skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works

Abstract

In order to understand the physical processes associated with fs-laser waveguide writing in glass, the effects of the laser repetition rate, the material composition and feature size were studied. The resulting material changes were observed by collecting Raman and fluorescence spectra with a confocal microscope. The guiding behavior of the waveguides was evaluated by measuring near field laser coupling profiles in combination with white light microscopy. Waveguides and Bragg gratings were fabricated in fused silica using pulse repetition rates from 1 kHz to 1 MHz and a wide range of scan speeds and pulse energies. Two types of fluorescence were detected in fused silica, depending on the fabrication conditions. Fluorescence from self trapped exciton (E' δ) defects, centered at 550 nm, were dominant for conditions with low total doses, such as using a 1 kHz laser with a scan speed of 20 μm/s and pulse energies less than 1 μJ. For higher doses a broad fluorescence band, centered at 650 nm, associated with non-bridging oxygen hole center (NBOHC) defects was observed. Far fewer NBOHC defects were formed with the 1 MHz laser than with the kHz lasers possibly due to annealing of the defects during writing. We also observed anmore » increase in the intensity of the 605 cm -1 Raman peak relative to the total Raman intensity, corresponding to an increase in the concentration of 3-membered rings for all writing conditions. The magnitude of this increase in waveguides fabricated with a 1 MHz laser was nearly twice that of waveguides fabricated with a 1 kHz laser. Additional waveguides were fabricated in soda lime silicate glasses to assess the effects of changing the glass composition. These waveguides formed around, not inside the exposed regions. This is distinctly different from fused silica in which the waveguides are inside the exposed regions. A comprehensive analysis of all the experimental results indicates that good waveguides are formed below the actual damage threshold of the glass. The rapid quenching model, which correlates the refractive index of the modified material to its cooling rate, explains the effect of composition on waveguide behavior.« less

Authors:
 [1]
  1. Univ. of California, Davis, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE; National Science Foundation (NSF)
OSTI Identifier:
899386
Report Number(s):
UCRL-TH-221547
TRN: US200708%%261
DOE Contract Number:
W-7405-ENG-48; DMR-03070
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; DEFECTS; EXCITONS; FABRICATION; FLUORESCENCE; GLASS; LASERS; MICROSCOPY; OXYGEN; QUENCHING; REFRACTIVE INDEX; SILICA; SILICATES; SPECTRA; VELOCITY; WAVEGUIDES

Citation Formats

Reichman III, Wilbur Jordan. Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works. United States: N. p., 2006. Web. doi:10.2172/899386.
Reichman III, Wilbur Jordan. Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works. United States. doi:10.2172/899386.
Reichman III, Wilbur Jordan. Sun . "Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works". United States. doi:10.2172/899386. https://www.osti.gov/servlets/purl/899386.
@article{osti_899386,
title = {Understanding How Femtosecond Laser Waveguide Fabrication in Glasses Works},
author = {Reichman III, Wilbur Jordan},
abstractNote = {In order to understand the physical processes associated with fs-laser waveguide writing in glass, the effects of the laser repetition rate, the material composition and feature size were studied. The resulting material changes were observed by collecting Raman and fluorescence spectra with a confocal microscope. The guiding behavior of the waveguides was evaluated by measuring near field laser coupling profiles in combination with white light microscopy. Waveguides and Bragg gratings were fabricated in fused silica using pulse repetition rates from 1 kHz to 1 MHz and a wide range of scan speeds and pulse energies. Two types of fluorescence were detected in fused silica, depending on the fabrication conditions. Fluorescence from self trapped exciton (E'δ) defects, centered at 550 nm, were dominant for conditions with low total doses, such as using a 1 kHz laser with a scan speed of 20 μm/s and pulse energies less than 1 μJ. For higher doses a broad fluorescence band, centered at 650 nm, associated with non-bridging oxygen hole center (NBOHC) defects was observed. Far fewer NBOHC defects were formed with the 1 MHz laser than with the kHz lasers possibly due to annealing of the defects during writing. We also observed an increase in the intensity of the 605 cm-1 Raman peak relative to the total Raman intensity, corresponding to an increase in the concentration of 3-membered rings for all writing conditions. The magnitude of this increase in waveguides fabricated with a 1 MHz laser was nearly twice that of waveguides fabricated with a 1 kHz laser. Additional waveguides were fabricated in soda lime silicate glasses to assess the effects of changing the glass composition. These waveguides formed around, not inside the exposed regions. This is distinctly different from fused silica in which the waveguides are inside the exposed regions. A comprehensive analysis of all the experimental results indicates that good waveguides are formed below the actual damage threshold of the glass. The rapid quenching model, which correlates the refractive index of the modified material to its cooling rate, explains the effect of composition on waveguide behavior.},
doi = {10.2172/899386},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this thesis or dissertation.

Save / Share:
  • A specially constructed CO/sub 2/ waveguide TE laser has several advantages over a conventional CO/sub 2/ TE laser on account of its compact size, higher repetition rate, purity of polarization state and so on. This dissertation is dedicated to a comprehensive study of this particular laser device both theoretically and experimentally. A five-temperature model of the laser system is derived and then solved numerically. The relative numerical results are in close agreement with the experimental data. Also, the laser output signature and polarization state are very accurately predicted by this theory. However, discrepancy exists between the theoretically predicted and measuredmore » output power which is due to the assumption of a uniform electrical discharge in the theory. The low laser efficiency of about 1% is due to the large E/N ratio required to break down the discharge. Therefore it is concluded that various preionization schemes could be employed to enhance the laser efficiency and produce more uniform discharges such that the theory would give a more accurate description of this particular laser device.« less
  • A new type of waveguide laser is investigated. The waveguide is a single surface concave metal waveguide that also doubles as the grounded electrode in a radio frequency excited gaseous discharge. Theoretical studies on the modes and frequency characteristics of the laser have been performed. The modes of the waveguide are shown to be well represented by Hermite-Gaussian functions parallel to the waveguide and by the Airy function perpendicular to the waveguide. The output of the laser is shown to evolve approximately into an elliptical Gaussian beam in the far field. Numerical calculations for a metal waveguide carbon dioxide lasermore » operating at 10.6 ..mu..m indicate that its operating efficiency and mode stability are comparable to conventional dielectric waveguide carbon dioxide lasers. Two metal waveguide carbon dioxide lasers have been built to verify the results of the theoretical studies. One laser is designed to run multimode. The frequency differences between longitudinal and transverse modes have been measured with a HgCdTe photodiode detector and are found to be in agreement with theory. The resistance and capacitance of the laser have been measured at RF frequencies and found to be roughly the values of the other RF excited lasers. The other laser is designed to run lowest transverse order mode. Near and far field scans of the laser output have been taken and shown to be in agreement with computer calculations. Except with severe misalignment, the laser operates only in the lowest order transverse mode. Both lasers demonstrate output powers in the one to two watt range with operating efficiencies comparable to conventional CO/sub 2/ lasers.« less
  • Femtosecond lasers are a powerful tool for a wealth of applications in physics, chemistry and biology. In most cases, however, their use is fundamentally restricted to a rather narrow spectral range. This thesis deals with the construction and characterization of a femtosecond light source for spectroscopic applications which overcomes that restriction. It is demonstrated how the output of a continuously pumped Ti:sapphire femtosecond oscillator is amplified to the μJ level,while the pulse duration remains below 100 fs. A combination of continuous pumping, acousto-optic switching and Ti:Al 2O 3 as a gain medium allows amplification at high repetition rates. By focusingmore » the high energy pulses into a sapphire crystal, a broad-band continuum can be generated, extended in wavelengths over several hundred nanometers. To accomplish amplification of three orders of magnitude while maintaining the pulse length, a regenerative multipass amplifier system was built. The thesis describes theoretical design, realization and characterization of the system. Theoretical calculations and preliminary measurements were carried out and allow a critical evaluation of the final performance.« less
  • All models of lasing action require knowledge of the physical parameters involved, of which many can be measured or estimated. The value of the terminal level lifetime is an important parameter in modeling many high power laser systems since the terminal level lifetime can have a substantial impact on the extraction efficiency of the system. However, the values of the terminal level lifetimes for a number of important laser materials such as ND:YAG and ND:YLF are not well known. The terminal level lifetime, a measure of the time it takes for the population to drain out of the terminal (lower)more » lasing level, has values that can range from picoseconds to microseconds depending on the host medium, thus making it difficult to construct one definitive experiment for all materials. Until recently, many of the direct measurements of the terminal level lifetime employed complex energy extraction or gain recovery methods coupled with a numerical model which often resulted in large uncertainties in the measured lifetimes. In this report we demonstrate a novel and more accurate approach which employs a pump-probe technique to measure the terminal level lifetime of 16 neodymium-doped materials. An alternative yet indirect method, which is based on the ``Energy Gap Law,`` is to measure the nonradiative lifetime of another transition which has the same energy gap as the transition of the terminal level lifetime. Employing this simpler approach, we measured the lifetime for 30 neodymium-doped materials. We show for the first time a direct comparison between the two methods and determine that the indirect method can be used to infer the terminal level lifetime within a factor of two for most neodymium-doped glasses and crystals.« less
  • This dissertation explicates some of the factors that have, in practice, shaped the choice and functioning of forms of government involvement in the provision of different goods and services. The inquiry focuses on the evolution of government involvement in three different urban public utility industries - water works, electric utilities, and cable television. Because they each employ fixed, specialized, and networked distribution systems, the three industries manifest similar natural monopoly forms of market failure. From similar beginnings, however, forms of government involvement in the three industries have evolved differently. In water works, the predominant trend has been to direct provisionmore » under municipal ownership; in electric utilities the trend has been toward continued private provision under state regulation; in cable television, franchise contracting has thus far survived, but in vitiated form. Detailed examinations of case studies as well as broad trend analyses are employed to help explain this outcome. It is found that neither direct competition between operating firms nor short-term contracting and recurrent bidding arrangements can be relied upon to consistently protect public interests in these services.« less