We present a high-speed and highly scalable silicon optical modulator based on the free carrier plasma dispersion effect. The fast refractive index modulation of the device is due to electric-field-induced carrier depletion in a Silicon-on-Insulator waveguide containing a reverse biased pn junction. To achieve high-speed performance, a travelling-wave design is used to allow co-propagation of electrical and optical signals along the waveguide. We demonstrate high-frequency modulator optical response with 3 dB bandwidth of ~20 GHz and data transmission up to 30 Gb/s. Such high-speed data transmission capability will enable silicon modulators to be one of the key building blocks for integrated silicon photonic chips for next generation communication networks as well as future high performance computing applications.
Abstract-We present a seamless integration of spin-based memory and logic circuits. The building blocks are magnetologic gates based on a hybrid graphene/ferromagnet material system. We use network search engines as a technology demonstration vehicle and simulate a high-speed, small-area, and low-power spin-based circuit.Index Terms-Network search engines, spintronics.T HE CONTINUED Moore's law scaling in CMOS integrated circuits poses increasing challenges to provide lowenergy consumption, sufficient processor speed, bandwidth of interconnects, and memory storage [1]. Currently, microprocessors rely on the von Neumann architecture consisting of central processing units connected by some communication channel to memory. The bottleneck due to the communication access and memory access is the underlying reason for the widening gap between the fast improving transistor performance and our relatively stagnant programs execution speed. Such bottlenecks are particularly obvious for data-intensive applications, where most of the actions involve accessing or checking data (rather than doing complex computation). Network routers are a classical example where the Internet Protocol address is compared with a list of patterns to find a match. Conventional CMOS implementation of such circuits suffers from scalability issues, making them ineffective for larger search problems that are increasingly important to modern workloads. In this brief, we propose a paradigm change for these applications using spintronics [2]- [5]. We design a 3.2-Mbit spintronic search engine with a < 1 mm 2 total chip area and 23-W power consumption. It consists of 25 000 words of 128 bits. The performance is assessed via circuit simulation. A Magnetologic gate (MLG) is adopted as a basic building block due to its favorable properties of spin amplification, speed, and scalability [2]. Here, we summarize the MLG operation. Detailed explanations are provided in [2] and [6]. Fig. 1 shows a universal and reconfigurable MLG that consists of five ferromagnetic (FM) electrodes on top of a nonmagnetic layer. FM regions are inherently nonvolatile, preserving the direction of magnetization without power supply. This nonvolatility has been extensively used for robust information storage in magnetic hard drives and magnetic random access memory (MRAM) devices [7]. Here, we show how it can also be used for high-performance magnetologic. The magnetization itself reflects that the FM electrode has an unequal number of electrons with two different spin projections (up and down; minority and majority). The MLG design employs a stack of FM layers where the elongated permalloy layer (Py) is the free magnetic layer into which the information is encoded. The MLG operation relies on the generation of nonequilibrium spin accumulation when spin-polarized electrons tunnel from the free layer into the nonmagnetic layer via the MgO tunneling barrier. The magnitude of the spin accumulation in the nonmagnetic layer strongly depends on the relative orientation of the magnetizatio...
Abstract-This paper presents a new optical interconnect system for intra-chip communications based on free-space optics. It provides all-to-all direct communications using dedicated lasers and photodetectors, hence avoiding packet switching while offering ultra-low latency and scalable bandwidth. A technology demonstration prototype is built on a circuit board using fabricated germanium photodetectors, micro-lenses, commercial vertical-cavity surface-emitting lasers, and micro-mirrors. Transmission loss in an optical link of 10-mm distance and crosstalk between two adjacent links are measured as 5 dB and -26 dB, respectively. The measured small-signal bandwidth of the link is 10 GHz.
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