Optical Sensing

About

Aston’s history in the field of Optical Sensing extends back to the early 90s, with its precursor (the Photonics Research Group) playing a leading role in the research and development of fibre gratings.

Our experienced research team draws on a variety of disciplines and academic backgrounds to continue our history of groundbreaking research into the many potential uses of optical sensors.

Our activity includes traditional grating sensors and those based on different kinds of fibre, such as:

Polymer
Multi-core
Photonic crystal fibres.

Alongside different materials, our research also opens up new and unique areas of application, including fuel system monitoring in the aerospace industry for example.

In recent years, our work in the field of Optical Sensing has broadened beyond fibre grating sensors, with successes in a range of areas.

Our work on Optical Coherence Tomographic (OCT) imaging resulted in a commercial system capable of producing real-time 3D images of flexible contact lenses as well as a 3D calibration target for OCT imaging systems manufactured using one of AIPT’s ultra-short pulse laser micromachining systems.

Other areas of progress include:

Advances in semiconductor laser technology enabling the development of low-cost tuneable diode laser spectroscopy systems
Effective countermeasures to increasingly powerful, low cost, hand-held lasers that pose a threat to pilots and drivers who may be targeted.

We are also in the process of developing photonic technologies for the agri-tech and agri-food sectors, such as low-cost multispectral imaging systems.

These technologies have a wide range of potential benefits, such as the ability to quickly assess the amount of micro- and nano-plastics in the food chain, speed up food quality monitoring, and even allow contaminants in food manufacturing to be detected in real-time.

Our Projects

Coherence detection for identifying lasers

A program of investigating laser detection through the detection of coherence has been ongoing for a few years. This work discriminates lasers from bright backgrounds based on the inherent coherence length of the source. This programme is supported by DSTL who are sponsoring a PhD student looking at “New directions in laser detection”. Current investigations involve drawing rectangular Zernike mode patterns on a micromirror array (digital holography) to manipulate focusing onto a camera facilitating detection. An extension to the coherence detection technique involves observing coherence at the individual photon level – Diagram shows modelled photon detection data. Such a system would represent the most sensitive generic laser detector ever built. This approach has recently been shown to offer an advantage to SETI in terms of sensitivity.

Benton, D. M. (2019). A Proposed Method for a Photon counting Laser Coherence Detection System to Complement Optical SETI. Publications of the Astronomical Society of the Pacific, 131(1001), 074501.

Graphene oxide coated fibre gratings for humidity sensing applications

Measurement of humidity is important in many scientific, industrial and medical applications and fibre-optic humidity sensors present unique advantages of compact size, lightweight, low cost, immunity to electromagnetic interference, and remote and distributed measurement. Highly soluble in water, graphene oxide (GO), an important derivative of graphene, is considered as a very promising material for humidity sensing. Current research takes advantage of long period gratings and tilted Bragg gratings in order to facilitate interaction of the guided light with the graphene oxide coating. The thin coating promotes a rapid response (~42ms), which enables for example the monitoring of human breath.

Graphene oxide-deposited tilted fiber grating for ultrafast humidity sensing and human breath monitoring. B Jiang, Z Bi, Z Hao, Q Yuan, D Feng, K Zhou, L Zhang, X Gan, J Zhao, Sensors and Actuators B: Chemical 293, 336-341.

Soil pore pressure monitoring

AIPT has been at the forefront of developing the technology of optical fibre grating sensors in polymer-based optical fibres, seeking to exploit the different material properties of polymers compared to silica. One feature of some polymers is their ability to absorb water in an equilibrium process with the surrounding environment. When a fibre fabricated from such a polymer contains a Bragg grating, the wavelength of the grating will change, depending on the degree of saturation in the environment around the fibre. Previously, this has been exploited for humidity sensing and to detect the small quantities of water that can be found in aviation fuel. Our most recent work has shown that this approach can be used to detect the saturation of soils, which has important application in civil and geotechnical engineering.

M. Mehravar, H. Yang, Wei Zhang, and D. J. Webb "Ground-water monitoring using polymer optical fibre Bragg gratings", Proc. SPIE 11199, Seventh European Workshop on Optical Fibre Sensors, 111991M (28 August 2019); https://doi.org/10.1117/12.2541326