Single nanoparticle detection using split-mode microcavity Raman lasers

Abstract

Ultrasensitive nanoparticle detection holds great potential for early-stage diagnosis of human diseases and for environmental monitoring. In this work, we report for the first time, to our knowledge, single nanoparticle detection by monitoring the beat frequency of split-mode Raman lasers in high-Q optical microcavities. We first demonstrate this method by controllably transferring single 50-nm-radius nanoparticles to and from the cavity surface using a fiber taper. We then realize real-time detection of single nanoparticles in an aqueous environment, with a record low detection limit of 20 nm in radius, without using additional techniques for laser noise suppression. Because Raman scattering occurs in most materials under practically any pump wavelength, this Raman laser-based sensing method not only removes the need for doping the microcavity with a gain medium but also loosens the requirement of specific wavelength bands for the pump lasers, thus representing a significant step toward practical microlaser sensors.stimulated Raman scattering | optical microcavity | mode splitting | optical sensor | label free S timulated Raman scattering holds great potential for various photonic applications, such as label-free high-sensitivity biomedical imaging (1) and for extending the wavelength range of existing lasers (2), as well as for generating ultra-short light pulses (3). In high Q microcavities (4), stimulated Raman scattering, also called Raman lasing, has been experimentally demonstrated to possess ultra-low thresholds (5-12), due to the greatly increased light density in microcavities (13). Such microcavity Raman lasers hold great potential for sensing applications. In principle, Raman lasing initially occurs in the two initially degenerate counter propagating traveling cavity modes. These two modes couple to each other due to backscattering when a nanoscale object binds to the cavity surface. For a sufficiently strong coupling, in which the photon exchange rate between the two initial modes becomes larger than the rates of all of the loss mechanisms in the system, two new split cavity modes form (14-18) and lase simultaneously. Thus, by monitoring the beat frequency of the split-mode Raman lasers, ultrasensitive nanoparticle detection can be realized.In this work, we report, to our knowledge, the first experimental demonstration of single nanoparticle detection using split-mode microcavity Raman lasers. The sensing principle is first demonstrated in air, by controllably binding or removing single 50-nm-radius polystyrene (PS) nanoparticles to and from the cavity surface using a fiber taper (19) and measuring the changes in the beat frequency of the two split Raman lasers. Real-time single nanoparticle detection is then performed in an aqueous environment by monitoring the discrete changes in beat frequency of the Raman lasers, and a detection limit of 20 nm in particle radius is realized. This microcavity Raman laser sensing method holds several advantages. On the one hand, the beat frequency of the Raman las...

Electromagnetically induced transparency in optical microcavities

“…Most importantly, the optical microcavity systems allow for on-chip integration and room-temperature operation, and the resonant modes can be tuned to almost any wavelength range. With the rapid development of the micro/nano fabrication techniques, optical microcavities with ultrahigh quality factors (Q) and small mode volumes are widely studied [68][69][70], which have sought applications ranging from fundamental physics to applications, such as cavity quantum electrodynamics [71,72], nonlinear optics [73], low-threshold microlasing [74], and biosensing [75][76][77][78][79][80][81][82].…”

Detection of Single Nanoparticles Using the Dissipative Interaction in a High-QMicrocavity

“…In addition, the tunable laser or a high-resolution spectrometer in the conventional microcavity sensing setups could be replaced by other types of coherent measurement methods such as the microcavity lasing beat note [42,44,45] or cavity ring-up spectroscopy [17].…”

“…Via reactive sensing, a single virus [28,29] and a single nanoparticle [30][31][32][33] have been detected experimentally. Furthermore, by employing surface plasmon resonance (SPR) enhancement [34][35][36][37][38][39][40][41], microcavity lasing [42][43][44][45], the noise suppression technique [46], or exceptional point [47], a better sensing ability can still be achieved.…”

Mass sensing by detecting the quadrature of a coupled light field

“…By detecting the shift of WGMs, the ultra-sensitive size sensing can be realized [12][13][14]. In addition, the dispersion of nanoparticles will induce the mode splitting [15][16][17][18][19][20][21][22][23][24][25][26][27] or mode broadening [28][29][30], and will also cause the linewidth change [31] which can be used for size sensing as well.…”