SEMINAR: Physics Seminar

Abstract: I will start by providing an introduction to the Institute for Photonics and Advanced Sensing (IPAS) at the University of Adelaide and then examine in detail one of the spectroscopic technologies created within my research group to demonstrate an example of the benefits of the trans-disciplinary approach advocated by the institute.

Spectroscopy is a key technology for both fundamental and applied science. A long-held desire has been the development of a means to continuously acquire broadband spectral data with high time and frequency resolution at the same time. A wealth of new information could be obtained if one were to observe materials undergoing a dynamical change induced by a chemical, optical or physical process.

We have created two techniques that can enable one to obtain such data:

In the first case we were interested in examining complex molecular samples with an aim to providing real-time and quantitative measurements of the concentration of the various components. In the longer term we want to apply this device to creating non-invasive disease diagnosis by examination of breath samples. Our approach is to illuminate a molecular gas sample with a laser frequency comb generated by a mode-locked laser. The laser comb consists of thousands of different coloured laser signals that each interact with the sample. We have developed a technique that spatially separates each of the laser colours so that they can be imaged on a camera. This technique allows us to measure the transmittance of each laser mode separately and simultaneously and thereby obtain a complete picture of the sample across a very broad swathe of the spectrum.

In the second case we are interested in studying faster phenomena in fundamental atomic physics. Here we instead generate our frequency comb using modern electro-optical techniques. We use this novel frequency comb to make continuous observations of cesium vapour with a 2µs time resolution and a 10MHz frequency sampling (320 independent spectral channels). We independently detect the incident and transmitted frequency combs on two fast photodiodes. Appropriate processing of these signals can yield the complex transmittance of the cell with very high time sampling. We then perturb this vapour using a pulsed laser and are able to observe the response of the vapour to this step perturbation. The electro-optical comb allows us to see previously unobserved effects, including a temporal evolution of the amplitude and lineshape of the spectrally burnt features, as well the creation of a broad pedestal of additional absorption surrounding each of the narrow burnt features.

Biography Prof Andre Luiten is Director of the Institute for Photonics and Advanced Sensing (IPAS) and Chair of Experimental Physics at the University of Adelaide. He is a Fellow of the Australian Institute of Physics. Prof Andre Luiten obtained his PhD in Physics from the University of Western Australia in 1997, for which he was awarded the Bragg Gold Medal. He has subsequently held three fellowships from the Australian Research Council. For his efforts Andre was the joint inaugural winner of the WA Premier’s Prize for Early Career Achievement in Science. Andre moved to the University of Adelaide in 2013 to take up the Chair of Experimental Physics as well as a South Australian Research Fellowship from the Premier’s Research and Innovation Fund. He published 6 book chapters and authored over 100 journal papers (with ~2,200 citations) and over 100 conference papers, and has raised over $18M for research. Prof Luiten’s work has aimed at the development of state-of-the-art instruments across many diverse fields of physics and is particularly excited by the possibility of applying these instruments to solve problems, or to make measurements, that were not previously possible