Fiber Bragg gratings have become an important element in the fields of telecommunications and fiber optical sensing. Their small size, light weight and high tunability have made them ideal for many unique applications. In this paper the fabrication of these devices is investigated. Following a review of current literature and a discussion of the mechanisms underlying the photosensitivity of optical fibers, a new technique for writing fiber Bragg gratings is presented. This technique uses a diode-pumped Nd:YAG laser operating at 266 nm with pulse energies up to 137 ��J per pulse to write high quality gratings in standard optical fiber. This technique allows for the writing of variable wavelength gratings using a standard diffractive optical element (phase mask). The new technique has much lower setup and laser stability requirements than the conventional methods of writing variable wavelength fiber Bragg gratings. Furthermore, it is found to be very tunable and extremely robust, allowing for extended writing times. A preliminary study of the time evolution of the writing process is also presented. It is evident that the process of grating inscription is very complicated and is not always adequately described by current models. In addition. it appears that the process is strongly dependent upon pulse energy and is accelerated by simultaneous heating of the fiber with a C0��� laser and by heating due to the writing laser. A brief study of the thermal stability of different gratings is then given to determine some of the thermal stability properties of the fiber Bragg gratings written at OSU. / Graduation date: 2001

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--Lehigh University, 2002. / Includes vita. Includes bibliographical references (leaves 164-175).

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Powers, John P. Second Reader: Michael, Sherif. "September 1990." Description based on title screen viewed on December 17, 2009. DTIC Descriptor(s): Semiconductor lasers, amplifiers, output, optical properties, environments, degradation, monitoring, communication equipment, modular construction, alternating current, optical communications, lasers, thermistors, drives, transmitters, power, circuits, direct current, photodiodes, analog systems, diodes, fiber optics. DTIC Identifier(s): Semiconductor lasers, intensity modulation, theses. Author(s) subject terms: Semiconductor laser diode; thermoelectric cooling; laser diode driver; intensity modulation. Includes bibliographical references (p. 103-105). Also available in print.

published_or_final_version / abstract / toc / Mechanical Engineering / Master / Master of Philosophy

An interferometric method for measuring the total dispersion of short lengths of optical single mode fiber has been demonstrated. An analysis of the system in terms of linear system theory has also been carried out. The experiments were performed using a multimode GaAlAs semiconductor laser to measure the total dispersion of a borosilicate single mode optical fiber at a wavelength of approximately .873 μm. The experiments were conducted using various combinations of laser spectral width and fiber length. Changing the drive current to the laser enabled its spectral width to be varied from 2.3 nm to 5.8 nm FWHM. The fiber length was varied from approximately 0.2 m to 1.0 m. An analysis was also carried out to explain the effects on the interferograms of the unequal mode spacing of the multimode GaAlAs laser. Two methods of approximating the amount of variation of the laser mode spacing were also developed based on analysis of the interferograms. Analysis of the auto-correlation interferogram allowed the GaAlAs laser spectral width to be determined. This data was then used to compute a cross-correlation interferogram and then compared with the measured cross-correlation interferogram. The value of the fiber dispersion used in calculating the cross-correlation interferogram was varied until the computed interferogram agreed with the measured interferogram, this determined the value of the dispersion for the fiber that was used in that experiment. The experimentally determined value of the total dispersion of the single mode optical fiber used in these experiments agreed very well with published results.

The work embodied in this dissertation is specifically focused on the evanescent interaction of light with thin-films which has lead to two related instrument based projects: i) the Electroactive Fiber-Optic Chip (EA-FOC) and ii) Attenuated Total Reflectance (ATR) spectroscopy of novel materials. The EA-FOC combines the sensitivity of an electroactive total internal reflection element (20 to 50 times more sensitive than a transmission experiment) with the ease of use of fiber-optic based CCD spectrometers. A side-polished optical fiber, in a V-groove glass mount, forms the planar platform, which allows access to the evanescent field escaping from the fiber core. The exposed evanescent field, which was used to probe molecules or molecular assemblies supported by the platform, has an interaction area ca. 0.05 cm squared. Thin-film and bulk absorbing samples, and waveguide modeling calculations were initially used to evaluate the sensitivity of the FOC platform, which was found to be analogous to ATR instrumentation. The wavelength range of the FOC platform was increased to include the near-UV and applied to monitor adsorption of a protein film. Fluorescence applications of the FOC were demonstrated using a fluorescence bioassay and a drop cast nanoparticle film. Finally, a transparent conducting oxide film, ITO, was added to the surface of the platform to complete the EA-FOC for spectroelectrochemical applications. A methylene blue redox couple and an electrodeposited ultra-thin PEDOT film were used to probe the capabilities of the EA-FOC. The EA-FOC was shown to be a multifunctional platform for advanced sensor technologies requiring absorbance, fluorescence, and electrochemical detection or a combination thereof.ATR spectroscopy of novel materials included the evaluation of two architectures: i) a pH sensitive polyelectrolyte film and ii) surface capture of a nanoparticle film. Absorbance spectra of a polyaniline/polyacetic acid self-assembled bilayer were evaluated with respect to pH and potential using ATR spectroscopy; the ultimate application of the polymer signal transduction layer was to monitor proton transport across a lipid-bilayer. Additionally, ATR spectroscopy was used to monitor adsorption of pyridine capped nanoparticles on a silyl-propyl-thiol modified surface.

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