Highly sensitive microdisk laser sensor for refractive index sensing via periodic meta-hole patterning.

Abstract

Microdisk lasers have emerged as compact on-chip optical sensors due to their small size, simple structure, and efficient lasing capabilities. However, conventional microdisk laser sensors face challenges in enhancing interactions with external analytes, as their energy remains predominantly confined within the laser material. In this study, we present a novel microdisk laser sensor incorporating periodic meta-hole patterning, designed to enhance external interaction while maintaining the integrity of the whispering gallery mode (WGM). Numerical simulations show that in an InGaAsP microdisk laser (5 μm diameter, 250 nm thickness), the WGM remains stable with periodic meta-holes (period <i>a</i> = 340 nm, diameter <i>d</i> < 0.4<i>a</i>), achieving a resonant wavelength near 1,500 nm. The inclusion of meta-holes led to a substantial improvement in sensitivity, reaching up to 100.8 nm/RIU - a 2.26-fold increase over nonpatterned microdisks. Experimental validation confirmed lasing in structures with a <i>d</i>/<i>a</i> ratio of 0.32, achieving a maximum sensitivity of 74.5 nm/RIU, which represents a 2.02-fold enhancement compared to nonpatterned designs. This advancement in microdisk laser design not only opens new possibilities for high-performance, miniaturized optical sensors but also holds significant potential for integration into next-generation on-chip sensing technologies.