Self-referenced sensing via mode splitting in coupled liquid-crystal microlasers.

Mode splitting in coupled whispering gallery mode microcavities provides a useful basis for self-referenced optical sensing. Here, we present a coupled liquid crystal (LC) microlaser system for mode splitting sensing. Both theoretical and experimental results show that the mode splitting separation varies with the refractive-index detuning between two microcavities. Stearic-acid doping in the sensing cavity converts pH-induced LC molecule reorientation into refractive-index detuning in the coupled system. To verify its practical applicability, adenosine detection is further realized with an approximately linear response. The results demonstrate the feasibility of self-referenced sensing based on coupled LC microlasers, suggesting a general sensing strategy for detecting other analytes via modification of functional dopants or reaction systems.