Optical mode structure

Optical Mode Structure in Thin Film Organic Structures. Optimization of Bilayer Geometries... 

The WGM laser mode structure is determined by the droplet size and shape (which can be influenced by optical trapping forces26), laser polarization, and dye concentration. ... 

All these waveguiding films lack one important feature that would be necessary for true lasing They do not have a resonator for optical feedback that would lock the optical modes traveling in the gain direction. The thin-film waveguide confines the optical modes in one direction (in the vertical), but in the other two dimensions the modes have translational and rotational symmetry. The incorporation of resonator structures into the thin films in order to get true organic solid-state lasers will be described next. 

One class of laser resonators is based on circular structures like spheres, disks, and rings. In these structures, the optical modes form closed circular loops and... 

One final type of laser resonator, which is also applicable for molecular glasses, should be mentioned The random laser, based on coherent backscat-tering in an amplifying medium [212, 213]. In these structures, strongly scattering nanoparticles like Ti02 colloids are randomly dispersed in the amorphous films leading to self-contained optical paths and thus to the localization of optical modes. Since disordered structures are much easier to produce than ordered... 

In addition to the acoustical modes and MSo, we observe in the first half of the Brillouin zone a weak optical mode MS7 at 19-20 me V. This particular mode has also been observed by Stroscio et with electron energy loss spectrocopy. According to Persson et the surface phonon density of states along the FX-direction is a region of depleted density of states, which they call pseudo band gap, inside which the resonance mode MS7 peals of. This behavior is explained in Fig. 16 (a) top view of a (110) surface (b) and (c) schematic plot of Ae structure of the layers in a plane normal to the (110) surface and containing the (110) and (100) directions, respectively. Along the (110) direction each bulk atom has six nearest neighbors in a lattice plane, while in the (100) direction it has only four. As exemplified in Fig. 17, where inelastic... 

J. Petracek, Modelling of optical waveguide structures by the mode matching method, Assoc. Prof, thesis, (Bmo Technical University, 2004, in Czech). 

The spectral width of a pulse train emitted by a femtosecond laser can be significantly broadened in a single mode fiber [27]. This process that maintains the mode structure is described in the time domain by the optical Kerr effect or selfphase modulation. The first discussion is simplified by assuming an unchanging pulse-shape under propagation. After propagating the length l the intensity dependent refractive index n(t) = n0 + ri2/(f) leads to a self induced phase shift... 

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