Jin-Ming Cui

Plasmon modes of silver nanowire on a silica substrate

Plasmon mode in a silver nanowire is theoretically studied when the nanowire is placed on or near a silica substrate. It is found that the substrate has much influence on the plasmon mode. For the nanowire on the substrate, the plasmon (hybrid) mode possesses not only a long propagation length but also an ultrasmall mode area. From the experimental point of view, this cavity-free structure holds a great potential to study a strong coherent interaction between the plasmon mode and single quantum system (for example, quantum dots) embedded in the substrate.

Broadband integrated polarization beam splitter with surface plasmon

A broadband integrated waveguide polarization beam splitter consisting of a metal nanoribbon and two dielectric waveguides is proposed and numerically investigated. This surface plasmon based device provides a unique approach for polarization sensitive manipulation of light in an integrated circuit and will be essential for future classical and quantum information processes.

Fiber-integrated diamond-based magnetometer

We demonstrated a fiber-integrated diamond-based magnetometer in this paper. In the system, the fluorescence of nitrogen vacancy (NV) centers in nanodiamonds deposited on a tapered fiber was coupled to the tapered fiber effectively and detected at the output end of the fiber. By using this scheme, optically detected electron spin resonance spectra were recorded for single NV centers. The results confirmed that such a tapered fiber-nanodiamond system can act as a magnetometer. Featured with excellent portability, convenient fabrication, and potential for further integration, the constructed system has been demonstrated to be a practical magnetometer prototype.

Modified transmission spectrum induced by two-mode interference in a single silica microsphere

We theoretically and experimentally study the resonant transmission spectrum of light in a fibre taper coupled with a single silica microsphere cavity system, where two whispering-gallery modes (WGMs) are simultaneously excited. By changing the taper position (correspondingly, tuning the resonant frequencies of the two WGMs and modulating their coupling conditions with the fibre taper), a sharp electromagnetically-induced- transparency-like window can be observed in the transmission spectrum. This line shape origins from the taper-mediated interference between two co-existing WGMs in a single microsphere. This measurement result agrees well with the theoretical analysis.

Temperature dependent energy level shifts of nitrogen-vacancy centers in diamond

Magnetic resonance and fluorescence spectra of nitrogen-vacancy (NV) color centers ensemble in high purity diamond sample were measured, with temperature ranging from 5.6 K to 295 K. Both microwave and optical transition energies have similar nonlinear temperature dependent changes, which might mainly originate from the local thermal expansion. As the frequency shifts will reduce the fidelity of resonant quantum control, the present results demonstrate the necessity of taking temperature fluctuation into consideration. For temperature below 100 K, the transition energies show tendencies to be constant, which indicate higher stability and performance in applications with NV centers.

Movable Fiber-Integrated Hybrid Plasmonic Waveguide on Metal Film

A waveguide structure consisting of a tapered nanofiber on a metal film is proposed and analyzed to support highly localized hybrid plasmonic modes. The hybrid plasmonic mode can be efficiently excited through the in-line tapered fiber based on adiabatic conversion and collected by the same fiber, which is very convenient in experimentation. Due to the ultrasmall mode area of plasmonic mode, the local electromagnetic field is greatly enhanced in this movable waveguide, which has the potential for enhanced coherence light emitter interactions, such as waveguide quantum electrodynamics, single emitter spectrum, and nonlinear optics.

Quantum statistical imaging of particles without restriction of the diffraction limit.

A quantum measurement method based on the quantum nature of antibunching photon emission has been developed to detect single particles without the restriction of the diffraction limit. By simultaneously counting the single-photon and two-photon signals with fluorescence microscopy, the images of nearby nitrogen-vacancy centers in diamond at a distance of 8.5±2.4  nm have been successfully reconstructed. Also their axes information was optically obtained. This quantum statistical imaging technique, with a simple experimental setup, can also be easily generalized in the measuring and distinguishing of other physical properties with any overlapping, which shows high potential in future image and study of coupled quantum systems for quantum information techniques.

High-Q and Unidirectional Emission Whispering Gallery Modes: Principles and Design

The general principles of the unidirectional emission of a high-Q whispering gallery mode (WGM) in deformed circular microcavities are studied and presented in this paper. In the phase space of deformed microcavities, light in the chaotic sea leaks out from the cavity through specific refraction regions, the positions of which are determined by the stable islands and the unstable manifolds. By changing the cavity shape, we can tune the positions of the refraction regions, as well as fixed points, to achieve unidirectional emission with narrow angular divergence. The microcavity with high-Q and unidirectional emission makes high-efficient free-space excitation and collection possible; thus, it can be applied for far-field detection of nanoparticles and low-threshold lasers with collimated emission.

Ringing phenomenon in silica microspheres

Whispering gallery modes in silica microspheres are excited by a tunable continuous-wave laser through the fiber taper. Ringing phenomenon can be observed with high frequency sweeping speed. The thermal nonlinearity in the microsphere can enhance this phenomenon. Our measurement results agree very well with the theoretical predictions by the dynamic equation.

Anti-bunching and luminescence blinking suppression from plasmon-interacted single CdSe/ZnS quantum dot

CdSe/ZnS colloidal quantum dots generally exist as blinking phenomena during the luminescence process that remarkably influences its applications. In this work, we used the surface plasmonic effect to effectively modulate single quantum dots. Obvious contrasts have been observed by comparing single quantum dots on silica and gold films. The surface plasmon is shown to obviously suppress the blinking of single quantum dots. With further demonstrated second- order correlation measurements, an anti-bunching effect was observed. The anti-bunching dip gives the smallest value of g(2)(0) = 0.15, and the lifetime of the exciton has been reduced. This method presents the applications potential towards tunable high-emitting-speed single photon sources at room temperature.