The structure of optical thin films changes depending on various parameters. Typical these parameters are materials,
coating methods and coating parameters (for example, assisted ion beam power etc.). For example, titanium dioxide thin
films prepared by IAD (Ion Assisted Deposition) method take the column structure. Foggy levels of the deposited film
depend on the film structure. Recently, the foggy levels are measured using a haze meter. But weak foggy sample with
small haze value does not correspond to visual inspection. In this work, optical thin films were characterized by not only
the intensity of the scattered light but also wavelength parameter. As a result, it was found that the estimation of the
structure of optical thin films was possible by using the wavelength dependence of the scattered light.
Recently, optical thin films have been increasingly needed in optical components. SiO2 is most frequently used as a low-
refractive-index material of optical thin films. The stress of the film is an important parameter that relates to the adhesion
of the film. However, the long-term time dependence of the stress has not been thoroughly discussed for SiO2 optical
thin films. In this report, the time dependence of the stress of SiO2 optical thin film is discussed in terms of optical
characteristics in the infrared region. The optical properties and the structure of SiO2 optical thin films deposited by
vacuum deposition (using an EB) and ion-assisted deposition (IAD) were observed by FT-IR, XRD and SEM. The stress
of SiO2 optical thin films was measured using an interferometer to determine the change in the substrate shape. The SiO2
thin films prepared by both vacuum deposition and IAD exhibited compression stress. Decreases in the stress of the films
deposited by vacuum deposition were observed to continue for more than 1000 hours. This result is different from that of
the conventional stress model in which the stress changes stop after about one week. The stresses of the films prepared
by IAD were observed to change little. Optical absorption by Si-O bonds was observed at 1100cm-1. The change in
bonds from Si-O to Si-OH was observed in the film deposited by vacuum deposition. It is thought that this result of the
change in bonds was related to the decrease in the stress of the films.
Laser cutting of carbon (C) and silicon carbide (SiC) fibers was performed using a second harmonic generation (SHG) sheet beam of Q-switched Nd:YAG laser with an out put energy of 4J/pulse, pulse width of 10ns and a fluence of 3.0J/cm2. The beam was irradiated respectively on monofibers of C and SiC placed on an optical glass slide in air at room temperature. A single pulse was irradiated every one second and repetition number of shot pulses N was varied from N=10 to 40 pulses. Cutting of C and SiC fibers occurred for N = 20-40 pulses. A cut portion of C fiber fixed on the substrate for one end in tension free was found to have very sharp wedge like profile. Laser irradiation for C fiber fixed with both ends on the substrate made the fiber fractured with thinner fiber diameter. Similar profile was also observed in a SiC fiber at the cut portion. Smooth flat surface of laser cut portion of C and SiC fibers suggested a laser ablation by evaporation. In the SiC fiber, sticky and viscous layer was observed at the cut surface, suggesting vitreous silica formed by oxidation of laser-irradiated fiber.
Microlenses were formed directly on a surface of a glass plate by using CO2 laser. This method has the merit of complete dry processing and presents simple way of microlens fabrication. We discuss about the formation process and mechanism through the characterization of irradiation parameters and the glass composition. When the surface of a glass plate is heated locally to a working point of the glass material by a focused CO2 laser beam, a microlens is formed owing to surface tension. It was found possible to fabricate microlens easily placed at different focal position by controlling a laser power and an irradiation time. The volume of the fabricated microlens was found to be dependent on laser irradiation energy (laser power x irradiation time) and irradiated position. When a Corning 7059 glass plate was used, a convex microlens was obtained at the energy density smaller than ca. 100 (μJ/μm2).
Microlenses were formed directly on a surface of a glass plate by using CO2 laser. This method has the merit of complete dry processing and presents simple way of microlens fabrication. We discuss about the formation process and mechanism through the characterization of irradiation parameters and the glass composition. When the surface of a glass plate is heated locally to a working point of the glass material by a focused CO2 laser beam, a microlens is formed owing to surface tension. It was found possible to fabricate microlens easily placed at different focal position by controlling a laser power and an irradiation time. The volume of the fabricated microlens was found to be dependent on laser irradiation energy (laser power x irradiation time) and irradiated position. When a Corning 7059 glass plate was used, a convex microlens was obtained at the energy density smaller than ca.100 (μJ/μm2 ). The dynamical stress change of the microlens was measured in-situ by using the ellipsometry analysis to make clear the formation process of microlens. The T-FDP (four detectors polarimeter of transmission type) was used for this analysis.
The laser medium made of a single crystal is generally limited in several factors to fabricate large size crystals and to dope optically active elements heavily. For the improvement of these factors, it is proposed to use ceramics for the laser. We have succeeded to fabricate highly transparent ceramics ruby by using CIP and vacuum sintering techniques. The fluorescence spectrum of Cr ions in the ceramics ruby corresponded to that of a single crystal.
It is required for the optical amplifier to make down sizing and also to have high efficiency to meet the demands for processing higher density of information. Especially, the film-type optical amplifier is advantageous in the field of the optical integrated circuit. From such a point, we are studying the potential materials for a waveguide-type optical amplifier with higher efficiency. The Al2O3 is possible to deposit by the vacuum deposition method using an electron beam which is excellent about the mass production. In this study, we examined about the Al2O3 film system as a matrix medium doped with transition elements of Cr or Co as optically active elements. These films doped with transition elements at various concentrations were characterized using absorption spectroscopy and photoluminescence (PL) et al for their optical and electrical properties. As a result, optically active films were deposited by optimizing the electron beam vacuum deposition condition. It was found that the property of the film changed from an insulator-like to a metal-like behavior at the doping rate of around 30at. percent due to the precipitation of the metallic phase of doped transition elements.
Silver halide photographic plates and photo-polymers have been utilized for the holographic recording. These materials are available only for recording of still pictures, and require complex developing process and relatively long time for recording and reproduction of the image. As an alterative, image recording using bismuth sillenite compound has been researched. The BGO and BSO single crystal bulk samples have been sued for these studies. On such background, we aimed to fabricate BGO and BSO films for image recording. Thin films have merits in device integration and mass production. We have already found out the process condition to obtain good crystalline BGO films on glass substrates. The film with crystalline phase only was obtained at the substrate temperatures above 200 degrees C. In this paper, BGO and BSO films were deposited on glass substrates and the ITO conducting films on the glass substrates using RF magnetron sputtering method. Preliminary image recording experiments were carried out for a BSO single crystal and its film. Image recording properties were characterized for the polycrystalline films with different film thickness by recording interference fringes using the Ar ion laser.
Silver halide photographic plates and photosensitive polymers have been utilized for the holographic recording. These materials are available only for recording of still pictures and require complex developing processes and a relatively long time for recording and reproduction of the image. As an alternative, image recording using bismuth silenite compounds has been researched. The BSO and BGO single crystal bulk samples have been used for these studies. We aimed to fabricate BGO and BSO films appropriate for image recording. Films have merits in device integration and mass production. The process condition to obtain a good crystalline film was studied. The film with crystalline phase only was obtained at the substrate temperatures above 200C.
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