Da-Ren Chen

Single virus and nanoparticle size spectrometry by whispering-gallery-mode microcavities

Detecting and characterizing single nanoparticles and airborne viruses are of paramount importance for disease control and diagnosis, for environmental monitoring, and for understanding size dependent properties of nanoparticles for developing innovative products. Although single particle and virus detection have been demonstrated in various platforms, single-shot size measurement of each detected particle has remained a significant challenge. Here, we present a nanoparticle size spectrometry scheme for label-free, real-time and continuous detection and sizing of single Influenza A virions, polystyrene and gold nanoparticles using split whispering-gallery-modes (WGMs) in an ultra-high-Q resonator. We show that the size of each particle and virion can be measured as they continuously bind to the resonator one-by-one, eliminating the need for ensemble measurements, stochastic analysis or imaging techniques employed in previous works. Moreover, we show that our scheme has the ability to identify the components of particle mixtures.

Detecting and measuring single viruses and nanoparticles with an optical microresonator

We show that adsorption of individual viruses and nanoparticles leads to discrete changes in the mode splitting spectra of a whispering-gallery-mode (WGM) microcavity, which enables a single nanoparticle spectrometry scheme to measure each particle.

On-chip Optical Resonators for Single Nanoparticle Detection and Measurement

We demonstrated a self-reference sensing technique using a high-quality Whispering-Gallery-Mode resonator for detection and measurement of single nanoparticles down to 20 nm. Our approach could measure both dielectric and metallic nanoparticles in a single-shot measurement.

Optical detection of nanoparticles by mode splitting in whispering-gallery-mode microcavities

Optical microcavities with high quality factors (Q factor) and small mode volumes have shown their potentials in various sensing applications. Here we experimentally demonstrate the real-time detection of single nanoparticles down to 30 nm in radius, using an ultra-high-Q microtoroid on a silicon chip. Mode splitting phenomenon of WGMs caused by their strong interactions with a single nanoparticle is utilized as the sensing signal. Frequency and linewidth information of the split modes is used to accurately derive the size of the particle detected. Theoretical calculations and finite element simulations are in good agreement with the experimental results. The mode splitting technique provides a self-reference scheme that is more immune to noise than the techniques based on the detection of changes of a single mode.

Single nanoparticle detection by mode splitting in ultra-high-Q microtoroid

We experimentally demonstrate that a single nanoparticle can induce mode splitting of MHz in an ultra-high-Q microtoroid resonator, which can be used to extract information of the nanoparticle. Analytical model matches well with the experiments.