident laser beam to obtain the amplitude ratio of the S and P waves versus the rotation angle of the QWP. Thus the cell parameters, including the twisted angle [PHI], untwisted phase retardation [GAMMA], rubbing direction angle [alpha], and cell gap d, of a TN-LC cell are obtained simultaneously by best fitting the detected amplitude ratio with a prediction based on the transfer matrix of TN-LC cell. 2D distributions of ([PHI], [GAMMA]. [alpha], d) are then obtained either by scanning the TN-LC cell or by using a CCD camera for high-speed measurement. In this experiment, the stability of the amplitude-ratio measurement of the proposed ASHE was 0.5%. The goal is to integrate the rotating elliptical wave plate with the TN-LC cell in a heterodyne ellipsometer to obtain cell parameters at amplitude sensitivity. This increases not only the sensitivity of the measurement but also the possibility of extending the 2D distribution of cell parameters in real time. OCIS codes: 120.3180, 120.2130, 040.2840.

We have investigated the interaction of D-amino acid oxidase (DAAO) with single-walled carbon nanotubes (CNT) by spectroscopic ellipsometry. Dynamic adsorption experiments were performed at different experimental conditions. In addition, the activity of the enzyme adsorbed at different conditions was studied. Our results indicate that DAAO can be adsorbed to CNT at different pH values and concentrations by a combination of hydrophobic and electrostatic interactions. Considering that the highest enzymatic activity was obtained by adsorbing the protein at pH 5.7 and 0.1 mg x [mL.sup.-1], our results indicate that DAAO can adopt multiple orientations on the surface, which are ultimately responsible for significant differences in catalytic activity.

We introduce single angle-of-incidence (SAI) ellipsometry [U.S. patent application 20070024850 (14 July 2006)] as a technique to completely identify, i.e., totally characterize, film--substrate systems. We show that only one measurement of the ellipsometric function [rho] at one angle of incidence and one wavelength is totally sufficient to determine the optical constant of the film [N.sub.1], its thickness d, and the substrate's optical constant [N.sub.2]. Obviously, it is also sufficient for characterizing only the film, determining [N.sub.1] and d, and for characterizing only the substrate, determining [N.sub.2] and d, as well as for characterizing only bare substrates. An inverse genetic algorithm (IGA) for complete identification is presented that is based on a physical condition of the transparent-film--absorbing-substrate system. This IGA is used to identify the film--substrate system in four separate cases. We show that removing the film thickness from the fitness function of the genetic algorithm and using the defined optimum population size to characterize the film reduces the computational effort from 20,000 to 69 fitness-function calculations; the number of calculations to characterize an absorbing layer is reduced from 80,000 to 180. This is a very significant reduction and is very welcome in real-time applications. An error analysis is presented that shows that the IGA is resilient to, not affected by, random experimental errors and that it gives very good results in the presence of both random and systematic errors of the ellipsometer system. Experimental results are given that also prove the robustness, stability, and high accuracy of the method. We present data only for the Si[O.sub.2]--Si film--substrate system, but the IGA works for any film--substrate system, physical or not. OCIS codes: 120.2130, 310.6860.

The French Laser Megajoule (LMJ) is designed and constructed by the French Commissariat a l'Energie Atomique (CEA). Its amplifying section needs highly reflective multilayer mirrors for the flash lamps. To monitor and improve the coating process, the reflectors have to be characterized to high accuracy. The described spectrophotometer is designed to measure normal specular reflectance with high repeatability by using a small spot size of 100 [micro]m. Results are compared with ellipsometric measurements. The instrument can also perform spatial characterization to detect coating nonuniformity. OCIS codes: 120.1840, 120.3930, 120.3940, 120.5700.

A procedure is described to allow selective cancellation of polarized scattering within optical substrates and multilayers. It is shown how bulk scattering (respectively surface) can be directly eliminated while the remaining roughness (respectively bulk) signal is still measurable. The same procedure can be applied to isolate a single interface or bulk within a stack or to detect slight departure from perfect correlation within multilayers. Experiments and a procedure for selective imaging in random media are described. OCIS codes: 110.0110, 110.7050, 120.0120, 120.5820.

Sequential surface plasmon resonance imaging (SPRI) and imaging ellipsometry (IE) measurements are realized with a single set of optical components mounted on a goniometer. The sample situated on top of a triangular prism is positioned in the center of the goniometer. The resultant setup (SPRI/IE) can be used to examine the same surface region above (IE) and below (SPRI) the sample. Thickness values of silver stripes sputtered onto a gold substrate were determined by SPRI and IE, and the results were compared to establish the validity of the method. The SPRI/IE setup was also used to monitor the thickness of phospholipid films of different layer numbers. SPRI measurements were found to be more accurate for ultrathin films, whereas the IE results are more reliable for films whose thicknesses approach or exceed the distance encompassed by the evanescent wave of the surface plasmon. Thus, utilizing these two techniques sequentially facilitates the continuous monitoring of film thickness variation over a wide thickness range with high fidelity and provides a viable approach to image the surface regions with large topographic fluctuations.

The polarization-dependent transmission of a basic anisotropic feedback system (Fabry-Perot resonator) is mathematically modeled by means of the Jones-matrix formalism. Detailed numerical simulations of the resonance case are performed. Small phase anisotropies as well as small polarization-dependent losses of the resonator components can be extremely amplified by resonant feedback. The amplification factors depend on the magnitudes of amplitude and phase anisotropy and their mutual interactions as well as on the polarization-independent system parameters (forward transmission, system feedback). However, for higher phase anisotropies, saturation effects occur and, therefore, the anisotropy amplification factors decrease. Our experimental investigations applying anisotropic Fabry-Perot resonators in different ellipsometer systems confirm the predicted amplification of phase and loss anisotropies in resonance operation. OCIS codes: 120.2130, 120.2230, 140.4780, 260.2130, 260.5430, 260.5740.

Variable angle spectroscopic ellipsometry is used as a tool to characterize properties such as optical constant, thickness, refractive index depth profile, and pore volume fraction of single and bilayer porous low-k films. Further analyses show that this nondestructive measurement tool could be used to characterize single-and multigraded layer porous films quickly and effectively.

Nonlinear optical null ellipsometry (NONE) measurements of chiral interfaces allowed direct experimental measurement of the linear interracial optical constants in surface second harmonic generation (SHG) measurements. Since phase information is retained in NONE measurements, the real and imaginary components of the interfacial refractive index (n and k, respectively) were uniquely obtained from the measured chiral [chisquare] tensor elements of a fluorescein-labeled bovine serum albumin film. The sensitivity of the calculated [chisquare] tensor elements on the assumed values of the interfacial optical constants allowed measurements of n and k to four significant figures with no additional adjustable parameters and independent of molecular symmetry. The optical constants measured by SHG agreed within a relative error of 0.8% with values predicted independently using a simple effective medium approximation, also with no adjustable parameters. Additionally, those same optical constants produced relationships between the achiral [chisquare] tensor elements in excellent agreement with predictions for systems exhibiting weak orientational order. This study suggests that the far-field intensity and polarization state of the nonlinear optical beam may be largely independent of the near-field optical constants within the interfacial layer in the limit of a film thickness much less than the wavelength of light.

Spectroscopic ellipsometry is used to study GaN films during growth by metalorganic vapor phase epitaxy (MOVPE) in correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). It is concluded that under normal growth conditions in MOVPE in contrast to PAMBE the surface is not terminated by a Ga bilayer.

A detailed study of the near dc magnetization reversal mode in a Co thin film with in-plane uniaxial anisotropy is presented, using generalized magneto-optical ellipsometry. The critical angular-jump fields, as determined from a coherent rotation model, were adequately described by a single anisotropy constant.