Jiachao Li

Theoretical investigation of a plasmonic sensor based on a metal–insulator–metal waveguide with a side-coupled nanodisk resonator

Abstract. A plasmonic sensor based on a metal–insulator–metal waveguide with a side-coupled nanodisk resonator is proposed and numerically investigated using a finite-difference time-domain method. The numerical simulation results indicate that more than one sharp resonance dip appears in the transmission spectrum in the telecommunication regime, and each resonance wavelength has a linear relationship with the refractive index of the dielectric in the resonator. In addition, the sensing characteristics of the structure and the influence of its structural parameters are analyzed in detail by investigating the transmission spectra. As a refractive-index sensor, its sensitivity can reach as high as 1150 nm per refractive index unit near the resonance wavelength of 1550 nm, and its sensing resolution can reach 10−6 for a wavelength resolution of 0.01 nm. Furthermore, by employing the relationship between the temperature and the refractive index, the temperature-sensing characteristics of the structure are also discussed. Near the resonance wavelength of 1550 nm, the temperature sensitivity can reach 0.45  nm/°C. The sensor has a compact and simple structure and may find many potential and important applications in optical networks-on-chip and on-chip nanosensors.

Exploiting Optics Chaos for Image Encryption-Then-Transmission

A novel symmetric image encryption-then-transmission system based on optical chaos using semiconductor lasers is proposed. In this paper, with identical chaotic injection from a master laser, two slave lasers (SL1 and SL2) can output similar chaotic signals served as chaotic carrier to transmit image. Meanwhile, the chaotic signal of SL1 can be used to generate the key of the encryption scheme. After employing the three-dimensional (3D) cat map and logistic chaotic map, the positions of image pixels are shuffled, and the relationship between the cipher-image and the plain-image is confused simultaneously. Therefore, the system can resist the common attacks such as statistical attack, differential attack, and brute force attack. Through numerical simulations, the high quality chaos synchronization between SL1 and SL2 is obtained. When the chaos masking technique is adopted, the image encrypted by the proposed encryption scheme can be successfully transmitted and decrypted in a 10 km single mode fiber channel from SL1 to SL2, which is accompanied by a bit error rate of less than 6.18 × 10-19. Exhaustive tests about security analysis are carried out, demonstrating the valuable feasibility and high security of the image encryption-then-transmission system.

Theoretical Investigation of a Plasmonic Demultiplexer in MIM Waveguide Crossing with Multiple Side-Coupled Hexagonal Resonators

A novel plasmonic demultiplexer in metal-insulator-metal (MIM) waveguide crossing with multiple side-coupled hexagonal resonators is proposed and numerically investigated. The operating principle of the structure is analyzed by using the temporal coupled-mode theory. It is found that wavelength demultiplexing can be realized by modulating locations of resonators, which is validated by finite-difference time-domain (FDTD) simulations. In addition, the influences of structural parameters on transmission characteristics are studied by simulations. Simulation results reveal that the demultiplexed wavelength, transmission efficiency, and bandwidth of each channel can be manipulated by adjusting structural parameters of the demultiplexer. The proposed demultiplexer will provide an alternative for the design of highly integrated optical circuits and complex waveguide networks.

A plasmonic refractive index sensor based on a MIM waveguide with a side-coupled nanodisk resonator

Based on a metal-insulator-metal (MIM) waveguide with a side-coupled nanodisk cavity, the sensor using the surface plasmon polaritons (SPPs) refractive index is investigated and studied numerically. The finite-difference time-domain (FDTD) method is used to simulate the performance of the sensor. The numerical simulation result indicates that all the resonance wavelengths in the transmission characteristic of the structure have a linear relationship with the refractive index of the cavity. Furthermore, the sensitivities of the sensor in this paper for the refractive index can be achieved as high as 1320 nm RIU for the mode1, 812.5 nm RIU for the mode2, 600 nm RIU for the mode3, respectively. Besides, the influences of the structural parameters on the transmission characteristic and the sensing characteristic are also studied in detail by the FDTD method. The sensor with compact and simple structure not only can be used to measure the temperature based on the linear relation between the refractive index and temperature, but also has many potential applications in optical networks on chip and On-chip sensor networks.

Formal Analysis of Crosstalk Noise in Mesh-Based Optical Networks-on-Chip with WDM

Optical networks-on-chip (ONoCs) using wavelength division multiplexing (WDM) technology is one of the most promising candidates in tacking multichannel communication on the single waveguide in multicore systems-on-chip. However, compared to the traditional ONoCs with single wavelength transmitting, ONoCs employing WDM can be more susceptible to the influence of the crosstalk noise, especially the nonlinear noise generated by the four-wave mixing (FWM) effect. Consequently, the crosstalk noise can result in the signal distortion and performance degradation, even constrain the scalability of the WDM-based ONoCs. In this paper, a formal systematical analysis model including the crosstalk noise and optical signal-to-noise ratio (OSNR) analysis in mesh-based ONoCs using WDM is presented at device, router, and network levels. To demonstrate the feasibility of the proposed method, we exploit a numerical simulation example of mesh-based ONoCs using the optimized crossbar and Crux optical routers with eight optical wavelengths. The simulation results show that the crosstalk noise is the critical element for the OSNR diminution and the scalability constraint of the mesh-based ONoCs using WDM. For example, the input power is 0 dBm in the worst case, when the mesh-based WDM-based ONoCs size using optimized crossbar is 4 × 4, the average FWM noise power, linear noise power, and OSNR are -37.61 dBm, -38.86 dBm, and 4.26 dB, respectively, and these values are -37.78 dBm, -38.95 dBm, and -13.65 dB when the scale of network is 6 × 6.

Dynamics of 1550-nm VCSELs With Positive Optoelectronic Feedback: Theory and Experiments

Nonlinear dynamics of a 1550-nm vertical-cavity surface-emitting laser with positive optoelectronic feedback are studied both numerically and experimentally. A mapping of dynamical states is presented in the parameter space of feedback delay time and feedback strength, where different states are identified and shown. A bifurcation diagram of the extrema of output peak series versus the feedback delay time is plotted. Various nonlinear dynamical behaviors, including regular pulsing, quasi-periodic pulsing, and chaotic pulsing, have been numerically and experimentally observed. Both numerical simulation and experimental observation indicate that the laser enters a chaotic pulsing state at certain delay times of the feedback loop through a quasi-periodic route.

Exploring crosstalk noise generated in the N-port router used in the WDM-based ONoC

Abstract. Compared with optical network-on-chip (ONoC) with single wavelength, ONoC adopting wavelength division multiplexing (WDM) technology possesses a very prominent advantage—higher bandwidth. Therefore, WDM-based ONoC has been considered one of the most promising ways to relieve the rapidly increasing traffic load in communication systems. A WDM-based router, as the core equipment of WDM-based ONoC, is influenced by crosstalk noise, especially the nonlinear crosstalk noise generated by the four-wave mixing effect. Thus, to explore the performance of the N-port nonblocking optical router using WDM, we propose a universal analytic model to analyze the transmission loss, crosstalk noise, optical signal-to-noise ratio (OSNR), and bit error ratio (BER). The research results show that crosstalk noise varies along with signals at different wavelengths in the same channel. For signals with the same wavelength, the noises generated in the different transmission paths are obviously different from each other. For research of transmission loss, OSNR, and BER, similar results can be obtained. Based on the eye diagrams, we can learn that crosstalk noise will cause signal distortion to a certain extent. With this model, capability of this kind of multiport optical router using WDM can be understood conveniently.

Universal method for crosstalk noise and transmission loss analysis for N-port nonblocking optical router for photonic networks-on-chip

Abstract. Crosstalk noise and transmission loss are two key elements in determining the performance of optical routers. We propose a universal method for crosstalk noise and transmission loss analysis for the N-port nonblocking optical router used in photonic networks-on-chip. Utilizing this method, we study the crosstalk noise and transmission loss for the five-, six-, seven-, and eight-port optical routers. We ascertain that the crosstalk noise and transmission loss are different for different input–output pairs. For the five-port optical router, the maximum crosstalk noise ranges from 0 to −7.07  dBm, and the transmission loss ranges from −9.05 to −0.51  dB. Furthermore, based on the crosstalk noise and transmission loss, we analyze optical signal-to-noise ratio (OSNR) and bit error ratio (BER) for the five-, six-, seven-, and eight-port nonblocking optical routers. As the number of ports increases, the minimum average OSNR decreases and the average BER increases. In addition, in order to present the performance of the routers more visually, a fiber-optic communications system is designed to simulate the transmission processes of the signals of the different paths of the routers in Optisystem. The results show that the power amplitude of the input signal is obviously higher than the corresponding output signal. With this method, we can easily evaluate the transmission loss, crosstalk noise, OSNR, and BER of high-radix nonblocking optical routers and conveniently study the performance of the N-port optical router.

A general crosstalk noise analysis model for the N-port nonblocking optical router in ONoC using WDM

The optical network-on-chip (ONoC) using WDM is the most promising candidate in MPSoCs for their strengths of high communication bandwidth, high energy efficiency, high transmission speed, lower latency and power dissipation. However, when WDM is utilized, new crosstalk noises are introduced, especially the four-wave mixing (FWM) crosstalk noise. In this paper, we propose a general crosstalk noise analysis model for the N-port nonblocking optical router in ONoC using WDM. As a case study, the transmission loss, crosstalk noise, and optical signal-to-noise ratio (OSNR) of the five-, six-port routers with eight wavelengths are presented. The results show the average OSNR is different for the different wavelength signals transmitted in the both routers. For the same channel, the OSNR is different among the signals with different wavelengths. For the same wavelength signal, the OSNR of different channels is also distinct.

Performance optimization in Torus-based optical networks-on-chip

In this paper, the insertion loss and crosstalk noise of M × N Torus-based optical networks-on-chip (ONoCs) is systematically analyzed, which caused performance degradation. The proposed analysis model can be applied to arbitrary 5×5 routers and Torus-based ONoCs. When traditional non-blocking five-port optical routers used in the original Torus structure, its suffered lager Bit Error Rate (BER) in a small scale. The router optimization and angle optimization method is used for achieving a better quality of network communication and performance improvement. The numerical results show the signal-to-noise ratio (SNR) of the worst-case transmission link in Torus-based ONoCs with certain size. When the network scale of Torus-based ONoC is 6×6 and the input power is 0 dB, the SNR of Torus-based ONoC using Crux router is 21.66 dB, which is 7.06 dB higher than optimized Crossbar router. With angle optimization further used in router level and network level, the SNR can reach to 23.87 dB. Moreover, we also find that a better SNR can be got with M gradually close to N .