The paper “Diamond in Tellurite Glass: a New Medium for Quantum Information” published in Advanced Materials shows the world a new hybrid material with implications for quantum information processing and is understandably attracting quite a lot of attention. The fundamental question posed by this research is: if diamond nano-crystal powder is mixed into molten glass, will the special properties of those crystals be retained in a useful way? To answer this question the team made several ‘billets’ of tellurite glass mixed with diamond nano-crystals, extruded them into structured ‘pre-form’ rods which were then drawn into Micro-structured Optical Fibres ‘MOF’. Team members from the University of Melbourne then examined the fibres to see how the crystals were distributed in the glass and performed tests to see if they retained their special single photon emission property.

As Melbourne based collaborator Andrew Greentree explains in the audio that accompanies this writing, the diamond nano-crystals are commercially available and were carefully selected for their emission properties and likely ability to survive the fibre fabrication process. These particular crystals have a nitrogen vacancy colour centre that emits light (as single photons) at a rate of about one every 10 nano-seconds. This is a very bright emission that can be seen through a microscope – unlike the tiny (30 nm diameter) crystals themselves. That said, special skills and a computer controlled microscope were required to find and count the crystals in a section of the special tellurite glass fibre.

Matt Henderson gives us a sense of how tricky it was to mix the diamond powder into the glass and to prevent bad things from happening to the tiny nano-crystals at high temperatures. While the crystals did mix with the molten glass, they tended to ‘clump together’ in these early fabrication runs. Using even smaller quantities of diamond powder and distributing it more evenly throughout the glass will be a focus of future work. Matt also points out that it is not exactly easy to find small numbers of tiny crystals in a ‘huge’ (about the width of a human hair and a few centimetres long) piece of fibre. These images show the light emitting from the diamond nano-crystals as a laser is aimed into the fibre.

The great news is that despite the perils of exposing the diamond nano-crystals to a rather harsh process and their tendency to clump together in the glass, it is still possible to detect single photon emission from a piece of the special micro structured fibre. This is shown in the classic ‘V’ dip in the chart at figure 3c in the paper. The challenge for future research will be to fabricate a much smaller fibre with far fewer diamond nano-crystals and to couple that fibre with a laser in such a way that exactly one photon is emitted each and every time the laser is fired. A source like this could be used to send perfectly secure quantum messages, re-define the standard for how we measure light intensity & react that nano particle with its environment to create new sensors.

Pretty cool eh? IPAS director Prof Tanya Monro thinks so and is particularly optimistic about the potential for this approach which harnesses properties unique to the nano-scale in a platform that is able to be fabricated and manipulated at the macro or micro scale. This blend of materials science, photonics & nano-tech is definitely an area to keep an eye on – and watch out when a cheap, reliable, robust single photon source is developed. I think that will turn out to be one of those ‘tipping points’ we will look back on, possibly through the output device of our shiny new quantum computer.

Mike Seyfang for IPAS “talking papers” series.

Links

Audio:

http://media.ipasadelaide.com/2011/TalkingPapers04MattTanyaAndrew.mp3

Images:

http://www.flickr.com/photos/mikeblogs/6318024388/

http://www.flickr.com/photos/mikeblogs/6349490460/

Paper:

http://onlinelibrary.wiley.com/doi/10.1002/adma.201100151/full

Extras: http://youtu.be/ur3-QZRcacE http://youtu.be/D4Ckwc94ZhE http://youtu.be/PyMQsvjgqv8

IPAS would like to acknowledge the work of all collaborators listed in the paper and the support from the ARC through Federation and QEII fellowships.

The winners of the Australian Academy of Science 2012 awards for scientific excellence have been announced.

Congratulations to Prof Tanya Monro, winner of the Pawsey Medal for research in physics.

In announcing the medals and awards, Academy President Professor Suzanne Cory said:
“Each year, it is the Academy’s privilege to recognise excellence in diverse fields of science. Several of the awards celebrate career-long contributions by some of Australia’s most distinguished researchers; others draw attention to remarkable discoveries made by younger investigators. The Academy warmly congratulates each of these outstanding awardees.”

Tanya will receive her medal at the Academy’s annual conference being held from 2 to 4 May 2012.

Congratulations to Prof Tanya Monro and Dr Alexandre Francois, inventors of the the VESPR (versatile enhanced surface plasmon resonance) sensor, shortlisted as one of the top 5 inventions in the Australian Innovation Challenge, health category.

With the VESPR sensor, patients will be able to get rapid diagnoses of diseases such as cancer, HIV and influenza from their GP.

“It combines biotechnology and photonics – the booming field based on photons, or “packets” of light. In trials, the patented device detected an inactivated flu virus within five minutes. VESPR is potentially capable of screening for multiple pathogens in small sample volumes quickly and with high specificity. “says Prof Tanya Monro.

The device is cheap to manufacture and easy to use. The team hopes it will be on the international market within a few years.

The winner will be announced 7 December by Senator Carr in Queensland. Dr Alexandre Francois and Prof Tanya Monro will be attending the event.

Work led by Alexandre Francois shows that whispering gallery modes (WGM) can be excited and detected in dye doped micro spheres via a microstructured optical fibre (MOF). By sticking a tiny sphere to the end of a very thin fibre and running a series of experiments Alex & Kris have demonstrated a new architecture for sensors that not only works but provides a substantial increase in excitation & collection efficiency. The overall efficiency of this robust architecture is 200 times greater than that of more conventional schemes.

The curiously named “whispering gallery mode” refers to a special kind of resonance that occurs when light is trapped within a resonator by total internal reflection. I remember sitting in an IPAS seminar in which Kris Rowland eloquently and with much wit described WGMs using a picture like the one below:

To quote Kris from that presentation “A whispering gallery mode is said to exist when a light wave bouncing around the perimeter of a resonator returns in phase. This means that after one round trip, when the wave “catches its tail”, the wave overlaps itself identically.“

So, exactly how does one precisely position a tiny (10 micrometer) polystyrene sphere on the end of a very thin (130 micrometer) glass fibre? To get those dimensions in perspective, consider that a human hair is typically around 18-80 micrometre in diameter. It turns out that after a bit of ‘playing around’ (quite literally so, according to this audio grab from IPAS director, Prof Tanya Monro) the sphere tends to centre itself on one of the three holes in the MOF and stick there by a combination of electrostatic and surface forces. The end result – a compact and robust architecture for applications such as localized in-vivo/vitro biosensing.

Which leads us to the future…

IPAS are now actively looking for researchers with questions that can (only) be answered by “in vivo” measurement of bio-molecules. There is rich medical information that we cannot currently measure by taking measurements of externally accessible bodily fluids or with existing sensing technologies. This new technique opens up the possibility of increasing out understanding of the origins of disease and our response to treatment at a local level inside our bodies. Imagine, for example,  being able to measure the response of a tumor to a new cancer treatment in real time ( “in vivo” and “in situ”). It is hoped that the development of specific sensors based on this new architecture will be extremely useful.

To paraphrase Tanya from the audio interviews that accompany this story:

“one day clinicians may have a little kit of spheres that have been functionalised to detect all their favorite bio markers and make a clinical decision on which ones to pick up on the end of a fibre and stick into the patient”.

Ouch!

Mike Seyfang for IPAS “talking papers” series

We are delighted to announce that the IPAS 2010 annual report is now available for downloading. For all the information on IPAS in 2010, check it out!

These were:

Gavin Rowell – Discovery Project - Dark gas and the formation of molecular clouds – $315k – UNSW

Jesper Munch – Discovery Project - Three-Mode interactions and optical springs in high power optical cavities - $370k –  UWA

Gavin Rowell – LIEF - The Nanten2 sub-millimetre telescope – $750k – UNSW

Tara Pukala – LIEF - Strengthening merit-based access and support at the new National Computing Infrastructure petascale supercomputing facility – $650k – ANU

Congratulations to all!

This included three Discovery Projects, one LIEF Project and one Linkage Project. The projects spanned the development of new sensing technologies for wine production, defining peptide structure for cataract, Alzheimer’s disease, cancer, and cardiovascular disease, genetic evolution,  nanoporous material development, nanodiamond in glass for nanosensing, and X-ray diffraction equipment.

Stephen Warren-Smith and Sabrina Heng joined forces under Tanya’s guidance and with support from Andrew Abell, worked in the space between their two disciplines – Physics and Chemistry. Sabrina and her colleagues adapted an existing commercially available synthetic compound (a ‘flurophore’ called lumogallion). This new ‘compound 3′ is designed to stick to the glass surfaces of the micro-structured fibre while retaining or enhancing fluorescence in the presence of aluminium ions. Sabrina tells me they made good progress with ‘compound 3′ because it only takes a few steps to make, is made from low cost ingredients and provides a reasonably high yield.

While the compound did bind well to the fibre surface, it did so in such a way that may have impacted on sensitivity and was easily removed. There is room for improvement here. Stephen tells me there are many ways in which the binding may be improved – by tweaking the chemistry of the flurophore and/or that of the polyelectrolyte intermediate layer to which the fluorophore attaches.  Alternatively, there are other ways to approach the coating (or ‘functionalisation’) of the micro-structured fibres to try in future research. One of the challenges faced is in quantifying (or even seeing) the extent to which the flurophore has coated the fibre surface – the subject of current work by other IPAS researchers. Tanya informs me that this is the first time IPAS has produced a variant of a known flurophore that  has been adapted to enable surface functionalisation. This approach means there is great potential for development that benefits from the economy of scale.

Something that surprised me while collecting photographs of the equipment used in this research was the small scale of everything. While the paper does contain phrases such as “approximately 2 mL of the reaction mixture was used for the experiment” I did not imagine the nitrogen pumping apparatus, or the fluorescence cuvettes at a realistic scale. Stephen reminded me that one of the key features of micro-structured optical fibres is their tiny (less than a human hair) outer diameters which makes them ideal for sensing in-situ. Furthermore, they can be as short (or long) as required to transmit the fluorescence information from the sample to the detector. As you can hear in this short audio recording with Prof Monro, Stephen’s experimental work is the first to record this type of “dip-sensing”  that works in only a few nano-litres of liquid.

Only 2x600mm lengths of the specially enhanced fibre were used for this work – and working lengths of 60mm after surface coating (or ‘functionalisation’) were used to perform the sensing measurements. I recorded some audio from a conversation with Stephen which gives a great behind the scenes look at the remarkable teamwork required to envisage, design, create and characterise this new platform for sensing. It goes something like this…

The micro-structured fibre lengths were flushed with a saline solution of polyelectrolyte (PAH) for 30 mintues. Each 600mm length of fibre had to be cleaned by pumping water through for 30 minutes then dried by flushing with nitrogen gas for a futher 30 minutes. Visual inspection was done using an optical microscope which is quite fiddly and laborious – especially since it is not possible to see fluids inside – only the meniscus that forms at the barrier between fluid and air can be seen.

Early work on the chemical attachment concept originated with Dr Markus Pietsch who is now at the University of Cologne hospital in Germany. Fellow IPAS researcher Alexandre Francois suggested the polyelectrolyte approach which first binds an intermediate layer to the glass fibre via electrostatic forces. The modified flurophore then attaches chemically to this intermediate layer via covalent bonds. Roger Moore (no, not that one!) found a way to ‘inflate’ the tiny holes inside the  ’wagon-wheel’ fibre using positive gas pressure during the drawing process. This is needed to avoid blockage of the holes during the flushing and coating steps required to functionalise the surface and to enable liquid sample to enter the holes during dip sensing. Peter Hoffmann (now deputy director of IPAS) provided access to a Typhoon imager used in the glass slide characterisation. The whole effort was made possible thanks to funding from the DSTO and ARC for Tanya Monro’s Federation Fellowship program.

This paper opens the door to a whole new platform for sensing that will allow IPAS to build tools for further research and to partner with industry in developing products with a diverse range of applications in fields from medicine, the environment and agriculture through to defence industries. The commercial opportunity for sensors based on this platform are enhanced by some of the new discoveries and potential for cost effective scale.

Links:

paper “Fluorescence-Based Aluminum Ion Sensing using a Surface Functionalized Microstructured Optical Fiber“ 

audio recording

Post written by

Mike Seyfang for IPAS “talking papers” series