Optical heterodyne detection for ultra-high Q micro-disk laser sensor

In this paper, we propose a bio-sensing method using optical heterodyne detection for ultra-high Q micro-disk laser (MDL) sensor platform. MDL structure with ultra-high Q-factor (> 108) has advantage in detecting a small variation of the lasing wavelength. For example, when a single molecule is attached to sidewall of MDL, the lasing wavelength is changed by sub-pm. Optical spectrum analyzer (OSA) has limits to detect sub-pm variation in the resonant wavelength because of the spectral resolution. In order to overcome this limitation, we used a heterodyne detection method which needs two MDLs with the same characteristics.