11 results
Search Results
Now showing 1 - 10 of 11
- ItemModulation Linearity Characterization of Si Ring Modulators(Washington, DC : OSA, 2021) Jo, Youngkwan; Mai, Christian; Lischke, Stefan; Zimmermann, Lars; Choi, Woo-YoungModulation linearity of Si ring modulators (RMs) is investigated through the numerical simulation based on the coupled-mode theory and experimental verification. Numerical values of the key parameters needed for the simulation are experimentally extracted. Simulation and measurement results agree well. With these, the influence of input optical wavelength and power on the Si RM linearity are characterized.
- ItemA physical origin of cross-polarization and higher-order modes in two-dimensional (2D) grating couplers and the related device performance limitations(Bristol : IOP Publishing, 2021) Georgieva, Galina; Voigt, Karsten; Seiler, Pascal M.; Mai, Christian; Petermann, Klaus; Zimmermann, LarsWe explore scattering effects as the physical origin of cross-polarization and higher-order modes in silicon photonic 2D grating couplers (GCs). A simplified analytical model is used to illustrate that in-plane scattering always takes place, independent of grating geometry and design coupling angle. Experimental investigations show furthermore that grating design parameters are especially related to the modal composition of both the target- and the cross-polarization. Scattering effects and the associated cross-polarization and higher-order modes are indicated as the main reason for the higher 2D GC insertion loss compared to standard 1D GCs. In addition, they can be responsible for a variable 2D GC spectrum shape, bandwidth and polarization dependent loss.
- ItemOptimization of Multi-Level Operation in RRAM Arrays for In-Memory Computing(Basel : MDPI, 2021) Pérez, Eduardo; Pérez-Ávila, Antonio Javier; Romero-Zaliz, Rocío; Mahadevaiah, Mamathamba Kalishettyhalli; Pérez-Bosch Quesada, Emilio; Roldán, Juan Bautista; Jiménez-Molinos, Francisco; Wenger, ChristianAccomplishing multi-level programming in resistive random access memory (RRAM) arrays with truly discrete and linearly spaced conductive levels is crucial in order to implement synaptic weights in hardware-based neuromorphic systems. In this paper, we implemented this feature on 4-kbit 1T1R RRAM arrays by tuning the programming parameters of the multi-level incremental step pulse with verify algorithm (M-ISPVA). The optimized set of parameters was assessed by comparing its results with a non-optimized one. The optimized set of parameters proved to be an effective way to define non-overlapped conductive levels due to the strong reduction of the device-to-device variability as well as of the cycle-to-cycle variability, assessed by inter-levels switching tests and during 1 k reset-set cycles. In order to evaluate this improvement in real scenarios, the experimental characteristics of the RRAM devices were captured by means of a behavioral model, which was used to simulate two different neuromorphic systems: an 8 × 8 vector-matrix-multiplication (VMM) accelerator and a 4-layer feedforward neural network for MNIST database recognition. The results clearly showed that the optimization of the programming parameters improved both the precision of VMM results as well as the recognition accuracy of the neural network in about 6% compared with the use of non-optimized parameters.
- ItemModeling Photodetection at the Graphene/Ag2S Interface(Weinheim : Wiley-VCH, 2021) Spirito, Davide; Martín-García, Beatriz; Mišeikis, Vaidotas; Coletti, Camilla; Bonaccorso, Francesco; Krahne, RomanMixed-dimensional systems host interesting phenomena that involve electron and ion transport along or across the interface, with promising applications in optoelectronic and electrochemical devices. Herein, a heterosystem consisting of a graphene monolayer with a colloidal Ag2S nanocrystal film atop, in which both ions and electrons are involved in photoelectrical effects, is studied. An investigation of the transport at the interface in different configurations by using a phototransistor configuration with graphene as a charge-transport layer and semiconductor nanocrystals as a light-sensitive layer is performed. The key feature of charge transfer is investigated as a function of gate voltage, frequency, and incident light power. A simple analytical model of the photoresponse is developed, to gain information on the device operation, revealing that the nanocrystals transfer electrons to graphene in the dark, but the opposite process occurs upon illumination. A frequency-dependence analysis suggests a fractal interface between the two materials. This interface can be modified using solid-state electrochemical reactions, leading to the formation of metallic Ag particles, which affect the graphene properties by additional doping, while keeping the photoresponse. Overall, these results provide analytical tools and guidelines for the evaluation of coupled electron/ion transport in hybrid systems.
- ItemSi photonic-electronic monolithically integrated optical receiver with a built-in temperature-controlled wavelength filter(Washington, DC : Soc., 2021) Kim, Hyun-Kyu; Kim, Minkyu; Kim, Min-Hyeong; Jo, Youngkwan; Lischke, Stefan; Mai, Christian; Zimmermann, Lars; Choi, Woo-YoungWe present a Si photonic-electronic integrated ring-resonator based optical receiver that contains a temperature-controlled ring-resonator filter (RRF), a Ge photodetector, and receiver circuits in a single chip. The temperature controller automatically determines the RRF temperature at which the maximum transmission of the desired WDM signal is achieved and maintains this condition against any temperature or input wavelength fluctuation. This Si photonic-electronic integrated circuit is realized with 0.25-µm photonic BiCMOS technology, and its operation is successfully confirmed with measurement.
- ItemSilicon-organic hybrid photonics: Overview of recent advances, electro-optical effects and CMOS-integration concepts(Bristol : IOP Publishing, 2021) Steglich, Patrick; Mai, Christian; Villringer, Claus; Dietzel, Birgit; Bondarenko, Siegfried; Ksianzou, Viachaslau; Villasmunta, Francesco; Zesch, Christoph; Pulwer, Silvio; Burger, Martin; Bauer, Joachim; Heinrich, Friedhelm; Schrader, Sigurd; Vitale, Francesco; De Matteis, Fabio; Prosposito, Paolo; Casalboni, Mauro; Mai, AndreasIn recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon–organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon–organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given.
- ItemA 112 Gb/s Radiation-Hardened Mid-Board Optical Transceiver in 130-nm SiGe BiCMOS for Intra-Satellite Links(Lausanne : Frontiers Media, 2021) Giannakopoulos, Stavros; Sourikopoulos, Ilias; Stampoulidis, Leontios; Ostrovskyy, Pylyp; Teply, Florian; Tittelbach-Helmrich, K.; Panic, Goran; Fischer, Gunter; Grabowski, Alexander; Zirath, Herbert; Ayzac, Philippe; Venet, Norbert; Maho, Anaëlle; Sotom, Michel; Jones, Shaun; Wood, Grahame; Oxtoby, IanWe report the design of a 112 Gb/s radiation-hardened (RH) optical transceiver applicable to intra-satellite optical interconnects. The transceiver chipset comprises a vertical-cavity surface-emitting laser (VCSEL) driver and transimpedance amplifier (TIA) integrated circuits (ICs) with four channels per die, which are adapted for a flip-chip assembly into a mid-board optics (MBO) optical transceiver module. The ICs are designed in the IHP 130 nm SiGe BiCMOS process (SG13RH) leveraging proven robustness in radiation environments and high-speed performance featuring bipolar transistors (HBTs) with fT/fMAX values of up to 250/340 GHz. Besides hardening by technology, radiation-hardened-by-design (RHBD) components are used, including enclosed layout transistors (ELTs) and digital logic cells. We report design features of the ICs and the module, and provide performance data from post-layout simulations. We present radiation evaluation data on analog devices and digital cells, which indicate that the transceiver ICs will reliably operate at typical total ionizing dose (TID) levels and single event latch-up thresholds found in geostationary satellites.
- ItemNon-isothermal phase-field simulations of laser-written in-plane SiGe heterostructures for photonic applications(London : Springer Nature, 2021) Aktas, Ozan; Yamamoto, Yuji; Kaynak, Mehmet; Peacock, Anna C.Advanced solid-state devices, including lasers and modulators, require semiconductor heterostructures for nanoscale engineering of the electronic bandgap and refractive index. However, existing epitaxial growth methods are limited to fabrication of vertical heterostructures grown layer by layer. Here, we report the use of finite-element-method-based phase-field modelling with thermocapillary convection to investigate laser inscription of in-plane heterostructures within silicon-germanium films. The modelling is supported by experimental work using epitaxially-grown Si0.5Ge0.5 layers. The phase-field simulations reveal that various in-plane heterostructures with single or periodic interfaces can be fabricated by controlling phase segregation through modulation of the scan speed, power, and beam position. Optical simulations are used to demonstrate the potential for two devices: graded-index waveguides with Ge-rich (>70%) cores, and waveguide Bragg gratings with nanoscale periods (100–500 nm). Periodic heterostructure formation via sub-millisecond modulation of the laser parameters opens a route for post-growth fabrication of in-plane quantum wells and superlattices in semiconductor alloy films.
- ItemCMOS-Compatible Bias-Tunable Dual-Band Detector Based on GeSn/Ge/Si Coupled Photodiodes(Washington, DC : ACS Publications, 2021) Talamas Simola, Enrico; Kiyek, Vivien; Ballabio, Andrea; Schlykow, Viktoria; Frigerio, Jacopo; Zucchetti, Carlo; De Iacovo, Andrea; Colace, Lorenzo; Yamamoto, Yuji; Capellini, Giovanni; Grützmacher, Detlev; Buca, Dan; Isella, GiovanniInfrared (IR) multispectral detection is attracting increasing interest with the rising demand for high spectral sensitivity, room temperature operation, CMOS-compatible devices. Here, we present a two-terminal dual-band detector, which provides a bias-switchable spectral response in two distinct IR bands. The device is obtained from a vertical GeSn/Ge/Si stack, forming a double junction n-i-p-i-n structure, epitaxially grown on a Si wafer. The photoresponse can be switched by inverting the bias polarity between the near and the short-wave IR bands, with specific detectivities of 1.9 × 1010 and 4.0 × 109 cm·(Hz)1/2/W, respectively. The possibility of detecting two spectral bands with the same pixel opens up interesting applications in the field of IR imaging and material recognition, as shown in a solvent detection test. The continuous voltage tuning, combined with the nonlinear photoresponse of the detector, enables a novel approach to spectral analysis, demonstrated by identifying the wavelength of a monochromatic beam. © 2021 The Authors. Published by American Chemical Society.
- ItemToward Reliable Compact Modeling of Multilevel 1T-1R RRAM Devices for Neuromorphic Systems(Basel : MDPI AG, 2021) Perez-Bosch Quesada, Emilio; Romero-Zaliz, Rocio; Perez, Eduardo; Kalishettyhalli Mahadevaiah, Mamathamba; Reuben, John; Schubert, Markus Andreas; Jimenez-Molinos, Francisco; Roldan, Juan Bautista; Wenger, ChristianIn this work, three different RRAM compact models implemented in Verilog-A are analyzed and evaluated in order to reproduce the multilevel approach based on the switching capability of experimental devices. These models are integrated in 1T-1R cells to control their analog behavior by means of the compliance current imposed by the NMOS select transistor. Four different resistance levels are simulated and assessed with experimental verification to account for their multilevel capability. Further, an Artificial Neural Network study is carried out to evaluate in a real scenario the viability of the multilevel approach under study.