SiO2 Cladding Research Articles

Designing optical-fiber modulators by using magnetic fluids

To reduce interface loss between optical fibers and devices in telecommunication systems, the development of an optical-fiber-based device that can be fused directly with fibers is important. A novel optical modulator consisting of a bare fiber core surrounded by magnetic fluids instead of by a SiO2 cladding layer is proposed. Applying a magnetic field raises the refractive index of the magnetic fluid. Thus we can control the occurrence of total reflection at the interface between the fiber core and the magnetic fluid when light propagates along the fiber. As a result, the intensity of the outgoing light is modulated by variation in field strength. Details of the design, fabrication, and working properties of such a modulator are presented.

Investigation of Nonreciprocal Characteristics and Design of Interferometric Optical Isolator with Multimode Interference Coupler Operating with a Unidirectional Magnetic Field

A novel interferometric isolator that consists of multimode interference (MMI) couplers and operates under a unidirectional magnetic field has been proposed and designed to fabricate a high-performance waveguide magnetooptic isolator operating at a wavelength of 1.55 µm. The optical isolator has an upper HfO2 cladding layer in one arm of the interferometer, and the other arm is covered with a SiO2 cladding layer. By virtue of this configuration, the isolator operates under a unidirectional magnetic field. The optimized structure of the isolator was determined by a 3D beam propagation method.

Fabrication and Characterization of Non-Doped SiO2 Cladding Layer for Polarization-Insensitive Silica Waveguide by Using Plasma Enhanced Chemical Vapor Deposition

We developed a technique for fabricating the cladding layers of silica waveguides and used this technique to fabricate an arrayed waveguide grating (AWG). The technique consists of two deposition process of non-doped SiO2. The first deposition process is a two-step deposition process combining plasma-enhanced chemical vapor deposition (PECVD) using tetraethylorthosilicate (TEOS) gas with an etching-back non-doped SiO2 by RF sputtering, and the second is a deposition process by means of PECVD using SiH4 gas. The non-doped SiO2 cladding layer must meet requirements of a thickness over 10 µm without cracking and a refractive index the same as that of fused silica. By using this fabrication technique, these requirements are satisfied and narrow core-to-core gaps are successfully filled with non-doped SiO2 without producing voids. The developed silica waveguide with non-doped SiO2 cladding has a propagation loss of 0.07 dB/cm and the developed AWG has a polarization sensitivity of 0.001 nm, which is one order of magnitude lower than that of existing AWGs.

Magnetooptic Waveguide with SiO2 Cladding Layer Integrated on InP Substrate by Wafer Direct Bonding

Magnetooptic waveguides with a SiO2 cladding layer were fabricated on an InP substrate by the wafer direct bonding technique for the purpose of integrating a laser diode and an optical isolator. First, direct bonding between InP and sputter-deposited SiO2 on a Gd3Ga5O12 substrate was investigated. Bonding was achieved by surface treatment of both wafers and subsequent heat treatment in H2 ambient. By applying heat treatment in H2 ambient at temperatures ranging between 110 and 220° C, the magnetooptic waveguides were bonded to the InP substrate without deterioration of their optical properties.

Chlorination and vaporization of GeO2 component in SiO2:GeO2 porous preform in dehydration process by VAD method and spontaneous formation of SiO2 cladding layer during the dehydration by selective vaporization of GeO2

Abstract In order to prepare silica-based graded index fibers of uniform transmission quality and low OH content by the vapor phase axial deposition (VAD) method, the halogenation rates of various types of GeO2 as a function of the molar ratio of oxygen to chlorine and of temperature were measured. As a result, the behavior of both the hexagonal GeO2 and the solid solution GeO2 in the dehydration and consolidation processes has become clear, that is, the solid solution GeO2 having SiOGe bonds which is formed in the high temperature region is very stable in the dehydration and consolidation processes. On the other hand, the crystalline hexagonal GeO2 which is formed in the low temperature region is unstable for chlorination reaction in the dehydration process and for volatilization in the consolidation process. This effect has been applied for OH content, and bandwidth control of fibers and VAD fibers of low OH content with losses less than 1 dB/km at 1.39 μm without any cladding deposition process and also those of highly uniform bandwidth fluctuations within ± 100 MHz km in the longitudinal direction of the fibers were obtained.

Optical waveguides on silicon chips

Optical waveguides consisting of a SiOxNy (0≤x,y≤1) core and SiO2 cladding layers have been fabricated using Si LSI technologies. Low-pressure chemical vapor deposition (CVD) at 750 °C and remote-plasma CVD at 300 °C have been employed for the deposition of core materials. The propagation loss of ridge type waveguides depends on the size (thickness and width), refractive index and surface roughness of the core. A minimum loss of 1.5 dB/cm has been obtained. Micromirrors made from substrate-Si, poly-Si or Al, which change the light propagation direction, have been fabricated using wet-chemical or chemical dry etching. The light bending efficiency ranges from 60% to 80% depending on the material. Simulations and measurements of the propagation losses of branched and curved waveguides have been carried out. It is shown that the simulated results are in good qualitative agreement with the experimental data for both branched and curved waveguides. Single-chip integration of light emitting diodes (LEDs), micromirrors, waveguides, and photodetectors has been accomplished and the signal transfer from the LED to the photodetector has been verified.

Single-Chip Integration of Light-Emitting Diode, Waveguide and Micromirrors

Fundamental technologies for optical interconnection on a Si LSI chip have been developed using conventional silicon process technologies. The optical waveguides with SiOx Ny core and SiO2 cladding layers and Al micromirrors to change the light propagation direction have been fabricated by low-temperature deposition. Moreover, the single test chip integrated with a light-emitting diode (LED), photodiode, waveguides and micromirrors has been fabricated and signal transfer between LED and the photodetector has been achieved.

Micron-Size Optical Waveguide for Optoelectronic Integrated Circuit

Fundamental technologies for the optical interconnection in the VLSI chip have been developed by using conventional Si LSI technologies. The micron-size optical waveguide consisting of Si3N4 core and SiO2 cladding layers has been fabricated by low-pressure chemical vapor deposition (LPCVD) and atmospheric-pressure chemical vapor deposition (APCVD), respectively. The small lenses and the micron-size mirror which changes the light propagation direction from vertical to horizontal for the interlayer interconnection have also been fabricated.

Exact acoustic leaky wave solutions for single-mode fibres

Exact solutions of acoustic leaky modes in single-mode fibres have been presented using a complex root search method. The leaky mode of GeO2: SiO2 (core) and SiO2 (cladding) single-mode fibre has been obtained. The present method has been compared with an approximate method. It has been found that the attenuation along the fibre axis is much higher than that obtained from the approximate method.

Studies on the preparation and semiconductor properties of clad silicon fibers

This paper is a report of some novel and unconventional approaches to device fabrication without necessarily going through the planar fabrication techniques. The paper basically concerns the feasibility of drawing silicon in the form of fine fibers with an outside insulator layer. SiO2 (cladding). The codrawing of silicon and silicon dioxide to form fine single-crystalline SiO2-clad Si fibers presents the material directly for the fabrication of metal oxide semiconductor (MOS) devices. X-ray measurements show that internal core (silicon) is single crystalline in nature and the same orientation is maintained throughout the length of the fiber. Results on the experimental measurements made on fabricated MOS devices offer high transconductance, a large current-carrying capability, and substantial amplifications which can be imporved further. Good capacitance-voltage curves are observed with no built-in oxide charges.

Humidity-sensing effects of optical fibres with microporous SiO 2 cladding

Experiments are conducted in which humidity is measured using optical fibres with microporous SiO2 cladding. The optical fibre is found to possess the characteristics of a relative humidity sensor, and is suitable for multipoint measurement employing optical time domain reflectometry techniques.

Characteristics of pure silica core single-mode fiber

Abstract Single-mode fibers with low attenuation and sufficient reliability are especially important for long-span optical transmission systems. Conventionally, GeO2 has been added to the fiber core region in order to make a refractive index difference between the core and cladding. However, the addition of GeO2 increases Rayleigh scattering loss [1], and deteriorates the chemical stability against hydrogen atmosphere and γ-ray irradiation to bring about an increase in attenuation. [2][3] Therefore, pure silica core single-mode fiber was considered to be an ideal type of fiber, and it was succeeded in being fabricated by utilizing fluorine containing SiO2 cladding.

Polarization properties of single-mode fiber-optic waveguides with weak birefringence

Single-mode fiber-optic waveguides were constructed. They had an SiO2 + GeO2 core and an SiO2 cladding, with weak internal birefringence. These waveguides were capable of distortion-free transmission monochromatic linearly polarized laser radiation over fiber lengths of from several centimeters to several hundreds of meters. A study was made of changes in the birefringence which occurred when external mechanical forces were applied to a waveguide (bending, tension, compression, torsion). It was found that on winding a waveguide into a coil of particular radius, without applying tension, the birefringence remained weak, while if tension was applied during the winding process the birefringence increased sharply. The possibility of controlling the birefringence is of practical interest in constructing various types of optical devices.

Compound‐Glass Waveguides Fabricated by a Metal Evaporation Technique

Glass fiber optical waveguides consisting of a potassium silicate glass core and SiO2 cladding were produced by a potassium metal evaporation technique. An evacuated fused‐silica tube containing an evaporated deposit of K was heated to temperatures sufficient to form a uniform potassium silicide layer on its inner surface. This layer was oxidized and reacted with the SiO2tubing at high temperatures to form a potassium silicate glass. The tube was then collapsed to give a solid rod preform with a potassium silicate core. Fibers drawn from such preforms exhibit moderately low optical loss. The fabrication technique is described, and a representative loss spectrum is presented.

Low-loss optical glass fibre with Al 2 O 3 -SiO 2 core

Optical glass fibres, consisting of an Al2O3-SiO2 core and SiO2 cladding, were produced by using a glass growth technique of vapour deposition in a flame. The core measured from 4 to 10 μ in diameter, and the difference in refractive index between the core and the cladding was 0.003. The lowest loss of this fibre was 10 dB/km at 0.66 μm.