Oblique-incidence optical reflectivity

Oblique-Incidence Optical Reflectivity Difference Microscopy... 

Garcia-Uribe, A., et al. In-vivo characterization of optical properties of pigmented skin lesions including melanoma using oblique incidence diffuse reflectance spectrometry. Journal of Biomedical Optics 16(2), 020501 (2011)... 

Landry IP, Zhu XD, Gregg IP. Label-free detection of microarrays of biomolecules by oblique-incidence reflectivity difference microscopy. Optics Lett. 2004 29 581-583. 

Zhu X Landry JP, Sun YS, Gregg JP, Lam KS, Guo X. Oblique-incidence reflectivity difference microscope for label-free high-throughput detection of biochemical reactions in a microarray format. Appl. Optics. 2007 46 1890-1895. 

Let us first consider an oblique reflection of a light wave at a planar interface between two optically isotropic media. For a given amplitude and polarization of the incident wave, the reflected amplitude and polarization are determined from the continuity relation for the E and H fields at the interface. This leads to the complex Fresnel s equations [1] for the complex reflectivities of the p-polarized rp = Er pjEi p, and s-polarized waves, = Er,s/Ei s- The same applies to the transmitted waves. Here, i and r denote incident and reflected light respectively. 

Since the substrate may influence the anisotropic optical properties of the overlying film [595], the method of Buffeteau et al. [247, 566-568, 593] is conceptually more reliable when the MO is studied on solid transparent substrates, whereas the initial anisotropic optical constants are extracted from normal- and oblique-incidence transmission or polarized reflection of the same film on the same substrate. In the case when different substrates participate into the measurements (e.g., when MO in monolayers at the AW interface is studied), the comparison of the simulated and experimental spectra can be used for distinguishing chemical effects generated by specific film-substrate interactions [568b]. In particular, the kmm values derived from spectra of monolayers at the AW interface obtained by IRRAS are usually larger than those obtained by eUipsometric measurements of thin films on solid supports [247]. This difference has been attributed to a gradient in the optical properties of the interfacial water [71]. 

For stratified optical media (whose refractive indices are only a function of the coordinate normal to the film), Berreman introduced a 4 x 4 matrix method (now known as the Berreman 4x4 method) [14—18], in which the electric field and magnetic field (the sum of the fields of the light beam propagating in forward and backward directions) are considered. When the film is divided into slabs, the reflection at the interface between the slabs is taken into account. The Berreman 4x4 method works well for both normal and obliquely incident fight. Consider an optical film, such as a cholesteric liquid crystal in the planar texture (twisted nematic), whose dielectric tensor is only a function of the coordinate z, which is perpendicular to the film ... 

We computed the reflectance spectrum for obliquely incident plane wave radiation interacting with a system obeying Oseen s optical model. Figure 3 (bottom) shows the first and second order Bragg reflection bands that we predicted for certain principal values of the dielectric tensor. 

Ellipsometry was in fact the earliest optical technique to be applied to the study of electrode processes. It involves the determination of the change in polarisation state of an obliquely incident light beam upon specular reflection at a surface. In order to fully define a monochromatic light beam it is necessary, in addition to knowing the frequency, amplitude, and direction of propagation, to include information about the electric and magnetic vectors which describe the polarisation state. Since these vectors are orthogonal and related in amplitude it is, in fact, only necessary to consider one of them, and it is the electric vector that is usually chosen. If this vector lies in a plane then the beam is said to be plane polarized, and further if this plane lies parallel to the plane of incidence at a surface the beam is said to be p-polarised, whereas a beam polarised in a plane perpendicular to the plane of incidence is referred to as s-polarised. For any beam it is possible to resolve the electric vector into its s and p components, and when these components are of the same frequency but different phase and amplitude the beam is said to be elliptically polarised. This name arises from the... 

Almeida R.M., Pantano C.G. Vibrational spectra and structure of silica gel films spun on c-Si substrates. SPIE-Sol-Gel Optics 1990b 1328 329-337 Almeida R.M. Detection of LO modes in glass by infrared reflection spectroscopy at oblique incidence. Phys. Rev. B 1992 45 161-170... 

Popov K. V., Dobrowolski J. A., Tikhon-ravov A. V., Sullivan B. T. Broadband high-reflection multilayer coatings at oblique angles of incidence Applied Optics 36, 2139 (1997). 

FIGURE 4.34. An initially homeotropic nematic layer with oblique light incidence at an angle ie. The electric vector of the TM light wave is in the plane of incidence. 9 z) characterizes the spatial distribution of the optical ellipsoid. I = R + T, where R is reflectivity and T is transmittance, provided that absorption is absent. 

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