Portable microresonator-based label-free detector: monotonous resonance splitting with particle adsorption

Abstract

Whispering gallery mode resonators hold great promises as very sensitive detectors, with a wide range of applications, notably as biosensors. However, in order to monitor the fine variations in their resonances, a costly and bulky apparatus is required, which confines the use of these efficient tools within specialised labs. Here, we consider a micro-ring resonator that is completely covered by a Bragg grating and propose to functionalize it only over a quarter of its perimeter. As target molecules progressively bind to the active region of the resonator, some particular resonances near the edge of the band gap undergo monotonous frequency splitting. Such a splitting, within the GHz range, can be monitored by conventional electronics and, hence, does not require finely tunable lasers or spectrometers. Meanwhile, the ultrahigh sensitivity that is characteristic of whispering gallery mode resonators is maintained. This robust and sensitive self-heterodyne detection scheme may pave the way to portable whispering-gallery-mode-based detectors, and in particular to point-of-care diagnostic tools.

Experimental demonstration of multimode microresonator sensing by machine learning

“…By adjusting the applied voltage within the set range, many groups of transmission depths were extracted as the original data for the multimode sensing. It is expected that the cost of multimode sensor would be further reduced in the future, by employing a charged coupled device (CCD) and a reflection grating to directly acquire the cavity mode intensities [29], instead of using the OSA for measuring the transmission spectra [30,31].…”

Multi-Parameter Sensing in a Multimode Self-Interference Micro-Ring Resonator by Machine Learning

“…Based on WGM resonators, the sensing is typically realized by measuring the spectral changes in high resolution using a tunable laser or an optical spectrometer [6][7][8][9][10]. These spectral changes include mode shift, splitting and broadening, which is called reactive sensing [5,13,16,[20][21][22][23][24]. Alternatively, when WGM resonators detect absorptive target analytes, the probe light may be strongly absorbed and then the linewidth of WGM resonator mode is significantly broadened, which is exploited to implement the dissipative sensing [16,20].…”

Microring resonators with circular element inner-wall gratings for enhanced sensing

“…In the case of microring resonators, several strategies have been proposed to overcome this limitation, including ultrathin SOI microring resonators, 9) slotted waveguide microring resonators, 10) introduction of subwavelength grating structures [11][12][13][14] and photonic crystals inside the microring cavity, [15][16][17][18][19] and a microring with periodically arranged metal nanodisks. 20,21) The possibility to fabricate microrings with different perforation depths and arrangements opens a new degree of freedom in device design.…”