Yiwei Peng

The sensing characteristics of plasmonic waveguide with a ring resonator

A surface plasmon polaritons (SPPs) refractive index sensor which consists of two metal-insulator-metal (MIM) waveguides coupled to each other by a ring resonator is proposed. The transmission properties are numerically simulated by finite element method. The sensing characteristics of such structure are systematically analyzed by investigating the transmission spectrum. The results indicate that there exist three resonance peaks in the transmission spectrum, and all of which have a linear relationship with the refractive index of the material under sensing. Through the optimization of structural parameters, we achieve a theoretical value of the refractive index sensitivity as high as 3460nmRIU(-1). Furthermore, this structure can also be used as a temperature sensor with temperature sensitivity of 1.36nm/°C. This work paves the way toward sensitive nanometer scale refractive index sensor and temperature sensor for design and application.

Tuning the Fano resonances in a single defect nanocavity coupled with a plasmonic waveguide for sensing applications

A novel surface plasmon polaritons (SPPs) refractive index sensor based on a single defect nanocavity coupled with a metal–insulator–metal (MIM) waveguide is proposed and numerically simulated by using the finite difference time domain (FDTD) method with perfectly matched layer absorbing boundary condition. It is found that the defect structure can realize two Fano resonances and these two Fano resonances originate from two different mechanisms. The results demonstrate the liner correlation between the resonance wavelengths of the device and the refractive index of the material under sensing. Through the optimization of structural parameters, we achieve a theoretical value of the refractive index sensitivity as high as 1800.4 nmRIU−1. It could be utilized to develop ultra-compact nanodevice for high-resolution biological sensing.

Low-photon-number optical switch and AND/OR logic gates based on quantum dot-bimodal cavity coupling system.

We propose a new scheme based on quantum dot-bimodal cavity coupling system to realize all-optical switch and logic gates in low-photon-number regime. Suppression of mode transmission due to the destructive interference effect is theoretically demonstrated by driving the cavity with two orthogonally polarized pulsed lasers at certain pulse delay. The transmitted mode can be selected by designing laser pulse sequence. The optical switch with high on-off ratio emerges when considering one driving laser as the control. Moreover, the AND/OR logic gates based on photon polarization are achieved by cascading the coupling system. Both proposed optical switch and logic gates work well in ultra-low energy magnitude. Our work may enable various applications of all-optical computing and quantum information processing.

Optical nonlinearity in a quantum dot–microcavity system under an external magnetic field

We theoretically study the dynamics of a strongly coupled quantum dot–bimodal microcavity system under an external magnetic field, where the nondegenerate excitonic spin states caused by the Zeeman effect are coupled to both orthogonal cavity modes. We develop an effective cavity quantum electrodynamics model, demonstrate the polarization-related nonlinear response under a linearly polarized pulse excitation by calculating the time-resolved intracavity photon number, and investigate the dependence of system parameters on the nonlinearity. In addition, we show that, when driven by two pulses with perpendicular polarization and a relative time delay, the coupled system suppresses the delayed one, which can be applied to polarized optical switching at a single-photon level.

Ultra-strongly sub-Poissonian light generation in a quantum dot-bimodal cavity system

We theoretically investigate the sub-Poissonian light generation in a cavity quantum electrodynamics system of a single quantum dot coupled a bimodal nanocavity. It is shown in a recent work [Arka Majumdar et.al, Phys. Rev. Lett. 108, 183601 (2012)] that the system can generate strongly sub-Poissonian light when one of the cavity modes is driven coherently and resonantly. We study the two-mode coherent driving regime of the coupled system. The effect of additional cavity mode driving on the statistic characteristics of photon emission is presented by evaluating the zero-delay second-order correlation function g2(0). We interpret the optimization of sub-Poissonian feature by regulating the ratio between driving strengths of two cavity modes and observe that g2(0) can be reduced up to several orders of magnitude (g2(0))<10-4), comparing with one-mode driving system (g2(0)~0.1), indicating ultra-strongly sub-Poissonian light generation.

Advanced Numerical and Close-Form Solutions for Local Gain and Refractive Index of Quantum-Dot Semiconductor Optical Amplifiers in Steady State

Based on 2M+1 (M=40 for example) rate equations, advanced numerical solutions with a much faster speed of computation for gain and refractive index of quantum-dot semiconductor optical amplifiers in steady state have been presented.