Evanescent light wave

The most common principle used in optical biosensors for detection in the real part of the refractive index is evanescent wave detection, where the transducer optics are modified by changes in optical parameters of the medium in contact with the sensor surface via the interaction with the evanescent light wave penetrating into the ambient medium. As the evanescent wave decays exponentially from the surface, the most sensitive detection is just at the transducer surface. 

Fig. 22 Spectral dependence of the effective index of a surface plasmon on the interface of gold-water and the effective index of the evanescent light wave produced by a plane light wave incident on the gold film from an optical prism (BK 7 glass) under nine different angles of incidence...

Evanescent Light-Wave Atom Mirrors, Resonators, Waveguides, and Traps, Jonathan P. Dowling and Julio Gea-Barutcloche Optical Lattices, P S. Jessen and I. H. Deutsch Channeling Heavy Ions through Crystalline Lattices, Herbert F. Krause and Sheldon Datz... 

If one includes the employment of evanescent light waves in spectroscopic studies in the near-field area. Knoll and coworkers are among the first who reported on near-field Raman spectroscopy , though this approach was termed at that time (the early 1990s) as surface plasmon field-enhanced Raman spectroscopy and microscopy [104],... 

While the atomic trap based on the evanescent light wave uses a combination of laser field, static magnetic field and gravitational force the Joffe-Pritchard trap only... 

M. CopiC, C. S. Park, N. A. Clark, Theory of evanescent light wave scattering at the solid-nematic interface. Mol. Cryst. Liq. Cryst. 1992, 222, 111-118. 

The idea of reflecting an electron beam by an evanescent light wave is illustrated in Fig. 13.8. The internal reflection of a laser beam at a dielectric-vacuum interface produces an evanescent light wave with an intensity distribution given by... 

Dowling, J. P., and Gea-Banacloche, J. (1996). Evanescent light-wave atom mirrors, resonators wave-guides, and traps. In Advances in atomic, molecular and optical physics (ed. B. Bederson and H. Walther), vol. 37, pp. 1-94. Academic Press, San Diego. 

Incorrect conclusion 1 above is sometimes said to derive from the reciprocity principle, which states that light waves in any optical system all could be reversed in direction without altering any paths or intensities and remain consistent with physical reality (because Maxwell s equations are invariant under time reversal). Applying this principle here, one notes that an evanescent wave set up by a supercritical ray undergoing total internal reflection can excite a dipole with a power that decays exponentially with z. Then (by the reciprocity principle) an excited dipole should lead to a supercritical emitted beam intensity that also decays exponentially with z. Although this prediction would be true if the fluorophore were a fixed-amplitude dipole in both cases, it cannot be modeled as such in the latter case. 

Let us consider the possibility of reflection of electrons by an evanescent laser wave formed due to total internal reflection of femtosecond laser pulses from a dielectric-vacuum interface [4] (Fig. lb). Such a laser field was considered elsewhere [7, 8] to effect the mirror reflection of atoms (references to the latest works on the mirror reflection of atoms can be found in Refs. 9 and 10). The light intensity distribution in the evanescent wave in the vacuum may be represented in the form [11]... 

One can distinguish between methods in which absorption of the evanescent surface wave in different wavelength regions is measured (these are often called attenuated total reflection methods), and methods which use the evanescent wave to excite other, spectroscopic phenomena, like fluorescence and Raman scattering or light scattering. As the methods of conventional fluorescence spectroscopy have been shown to be exceptionally successful in studies of proteins and other biopolymers, their evanescent surface-sensitive counterparts will be reviewed first. 

Fluorescence from labeled adsorbed protein has also been excited with the evanescent surface wave created by integrated optics. Both optical fiber I60) and flat rectangular waveguides193) have been used. Interesting use of optical fiber as a remote protein sensor was demonstated the excitation light was sent down the fiber whose tip was immersed in protein solution, evanescently excited fluorescence was collected by the same fiber and delivered to a scanning monochromator 160). 

Evanescent electromagnetic waves can be excited at the interface of two optically transparent materials with different indexes of refraction. If a beam of light is incident on the interface from the material with the larger index of refraction and if the angle of incidence exceeds a certain critical value, then there will... 

Sensing of evanescent waves with an optical tip has been proposed for use as an optical device to sense AFM forces by means of an optical microlever which is illuminated by a laser under conditions of total internal reflection and which is connected to an atomic force tip [77], Thus tunneling photons from the microlever to the optical tip at the evanescent light coupling may be used for the feedback loop. This instrument combines noncontact AFM and PSTM techniques. 

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