Heterodyned toroidal microlaser sensor

Optical microcavity sensors have demonstrated success in detecting analytes with high sensitivity. Typically, the sensor output is monitored using oscilloscopes or optical spectrum analyzers; however, these instruments can significantly limit the sensing performance. In the present work, we address this limitation by developing a neodymium-doped toroid microlaser and heterodyning it with a reference laser. The resulting beat signal is analyzed on an electrical spectrum analyzer. By performing comparative temperature sensing experiments, we demonstrate that the heterodyning improves the detection limit over 60-fold while also improving the temporal resolution and the signal to noise ratio up to 50-fold.