Optical modes properties

Abstract The self-organized and molecularly smooth surface on liquid microdroplets makes them attractive as optical cavities with very high quality factors. This chapter describes the basic theory of optical modes in spherical droplets. The mechanical properties including vibrational excitation are also described, and their implications for microdroplet resonator technology are discussed. Optofluidic implementations of microdroplet resonators are reviewed with emphasis on the basic optomechanical properties. 

Painter O., Srinivasan, K., O Brien, J.D., Scherer, A., and Dapkus, P.D., 2001, Tailoring of the resonant mode properties of optical nanocavities in two-dimensional photonic crystal slab waveguides, J. Opt A Pure Appl. Opt. 3 S161-S170. 

At infrared wavelengths extinction by the MgO particles of Fig. 11.2, including those with radius 1 jam, which can be made by grinding, is dominated by absorption. This is why the KBr pellet technique is commonly used for infrared absorption spectroscopy of powders. A small amount of the sample dispersed in KBr powder is pressed into a pellet, the transmission spectrum of which is readily obtained. Because extinction is dominated by absorption, this transmission spectrum should follow the undulations of the intrinsic absorption spectrum—but not always. Comparison of Figs. 10.1 and 11.2 reveals an interesting discrepancy calculated peak extinction occurs at 0.075 eV, whereas absorption in bulk MgO peaks at the transverse optic mode frequency, which is about 0.05 eV. This is a large discrepancy in light of the precision of modern infrared spectroscopy and could cause serious error if the extinction peak were assumed to lie at the position of a bulk absorption band. This is the first instance we have encountered where the properties of small particles deviate appreciably from those of the bulk solid. It is the result of surface mode excitation, which is such a dominant effect in small particles of some solids that we have devoted Chapter 12 to its fuller discussion. 

Photonic band gap (PEG) materials represent a class of composites that are designed to monitor the properties of photons in much the same manner as semiconductors manipulate the electrons properties. These composites have been developed from ordered arrays of self-assembled nanometer-sized polyst3a ene spheres that have been repeatedly encapsulated with various polymeric systems. However, it has been recognized that PEG materials also support surface electromagnetic waves-optical modes that propagate at the interface of a PEG crystal [193]. 

Apart from acoustic phonons, which account for heat transport in insulating media, propagation of vibrational energy is usually not considered in crystals, as the dispersion of optical modes is normally very small over the Brillouin zone. However, there is an important class of optical vibrations in crystals for which spatial propagation can be the dominant property at optically accessible wave vectors. This class is identical with that of infrared active modes and its members are known as phonon-polaritons. ... 

The trigger photon is then selected by spatial and frequency filters and is detected by a single-photon counter. Conditioned on the detection event the non-local biphoton state collapses into a single photon state in the signal mode. The properties of this mode are determined by the optical mode of the pump photon and the spatial and spectral filtering in the trigger channel ... 

In this chapter we investigate and discuss the thermal, optical, electrical properties of the oligothiophene derivatives by means of differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and UV-Vis spectroscopy. The thin films of these compounds produced by solution cast and vacuum deposition methods are characterised by AFM measurements in contact and non-contact mode, and by X-ray diffraction. Finally, an ultra-thin OFET is built, and the transistor characteristics are determined. 

Several theoretical and experimental studies assess the vibrational properties of the high-pressure phases of silicon. A group-theoretical analysis of lattice vibrations in the -tin structure has been made by Chen [98]. In the vicinity of the F point, the optical modes consist of one longitudinal optical (LO) branch and at higher frequencies of a doubly degenerate transverse optical (TO) branch, both of which are Raman active. Zone-center phonon frequencies of Si-11 have been calculated as a function of pressure using the ab initio pseudopotential method... 

Such coherent nonlinear effects may also induce gain losses by the self-focusing effect, destroying the desired mode properties of the optical cavity. A power threshold has been estimated by Yariv (1967)... 

Schnepp and Ron (1969) carried out a complete lattice dynamical calculation for a-Na throughout the Brillouin zone, using the potential model of Kuan, Warshel, and Schnepp (1969). This model contains three parameters which were calibrated for the optical modes [librational assignments of Brith, Ron, and Schnepp (1969)] and the equilibrium properties of the solid. The lattice dynamics was formulated in terms of Eulerian angle librational displacements. Dispersion curves for the symmetry directions of the Brillouin zone and density of states functions were reported with and without translation-libration interactions. The results clearly demonstrated the importance of these interactions. Schnepp... 

Feit, M. D., and Fleck, J. A., Computation of mode properties in optical fiber waveguides by a propagating beam method, Appl. Opt, 19, 1154 (1980). 

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