scholarly journals Experimental Study and Analysis of Light Scattering Patterns of Bragg Fibers Fabricated in PECVD

2021 ◽  
Author(s):  
Zeba Naqvi ◽  
Tsing-Hua Her
Keyword(s):  
Light Scattering ◽  
Optical Fibers ◽  
Vapor Deposition ◽  
Fiber Quality ◽  
Chemical Vapor ◽  
Fiber Axis ◽  
Scattering Pattern ◽  
Angular Scattering ◽  
Beam Incident ◽  
Bragg Fibers

Abstract Light scattering patterns are commonly used in industry to assess fiber quality. In this work, scattering patterns of Bragg fibers are studied. Optical fibers are coated with alternating layers of Silicon Nitride and Silica using Plasma Enhanced Chemical Vapor Deposition. A laser beam incident perpendicular to the fiber axis scatters off creating patterns distinct from that of uncoated fibers which exhibit continuous front lobe. Effect of variation in layer properties, polarization, wavelength and fiber symmetry is observed in the patterns. Anomalous suppression and enhancement in angular scattering pattern is explained through a scattering angle diagram. Features in the pattern are mapped to reflectance of the Bragg stack and it is found that a stopband creates the anomalous features in the scattering.

Ni-Coated Optical Fibers by Electroless Plating

2000 ◽  
Vol 6 (S2) ◽  
pp. 456-457
Author(s):  
Yuli Lin ◽  
Li-Jang Hwang
Keyword(s):  
Optical Fibers ◽  
Vapor Deposition ◽  
Nuclear Power ◽  
Power Plants ◽  
Linear Expansion ◽  
Chemical Vapor ◽  
High Strength ◽  
Metal Coating ◽  
Chemical Plants ◽  
Silica Substrate

Optical fibers have been extensively employed in a variety of fields. However, the need of high strength, excellent resistance to moisture permeation and tolerance to heat becomes apparent when such optical fibers are used in nuclear power plants and chemical plants in particular. Plastic coatings as conventional made of optical fibers cables would be replaced by the optical fiber coated with a layer of metal.Several techniques have been applied to make a metal coating for the optical fibers. Dipping method, to pass optical fibers through a bath containing metal melt, was found the simplest. This dipping method, however, suffers from a disadvantage of a generation of a microbent due to the differences of the linear expansion between metal and the silica substrate [1]. Moreover, the control of the thickness was found difficult using the dipping method. Chemical vapor deposition was also used to form the metal coating on optical fibers.

The Utility of Laser Light Scattering in Assessing the Mixability of Reagents for Chemical Vapor Deposition

1993 ◽  
Vol 324 ◽  
Author(s):  
Bin Ni ◽  
Gene P. Reck ◽  
James W. Proscia
Keyword(s):  
Chemical Vapor Deposition ◽  
Light Scattering ◽  
Titanium Nitride ◽  
Tin Oxide ◽  
Vapor Deposition ◽  
Laser Light ◽  
Chemical Vapor ◽  
Reaction Chamber ◽  
Laser Light Scattering ◽  
Tin Oxide Films

AbstractThe premixability of reagents used in chemical vapor deposition reactors is important to insure that gas feed lines and nozzles do not become clogged with particulates during operation. Even if reactants are to be kept separate until introduced into a reaction chamber, it is desirable to limit the number of particles formed. A reactor which utilizes laser light scattering to monitor particulate formation when gaseous reagents are mixed is described. The reaction of tin (IV) chloride with water is commonly used to produce tin oxide films by chemical vapor deposition. It was found by the light scattering experiment that at temperatures above about 110°C the number of particulates formed is greatly reduced. Therefore, it would be most desirable that these reagents be mixed above this temperature when depositing tin oxide from this reaction. The reaction of titanium tetrachloride with various amine was also investigated by this method. This reaction has been demonstrated to produce titanium nitride above 450°C. For each case, it was observed that there was a temperature above which the number of particulates was significantly reduced. This temperature was always below the optimal temperature for producing titanium nitride films.

Rayleigh Light Scattering Measurements of Transient Gas Temperature in a Rapid Chemical Vapor Deposition Reactor

1999 ◽  
Vol 122 (1) ◽  
pp. 165-170 ◽  
Author(s):  
J. F. Horton ◽  
J. E. Peterson
Keyword(s):  
Chemical Vapor Deposition ◽  
Light Scattering ◽  
Flow Field ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Gas Temperature ◽  
Wafer Temperature ◽  
Carrier Gas ◽  
Rayleigh Light Scattering ◽  
Rayleigh Light

A laser-induced Rayleigh light scattering (RLS) system was used to measure transient gas temperatures in a simulated rapid chemical vapor deposition (RCVD) reactor. The test section geometry was an axisymmetric jet of carrier gas directed down, impinging on a heated wafer surface. RLS was used to measure instantaneous gas temperature at several locations above the wafer as it was heated from room temperature to 475 K. Gas flow rate and wafer temperature correspond to jet Reynolds number Rei=60, wafer maximum Grashof number GrH=4.4×106, and maximum mixed convection parameter GrH/Rei2=1200; all conditions typical of impinging jet reactors common in the numerical literature. Uncertainty of RLS transient temperature from a propagated error analysis was ±2–4 K. Peak gas temperature fluctuations were large (in the order of 25 to 75 °C). Both flow visualization and RLS measurements showed that the flow field was momentum dominated prior to heating initiation, but became unstable by GrH/Rei2=5. It then consisted of buoyancy-induced plumes and recirculations. Up to the peak wafer temperature, the flow field continued to be highly three-dimensional, unsteady, and dominated by buoyancy. RLS measurements are shown to provide information on carrier gas instantaneous temperature and flow field stability, both critical issues in RCVD processing. [S0022-1481(00)02401-4]

Experimental and Numerical Modeling Studies of Laser Chemical Vapor Deposition on Moving Optical Fibers

Volume 3 ◽  
2004 ◽  
Author(s):  
Kinghong Kwok ◽  
Wilson K. S. Chiu
Keyword(s):  
Chemical Vapor Deposition ◽  
Optical Fibers ◽  
Vapor Deposition ◽  
Atmospheric Pressure ◽  
Fiber Surface ◽  
Chemical Vapor ◽  
Transfer Model ◽  
Laser Chemical Vapor Deposition ◽  
Protective Films ◽  
The Relationship

An atmospheric-pressure laser-induced chemical vapor deposition (CVD) reactor has been developed that is capable of continuously depositing carbon protective films on moving optical fibers from several hydrocarbon precursors. The relationship between operating parameters and the carbon deposition temperature was investigated experimentally and the results indicate that they are highly dependent on the laser power density and the fiber’s drawing velocity. A computational heat transfer model was developed to calculate the fiber surface temperature during deposition and to provide a deeper understanding of the fundamental principles that govern laser heating and the carbon CVD processes. The surface temperatures obtained from experiments are compared with the calculated temperature in order to validate the numerical model.

Flow Regimes and Transitions in a Rapid Chemical Vapor Deposition Reactor Using Flow Visualization and Rayleigh Light Scattering

2000 ◽  
Author(s):  
Angelo G. Mathews ◽  
Jill E. Peterson
Keyword(s):  
Light Scattering ◽  
Flow Visualization ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Flow Regimes ◽  
Rayleigh Light Scattering ◽  
Flow Visualizations ◽  
Transition Points ◽  
Stable Flow ◽  
Rayleigh Light

Abstract Previous study of carrier gas flow in rapid chemical vapor deposition (RCVD) reactors has been limited mostly to numerical simulations and flow visualizations. In the present work flow regimes were observed and temperatures were measured in a vertical axisymmetric pedestal RCVD reactor using flow visualization and Rayleigh light scattering (RLS) for noninvasive temperature measurement. Flow visualizations revealed that the flow undergoes complex transitions between stable flow regimes as heating occurs. The two dominant stable flow regimes were buoyant stable (BS) and momentum stable (MS). RLS was used to determine the instantaneous carrier gas temperature at discrete points in the test section. The flow regimes and their transition points were easily recognized and agreed with flow visualization data. The flow visualizations and RLS tests showed identifiable trends in transition points between flow regimes and in the types of regimes encountered. These trends were dependent on Grashof number and Reynolds number.

In-Situ Light-Scattering Measurements During the CVD of Polycrystalline Silicon Carbide

1991 ◽  
Vol 250 ◽  
Author(s):  
Brian W. Sheldon ◽  
Philip A. Reichle ◽  
Theodore M. Besmann
Keyword(s):  
Silicon Carbide ◽  
Light Scattering ◽  
Polycrystalline Silicon ◽  
Chemical Vapor ◽  
Nucleation And Growth ◽  
Scattering Spectrum ◽  
Angular Scattering ◽  
Polycrystalline Silicon Carbide ◽  
Scattering Spectra

AbstractLight-scattering was used to monitor the chemical vapor deposition of silicon carbide from methyltrichlorosilane. The nucleation and growth of the SiC features caused changes in the surface topography that altered the angular scattering spectrum that was generated with a He-Ne laser. These scattering spectra were then analyzed to obtain information about the nucleation and growth processes that are occurring.

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