Biosensing Performance of a Plasmonic-Grating-Based Nanolaser

Abstract

—We introduce and numerically investigate a high-quality resonant structure formed by a dielectric low-order diffraction grating combining materials with high refractive index contrast. The proposed structure is capable of supporting multiple plasmonic modes owing to hybridization effects, modes having the characteristic of exhibiting remarkable sensing response to the change of the environment refractive index yet limited figure of merit. To improve the figure of merit, the proposed architecture is modified by adding a layer of semiconductor gain medium, as it can compensate the internal losses. The result is an active sensor showing multi-modal lasing behaviour, with very low threshold and large mode spacing. It is found that the device shows switchable response upon modification of the pump amplitude or polarization, a very important feature when it comes to sensing devices. Finally, the achieved figure of merit is 3400 RIU−1, one order of magnitude higher than the passive case and much higher than the theoretical limit for sensors based on Kretschmann configuration. Thus, the proposed architecture possesses great potentials as an optical sensor for bio-detection and environmental monitoring.