Showing papers by "Lan Yang published in 2011"
TL;DR: A whispering gallery mode microlaser-based real-time and label-free detection method that can detect individual 15-nm-radius polystyrene nanoparticles, 10-nm gold nanoparticles and influenza A virions in air, and 30 nm polystyren nanoparticles in water.
Abstract: There is a strong demand for portable systems that can detect and characterize individual pathogens and other nanoscale objects without the use of labels, for applications in human health, homeland security, environmental monitoring and diagnostics. However, most nanoscale objects of interest have low polarizabilities due to their small size and low refractive index contrast with the surrounding medium. This leads to weak light-matter interactions, and thus makes the label-free detection of single nanoparticles very difficult. Micro- and nano-photonic devices have emerged as highly sensitive platforms for such applications, because the combination of high quality factor Q and small mode volume V leads to significantly enhanced light-matter interactions. For example, whispering gallery mode microresonators have been used to detect and characterize single influenza virions and polystyrene nanoparticles with a radius of 30 nm (ref. 12) by measuring in the transmission spectrum either the resonance shift or mode splitting induced by the nanoscale objects. Increasing Q leads to a narrower resonance linewidth, which makes it possible to resolve smaller changes in the transmission spectrum, and thus leads to improved performance. Here, we report a whispering gallery mode microlaser-based real-time and label-free detection method that can detect individual 15-nm-radius polystyrene nanoparticles, 10-nm gold nanoparticles and influenza A virions in air, and 30 nm polystyrene nanoparticles in water. Our approach relies on measuring changes in the beat note that is produced when an ultra-narrow emission line from a whispering gallery mode microlaser is split into two modes by a nanoscale object, and these two modes then interfere. The ultimate detection limit is set by the laser linewidth, which can be made much narrower than the resonance linewidth of any passive resonator. This means that microlaser sensors have the potential to detect objects that are too small to be detected by passive resonator sensors.
599 citations
TL;DR: It is shown 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.
Abstract: 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.
94 citations
TL;DR: In this paper, the authors investigated the scattering process in an ultrahigh-mathrm{Q}$ optical microcavity coupled to subwavelength scatterers by introducing splitting quality, a dimensionless parameter defined as the ratio of the scatterer-induced mode splitting to the total loss of the coupled system.
Abstract: We investigate scattering process in an ultrahigh-$\mathrm{Q}$ optical microcavity coupled to subwavelength scatterers by introducing splitting quality ${\mathcal{Q}}_{\mathrm{sp}}$, a dimensionless parameter defined as the ratio of the scatterer-induced mode splitting to the total loss of the coupled system. A simple relation is introduced to directly estimate the Purcell factor from single-shot measurement of transmission spectrum of scatterer-coupled cavity. Experiments with polystyrene (PS) and gold (Au) nanoparticles, erbium ions, and Influenza A virions show that Purcell-factor-enhanced preferential funneling of scattering into the cavity mode takes place regardless of the scatterer type. Experimentally determined highest ${\mathcal{Q}}_{\mathrm{sp}}$ for single PS and Au nanoparticles are 9.4 and 16.19 corresponding to Purcell factors with lower bounds of 353 and 1049, respectively. The highest observed ${\mathcal{Q}}_{\mathrm{sp}}$ was 31.2 for an ensemble of Au particles. These values are the highest ${\mathcal{Q}}_{\mathrm{sp}}$ and Purcell factors reported up to date.
49 citations
TL;DR: In this article, the size range of particles that induce mode splitting in a microsphere in water was determined as a function of the resonator mode volume and quality factor, and the results were confirmed by the experimental observations.
Abstract: Whispering gallery mode (WGM) optical resonators utilizing resonance shift (RS) and mode splitting (MS) techniques have emerged as highly sensitive platforms for label-free detection of nanoscale objects. RS method has been demonstrated in various resonators in air and liquid. MS in microsphere resonators has not been achieved in aqueous environment up to date, despite its demonstration in microtoroid resonators. Here, we demonstrate scatterer-induced MS of WGMs in microsphere resonators in water. We determine the size range of particles that induces MS in a microsphere in water as a function of resonator mode volume and quality factor. The results are confirmed by the experimental observations.
48 citations
TL;DR: In this paper, a narrow-linewidth on-chip toroid Raman laser was reported, achieving a power level of 21 μW and a standard deviation of 0.17 μW.
Abstract: In this paper, we report a narrow-linewidth on-chip toroid Raman laser. Under free-running condition, we have obtained the minimum fundamental linewidth of 3 Hz and the maximum unidirectional output power of 223 μW. Lasing under the same condition in continuous-wave mode over 90 min is achieved at an average power level of 21 μW and a standard deviation of 0.17 μW. We further derived the frequency noise spectrum and identified an enhancement of frequency noise due to Kerr non linearity. In addition, we have observed the shifting of relaxation oscillation frequency as a consequence of weak mode splitting.
43 citations
TL;DR: In this paper, an optothermal resonance scanning scheme was proposed to obtain stable spectra of resonant modes in whispering gallery microresonators, where a resonance mode is thermally locked to a tunable laser and its wavelength is linearly scanned across the lasing line of a fixed wavelength laser.
Abstract: We demonstrate an optothermal resonance scanning scheme to obtain stable spectra of resonant modes in whispering gallery microresonators. A wavelength stability of 0.1 pm for a temperature variation of more than 10 °C is obtained. In this scheme, a resonance mode is thermally locked to a tunable laser, and its wavelength is linearly scanned across the lasing line of a fixed wavelength laser. The scheme enables reliable and accurate readings for whispering gallery mode (WGM) sensing platforms and allows the spectroscopy of WGM resonators within wavelength bands where tunable lasers are not available.
33 citations
TL;DR: In this paper, the size range of particles that induce mode splitting in a microsphere in water was determined as a function of the resonator mode volume and quality factor, and the results were confirmed by the experimental observations.
Abstract: Whispering gallery mode (WGM) optical resonators utilizing resonance shift (RS) and mode splitting (MS) techniques have emerged as highly sensitive platforms for label-free detection of nano-scale objects. RS method has been demonstrated in various resonators in air and liquid. MS in microsphere resonators has not been achieved in aqueous environment up to date, despite its demonstration in microtoroid resonators. Here, we demonstrate scatterer-induced MS of WGMs in microsphere resonators in water. We determine the size range of particles that induces MS in a microsphere in water as a function of resonator mode volume and quality factor. The results are confirmed by the experimental observations.
31 citations
TL;DR: In this paper, a single particle detection scheme with single particle resolution is presented, which is based on monitoring the transmitted light power which shows abrupt jumps with each particle binding to the taper surface.
Abstract: A nanoparticle detection scheme with single particle resolution is presented. The sensor contains only a taper fiber, thus offering the advantages of compactness and installation flexibility. The sensing method is based on monitoring the transmitted light power which shows abrupt jumps with each particle binding to the taper surface. The experimental validation of the sensor is demonstrated with polystyrene nanoparticles of radii 120 and 175 nm in the 1550-nm wavelength band.
30 citations
TL;DR: In this paper, the plasmonic structures to super-hydrophobic surfaces may offer a way around the problem of the detection of ultralow concentrations of molecules using nanoscale optical sensors, where diffusion acts on impractical timescales.
Abstract: The detection of ultralow concentrations of molecules using nanoscale optical sensors is hindered by the difficulty in bringing the two into contact, where diffusion acts on impractical timescales. Fortunately, introducing plasmonic structures to super-hydrophobic surfaces may offer a way around this problem.
4 citations
TL;DR: In this paper, a self-reference sensing mechanism based on mode splitting was proposed, where a high-quality optical mode in a WGM resonator splits into two modes due to intra-cavity Rayleigh scattering.
Abstract: Ultra-sensitive and label-free chemical and biological sensing devices are of great importance to biomedical research,
clinical diagnostics, environmental monitoring, and homeland security applications. Optical sensors based on ultra-highquality
Whispering-Gallery-Mode (WGM) micro-resonators, in which light-matter interactions are significantly
enhanced, have shown great promise in achieving compact sensors with high sensitivity and reliability. However,
traditional sensing mechanisms based on monitoring the frequency shift of a single resonance faces challenges since the
resonant frequency is sensitive not only to the sensing targets but also to many types of disturbances in the environment,
such as temperature variation and mechanical instability of the system. The analysis of the signals is also affected by the
positions of sensing targets on the resonator. Thus, it is difficult to distinguish signals coming from different sources,
which introduces 'false positive' detection. We report a novel self-reference sensing mechanism based on mode splitting,
a phenomenon in which a high-quality optical mode in a WGM resonator splits into two modes due to intra-cavity
Rayleigh scattering. In particular, we demonstrated that the two split modes that can be induced by a single nanoparticle
reside in the same resonator and serve as a reference to each other. As a result, a self-reference sensing scheme is
formed. This allows us to develop a position-independent sensing scheme to accurately estimate the sizes of
nanoparticles. So far we have achieved position-independent detecting and sizing of single nanoparticles down to 20 nm
in radius with a single-shot measurement using an on-chip high-quality WGM microtoroid resonator.
4 citations
01 May 2011
TL;DR: In this paper, a single-shot estimation of Purcell factor is demonstrated using the scatterer-induced mode-splitting spectra using synthetic nanoparticles, Erbium ions and Influenza A virions.
Abstract: Scattering process in a microcavity coupled to subwavelength scatterers is investigated using synthetic nanoparticles, Erbium ions and Influenza A virions. Direct and single-shot estimation of Purcell factor is demonstrated using the scatterer-induced mode-splitting spectra.
01 May 2011
TL;DR: In this article, a sensitive single nanoparticle detection scheme using a nano tapered fiber was presented, where experiments of detecting R = 120 nm and 175 nm polystyrene (PS) nanoparticles at 1550 nm wavelength band were demonstrated.
Abstract: We present a sensitive single nanoparticle detection scheme using a nano tapered fiber. Experiments of detecting R = 120 nm and 175 nm polystyrene (PS) nanoparticles at 1550 nm wavelength band are demonstrated.
04 Apr 2011
TL;DR: In this paper, a self-reference sensing technique using a high-quality Whispering-Gallery-Mode resonator was demonstrated for detection and measurement of single nanoparticles down to 20 nm.
Abstract: 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.
04 Apr 2011
TL;DR: In this paper, the authors demonstrate scatterer-induced mode splitting in Whispering-Gallery-Mode resonators as a new sensing scheme in water, which is used to detect polystyrene particles of radii 50nm with a similar size as influenza A virus.
Abstract: We demonstrate scatterer-induced mode splitting in Whispering-Gallery-Mode resonators as a new sensing scheme in water. It is used to achieve detecting polystyrene particles of radii 50nm with a similar size as influenza A virus.
01 May 2011
TL;DR: In this paper, the authors 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.
Abstract: 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.
01 May 2011
TL;DR: In this article, an optical microcavity laser is used for label-free detection of single nanoparticles, and the detection limit is significantly improved due to the ultra-narrow laser linewidth compared to the resonance linwidth of a passive laser.
Abstract: Optical microcavity laser is utilized for label-free detection of single nanoparticles. Detection limit is significantly improved due to the ultra-narrow laser linewidth compared to the resonance linewidth of a passive microcavity.
01 May 2011
TL;DR: In this article, the authors investigated the dynamics of mode splitting manipulated by two scatterers in an optical microresonator and explained the experimental results by a multiple-scatterer theory.
Abstract: Investigation of the dynamics of mode splitting manipulated by two scatterers in an optical microresonator is presented. The experimental results are explained by a multiple-scatterer theory and the applications on nanoparticle detection and sizing are discussed.
22 Dec 2011
TL;DR: In this article, self-pulsing behaviors in WGM microlasers due to nonlinear optical losses introduced by excited state absorption was discussed and a self-referencing detection of nanoparticles using WGM nano-lasers was demonstrated.
Abstract: Whispering-Gallery-Mode(WGM) resonators can significantly enhance light-matter interaction We discuss self-pulsing behaviors in WGM microlasers due to nonlinear optical losses introduced by excited state absorption Ultra-sensitive self-referencing detection of nanoparticles using WGM microlasers is demonstrated
TL;DR: In this paper, a self-referencing sensing technique using high-quality Whispering-Gallery-Mode (WGM) resonators for detection and measurement of single nanoparticles is discussed.
Abstract: We discuss a self-referencing sensing technique using high-quality Whispering-Gallery-Mode (WGM) resonators for detection and measurement of single nanoparticles. We also demonstrate self-heterodyne detection of nanoparticles with radius of 10 nm using WGM microlasers.