Digital Logic Introduction Using FPGAs

AbstractThe paper describes the adaptation of the Computer Architecture laboratory works given at the Faculty of Engineering in Foreign Languages from the University POLITEHNICA of Bucharest to the new trends in digital logic design. The laboratories are given in a gradual approach, starting with simulation, continuing with breadboard design and finishing with circuits made on perf-board. We are preparing now to complement the practical side of the laboratory with Field-Programmable Gate Array (FPGA) design, where the students will conceive, simulate, synthesize and implement the circuits already studied in the initial approach that used simulation followed by integrated circuits practical design

Optical computing by injection-locked lasers

A programmable optical computer has remained an elusive concept. To construct a practical computing primitive equivalent to an electronic Boolean logic, one should find a nonlinear phenomenon that overcomes weaknesses present in many optical processing schemes. Ideally, the nonlinearity should provide a functionally complete set of logic operations, enable ultrafast all-optical programmability, and allow cascaded operations without a change in the operating wavelength or in the signal encoding format. Here we demonstrate a programmable logic gate using an injection-locked Vertical-Cavity Surface-Emitting Laser (VCSEL). The gate program is switched between the AND and the OR operations at the rate of 1 GHz with Bit Error Ratio (BER) of 10e-6 without changes in the wavelength or in the signal encoding format. The scheme is based on nonlinearity of normalization operations, which can be used to construct any continuous complex function or operation, Boolean or otherwise.Comment: 47 pages, 7 figures in total, 2 tables. Intended for submission to Nature Physics within the next two week

Synchronizer-Free Digital Link Controller

This work presents a producer-consumer link between two independent clock domains. The link allows for metastability-free, low-latency, high-throughput communication by slight adjustments to the clock frequencies of the producer and consumer domains steered by a controller circuit. Any such controller cannot deterministically avoid, detect, nor resolve metastability. Typically, this is addressed by synchronizers, incurring a larger dead time in the control loop. We follow the approach of Friedrichs et al. (TC 2018) who proposed metastability-containing circuits. The result is a simple control circuit that may become metastable, yet deterministically avoids buffer underrun or overflow. More specifically, the controller output may become metastable, but this may only affect oscillator speeds within specific bounds. In contrast, communication is guaranteed to remain metastability-free. We formally prove correctness of the producer-consumer link and a possible implementation that has only small overhead. With SPICE simulations of the proposed implementation we further substantiate our claims. The simulation uses 65nm process running at roughly 2GHz.Comment: 12 page journal articl

Numerical treatment of localized fields in rigorous diffraction theory and its application to light absorption in structured layers

This work provides a contribution to the numerical problem of electromagnetic wave diffraction. For this purpose the widely used rigorous coupled-ave analysis (RCWA) is extended to an efficient treatment of incident light beyond the mere plane-wave input. This is essential for modern optical systems with laser or LED sources, which emit finite beams with various profiles. It thereby enables the rigorous analysis of focused light in structured media like in optical storage technology or in optical waveguide coupling. The new extension also dissolves the RCWA's restriction of handling purely linear polarized light sources. Due to a superior truncation scheme the new method inherently conserves energy during the modal propagation even within absorbing grating structures and despite the necessary numerical truncation. Another part of this work addresses the exact calculation of electromagnetic near fields and local absorption. The results are used to develop a photodetector that is fully compatible with the SOI-CMOS process and does not depend on typical optically active III-V materials. This enables the direct integration of an active, optical component in the manufacturing process of conventional electronic chips and might allow the development of new cost-effective optoelectronic hybrid components in the future, which combine the benefits of both technologies