Innovative Light-Delivery Technique Improves Biosensors
Microdisks are a type of microscale resonator that use the whispering-gallery optical effect to confine and enhance light that enters the disk. Just as the curved walls of a whispering gallery carry sound waves to allow whispers to be clearly heard across a room, the curved inner surface of a microdisk carries light waves across the disk, enhancing the light. This allows the microdisk to boost a light-based signal coming from a cell, protein or virus of interest, allowing more sensitive detection of subtle changes associated with diseases such as lupus, fibromyalgia and certain heart problems.
“Although there are whispering gallery mode micro-resonators that can already be used to resolve single molecules, their application is limited by problems in device repeatability, stability and wavelength range,” said research team leader Qinghai Song from Harbin Institute of Technology, China. “Our new design enables excellent device performance that works with a variety of wavelengths with low cost, higher stability and better device repeatability.”
In Optica, The Optical Society’s journal for high impact research, the researchers detail their new end-fire injection configuration, which offers a simple, cost-effective and efficient way to get light into the microdisk resonator. They also show that devices using microdisks and end-fire injection can be used to detect temperature changes and the presence of nanoparticles.
The researchers’ ultimate goal is to use their new end-fire injection technique to create a portable and low-cost sensor that can detect changes in cells that are early indicators of cancer. However, they point out that the new light-coupling configuration could also be useful for integrated photonic circuits for communication applications and a variety of sensors such as those used in homeland security or environmental monitoring.