Zhoufeng Ying

Ultracompact TE-Pass Polarizer Based on a Hybrid Plasmonic Waveguide

An ultracompact and broadband TE-pass polarizer based on a hybrid plasmonic waveguide is proposed on the silicon-on-insulator platform. The optimized design has an active region as small as 0.8 μm, which is the shortest polarizer reported until now, and exhibits high polarization-dependent transmission imposing a TM mode cutoff while leaving the TE mode almost unaffected. Finite-difference time-domain simulation reveals an insertion loss <;1 dB and an extinction ratio of 19 dB. The extinction ratio could be further improved to 25 dB over 300-nm bandwidth, with an insertion loss of 2.5 dB.

Nano-optical conveyor belt with waveguide-coupled excitation.

We propose a plasmonic nano-optical conveyor belt for peristaltic transport of nano-particles. Instead of illumination from the top, waveguide-coupled excitation is used for trapping particles with a higher degree of precision and flexibility. Graded nano-rods with individual dimensions coded to have resonance at specific wavelengths are incorporated along the waveguide in order to produce spatially addressable hot spots. Consequently, by switching the excitation wavelength sequentially, particles can be transported to adjacent optical traps along the waveguide. The feasibility of this design is analyzed using three-dimensional finite-difference time-domain and Maxwell stress tensor methods. Simulation results show that this system is capable of exciting addressable traps and moving particles in a peristaltic fashion with tens of nanometers resolution. It is the first, to the best of our knowledge, report about a nano-optical conveyor belt with waveguide-coupled excitation, which is very important for scalability and on-chip integration. The proposed approach offers a new design direction for integrated waveguide-based optical manipulation devices and its application in large scale lab-on-a-chip integration.

Extraordinary Optical Transmission in a Hybrid Plasmonic Waveguide

Extraordinary optical transmission in free space through nanohole arrays has been widely investigated over the past two decades. However, because of its intrinsic nature of periodicity, it suffers from poor integration with nano-/micro-systems. Here, by folding a periodic grating into a compact cavity, we propose a waveguide-based structure within subwavelength, which also exhibits extraordinary optical transmission. Thus, lots of promising applications realized in metallic films can now be migrated onto integrated waveguides in an ultracompact way. Comparing the characteristics of the proposed integrated device and the conventional periodic structure, we reveal the nature of the unexpected transmission spectrum. Based on this principle, a collinear broadband (~500 nm) polarizer with extinction ratio of >17.8 dB is proposed, with an ultrashort length of 450 nm. Furthermore, this structure has the potential in biological applications when integrated into lab-on-a-chip or microfluidic system. As an example, a biosensor with enhanced sensitivity of 775 nm/RIU is presented.

Electro-optic modulator based gate transient suppression for sine-wave gated InGaAs/InP single photon avalanche photodiode

Abstract. Capacitive gate transient noise has been problematic for the high-speed single photon avalanche photodiode (SPAD), especially when the operating frequency extends to the gigahertz level. We proposed an electro-optic modulator based gate transient noise suppression method for sine-wave gated InGaAs/InP SPAD. With the modulator, gate transient is up-converted to its higher-order harmonics that can be easily removed by low pass filtering. The proposed method enables online tuning of the operating rate without modification of the hardware setup. At 250 K, detection efficiency of 14.7% was obtained with 4.8×10−6  per gate dark count and 3.6% after-pulse probabilities for 1550-nm optical signal under 1-GHz gating frequency. Experimental results have shown that the performance of the detector can be maintained within a designated frequency range from 0.97 to 1.03 GHz, which is quite suitable for practical high-speed SPAD applications operated around the gigahertz level.

OPERON: optical-electrical power-efficient route synthesis for on-chip signals

As VLSI technology scales to deep sub-micron, optical interconnect becomes an attractive alternative for on-chip communication. The traditional optical routing works mainly optimize the path loss, and few works explicitly exploit the optical-electrical co-design of on-chip interconnects. To overcome these limitations, we present an efficient framework that directs the hybrid optical and electrical routes with a global view of power optimization. In this framework, on-chip signal bits are processed as hyper nets; the combination of optical and electrical routes are designed for hyper nets; then a formulation is given to find the appropriate solution of each hyper net and follows a speed-up algorithm; a min-cost max-flow network is utilized to reduce the consumed optical waveguides. Experimental results demonstrate the effectiveness of the proposed framework.

Microresonator-based electro-optic full adder for optical computing in integrated photonics (Conference Presentation)

Due to the bottleneck in the continuation of Moore’s law as well as the drastically increasing trend of bandwidth, silicon photonics has emerged as the most promising candidate for implementing next-generation communication networks with ultralow power and ultrahigh speed. Recently, optical computing in integrated photonics, which outperforms electrical counterparts both in power consumption and bandwidth, has attracted a renewed interest due to the accessibility and maturity of ultracompact passive and active integrated components. However, up to now, most of relevant research about optical computing still focus on the realization of fundamental logic gates, not even close to feasible large-scale computing system. In this paper, we demonstrate a high-speed ripple-carry electro-optic full adder using micro-resonators. This approach adopts photons instead of electrons to realize logic operations as well as transfer carry signals from one bit to the next, while all the control signals of operands are applied simultaneously at and within every clock cycle. Thus, the severe latency issue that accumulates as the size of full adder increases can be circumvented, allowing for the improvement in computing speed. This approach also outperforms the conventional electrical counterpart in terms of power consumption due to the relatively smaller propagation loss and switching energy.

Comparison of microrings and microdisks for high-speed optical modulation in silicon photonics

The past several decades have witnessed the gradual transition from electrical to optical interconnects, ranging from long-haul telecommunication to chip-to-chip interconnects. As one type of key component in integrated optical interconnect and high-performance computing, optical modulators have been well developed these past few years, including ultrahigh-speed microring and microdisk modulators. In this paper, a comparison between microring and microdisk modulators is well analyzed in terms of dimensions, static and dynamic power consumption, and fabrication tolerance. The results show that microdisks have advantages over microrings in these aspects, which gives instructions to the chip design of high-density integrated systems for optical interconnects and optical computing.The past several decades have witnessed the gradual transition from electrical to optical interconnects, ranging from long-haul telecommunication to chip-to-chip interconnects. As one type of key component in integrated optical interconnect and high-performance computing, optical modulators have been well developed these past few years, including ultrahigh-speed microring and microdisk modulators. In this paper, a comparison between microring and microdisk modulators is well analyzed in terms of dimensions, static and dynamic power consumption, and fabrication tolerance. The results show that microdisks have advantages over microrings in these aspects, which gives instructions to the chip design of high-density integrated systems for optical interconnects and optical computing.

Nanophotonic devices for power-efficient computing and optical interconnects

To solve the problem in huge power consumption of the data centers and cloud computing, we design an extreme optical adder architecture suitable for ultra-high bit count. n-bit full adder are full implementable on a silicon platform using guided wave optics.

Plasmonic non-concentric nanorings array as an unidirectional nano-optical conveyor belt actuated by polarization rotation

We report a nano-optical conveyor belt containing an array of gold plasmonic non-concentric nanorings (PNNRs) for the realization of trapping and unidirectional transportation of nanoparticles through rotating the polarization of an excitation beam. The location of hot spots within an asymmetric plasmonic nanostructure is polarization dependent, thus making it possible to manipulate a trapped target by rotating the incident polarization state. In the case of PNNR, the two poles have highly unbalanced trap potential. This greatly enhances the chance of transferring trapped particles between adjacent PNNRs in a given direction through rotating the polarization. As confirmed by three-dimensional finite-difference time-domain analysis, an array of PNNRs forms an unidirectional nano-optical conveyor belt, which delivers target nanoparticles or biomolecules over a long distance with nanometer accuracy. With the capacity to trap and to transfer, our design offers a versatile scheme for conducting mechanical sample manipulation in many on-chip optofluidic applications.

Switching of nanoparticles in large-scale hybrid electro-optofluidics integration

We numerically demonstrate the scheme of independent optofluidic switching of nanoparticles on a silicon-based lab-on-a-chip system, using an electronic logic activated ring-assisted Mach-Zehnder interferometer (RAMZI). By using the carrier injection method with a tiny refractive index change of 8.00×10-4 to adjust the phase delay of a ring resonator sitting on one arm of the MZI, the light passing through could be switched to any output port of MZI followed by a directional coupler (DC). Meanwhile, the trapping force and scattering force of the guided lightwave could provide the actuation for sample delivery. Therefore, the switching logic of the guided mode is mapping to its loaded sample of nanomaterials. Our structure possesses high compactness, scalability, and time-effectiveness and, thereby, it is very appropriate for on-chip optical manipulation. The introduction of the RAMZI and cascaded RAMZIs in an optofluidic chip can form a scalable switching module with an independent electronic logic trigger signal, and make the chip dynamically configurable and scalable, which is very critical and opens a new horizon for the large-scale hybrid electro-optofluidics integration of a lab-on-a-chip system.