Singe Nanoparticle detection using the dissipative interaction with a high-Q microcavity

Abstract

Ultrasensitive optical detection of nanometer-scaled particles is highly desirable for applications in early-stage diagnosis of human diseases, environmental monitoring, and homeland security, but remains extremely difficult due to ultralow polarizabilities of small-sized, low-index particles. Optical whispering-gallery-mode microcavities, which can enhance significantly the light-matter interaction, have emerged as promising platforms for label-free detection of nanoscale objects. Different from the conventional whispering-gallery-mode sensing relying on the reactive (i.e., dispersive) interaction , here we propose and demonstrate to detect single lossy nanoparticles using the dissipative interaction in a high-Q toroidal microcavity. In the experiment, detection of single gold nanorods in an aqueous environment is realized by monitoring simultaneously the linewidth change and shift of the cavity mode. The experimental result falls within the theoretical prediction. Remarkably, the reactive and dissipative sensing methods are evaluated by setting the probe wavelength on and off the surface plasmon resonance to tune the absorption of nanorods, which demonstrates clearly the great potential of the dissipative sensing method to detect lossy nanoparticles. Future applications could also combine the dissipative and reactive sensing methods, which may provide better characterizations of nanoparticles.

Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

“…In this case, the sensor responds to the losses induced by a nanoparticle due to absorption and scattering. Plasmonic nanoparticles [3,73], dielectric nanoparticles [74], and virus particles [75] were detected in this way. A third sensing principle is the monitoring of split resonances by tracking the wavelength and linewidth difference of the split modes.…”

Single Nanoparticle Detection Using Optical Microcavities

“…[13][14][15][16][17][18][19][20] Over the past few years, optical sensing methods, featuring low cost, miniature fingerprint, non-invasiveness, fast response, and high sensitivity have been developed. [47][48][49][50][51][52][53] The rapid progress in microcavity sensing has led to several recent reviews, [54][55][56][57][58][59][60][61][62][63] but none of them focus mainly on single nanoparticle detection. [30][31][32][33][34][35][36][37] Microcavity sensing has seen tremendous progress and the sensing performance has been demonstrated by detecting single nanoparticles and single biological molecules.…”

Cavity ring-up spectroscopy for dissipative and dispersive sensing in a whispering gallery mode resonator

“…As predicted by theory, the peak height changes linearly with κ e /κ. If the system experiences an intrinsic dissipation change due to environmental conditions, the peak height should maintain an inverse relationship to intrinsic dissipation under a certain coupling condition, which is the gap between the taper and the microsphere in our case (in more complicated situations, the coupling is not only determined by the gap but also the dissipation of the surrounding environment [22]). In a more complicated scenario, where both dispersion and dissipation exist, a measurement of the peak height may still be sufficient.…”

“…dispersive) frequency shift of the whispering gallery modes [19] as a result of perturbations that may be present. Alternatively, a perturbation may increase the optical linewidth of the WGM by introducing more dissipation [21,22], or may change the back-scattering strength [23] and subsequent mode splitting if modal coupling is present [17,20]. The optomechanical properties of WGRs can also be used for force [24] or viscosity sensing [25].…”