Fabry-Perot

Machtie P, Muiier C and Heim C A 1994 A thin absorbing iayer at the center of a Fabry-Perot interferometer J. Physique ii 4 481-500... 

An alternative approach to obtaining microwave spectroscopy is Fourier transfonn microwave (FTMW) spectroscopy in a molecular beam [10], This may be considered as the microwave analogue of Fourier transfonn NMR spectroscopy. The molecular beam passes into a Fabry-Perot cavity, where it is subjected to a short microwave pulse (of a few milliseconds duration). This creates a macroscopic polarization of the molecules. After the microwave pulse, the time-domain signal due to coherent emission by the polarized molecules is detected and Fourier transfonned to obtain the microwave spectmm. 

Fabry-Perot modes FabuLte Face powders Facial edema F-acid [92-40-0]... 

Most of the lasers discussed operate in a small number of discrete longitudinal modes, the Fabry-Perot modes. The individual modes are very narrow, much less than 0.01 nm, but are separated by spectral distances of ca 1.0 nm. Thus the overall width of the laser spectmm may exceed 4—5 nm. 

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-... 

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).

Durand, M. (1984), Use of Optical Fibers for Velocity Measurement by Laser Doppler Interferometry with a Fabry-Perot Interferometer. In High Speed Photography and Photonics, Proc. SPIE, 491 (edited by M. Andre and M. Hugenschmidt), pp. 650-656. 

Electrically Tunable Micromachined Fabry-Perot Interferometer The... 

Fabry-Perot interferometer is an optical resonator consisting of two parallel mirrors. Fabry-Perot interferometers can be made by silicon bulk microma-chining." " Silicon surface micromachining is also a suitable technique for making interferometers for infrared wavelengths. 

Figure 13.55 shows the principle of a gas sensor based on an electrically tunable micromachined Fabry-Perot interferometer, and the shifting ol the pass band controlled by rhe tuning voltage. 

Jerman, J. H., and D. ]. Clift. Miniature Fabry-Perot Interferometers Micromachined in Silicon for the Use in Optical Fiber WDM Systems. Transducers 91 Conference, Digest of Technical Papers (1991), pp. 372-375. 

Blomberg, M., A. Torkkeli, A. Lehto, C. Helenelund, M. Viitasalo. Electrically Tuneable Micromachined Fabry-Perot Interferometer in Gas Analysis. Phystca Scripta T69 (1997), pp. 119-121. 

Abstract This tutorial shows how fundamental is the role plaid by interferences in many of the physical processes involved in astrophysical signal formating and consequently instmmentation. It is obvious in interferometry. Grating spectroscopy is explained within the same framework as Young experiment, and Fabry-Perot filters are explained as Michelson interferometers.Polarization interferences, used in Lyot filters, are discussed, emphasizing the analogy with echelle gratings. 

Fabry-Perot interferometers, polarization interference, birefringence, Lyot filters... 

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

We have seen how the presence of shot noise dictates some key choices minimum laser power, beam and mirror diameter, necessity to use Fabry-Perot cavities in the arms. Other noise sources will fix other important optical parameters. 

At 10Hz in a typical Nd-YAG laser 1000Hz/- /Hz, and the typical finesse asymmetry is of the order of one percent. In order to detect a gw signal the laser frequency noise has to be lowered by six orders of magnitudes (compared to the noise of a free running laser), and the two arms made as identical as possible. In order to achieve this complex frequency stabilization methods are employed in all interferometric detectors, and in order to insure the perfect symmetry of the interferometer, all pairs of Virgo optical components are coated during the same run (both Fabry-Perot input mirrors then both end mirrors are coated simultaneously). 

Multicavity filters. Multicavity Fabry-Perot filters are used to make very narrow transmission filters. A simple Fabry-Perot cavity (see Ch. 2) consists of a halfwave layer surrounded by two reflectors of typically 10 layers each. Figure 4 shows three transmission profiles obtained with one, two or three cavity filters. The three cavity HL) 5HH(LH) 5) " 3 filter has a 1.2 nm bandwidth. It has 60 layers. Note that the three-peak top of the transmittance. Each cavity has to be well adapted to the following one if not the resulting transmittance can be very poor. Such cavities are broadly used in telecoms in between arrays of antennas for cell phones. 

Figure 4. Transmittance of a multicavity Fabry-Perot filter.

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]. 

Woodruff, S. D. and Yeung, E. S., Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry, Anal Chem., 54, 1174, 1982. 

Spectral line shape studies by Frommhold and Biondi60 (using Fabry-Perot interferometry) indicated measurable broadening of several lines coming from Ne2 and Ar2 recombination. The authors showed that dissociative recombination,... 

Semiconductor laser diodes are widely used in CD players, DVDs, printers, telecommunication or laser pointers. In the structure, they are similar to LEDs but they have a resonant cavity where laser amplification takes place. A Fabry-Perot cavity is established by polishing the end facets of the junction diode (so that they act as mirrors) and also by roughening the side edges to prevent leakage of light from the sides of the device. This structure is known as a homojunction laser and is a very basic one. Contemporary laser diodes are manufactured as double heterojunction structures. 

Mitchell G.L., A review of fabry-perot Interferometric sensors, in Optical Fiber Sensors, Proc.6th Int.Conf. OFS 89 (1989), H.J.Arditty, J.P.Dakin, R.ThKersten eds., Springer-Verlag, pp. 450-478. 

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