Breakthrough light source for early detection of disease and pollution

Nateesh and Darren

PhD student, Neetesh Singh and project leader, Dr Darren Hudson.

03-09-2015

CUDOS researchers at the Australian National University and the University of Sydney have made a major advancement towards the design of inexpensive monitoring devices that can detect human disease and air pollution at very small levels.

Important molecules for health, medicine, and security screening, can be sensitively detected in the mid-Infrared (mid-IR) wavelength range. Detection of these molecules at very small levels could open the door for many applications ranging from human breath analysis for early, non-invasive detection of disease, to providing better monitors for air quality.

Dr Darren Hudson and PhD candidate, Neetesh Singh from CUDOS’ University of Sydney node, explained that the mid-IR range of the electromagnetic spectrum covers wavelengths from 2 µm to 20 µm (for reference our eyes see photons with wavelengths from 0.4 µm – 0.7 µm). However, unlocking the detecting power of the mid-Infrared has remained challenging due to the lack of high brightness photon sources.

“Current technology relies on expensive lasers that operate in a limited range in the mid-IR, low brightness glow-bar technology, or synchrotron radiation. All of these options have major drawbacks that have kept mid-IR detection systems from being used in various applications that will benefit society,” said Dr Hudson. “One potential path to overcome these drawbacks is to develop a small-footprint ‘supercontinuum’ source”.

Supercontinuum generation is a nonlinear optical process whereby a laser with a relatively small spectral width undergoes a massive broadening in a dielectric medium. It has been known for some time that this technique could potentially allow for a high-brightness, mid-IR spanning spectrum to be generated in a small, low-cost device”.

In their paper ‘"Mid-IR supercontinuum generation from 2-6 µm in a
silicon nanowire", published today in the high profile journal Optica of the Optical Society of America, lead authors, Mr Sing and Dr Hudson (also the project leader) and his team demonstrated for the first time ultra-broad supercontinuum generation from 2-6 μm in silicon (a CMOS platform – which is the backbone of almost every electronic-chip used today). This has been achieved by using silicon on sapphire (SOS) waveguides, which can guide mid-Infrared waves with low loss and high nonlinearity.

The supercontinuum generated in this photonic chip represents both the widest spectrum and longest wavelength generated to date in any silicon platform, and establishes SOS as a promising new platform for integrated nonlinear photonics in the mid-IR.

“We have shown that silicon has the potential to be a broadband ‘white laser’ source that can be used for spectroscopy, molecular sensing, and frequency metrology for precise measurement of optical frequencies, all in a widely available CMOS platform”, said Mr Singh. “The silicon on sapphire platform now appears to be a promising path forward for integration of electronic and mid-IR photonics on a single device”.

The experiment took advantage of a unique laser source and experimental setup constructed at the Australian National University by ANU Ph.D. student Ivy Yu, Professor Barry Luther-Davies, and Mid-IR Science Leader Stephen Madden.

The success of this project was made possible by the collaboration of two universities and an Australian industry partner. Professor Eggleton, Director of CUDOS and co-author on the paper says that the key to this breakthrough has been the collaboration with Silanna Semiconductor a Sydney company that fabricates commercial integrated semiconductor electronic devices for communications, power and space programs.

“Silanna’s SOS platform and CMOS fabrication capability is unique and world-leading and has been crucial to the success of this project and the path to manufacture of our photonic devices,” he said. “While the CUDOS node of the Australian National University provided critical support for the experiments”.