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A day in the life of a laser scientist. Dr Helen Pask Macquarie University Vice-Chancellor’s Innovation Fellow, Department of Physics and Engineering, Macquarie University, NSW 2109, Australia. Purpose of my talk. Celebrate the 50 th anniversary of the laser
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A day in the life of a laser scientist Dr Helen Pask Macquarie University Vice-Chancellor’s Innovation Fellow, Department of Physics and Engineering, Macquarie University, NSW 2109, Australia
Purpose of my talk • Celebrate the 50th anniversary of the laser • 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
Overview • What’s a laser? • Properties of laser light • Famous lasers, including the first laser • My job and a few projects I am working on • Multiwavelength lasers for treating retinal diseases • Remote sensing of water temperature • Terahertz lasers
What’s a laser – Light Amplification by Stimulated Emission of Radiation Laser gain medium: Gas: CO2, N2 Liquid: dye Solid: Nd:YAG, ruby, diamond, jelly Means of excitation: eg. flashlamp, laser, sun, electrical current, chemical reaction Before amplification – laser photon incident on excited ion. Mirrors trap laser photons in the cavity, and a laser beam is output through the end mirror After amplification – de-excited ion and two laser photons.
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
www.explainthatstuff.com Lawrence Livermore National Security, LLC, and Lawrence Livermore National Laboratory 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
How lasers impact on our lives Lasers have revolutionised: • Manufacturing • Medicine • Defence • Science Lasers are there: • When we go shopping • When we watch movies • Log on to the internet • Talk on the phone http://www.laserfest.org/lasers/innovations.cfm Credit: Trumf
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.
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.
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.
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
Multi wavelength Raman laser Up to 20% of the diode pump light is converted to green or yellow
Lasers are used to measure water depth along the coast of Australia (http://www.navy.gov.au) Project 2: Remote sensing of water temperature (LIDAR = Light Detection and Ranging) 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. (http://www/physics.ucsd.edu)
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.
Some questions we need to answer • 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 • 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)
Project 3: Terahertz Lasers – “the last frontier of the electromagnetic spectrum” • THZ Applications: personnel screening, substance identification, explosives detection, military, medical, biological, pharmaceutical • THz radiation: • non-destructive, non-ionising (cf x-rays) • Penetrates fabric, packaging, skin (<1mm), but not metal or water. Many applications, but serious lack of practical sources. Credit: Teraview
THz output Nd:YAG diode pump MgO:LiNbO3 Q-switch HR mirrors to resonate fundamental (1064nm) HR mirrors to resonate Stokes (~1070-1075nm) 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!
Getting Here Maths, Physics and Chemistry at High School 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 Since 2006, Vice Chancellor’s Innovation Fellow.
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”
