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A day in the life of a laser scientist

Dr Helen PaskMacquarie University Vice-Chancellor’s Innovation Fellow,

Department of Physics and Engineering,

Macquarie University, NSW 2109, Australia

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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

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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

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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

Liquid: dye Solid: Nd:YAG, ruby, diamond, jelly

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 mediumHigh directionality - laser light has very low divergence, a consequence of the many passes between mirrors and the amplification processCoherence - 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

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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

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How lasers impact on our lives

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

Lasers have revolutionised:• Manufacturing • Medicine• Defence• Science

Credit: Trumf

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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)

Lasers are used to measure water depth along the coast of Australia (http://www.navy.gov.au)

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.

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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 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.

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Addressing the Terahertz problem

diodepump

HR mirrors to resonate fundamental (1064nm)

Q-switch MgO:LiNbO3

Nd:YAG

HR mirrors to resonate Stokes (~1070-1075nm)

THz output

1. Start with the most robust, well-established technology - Solid-State Nd lasers.

2. Developing new methods for frequency conversion to the THz spectral region

3. So far, so good. Watch this space!

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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.

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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 – 16th May 2010 till 16th May 2011.