Sample heading textA day in the life of a laser scientist
Dr Helen Pask
Department of Physics and Engineering,
Macquarie University, NSW 2109, Australia
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Purpose of my talk
Highlight the prominence of lasers in our lives
Science/Physics/Lasers is fun
Finding the answers to problems is fun
“You guys” will develop new applications for lasers that I can’t even imagine – in the next 50 years
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Overview
My job and a few projects I am working on
Multiwavelength lasers for treating retinal diseases
Remote sensing of water temperature
Terahertz lasers
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What’s a laser – Light Amplification by Stimulated Emission of Radiation
Before amplification – laser photon incident on excited ion.
After amplification – de-excited ion and two laser photons.
Laser gain medium:
Gas: CO2, N2
Means of excitation: eg. flashlamp, laser, sun, electrical current, chemical reaction
Mirrors trap laser photons in the cavity, and a laser beam is output through the end mirror
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Basic Properties of Laser Light
Laser Light has some distinctive features compared to other light sources
Monochromatic – laser light has very narrow spectral range ( ie very pure colour) due to the discrete energy levels in the excited atoms or ions which make up the laser medium
High directionality - laser light has very low divergence, a consequence of the many passes between mirrors and the amplification process
Coherence - laser light waves (photons) have the same phase, due to the nature of the light amplification process. This gives rise to laser “speckle”.
www.adaptiveoptics.org
Some famous lasers… the first laser
50 years ago, on May 16th 1960, Theodore Maiman demonstrated the first laser. It was a ruby laser, pumped by a pulse of light from helical flashlamp.
Photo courtesy of HRL Laboratories, LLC
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Big and Small Lasers
The world's largest laser was completed in 2009, designed to create a nuclear reaction like the one at the centre of the sun. 192 laser beams will be focused on a tiny target at the centre of an enormous spherical target chamber, creating temperatures of up to 100 million degrees. This building which houses the laser is the size of a football stadium. It is the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California.
Somewhat more modest is the diode laser in a CD player
Lawrence Livermore National Security, LLC, and Lawrence Livermore National Laboratory
www.explainthatstuff.com
How lasers impact on our lives
Lasers are there:
Talk on the phone
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My Job – Laser Physicist/Optical Engineer
Working with Industry – understanding what applications people have for lasers, then figuring out how to make a laser that will make the application work as well as possible. (CSIRO, laser manufacturers, medical companies and DSTO (Defence Science and Technology Organisation)
Inventing stuff and entrepeneurship: We invented a new type of laser and in 2004 formed a company to commercialise it.
Commercialising research: Finding ways for some of the great research that we do at Macquarie to be taken up by companies and ultimately benefit our community.
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Project 1: Wavelength-selectable lasers
We have demonstrated a unique laser system in which the laser output can be efficiently channelled “on-demand” into several visible wavelengths
There are many applications where the ability to get several wavelengths from a laser source is highly valued
Ophthalmology is one of these.
The invention has been patented and licensed.
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Step 1: Making yellow lasers for retinal photocoagulation
This yellow laser is being developed by my colleagues and I with companies in Adelaide and Brazil. It will be used for laser eye surgery of the retina.
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Wavelength-selectable lasers for ophthalmology
Funded jointly by the ARC (Australian Research Council) and Opto Global (an Australian ophthalmic company)
Ideally, a retinal surgeon should choose his/her laser wavelength to best suit the procedure and the particular patent. Our laser is designed to offer this flexibility
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So how do we do it?
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Multi wavelength Raman laser
Up to 20% of the diode pump light is converted to green or yellow
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Project 2: Remote sensing of water
temperature (LIDAR = Light Detection and Ranging)
(http://www/physics.ucsd.edu)
A new laser project I have just started will try to determine the temperature of the sea and inland waterways as a function of depth. This could help predict ocean currents, monitor climate change and to understand algal blooms and salinity.
Lasers are used to measure water depth along the coast of Australia (http://www.navy.gov.au)
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Raman Spectroscopy for remote-sensing
- water temperature depth profiling -
C.V. Raman is the father of the Raman Effect. When green light is scattered by water, a substance, a small (1 in 106) fraction is found have a different frequency (red).
www.aps.org
This “lumpy” spectrum can be analysed to give information about the temperature and salinity of the water sample.
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Some questions we need to answer
But first, we need to understand:
How the optical properties of the water impact on the accuracy of temperature measurement?
How the optical properties (absorption, scattering, transmission, fluorescence) depend on the sample environment (eg fresh/salt, clear/turbid, high/low organics)
In principle, we can apply this method using land, sea or air-based platforms. If sucessful,
it will provide inputs for hydrologic modelling of water circulation along coast lines and in inland waterways.
Monitoring environmental conditions that trigger algal blooms
Assessing environmental health of waterways
www.oceandatacenter.ucsc.edu
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Project 3: Terahertz Lasers – “the last frontier of the electromagnetic spectrum”
Credit: Teraview
THz radiation:
Penetrates fabric, packaging, skin (<1mm), but not metal or water.
Many applications, but serious lack of practical sources.
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Addressing the Terahertz problem
1. Start with the most robust, well-established technology - Solid-State Nd lasers.
Developing new methods for frequency conversion to the THz spectral region
So far, so good. Watch this space!
diode
pump
Q-switch
MgO:LiNbO3
Nd:YAG
THz output
Getting Here
Science at University – a bit of everything including kayaking, bushwalking, ski-touring…..
Honours year in Physics – physics of gas discharges
PhD project on laser Physics
Postdoctoral work in UK – optical fibre lasers and amplifiers
UK to Australia in a small steel yacht
ARC Fellowship at Macquarie (5years)
Completed NSW Enterprise workshop
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Some highlights of my job
Light is fantastic and amazing to work with!
I never get bored with my job
Many opportunities to be imaginative, creative and innovative
Good balance of independence and teamwork
Travel and living overseas
Working with scientists around the world (UK, Japan, Brazil, China)
Started up a laser company
Pretty good salary
Career + family
A career in science is an opportunity to “do something worthwhile” and perhaps “make the world a better place”
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LaserFest Sydney –
Raman shift
3225, 3425, 3520, 3612 and 3060 cm
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