Al<inf>2</inf>O<inf>3</inf> Microresonator Based Passive and Active Biosensors

Abstract

Al 2 O 3 microresonators were realized for sensing applications of both passive and active devices. Passive microring resonators exhibited quality factors up to 3.2×10 5 in air. A bulk refractive index sensitivity of ~100 nm/RIU was demonstrated together with a limit of detection of ~10-6 RIU. Functionalizing their surface allowed for the label-free detection of the biomarker rhS100A4 from urine with a limit of detection of 3 nM. Furthermore, single-mode Al 2 O 3 :Yb 3+ microdisk lasers were realized that could operate in an aqueous environment. Upon varying the bulk refractive index their lasing wavelength could be tuned with a sensitivity of ~20 nm/RIU and a LOD of ~3×10-6 RIU.

Al2O3microring resonators for the detection of a cancer biomarker in undiluted urine

“…This feature allows for the development of laser-based biosensors to achieve narrower linewidths, higher sensitivities and novel sensing functionalities [35,36]. However, the only reports of optical sensors using the Al 2 O 3 photonic platform are the realization of a dual-wavelength Al 2 O 3 distributed feedback laser whose evanescent field was used to detect the presence of glass microspheres of diameters ranging between 1 µm and 20 µm [37] and the usage of an Al 2 O 3 :Yb 3+ microdisk laser integrated on chip and operating in an aqueous environment to detect minute bulk refractive index variations [38]. Furthermore, high quality factor (Q) undoped Al 2 O 3 MRRs were recently demonstrated by Su et al [39], although they were not utilized for biosensing applications.…”