Fabry-Perot fringes

Figure 3.10. Fabry-Perot fringe records of a moving reflector. Comparison of the two different records suggest superior fringe signals when optical fibers are used to transmit light signals (Gidon et al., 1984).

Figure 4. Fabry-Perot interference (a) Fabry-Perot etalon, (b) Fabry-Perot fringes, (c) Etalon transmission function for different plate transmissions.

Interferometry on porous silicon The average refractive index of the porous silicon layer is affected by analyte adsorption, resulting in a shift of the Fabry Perot fringes 6,18... 

Fabry-Perot fringes 1.3 GHz apart provide the frequency scale (from ref. 21). 

Fig. 23.9 Observed excitation spectra 6sl9d —> 9dn d in neutral Ba (b) circular, (c) linear polarization of laser beams and (d) computed spectra. The sharp resonances A, B and C correspond respectively to 6sia — 9d5/2,6s1/2 — 9d3/2 and 5d — lOg ionic transitions used as standard calibrations with the Fabry-Perot fringes (a) (from ref. 31).

Fig. 16.14. Wavelength shift of a single Fabry-Perot fringe as a function of exposure time to organic vapors. As the fraction of acetone was increased, greater and more rapid shifts in the reflectance spectrum were measured. (M. J. Sailor is thanked for permission to reprint this figure.)...

The photonic-structure-based colorimetric sensors are not limited to PCCAs. Other examples utilize porous sihcon (PSi) transducer. For example. Sailor etal. reported PSi modified with Protein A to selectively detect inununoglob-ulin G (IgG). The sensor operates by measurement of the Fabry-Perot fringes in the white light reflection spectrum from the porous silicon layer. Another example demonstrated the use in PSi for identification of gram-negative bacteria. 

The spectrum below is recorded in fluorescence from a collimated cesium atomic beam, excited on the D F transition by a single mode tunable dye laser. The D level is populated in cascade decay from the P state, which is excited with a broadband CW dye laser. The Fabry-Perot fringes at the bottom correspond to a free spectral range of 50 MHz. 

To record tlie profile of a spectral line, the Fabry-Perot fringe pattern was scanned across the pinhole by slowly changing the pressure of carbon dioxide in a chamber surrounding the etalon. In the early work the intensity of the light received by a photomultiplier placed behind a similar... 

The advent of lasers allowed optical interferometry to become a useful and accurate technique to determine surface motion in shocked materials. The two most commonly used interferometric systems are the VISAR (Barker and Hollenbach, 1972) and the Fabry-Perot velocity interferometer (Johnson and Burgess, 1968 Durand et al., 1977). Both systems produce interference fringe shifts which are proportional to the Doppler shift of the laser light reflected from the moving specimen surface. Both can accommodate a speci-... 

The surface forces apparatus (SEA) can measure the interaction forces between two surfaces through a liquid [10,11]. The SEA consists of two curved, molecularly smooth mica surfaces made from sheets with a thickness of a few micrometers. These sheets are glued to quartz cylindrical lenses ( 10-mm radius of curvature) and mounted with then-axes perpendicular to each other. The distance is measured by a Fabry-Perot optical technique using multiple beam interference fringes. The distance resolution is 1-2 A and the force sensitivity is about 10 nN. With the SEA many fundamental interactions between surfaces in aqueous solutions and nonaqueous liquids have been identified and quantified. These include the van der Waals and electrostatic double-layer forces, oscillatory forces, repulsive hydration forces, attractive hydrophobic forces, steric interactions involving polymeric systems, and capillary and adhesion forces. Although cleaved mica is the most commonly used substrate material in the SEA, it can also be coated with thin films of materials with different chemical and physical properties [12]. 

The Fabry-Perot type used by Benard, which produces fringes of equal thickness, is shown schematically in Fig. 6. Monochromatic light from a source S is collimated by the lens L and is directed vertically onto the... 

In the case of very thin samples in transmission measurements, Fabry-Perot interference fringes can arise as a result of sample-support interactions which can manifest as an oscillatory signal that convolutes the data and further complicates the data interpretation process. Though proper modeling of these feamres can produce the tme absorbance while also revealing additional information about the sample, a workaround is to utilize a diffuse reflectance or absorption configuration as detailed below. 

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