How optical sensors could quickly detect infrastructures at risk of collapse
AUTHOR : Peng Adam Li

Around the world aged public infrastructure, such as bridges and roads, are under immense pressure. Self-powered, long-lasting vibration sensors that can detect whether a structure is in imminent danger of collapse could help to address this serious issue by providing early warning signs.

Traditional sensors are mostly based on electrical signals, and billions of people have benefited from the convenience of electronic devices such as mobile phones and supercomputers. However, a common thread binds them all together: thousands of different integrated electronic parts performing energy-consuming functions.

If the electronic parts are replaced with optical elements, a computer will become more efficient and generate less heat; a mobile phone becomes thinner and lighter.

My research makes use of the optical, electrical, and mechanical characteristics of a novel material, known as aluminium nitride, to build a ring-resonator modulator, which has a ring structure. The modulator is one of the most fundamental elements of a device because it uses a technique that can add information to an electronic or optical signal.

Certain wavelengths of light are trapped inside the ring-resonator modulator. If there are continuous wavelengths of light at the input after passing through the ring-resonator there will be sharp dips appearing in the output.

Aluminium nitride provides a wide transparent window to light wavelengths, which makes it an ideal platform to convey light signals over a wide range, allowing for the development of a self-powered vibration sensor that can monitor large structures.

Changes at the output light are extremely sensitive to any change of the signal. If a tiny fracture appears on an aircraft or a bridge, technicians could quickly see the variation of the light on the vibration sensor and act immediately.

It is hoped that such a sensor, using the novel aluminium nitride-based optical modulator, could also improve safety in potentially explosive environments, such as petrol stations.

Traditional sensors could pose a serious risk because the sudden change of an electricity signal generates sparks and could light up the oil in a petrol station. A light signal is not limited by this potential safety flaw.

This project aims to demonstrate why fast, responsive, lightweight and small optical sensors are ideal for monitoring large structures in challenging environments.