The backscattering signal at small grazing angles is very important for vehicle re-entrance and missile tracking applications. It is also useful in FTIR grazing angle microscopy. Recently, we performed an experimental study of the far-field scattering at small grazing angles, especially the enhanced backscattering at grazing angles. For a randomly weak rough dielectric film on a reflecting metal substrate, a much larger enhanced backscattering peak is measured.

Recently a physical medium was fabricated in which both the effective permittivity ε(ω) and the effective permeability μ(ω) are simultaneously negative over a restricted frequency range. Thus, in this frequency range, such a medium is left--handed, and is characterized by a negative refractive index. A left--handed medium should exhibit unusual phenomena associated with the propagation and scattering of electromagnetic waves. In our paper we study the scattering of p- and s-polarized electromagnetic waves from a weakly rough one--dimensional random surface of a left--handed medium. We assume that the surface profile function is a single-valued function of the coordinate in the mean plane of the surface that is normal to its grooves and ridges, and constitutes a zero-mean, stationary, Gaussian random process. We show that in contrast to nonmagnetic media with a negative dielectric function, the planar surface of a left--handed medium can support both p- and s-polarized surface electromagnetic waves. The reflectivity of such a surface as a function of the angle of incidence displays structure associated with the existence of a Brewster angle in both polarizations and the existence of a critical angle for total internal reflection in both polarizations. The angular distribution of the intensity of the light that has been scattered incoherently displays an enhanced backscattering peak, and Yoneda bands, for both polarizations of the incident light.

The phenomenon of enhanced backscattering in the scattering of light from a randomly rough surface is the presence of a well-defined peak in the retroreflection direction in the angular dependence of the intensity of the light scattered diffusely from the surface. A striking feature of this phenomenon is that it occurs for any angle of incidence. Suppose, however, that one would like to have a random surface that displays enhanced backscattering for only a single, specified, angle of incidence. Such a surface could be useful, for example, in situations where one wishes to position a source (and hence the detector) at a specified direction with respect to the site at which the scattering surface is situated. In this paper we show how a one-dimensional random surface can be generated that produces an enhanced backscattering peak for only a specified angle of incidence when illuminated by p-polarized light whose plane of incidence is perpendicular to the generators of the surface. This surface is defined by a power spectrum (the Fourier transform of the surface height autocorrelation function) given by g(Q) = (π)/(4(Δ)k)[θ (Q-k₁+Δk)θ(k₁+Δk-Q)+θ(Q-k₂+Δk-Q)θ (k₂+Δk-Q)+θ(-Q-k₁+Δk)θ (k₁+Δk+Q)+θ(-Q-k₂+Δk)θ (k₂+Δk+Q)], where θ(z) is the Heaviside unit step function, k₁= k_R-k₀,k₂=k_R-k_{0, k(subscript R} is the real part of the wavenumber of the surface plasmon polariton of frequency ω supported by the planar vacuum-metal interface, and k₀ is related to the angle of incidence measured clockwise from the x₃-axis by k₀=(ω/c)sinθ₀. An explanation is provided for why a surface defined by this power spectrum produces enhanced backscattering at only the angle of incidence given by θ_s=-θ₀, and it is confirmed by numerical calculations of the angular dependence of the intensity of the light scattered diffusely from it.

In a recent theoretical study of the scattering of a surface plasmon polariton by a circularly symmetric protuberance or indentation on an otherwise planar metal surface in contact with vacuum, it was found that the angular dependence of the intensity of the volume electromagnetic waves scattered into the vacuum region possesses a maximum in the plane of incidence at a polar scattering angle of approximately 28 degree(s). This suggests that if a p-polarized volume electromagnetic field in the form of a beam of finite width is incident on the same surface defect, the efficiency of exciting a surface plasmon polariton will be greatest for a polar angle of incidence close to 28 degree(s). To test this hypothesis, in this paper we study this problem theoretically. The reduced Rayleigh equations for the amplitudes of the p- and s-polarized components of the scattered field are reduced to a set of one-dimensional integral equations by exploiting the circular symmetry of the surface defect, which is assumed to have a Gaussian form. The efficiency of exciting surface plasmon polaritons in this fashion is calculated as a function of the polar angle of incidence, and is found to be maximal when this angle is close to 28 degree(s).

Following our previous study of inverse scattering with one-dimensional perfectly conducting surfaces, we consider the applicability of the proposed inverse scattering algorithm to the case of surfaces of more general materials. In particular, results corresponding to glass and silver surfaces are presented. The algorithm, based on wavefront matching principles, is used to reconstruct one-dimensional surface profiles from far-field amplitude scattering data calculated using rigorous techniques. The study is complemented by considerations of the tolerance of the algorithm to noise in the data.

A phase-shifting interference microscope based on the integrating-bucket technique with sinusoidal phase modulation is used to characterize metallic interconnections of flat panel displays. The system uses four frames obtained by integration of the time-varying intensity in an interference pattern during the four quarters of the modulation period. Phase images are produced in real-time at a rate of several Hertz. On single material surfaces, the topology can be deduced directly. When different kinds of materials are present on the surface, like metallic interconnections on glass panel, we show that it is necessary to correct results from the phase change on reflection induced by the difference in refractive indices. Results are compared to scanning tip measurements. The microscope is mounted on a XYZ table to map the surface of the flat panel displays. The homogeneity of the height of metallic interconnections on the entire surface of the panel can be automatically determined. Additional information like metallic surface roughness is also available.

A major problem of in-situ surface characterization with angle-resolved light scatter (ARS) measurements is the fast and accurate acquisition of surface parameters with respect to industrial applications. The paper deals with design considerations and applications of an ARS sensor based on a calibrated CMOS photo detector array (CPDA) and an elliptical mirror system (EMS). In the first part of the paper the basic design approach of the ARS sensor system LARISSA will be presented. In the second part of the paper the characteristics of the CPDA and of the EMS will be discussed including considerations of design problems and solutions. In the third part of the paper experimental results from ARS measurements on PSL particles on Si wafers (particle diameters 5micrometers and 10(Mu) m) by using the CPDA will be considered in comparison with simulation results. Finally, the design progress will be summarized and the applicability of the ARS sensor will be discussed with respect to industrial applications. Future design steps for other specific applications will be outlined. This paper is a continuation of a previous paper.

Surface properties and optical properties of several deformable mirror arrays (DMA) without actuators were characterized. The mirror arrays are micro-electronic- mechanical system (MEMS) devices which were fabricated by Boston University for wavefront correction in adaptive optics. The surface properties measured for the samples agree with the properties specified for the BU-MEMS-DMA structures. Scattering and diffraction by the mirror arrays were measured at a wavelength of 632.8nm. The DMA with the etching pattern generates a diffraction pattern full of special structures. The broadening is serious for a rough sample while it is negligible for a smooth continuous membrane DMA. The diffraction pattern demonstrates that the DMA with an RMS roughness of 300nm is not suitable for the adaptive optics to correct for wavefront error. The continuous membrane DMA with roughness less than 10 nm are useful for adaptive optics.

Metallic and pearlescent coatings are becoming increasingly important in automotive, currency, and cosmetic applications. These coatings consist of metallic or dielectric platelets suspended in a binder, and are often applied between a pigmented basecoat, and a transparent topcoat. The scattering properties of these composite coatings vary depending upon the incident and viewing directions, as well as the wavelength. The complex nature of the scattering arises from the competition between multiple scattering sources: front surface reflection from the topcoat, reflection from the platelets, diffuse scattering from the pigmented undercoat, and scattering between platelets. The complex interplay between multiple scattering sources affects the ability to achieve quality control during the preparation of these coatings. In addition, the topcoat surface morphology, the properties of the pigmented basecoat, and the intrinsic properties, concentration, and angular distribution of the platelets influence the final appearance of the coating. In this paper, we will present models for light scattering from front surface facet reflection, subsurface flake reflection, and diffuse subsurface scattering. Experimental scattering measurements on pearlescent coatings show that the polarization can be well described in different geometry regimes by these different scattering sources. The models can be used to extract the slope distribution function of the flakes from the intensity data, but some aspects of the results behave inconsistently. Comparison is also made between experimental and calculated diffuse reflectance spectra. These results are intended to enable improved characterization of special effect coatings necessary for quality control and appearance modeling applications.

Due to the lack of fast switchable and sufficiently sensitive detectors for the near infrared (NIR) wavelength, the development of eye-safe, imaging, scannerless laser radar systems based on gated viewing is challenging. However, one basic approach is to use a pulsed Nd:YAG-OPO laser with 1574nm wavelength as transmitter and to gate an InGaAs-FPA camera with an electro-optical modulator (EOM) as receiver. With the EOM (a Pockels cell) the original integration time of the camera of 16ms is trimmed to the minimal exposure time (gate width) of 18ns. It is implemented in an adapted optics with focal length of 400mm. To guide the light with low divergence through the crystal of the EOM with a diameter of 5mm and a length of 80mm, the f-number was chosen to 26. Since the aperture of the EOM causes optical limitations, it is a decisive factor for the optical performance of the system. Additionally, because of the NIR laser light in conjunction with different target surfaces and the particularities of the receiver optics, artifacts in the laser radar images arise. In this paper we discuss the combination of target surface properties (e.g. reflectivity) and speckles, which cause a degradation of the quality of the range gated intensity images of the presented system. Since this leads to a reduction of the possible achievable contrast ratio, it affects directly the possible distance and depth resolution. The correlation of the target surface structure and the system performance will be analyzed, which is necessary to improve the current system design leading to enhanced system performance.

The goal of the present study was the elucidation of the level, down to which it is possible to reduce a reflectivity of aluminium in visible, near infrared, and vacuum ultraviolet wavelengths ranges by introduction of nitrogen atoms into the skin layer of aluminium. The used method consists in coprecipitating the aluminium and nitrogen ions, such that the nitrogen atoms introduced into the lattice of aluminium cause infringements of periodicity of the aluminium crystal lattice field owing to local deformations when forming strong and spatially-oriented covalence bonds with surrounding aluminium atoms. In such deformed Al-N system, namely, on borders of areas with broken periodicity of the Al lattice field, there will take place a scattering of free electrons. An increase in electron scattering intensity within the skin layer results in reduction of probability of release of secondary photons by free electrons excited by light wave in the skin layer. The latter will cause reduction of reflectivity of the surface of deformed aluminium lattice. Reflectivity measurements of samples of Al-N were carried out at ten wavelengths within a range from 400 up to 927 nm, and also at 121.6 nm. It turned out, evaporation of aluminium in argon plasma containing the nitrogen is really capable to lower reflectivity of such coating to values acceptable for practical applications, just down to a level of 4% in a visible range, 5% in near infrared, and 2% at 121.6 nm. So low levels of reflectivity (especially, at 121.6nm - the most intensive line of the short-wave part of ultraviolet solar spectrum) allow to apply this coating for reduction of solar stray light in instruments and to decrease the detectors noise of space equipment operating under conditions of open space and intensive solar ultraviolet illumination.

The coherence theory predicts that the correlation in the fluctuations of a source distribution can cause frequency shifts in the spectrum of the emitted radiation, even when the source is at rest relative to the observer. Recently, we have measured the angular spectrum redistribution, or frequency shifts from 1D and 2D rough surfaces with laser sources, and further verified the spectral and spatial coherent interference effect of a finite-band source.

The coherence theory predicts that the correlation in the fluctuations of a source distribution can cause frequency shifts in the spectrum of the emitted radiation, even when the source is at rest relative to the observer. Recently, we have measured the angular spectrum redistribution, or frequency shifts from 1D and 2D rough surfaces with a real image as a secondary source, and further verified the spectral and spatial coherent interference effect of a finite-band source.

In this work we present experimental and theoretical studies of the scattering of light propagating along a waveguide, a finite part of whose surface is randomly rough. We study the angular distribution of the intensity of the scattered light emerging from different parts of the rough surface. The angular distributions show a strong dependence on the distance of the radiating section from the front edge of the rough part of the waveguide. The experimental results are supported by theoretical studies of the problem. The angular distribution of the intensity of the light scattered into vacuum were calculated by means of a solution of the corresponding reduced Rayleigh equations.

In this work we consider a structure consisting of a dielectric medium characterized by a dielectric constant ε₁ in the region x₃ > H, a second dielectric medium characterized by a dielectric constant ε₂ in the region ζ(x₁) < x < H, and vacuum in the region x < ζ(x₁). The surface profile function ζ(x₁) is assumed to be a single-valued function of x₁ that is differentiable and constitutes a random process. The structure is illuminated from the region x₃ > H by s-polarized light whose plane of incidence is the x₁x₃-plane. By the use of geometrical optics limit of phase perturbation theory we show how to design the surface profile function ζ(x₁) in such a way that the mean differential transmission coefficient has a prescribed form within a specific range of the angles of transmission, and vanishes outside this range. In particular, we consider the case that the incident s-polarized light in incident normally on this structure, and the mean intensity of the transmitted light is constant within a specific range of the angle of transmission, and vanishes outside it. Numerical simulation calculations show that the transmitted intensity indeed has this property.

Adaptive photodetectors, based on non-steady-state photo-EMF, are suitable both for detection of fast phase modulation in one of the beams forming regular interference fringes and of fast transverse displacement of speckle patterns in a reference-less configuration. In particular, they were used for detection of lateral displacements of rough surfaces, including those induced by nanosecond laser pulses (laser ultrasonic). In combination with light sources of low temporal coherence (i.e. superluminiscent diodes) these detectors can be used for micron resolution profilometry of rough surfaces. In this paper we propose and demonstrate utilization of strong (quadratic) dependence of the photo-EMF signal on contrast of the detected light pattern for simple and fast evaluation of a correlation degree between speckle patterns reflected from the same rough surface at different wavelengths. Experimental results obtained with the GaAs photo-EMF detector and two different lines of a cw Ar-ion laser for transmittance and reflectance configuration (with ground glass and metal plates used as light scattering objects) are presented.

The condition of spectral invariance propagation of the spatially completely coherent light sources is studied from the diffraction theory. It is found that if the field distribution of light sources depends on frequency only through the variable (√kx,√ky), the spectrum of light will remain invariant on propagation. This scaling law may be generalized to the stationary light sources. But it can be destroyed by aperture. The spectral shifts of few cycle ultrashort pulses from aperture diffraction and a laser resonator with hard aperture are found and analyzed in detail.

Mueller matrix ellipsometry measurements are performed on accurately sizes polystyrene latex (PSL) and silicon oxide (SiO₂) spherical particles deposited on a crystalline silicon surface. The mean particle diameter ranges from 0.2 μm to 1.5 μm. An argon laser beam (wavelength 515 nm) is impinging on the sample at a fixed near grazing incidence angle. The Mueller matrix of the diffuse light scattered by the particles is measured in the plane of incidence as a function of the scattering angle. Results are presented and compared with exact theory.