Fabry-Perot effect

The metal layers frequently consist of chromium (semitransparent absorber metal) or aluminum (opaque reflector metal). Silicon dioxide or magnesium fluoride are the materials mostly used for the dielectric layers. In the case of pigment particles, there is a symmetrical arrangement of the layers, as shown in Figure 5.28, whereas optical coatings can also consist of a system of unsymmetrical layers. All these arrangements are the basis for an optical phenomenon called the Fabry-Perot effect... 

To demonstrate the method an example of a slow-wave optical structure is modelled. Such structures consist of a cascade of directly coupled optical resonators in order to enhance the nonlinear effects. The structure used here was recently defined within Working Group 2 of the European Action COST Pll (http //w3.uniromal.it/energetica/slow waves.doc). One period of the structure consists of one-dimensional Fabry-Perot cavity placed between two distributed Bragg reflectors (DBR) and can be described by the sequence... 

The diffraction grating monochromator is a specific example of mnltiple beam interference effects. Interference between multiple beams can be generated by both division of amplitude (as in the Fabry-Perot interferometer) or by division of wave front (as in the diffraction grating). (Figures 5.9 and 5.10)... 

The two examples shown demonstrate how an interference effect can be produced either by amplitude division of an incident beam, followed by retardation (achieved in this case by multiple reflection between the partially reflective parallel plates of a Fabry-Perot resonator) and recombination, or by division of the wave front at the multiple equally spaced slits of a diffraction grating, again followed by recombination. 

Enhancement of the Hght-matter interaction in a microscopic optical cavity is achieved because Hght trapped in the cavity has longer effective interaction time with absorbers. For short laser pulses, cavity length exceeding CTp allows avoidance of the interference between the pulses incident and reflected from the mirrors. Spectral selectivity of planar Fabry-Perot cavities can be used to achieve the localization at the resonant wavelength of the cavity. 

An illustration of this fact comes from the nonlinear Schrodinger equation. This equation describes an electromagnetic wave in a nonlinear medium, where the dispersive effects of the wave in that medium are compensated for by a refocusing property of that nonlinear medium. The result is that this electromagnetic wave is a soliton. Suppose that we have a Fabry-Perot cavity of infinite extend in the x direction that is pumped with a laser [6,7]. The modes allowed in that cavity can be expanded in a Fourier series as follows ... 

FAB FEA FEB FET FFP FIB FIELO FIR FLAPW FP FP-LMTO FWHM fast atom beam free A exciton free B exciton field effect transistor far field pattern focused ion beam facet-initiated epitaxial lateral overgrowth far infrared reflectance full-potential linearised augmented plane wave Fabry-Perot full-potential linear muffin-tin orbital full wave at half maximum... 

We have performed optically heterodyne-detected optical Kerr effect measurement for transparent liquids with ultrashort light pulses. In addition, the depolarized low-frequency light scattering measurement has been performed by means of a double monochromator and a high-resolution Sandercock-type tandem Fabry-Perot interferometer. The frequency response functions obtained from the both data have been directly compared. They agree perfectly for a wide frequency range. This result is the first experimental evidence for the equivalence between the time- and frequency-domain measurements. 

The dimensions of the sample are important in determining the performance of the spectrometer because the sample can extend over several wavelengths in several dimensions, at least in principle, which enhances interferometric effects within the sample. Neglecting losses in the sample for the moment, we note that if the sample is an integral number of half-wavelengths thick, it functions like a Fabry-Perot. In order to understand this, we will sketch a derivation that takes into account the index of refraction of the dielectric material and reflection from the sample-air interfaces. First, note that the optical phase difference across the sample is nkt, where n is the index of refraction and t is the thickness. The resonance condition for such a slab is given by Eq. (44) with kt replaced by nkt, namely,... 

Fig. 12. Fabry-Perot resonator with one mirror of variable reflectivity r, and one mirror of variable reflectivity r2 - (a) Dashed line = 0.9 solid line r-j = 0.8 dot-dash line r, = 0.7 and r-2 = 0.8. (b) Planar Fabry-Perot interferometer that shows the effect of beam growth between the mirrors. The transmitted beam is a superposition of all the partial waves to the right of m,.

Several comprehensive models for the emission of dipoles in a multilayer structure have been presented in the literature, which take into account the orientation of dipoles in the emitting layer (Bjork, 1991). Less elaborated expressions for the emission of a thin-film structure with an emitting layer can also be developed using an approach similar to the one presented by Smith for describing the transmittance of Fabry-Perot structures, using the concept of effective interfaces (Smith, 1958). We used this approach to obtain the following expression for bottom-emission OLEDs (similar to other expressions that can be found in the literature, for example Lee et al., 2002) ... 

The phenomenon known as "microcavity effect" refers to the enhancement or annihilation of the emitted irradiance related to the position of the emitting material relative to this resonance peak of the irradiance. A weak microcavity effect is usually present in conventional OLEDs because internal reflections are caused by the higher refractive index of the ITO anode compared to most organic layers, and the cathode is highly reflective (Bulovic, 1998). This is usually considered a nuisance, but has been exploited in microcavity OLEDs (Jordan, 1996). With Fabry-Perot filters, the phase condition for the appearance of resonance peaks is given by the following equation ... 

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