Temperature characteristics of optical parameters of phthalocyanine LB films and spin-coated films

The LB films and spin-coated films of tetra-neopentoxy phthalocyanine zinc (TNPPcZn) were prepared and annealed at different temperatures. Their refractive index (n) and extinction coefficient (k) were measured by p-polarized reflectance. The similar value of n and k, as well as similar changing tendency of it and k at varied annealing temperatures, was found between LB films and spin-coated films. In addition, the absorption curves of TNPPcZn LB films and spin-coated films in visible range at different annealing temperature were investigated. The results indicate that the changing tendency of the extinction coefficient of two kinds of TNPPcZn films obtained from two methods mentioned above were coincident. When the annealing temperature increased to 150 degrees C, the monomers of TNPPcZn films transformed to aggregates, n(f) and k(f) of the films increased. Further, n(f) and k(f) decreased as aggregates changed back to monomers again at the annealing temperature of 300 degrees C. The experimental results coincide well with the theoretical analysis. (C) 2004 Elsevier B.V. All rights reserved.

Optical and surface properties of hybrid TiO2/ormosil planar waveguide prepared by the sol-gel process

Two kinds of silanes, 3-glycidoxypropyltrimethoxysilane (GLYMO) and 3-trimethoxysililpropylmethacrylate (TMSPM), were used to prepare ormosil waveguide films by the sol-gel method. Thirty percent Ti(OBu)(4) and 70% silane were contained in the precursor sets. The properties of films were measured by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/VIS/NIR spectrophotometer (UV-vis), atomic force microscopy (AFM), m-line and scattering-detection method. The films from GLYMO and TMSPM precursors exhibit similar thickness (2.58 mu m for GLYMO, 2.51 mu m for TMSPM) and refractive index (1.5438 for GLYMO, 1.5392 for TMSPM, lambda=632.8 nm), but the film from TMSPM precursor has higher propagation loss (1.024 dB/cm, lambda=632.8 nm) than the film prepared from GLYMO (0.569 dB/cm, lambda=632.8 nm). Furthermore, the film prepared from TMSPM is easy to be opaque and cracks during coating whereas the same phenomenon was not found for the film prepared with GLYMO. It is confirmed that GLYMO is a better precursor than TMSPM for waveguide film preparation. (C) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Laser-induced damage morphology of high-reflective optical coatings

Two different kinds of 1064 nm high-reflective (HR) coatings, with and without SiO2 protective layer, were prepared by electron beam evaporation. Three-dimensional damage morphology, caused by a Nd:YAG pulsed laser, was investigated for these HR coatings. Development of laser-induced damage on HR coatings was revealed by both temperature field calculation and discrete meso-element simulation. Theoretical results met experimental very well. (C) 2004 Elsevier B.V. All rights reserved.

Effect of laser heating temperature on coating characteristics of Stellite 6 deposited by cold spray

Laser-assisted cold spray (LCS) is a new coating and fabrication process which combines some advantages of CS: solid-state deposition, retain their initial composition and high build rate with the ability to deposit materials which are either difficult or impossible to deposit using cold spray alone. Stellite 6 powder is deposited on medium carbon steels by LCS using N 2 as carrier gas pressure. The topography, cross section thickness, structure of the coatings is examined by SEM, optical microscopy, EDX. The results show that thickness and fluctuation of coating are improved with increased deposition site temperature. Porosity of coating is affected by N 2 and deposition site temperature. In this paper, it presents optimal coating using N 2 at a pressure of 3 MPa and temperature of 450°C and deposition site temperature of 1100°C.

Structural and optical characterization of vertical GaAs/GaP core-shell nanowires grown on Si substrates

GaAs nanowires were grown on Si (111) substrates. By coating a thin GaAs buffer layer on Si surface and using a two-temperature growth, the morphology and crystal structure of GaAs nanowires were dramatically improved. The strained GaAs/GaP core-shell nanowires, based on the improved GaAs nanowires with a shell thickness of 25 nm, showed a significant shift in emission energy of 260 meV from the unstrained GaAs nanowires. © 2010 IEEE.

NUMERICAL ANALYSIS OF A NOVEL 980nm MICROCAVITY SEMICONDUCTOR OPTICAL AMPLIFIER WITH HIGH GAIN AND LOW NOISE

A novel microcavity semiconductor optical amplifier ( MCSOA) was proposed by incorporating top and bottom distributed Bragg reflectors ( DBRs) into the waveguide structure of conventional traveling-wave semiconductor optical amplifiers(TW-SOAs). The incoming( outgoing) light beam incidented onto (escaped from) the waveguide structure at a oblique angle through two optical windows, where the top DBR was etched away, and anti-reflection coating was deposited. The light beams inside the optical cavity were reflected repeatedly between two DBRs and propagated along waveguide in a zigzag optical path. The performance of the MCSOA was systematically investigated by extensive numerical simulation based on a traveling-wave model by taking into account the comprehensive effects of DBRs on both the amplification of signals and the filtering of spontaneous emission( SE). Our results show that the MCSOA is capable of achieving a fiber-to-fiber gain as high as 40dB and a low noise figure is less than 3.5dB.

Side radical influence on the nonlinear optical properties and thermal stability of poled polymer films

Films of polyetherketone doped with the chromophores Disperse Red 1 (DR1) and Disperse Red 13 (DR13) were prepared by spin-coating method. By the in situ Second-harmonic Generation (SHG) signal intensity measurement, the optimal poling temperatures were obtained. For the investigated polyetherketone polymer doped with DR1 (DR1/PEK-c) and polyetherketone polymer doped with DR13 (DR13/PEK-c) films, the optimal poling temperatures were 150degreesC and 140degreesC, respectively. Under the optimal poling conditions, the high second-order nonlinear optical coefficient chi(33)((2)) = 11.02 pm/V has been obtained for the DR1/PEK-c; and for DR13/PEK-c at the same conditions the coefficient is 17.9 pm/V. The SHG signal intensity DR1/PEK-c could maintain more than 80% of its initial value when the temperature was under 100degreesC, and the SHG signal intensity of the DR13/PEK-c could maintain more than 80% of its initial value when the temperature was under 135degreesC. (C) 2002 Kluwer Academic Publishers.

Delay of the excited state lasing of 1310 nm InAs/GaAs quantum dot lasers by facet coating

In this letter, we present a facet coating design to delay the excited state (ES) lasing for 1310 nm InAs/GaAs quantum dot lasers. The key point of our design is to ensure that the mirror loss of ES is larger than that of the ground state by decreasing the reflectivity of the ES. In the facet coating design, the central wavelength is at 1480 nm, and the high- and low-index materials are Ta2O5 and SiO2, respectively. Compared with the traditional Si/SiO2 facet coating with a central wavelength of 1310 nm, we have found that with the optimal design the turning temperature of the ES lasing has been delayed from 90 to 100 degrees C for the laser diodes with cavity length of 1.2 mm. Furthermore, the characteristic temperature (T-0) of the laser diodes is also improved.

Sol-gel matrix modified microstructured optical fibre towards a fluoride sensitive optical probe

In this article, we report an optical fluoride probe based on microstructured polymer optical fibers (MPOFs) which is modified with morin-Al complex doped silica gel film. This probe is fabricated by sol-gel fluxion coating process. Sol solution doped with morin-Al is directly inhaled into array holes of MPOF and then forms morin-Al-gel matrix film in them. The sensing probe shows different fluorescence intensity to different fluoride ion concentrations in the aqueous solution. The range of response is 550 mmol/L, under the condition of pH 4.6. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

The mode control of asymmetric Fabry-Perot optical modulators with multiple quantum wells

The asymmetric Fabry-Perot (ASFP) mode position with the thickness of different index coating layer is calculated. The reason for the blue shift of the ASFP mode with the increasing thickness of low index coating layer is analyzed and this phenomenon is observed in experiments. With the wet-etching method, the ASFP mode can be tuned to the desired wavelength and thus the deviation of growth can be compensated. This method is used to improve the contrast ratio of modulators. With the ASFP mode located at different positions relative to the unbiased e-hh peak, different modulation characteristics are demonstrated.

Optical and structural properties of anodized AlxGa1-xAs layers

The optical and structural properties of anodized AlxGa1-xAs films were investigated by using optical reflectance, X-ray photoemission and Auger electron spectroscopy (XPS and AES). II was found that the anodization process occurs progressively from the surface to the bulk of AlxGa1-xAs and the formed oxidation film comprises mainly oxides of Al and Ga together with a relatively small amount of As. The refractive indexes of the anodized Al0.8Ga0.2As film and Al0.8Ga0.2As film itself were deduced to be about 1.80 and 3.25, respectively, indicating that the anodization film is desirable for anti-reflection coating of the surface of AlxGa1-xAs/GaAs solar cells. (C) 1997 Elsevier Science S.A.

Thermally Stable Guest-Host Polyetherketone Poled Polymer for Electro-Optical Applications

The high glass transition temperature polymer polyetherketone doped with disperse red 13 (DR13/PEK-c) has been prepared by the spin-coating method. Through in situ second-harmonic generation, the corona poling temperature was optimized by measuring the temperature dependence of the in situ second-harmonic generation signal intensity under the poling electric field. The linear electro-optic coefficients of the poled polymer films have been determined at 632.8 nm by using a simple interferometric technique. The polymer system was measured after 13 000 h, and found that it remained at 80% of its initial value.

1.55μm Fabry-Perot Thermo-Optical Tunable Filter with amorphous-Si as Cavity

A 1.55μm Fabry-Perot (F-P) thermo-optical tunable filter is fabricated. The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique. Due to the excellent thermo-optical property of a-Si, the refractive index of the F-P cavity will be changed by heating; the transmittance resonant peak will therefore shift substantially. The measured tuning range is 12nm, FWHM (full-width-at-half-maximum) of the transmission peak is 9nm, and heating efficiency is 0.1K/mW. The large FWHM is mainly due to the non-ideal coating deposition and mirror undulation. Possible improvements to increase the efficiency of heating are suggested.

Optical properties of organo-soluble polyimide thin films and their applications in liquid crystal displays

Three organo-soluble polyimide powders have been synthesized. Their imidization was verified by Fourier transform infrared (FTIR) and thermal gravimetric analysis (TGA) techniques. The amorphous morphology of their thin films were confirmed by X-ray diffraction. Polyimide thin films were prepared by solution casting or spin coating. UV-visible transmission spectra of thin films revealed that they are almost transparent in the range of visible light. With in-plane orientation, revealed by FTIR spectra, negative birefringence (Delta n) of thin films were observed, and refractive indices of the thin films along the film plane (n(TE)) and normal to the plane (n(TM)) were measured by a prism coupler. Because of negative birefringence of the thin films, they tan be substituted for the compensation films for twisted nematic liquid crystal displays (TN-LCDs) to extend their viewing angles. In this paper, a 90 degrees C TN-LCD and 120 degrees C TN-LCD were taken as examples to show the compensation effect of thin films of a qualified polyimide. (C) 1998 Elsevier Science S.A. All rights reserved.

Detection of Lead Contamination of Water and VOC Contamination of Air Using SOI Micro-Optical Devices

Micro-photonic SOI Mach-Zehnder interferometers were coated with solid-phase micro-extraction materials derived from polydimethylsiloxane to enable sensing of volatile organic compounds of the BTEX class in air. A different coating based on functionalized mesoporous silicates is used to detect lead Pb(II) with a detection limit of <;; 100 ppb in water.