Volume 88, Issue 11, 01 December 2000
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
88(2000); http://dx.doi.org/10.1063/1.1309038View Description Hide Description
We report the morphology, composition, and interaction mechanisms of siliconsurfacegratings fabricated with the fourth harmonic (266 nm) of a Q-switched Nd:YAG laser. We paid particular attention to the laser fluence dependence of silicongrating formation. It was found that at low fluence levels, grating formation was mainly caused by siliconoxidation. However, at high fluence levels gratings were formed with thermal ablation. In the former case, it was found that water vapor, instead of oxygen molecules, in the air was the key species providing oxygen for siliconoxidation. In the latter case, grating morphology was controlled by laser fluence level. These conclusions were supported by the measurement results of atomic force microscopy, energy-dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy, and chemical etching. The results of real-time monitoring of grating growth are also reported.
InAs quantum wires in InP-based microdisks: Mode identification and continuous wave room temperature laser operation88(2000); http://dx.doi.org/10.1063/1.1322381View Description Hide Description
We present the design, fabrication, and characterization of an optical microsource, which comprises InAs/InP quantum wires embedded in a suspended microdisk. Comparison between photoluminescence measurements and theoretical analysis allows for a clear identification of the whispering gallery modes. cw room temperature lasing operation is demonstrated.
Homeotropic polar anchoring energy of a nematic liquid crystal using the fully leaky waveguide technique88(2000); http://dx.doi.org/10.1063/1.1324695View Description Hide Description
Optical excitation of a series of fully leaky guided modes has been used to explore the director distortion of a hybrid-aligned nematic liquid crystal with a negative dielectricanisotropy (Merck-BDH, MLC 6608) under application of an acelectric field. Hybrid alignment is realized by the use of a lecithin film on the top glass plate and rubbed polyimide on the bottom plate, both plates having indium–tin–oxide coatings. Continuum theory is used to model the director profile through the cell. Fitting the fully leaky guided mode data both in transmission and reflection using optical multilayer theory together with continuum modeling gives the director profile both with and without applied fields. From this fitting the changes in the surface tilt angle and its gradient are obtained. Using this information the polar anchoring coefficient of the homeotropic surface is deduced. At 23.1 °C we find
88(2000); http://dx.doi.org/10.1063/1.1289487View Description Hide Description
Waveguidesfabrication in Z- and X-cut crystals by vapor zincdiffusion has been studied by secondary ion mass spectrometry and optical measurements. Compositional analysis of diffused substrates shows the formation of a Zn rich superficial layer, followed by a deeper region with decreasing Zn concentration. A subsequent thermal annealing process has been performed to let zinc ions further diffuse into the substrates. The composition profiles have been correlated with the refractive index profiles, reconstructed by optical reflectivity measurements. The results and the nature of the detected layers are discussed and correlated with previous x-ray studies obtained in the same samples.
88(2000); http://dx.doi.org/10.1063/1.1289793View Description Hide Description
We present experimental results of a Kretschmann-prism coupler method used in Raman scattering experiments with ultrathin (few nanometers) sol–gel films deposited on a metallic silver layer characterized by surface plasmon resonance (SPR) experiments. In this article, we describe a new optical device as an application of SPR properties and coupled with a micro-Raman scattering setup. The enhancement factor (150) of the Raman intensity in comparison to the classical way allows us to determine the critical thin films structure. Optical results are then discussed and compared to transmission electron microscopy.