Determination of surface roughness from light scattering measurements

We have measured the angular dependence of the p- and s-pollarized light scattered on films, which are supported by fine polished Suprasil substrates. To study the roughness of the surface we have varied the evaporation process and the thickness of the silver film. We quantitatively determine the roughness structure by using a non scalar scattering theory. The roughness structure is found in good agreement with measurements on the same films using ATR-techniques.     

Optical estimation of statistics of surface roughness from light scattering measurements

The relations between surface statistics and the near- and far-field scattered light statistics are surveyed, mainly using scalar diffraction theory. The methods which have been proposed and used are grouped and described according to whether they operate in the near-field or the far-field and whether they use monochromatic or polychromatic light. Several methods emerge as promising for practical application to non-contacting and non-destructive testing.Deterministic methods such as interference microscopy are not discussed.     

Temperature measurements by coherent Rayleigh scattering

We demonstrate, for the first time to our knowledge, the utility of coherent Rayleigh scattering (CRS) for temperature measurements in low-density gases and weakly ionized plasmas by measuring the translational temperature of neutral argon in a glow discharge. By analysis of the near-Gaussian spectral profile of the CRS signal, we determine temperatures with an uncertainty of 相似文献   

Focusing coherent light through opaque strongly scattering media

We report focusing of coherent light through opaque scattering materials by control of the incident wavefront. The multiply scattered light forms a focus with a brightness that is up to a factor of 1000 higher than the brightness of the normal diffuse transmission.     

Surface wave effect on light scattering from one-dimensional photonic crystals

Light scattering and reflection measurements using attenuated total reflection technique for s polarization of the incident light on a finite one-dimensional photonic crystal are reported. Angular specular reflection was measured experimentally to determine, the optimum thickness, the angular position of the surface mode, and the number of bi-layers of the system. It was demonstrated that the position of the surface mode inside the last film is close to the asymptotic value when the number of periods is increased. Spectral reflection measurements were made to determine experimentally the band gap width and measure the dispersion relation of the surface mode inside this band. The corresponding field amplitude was calculated (∣E∣²) showing that in resonant conditions it has a maximum near the surface. The angular dependence of the scattered light measured displays a peak caused by singles cattering and located approximately at the excitation angle of the surface electromagnetic mode. When the incident light is in resonance with the surface electromagnetic wave, it is found experimentally that the scattering of light is enhanced overall by approximately one order of magnitude in comparison with the off-resonance case.     

Super-sensitive phase estimation with coherent boosted light using parity measurements

We consider a passive and active hybrid interferometer for phase estimation, which can reach the sub-shot-noise limit in phase sensitivity with only the cheapest coherent sources. This scheme is formed by adding an optical parametric amplifier before a Mach-Zehnder interferometer. It is shown that our hybrid protocol can obtain a better quantum Cramer-Rao bound than the pure active(e.g., SU(1,1)) interferometer, and this precision can be reached by implementing the parity measurements. Furthermore, we also draw a detailed comparison between our scheme and the scheme suggested by Caves[Phys. Rev. D 23 1693(1981)], and it is found that the optimal phase sensitivity gain obtained in our scheme is always larger than that in Caves' scheme.     

Coherent light scattering spectroscopy for supersonic flow measurements

A unified discussion on coherent light scattering spectroscopy and its spectral dependence on molecular gas velocity, temperature and density is presented. The feasibility of using coherent Raman spectroscopy techniques for nonintrusive measurements of supersonic flow parameters is demonstrated and recent laboratory as well as wind tunnel experiments are reviewed. In addition, the advantages of using coherent Rayleigh-Brillouin spectroscopy for measuring high pressure flows are discussed.     

Single layer homogeneous model for surface roughness by polarized light scattering

In this paper a homogeneous single layer model for surface roughness by polarized light has been developed. It has been shown that the reflectance change in non-absorbing layer is directly proportional to the refractive index of the ambient and substrate media for s polarization but inversely proportional to the p polarization and it is directly proportional to the square of the thickness of the layer for both the polarization. In an absorbing layer, it has been shown that the thickness of the layer is equal to the twice of surface roughness of the single layer identical system for s polarization but it is ratio of twice of surface roughness to the square of refractive index of thin film for p polarization. The extinction coefficient of the layer is directly proportional to the thickness of that layer for both the polarization. The consequence of the scattered light on the specular reflectance and transmittance for oblique incidence shows that there is reduction in reflectance (in both non-absorbing and absorbing cases) and transmittance (in the absorbing case for p polarization only), due to roughness on the surface under the Drude effective-medium approximation. Thus such an absorbing layer provides a valid model for the effect of scatter on the transmittance for p polarization only.     

Determination of the autocorrelation function of height on a rough surface from coherent light scattering

Under the assumption of a Gaussian first order probability density function of height the autocorrelation function of height on a rough surface is obtained from the Fourier transform of the ensemble average far-field scattered light intensity. The theory of the method and some initial results are presented.     

On some manifestations of similarity in multiple scattering of coherent light

The similarity of the decay tendencies of statistical moments of optical fields and their combinations (the mean intensity, the temporal correlation function of the field fluctuations and the degree of polarization) due to coherent light propagation in the disordered media has been considered by using a simple phenomenological model with exponential relaxation. A theoretical consideration has been carried out for the case of light propagation through a disordered slab using the diffusion approximation. The validity of the concept of similarity has been demonstrated in experiments with water suspensions of polystyrene spheres for the light transmission mode even in the case of non-diffusion regimes of light propagation through a scattering substance.     

Polarization coherent anti‐stokes Raman scattering using noisy light

Several polarization studies on the noisy light version of coherent anti‐Stokes Raman scattering (CARS) exist in the literature. However, the full advantages of polarization CARS (P‐CARS), which are so useful in conventional and short‐pulse CARS methods, have not yet been exploited in the noisy light version. This work presents experimental realization of fully functional P‐CARS using noisy light. Several examples demonstrate the advantages brought by P‐CARS. This includes the ‘classic’ example of benzene in carbon tetrachloride. Also presented are the carbon–carbon double bond stretches in acrylonitrile and 1‐hexene. An interesting, and not fully understood, detection polarization angle dependence is discussed. Applications to an m‐xylene/benzene mixture and an alkaline solution of the amino acid phenylalanine are presented. Copyright © 2006 John Wiley & Sons, Ltd.     

Broadly tunable dual-wavelength light source for coherent anti-Stokes Raman scattering microscopy

The signal and idler beams from a picosecond, synchronously pumped optical parametric oscillator (OPO) provide the two colors necessary for coherent anti-Stokes Raman scattering (CARS) microscopy. The OPO provides a continuously tunable frequency difference between the two beams over a broad range of Raman shifts (100-3700 cm(-1)) by varying the temperature of a single nonlinear crystal. The near-infrared output (900-1300 nm) allows for deep penetration into thick samples and reduced nonlinear photodamage. Applications of this light source to in vivo cell and ex vivo tissue imaging are demonstrated.     

The dynamic angle-limited integrated scattering (DALIS) method for measuring scattering of light from optical surfaces with random roughness

A new and simple dynamic angle limited integrated scattering (DALIS) method is developed to examine optically smooth reflective surfaces with defined surface form. Our experimental results from two systems show advantages over conventional angle resolved scattering measurement (ARS) methods. By collecting scattered light in a given solid angle, our methods do not require a detection unit with an extremely large dynamic range. Unlike in the common ARS measurement method, here we use a simple linear translation stage to scan scattered light. The power spectrum density function and the autocorrelation function of the surface roughness can be recovered from the measured scattering pattern. This method can be applied to in-workshop inspection of optical polishing processes.     

Surface measurement using active vision and light scattering

This paper reviews the recent progress in surface measurement methods using active vision and light-scattering techniques. The active vision methods with different structured light patterns and the corresponding techniques are summarized. The surface roughness and defects inspection with light-scattering are discussed. After the review, an integrative method to measure surface waviness and form, roughness is proposed.     

Nonlinear diffraction in spontaneous three-wave and coherent four-wave light scattering by polaritons

Spontaneous three-wave and coherent four-wave scattering by polaritons in crystalline media with periodically modulated nonlinear quadratic susceptibility have been studied both theoretically and experimentally. Phase matching conditions and an expression for the scattering spectral line shape with due account of cascade processes in nonlinear diffraction for coherent Stokes polariton light scattering have been derived. Measurements of the light intensity distribution due to the three-and four-wave scattering in a LiNbO₃:Nd:Mg crystal with a periodic domain structure are in good agreement with theoretical results. The prospects for using the effects of nonlinear diffraction in spectroscopic studies of media with periodic distributions of nonlinear optical parameters, specifically, in precision measurements of the IR refractive index dispersion and determination of the period and profile of the quadratic susceptibility distribution are discussed. Zh. éksp. Teor. Fiz. 112, 2001–2015 (December 1997)