Ultraviolet and Visible Laser Applications
(including High-Power Gas Lasers)
The CLA's ultraviolet and visible lasers applications activities cover a wide range of laser development and applications research conducted by many different CLA researchers. Included under this heading is the development of metal vapour lasers, tunable UV solid state lasers, low cost gas discharge UV lasers, as well as applications including laser micromachining, 3-d imaging, and biophotonics. Some of these topics (micromachining and Biophotonics) are covered in separate CLA research areas.
High Performance Copper Vapour Lasers
The CLA has a long-standing program of investigation into the kinetics of metal vapour laser systems including those based on strontium (violet), barium (near-to-mid IR) and copper (green-yellow) vapours. These systems have been investigated for scaling output characteristics to match the requirements of applications is medical, industrial and scientific applications.
The CLA has developed a new class of copper vapour lasers - the 'kinetically-enhanced' copper vapour laser (KE-CVL) which uses small additions of hydrogen and halogen gases to the discharge which alter the plasma kinetics and dramatically improves the output power (by more than a factor of two) beam quality and pulse repetition rate of elemental copper vapour lasers. The most recent research focuses on the kinetics of KE-CVLs and the related Cu HyBrID laser systems. Kinetics investigations include Hook spectroscopy to map spatio-temporal evolution of key plasma species and comprehensive computer modelling. The CLA also has had an extensive program in investigating the beam quality of copper vapour laser systems. Devices with ultra-high (diffraction-limited) beam quality and systems with shaped far-field beam profiles have been developed, offering greater speed and precision in laser micromachining and greater efficiency in laser pumping and nonlinear frequency conversion. The CLA has also led the development of high average power (multi-Watt) deep UV sources based frequency doubled copper vapour lasers. Key applications of sources are high speed fabrication of fibre Bragg gratings and laser micromachining, particularly of polymers and dielectrics. Key frequency doubling technology has been licensed to Oxford Lasers Ltd (UK) who use techniques developed in the CLA for their precision micromachining system and fibre Bragg grating fabrication systems based on frequency doubled CVLs.
Today, we primarily use metal vapour lasers as research tools for projects including high speed imaging and laser pumping, and for laser micromachining.
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The CLA has developed several high-performance lasers having the following performance characteristics:
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Contacts: Dr Robert Carman, A/Prof David Coutts, Dr Graham Marshall, Dr Richard Mildren, Prof Jim Piper, Dr Michael Withford
Tunable Ultraviolet Lasers
Tunable solid-state UV sources based on cerium doped fluorides are being intensively investigated. Cerium laser UV tunability extends from 282 nm to 338 nm, a key wavelength range of interest for many biophotonics applications. We have developed miniature cerium lasers pumped by microchip Nd lasers for use in such applications. These lasers have high efficiencies and ultra-low thresholds. We have also developed a novel monolithic microchip tunable laser technology suitable for cerium, Ti:Sapphire and other tunable solid state lasers. Cerium lasers can be pumped by frequency doubled CVLs or by a variety of solid-state UV systems including frequency quadrupled Nd:YAG and frequency quadrupled, Raman shifted Nd:YAG lasers. We have access to many UV pump wavelengths in our laboratory allowing us to investigate many potential new cerium laser materials such as Ce:BYF (in collaboration with Prof Mauro Tonelli, NEST - Dipartimento di Fisica - Universita' di Pisa). Cerium lasers have the potential to provide continuous wave tunable UV output and may possibly be operated mode-locked to generate ultrafast UV pulses. We are working to develop the first CW and mode-locked cerium lasers. |
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Contacts: A/Prof David Coutts, Dr Kristie Johnson, Dr David Spence,
Colour Coded High Speed Imaging
| Pulsed lasers are used extensively as strobe sources for high speed imaging. Usually monochromatic lasers are used in combination with monochrome film or digital cameras. We are using specially formatted multi-wavelength (white light, and supercontinuum) visible laser sources to perform high speed imaging where extra information (spatial or temporal) is colour coded in the image. For example, in particle imaging velocimetry (PIV), a single light-sheet is usually used to illuminate one plane normal to a high speed camera, and particle images tracked or correlated in order to determine flow velocity distributions on a single plane. Stereoscopic techniques using multiple cameras can yield a third velocity component transverse to the illumination plane (3C 2D PIV). We have developed a technique using multiple coloured light sheets where colour codes the depth information for images recorded using a single colour digital camera. This technique has the potential to measure all three velocity components in a three dimensional volume of space (3C 3D PIV). For this application, Raman conversion of a UV/visible pulsed laser is used to generate a comb of wavelengths spanning the visible. |  |
Contact: A/Prof David Coutts, Dr David Spence
Tunable Visible/IR lasers
In addition to tunable UV lasers described above, solid-dye and Ti:sapphire lasers operating at high (kHz) pulse repetition rates are also actively being developed. Applications range from micromachining and ranging (fibre-pumped Ti:sapphire microchip lasers) to the biomedical (low cost solid-dye lasers). |
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Contact: A/Prof David Coutts
Yb:S-FAP lasers
In addition to tunable UV lasers described above, solid-dye and Ti:sapphire lasers operating at high (kHz) pulse repetition rates are also actively being developed. Applications range from micromachining and ranging (fibre-pumped Ti:sapphire microchip lasers) to the biomedical (low cost solid-dye lasers). Yb:S-FAP lasers operating on the 985 nm three-level transition could be frequency quadrupled to 246 nm which is an ideal wavelength for writing fibre Bragg gratings. We have developed a diode-pumped 985 nm Yb:S-FAP laser suitable for this application. |
Contact: A/Prof David Coutts
Low cost gas discharge UV lasers
| Practical and wavelength-agile ultraviolet and vacuum ultraviolet lasers spanning 100-180nm will significantly increase the flexibility of laser based manufacturing technologies. Our recent studies in capacitively coupled-discharge (dielectric barrier discharges) show that methods involving capacitively-coupled excitation are well suited to generating stable (or homogeneous) rare-gas discharges at the elevated pressures needed to generate vacuum ultraviolet laser emission. We are now using similar techniques to demonstrate new vacuum ultraviolet lasers in compact waveguides with increased wavelength agility and affordability. |  System used for studies into ultra-low-cost capacitively-coupled pulsed UV lasers |
Contacts: Dr Richard Mildren
Research support
Much of this research has been funded by the ARC (Discovery) and Macquarie University internal grants. We are also extremely grateful to the Clarendon Laboratory, Oxford University, for allowing Dr David Coutts to bring much of his laboratory equipment with him when he rejoined the CLA in 2003.