The polarized emission behaviors of the Eu3+ doped azo-polymer waveguide were reported in this paper. Affected by the azobenzene groups in the photoinduced orientation process by the 532nm linearly polarized laser, the ligands were realigned orderly perpendicular to the direction of the orientation direction. This leads to the polarized absorption and emission of the waveguide in the orientation direction. By an m-line apparatus based on the prism coupling technique, two guided modes propagation were observed in the waveguide at 650nm in TE polarizations.
The independent control of the upper and lower cutoff frequencies of the guided modes in coupled-cavity wavguides (CCWs) is investigated numerically. The CCWs are formed in a two-dimensional photonic crystal (2D PhC) consisting of a square array of dielectric rods in the air. The dielectric constant and radius of the rods in the perfect PhC is 11.56 and 0.18α, respectively, in which α is lattice constant. By using the plane wave expansion method (PWEM), the impact of two influencing factors on cutoff frequencies in CCWs is calculated systematically. Efficient methods have been demonstrated for tuning one cutoff frequency while keeping the other unchanged. The indepent control ranges of the upper and lower cutoff can be up to 67.85% and 68.57% of photonic band gap (PBG), respectively. The results can be applied to the design of PhC-based optical devices such as band filters and optical switches.
Azobenzene polymers show large optical anisotropy, and one can control the optical anisotropy by changing the alignment of the molecules with light. Azo groups fall perpendicularly to the direction of the electric field vector of the linear polarized light by photoisomerization. This reorientation induces anisotropy and the difference of refractive index parallel and perpendicular to the irradiating laser polarization direction. In this paper, the photoinduced birefringence induced with 532 nm light in films of azobenzene polymer has been studied as a function of temperature, light intensity. From the evolution of the birefringence induced by laser, the temperature effects on photochemical trans-cis-trans isomerization cycles have been probed and analyzed. The effect of laser-induced heating has been introduced to the buildup of photoinduced birefringence in azobenzene-side-chain copolymer. The curves for the buildup of birefringence were fitted with a modified function, namely, biexponential curves and Gaussian curves. The relationship of each parameter has been also presented. With the modified fitting function, we obtained better fitting result.
KEYWORDS: Polymers, Near field scanning optical microscopy, Near field optics, Polymer thin films, Anisotropy, Data storage, Near field, Optical microscopy, Physics, Polarization
We report the near-field investigation on azobenzene contained polymer films using scanning near-field optical microscopy. Nanometer scale dots and lines were inscribed on these films, and the topographies and transmitting images of these patterns could be obtained at the same time. The transmitting images were in agreements with the topographies, and it proved that trans-cis isomerization of the azobenzene moieties in the illuminated area induced both surface relief and anisotropy. The experimental results helped to discover the mechanism of the photo induced surface relief and anisotropy, and the agreement between the transmitting images and the topographies could be applied in pure optical writing/reading in high-density data storage.
In this paper, an off-axis holographic lens with the focal length of about 70mm is recorded in the azobenzene liquid crystal polymer film (azo-LCP) by 532nm YbVO4 double-frequency lasers and is reconstructed by a 633nm He-Ne laser. The particularity and main advantage of the work consists in writing and reading out the hologram at the same place, without moving, post-exposure adjusting or chemical processing. The converging and imaging property of the holographic lens is measured and analyzed.
A temperature-tunable polarization interference filter (PIF) made of YVO4 crystal has been presented and applied for wavelength monitoring of a distributed feedback (DFB) laser in a dense wavelength-division-multiplexing (DWDM) optical communication system. This novel device offers a flexible way to monitor the operating wavelength of the transmitter over a wide capture range. Monitoring resolution of 0.02 nm can be obtained by measuring the temperature variation of the filter while its transmission value is kept at a constant value.
With the increasing demand of optical storage capacity, multi-level (ML) optical storage based on multi-level-amplitude modulation is receiving more and more attention, for it transmits more information ove a fixed bandwidth channel by using the available SNR more efficiently. We proposed an ML optical storage technology in azo LCP film based on polarization angle division. In this paper, the write strategy is developed by a ML write-compensation system that corrects for non-linearities of the data signal. The dynamic transmittance range is extended with the full monotonic range of angle and the varaition of each amplitude level relative to our dynamic range is improved. The experiments of imroved linear and nonlinear 16-level storage in azo LCP are demonstrated. The effects of thickness non-uniformity on linear and nonlinear 16-level storage are discussed.
In this paper, two-photon bit data storage in azobenzene polymer liquid crystal (PLC) film using low-power continuous wave (CW) laser beam at 532 nm is proposed and demonstrated for the first time, the exposure threshold of the material is below 4 X 106 mw/cm2, and a bit data storage pattern is recorded by two-photon absorption (TPA). The data is easily erasable and rewritable by the light of the same wavelength as the recording light.
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