The results of a simulation of the optical properties of a silicon Fabry-Pérot resonator (with liquid crystal filler in the
cavity), operated on the shift of the interference bands in the infrared range are presented. The possibility of tuning the
reflection coefficient from 0 to 0.95 (or transmission coefficient from 1 to 0.05) by changing the refractive index by 0.1
in the cavity and using the stop-bands and resonance peaks of high order is demonstrated. The prototype Fabry-Pérot
resonators were fabricated by dry and wet etching of (100)Si and (110)Si. Some of the resonators were fabricated on a
silicon-on-insulator platform. A superposition of transmission peaks with reflection maxima, predicted from calculations,
was confirmed experimentally, using infrared microspectroscopy, with a temperature variation from 20 oC to 65 oC and
an applied electric field from 0V to 10V.
One dimensional periodic and non-periodic silicon photonic structures have been designed and fabricated on silicon-on-insulator
substrate for the investigation of the electro-tuning effect in composite system Photonic Crystal - Liquid
Crystal. The reflection spectra registered for non-periodic structures demonstrate the phase polarisation shift for bands
of high reflection, while for the periodic structure the shift of the photonic band gap edge was observed. Under an
applied electric field in the range from 2V to 10V, the shift of the polarised reflection spectra, caused by reorientation of
the LC director from planar to homeotropic alignment, has been obtained. A significant change in the refractive index
close to Δn=0.2, which is a characteristic feature for LC E7, has been achieved due to LC reorientation in all structures
just after LC infiltration. It was found that after switching-off the applied electric field the initial planar orientation of LC
molecules is not restored. This effect is related to weak anchoring of LC molecules to the silicon side-walls which
results in the transition of LC to the pseudo-isotropic alignment after the applied voltage is off. A relatively smaller (with
Δn=0.07), but highly reproducible electro-tuning effect was revealed during the LC reorientation from pseudo-isotropic
to homeotropic alignment. The shift of the edge of PBG by Δλ=0.16 or by Δλ/λ=1.6% in relative shift units was
observed in this case. The response time estimated under applied square shaped ac pulses of various frequencies was
found to be around 30 ms.
In this paper we describe a novel technique for the fabrication of aluminosilicate microfibres and microtubes which are
shown to act as optical cylindrical microresonators. The alumosilicate microfibres and microtubes were fabricated by
using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microfibres and
microtubes were studied using Scanning Electron Microscopy (SEM), micro-photoluminescence spectroscopy and
fluorescence lifetime imaging confocal microscopy. In the emission spectra of the micro-resonators we find very narrow
periodic peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors up to
3200. A strong enhancement in photoluminescence decay rates at high excitation power demonstrates the occurrence of
amplified spontaneous emission from a single microtube. These microtubes show a large evanescent field extending
many microns beyond the tube radius. Potential applications for these novel microresonators will be in the area of optical
microsensors for a single molecule detection of biological and chemical species, including anti-terrorism and defense
sectors.
We experimentally demonstrate very efficient non-phase-matched second- and third-harmonic generation from a macroporous GaP. The generated second-harmonic signal is independent of crystallographic orientation, and its enhancement is believed to be due to the light localization for which conditions exist in the studied samples of porous GaP. The nonlinear optical results are correlated with linear optical scattering studies and atomic-force microscopic images of the studied surfaces.
Demonstration of porous anodic alumina application for photonics and optoelectronics is presented. Investigation of photonic structures and nanocomposites based on porous anodic alumina is performed. Techniques of highly ordered porous structure formation are demonstrated. Features of nanocrystal template deposition into nanopores are discussed.
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