Principles of Neuromorphic Photonics

In an age overrun with information, the ability to process reams of data has become crucial. The demand for data will continue to grow as smart gadgets multiply and become increasingly integrated into our daily lives. Next-generation industries in artificial intelligence services and high-performance computing are so far supported by microelectronic platforms. These data-intensive enterprises rely on continual improvements in hardware. Their prospects are running up against a stark reality: conventional one-size-fits-all solutions offered by digital electronics can no longer satisfy this need, as Moore's law (exponential hardware scaling), interconnection density, and the von Neumann architecture reach their limits. With its superior speed and reconfigurability, analog photonics can provide some relief to these problems; however, complex applications of analog photonics have remained largely unexplored due to the absence of a robust photonic integration industry. Recently, the landscape for commercially-manufacturable photonic chips has been changing rapidly and now promises to achieve economies of scale previously enjoyed solely by microelectronics. The scientific community has set out to build bridges between the domains of photonic device physics and neural networks, giving rise to the field of \emph{neuromorphic photonics}. This article reviews the recent progress in integrated neuromorphic photonics. We provide an overview of neuromorphic computing, discuss the associated technology (microelectronic and photonic) platforms and compare their metric performance. We discuss photonic neural network approaches and challenges for integrated neuromorphic photonic processors while providing an in-depth description of photonic neurons and a candidate interconnection architecture. We conclude with a future outlook of neuro-inspired photonic processing.Comment: 28 pages, 19 figure

Understanding of On-Chip Power Supply Noise: Suppression Methodologies and Challenges

The on-chip activities of any modern IC are always inhibited due to the occurrence of power supply noise (PSN) in the chip power line. From many decades, researchers are pondering on what are the major issue of this PSN occurrence and how it can be suppressed without interfering the actual chip functioning. In the course of time, it is found that the uncontrolled triggering of the on-chip system clock and the unguarded on-chip power line is instigating the two major factors for the occurrence of PSN i.e., i(t) → instantaneous current and di/dt → current ramp or the rate of change of current over time. Both i(t) and di/dt are also the sub-factors to rise the PSN components like resistive noise and inductive noise respectively. In this chapter, we light upon the occurrence of resistive and inductive noise as well as depict their individual impact on the PSN occurrences. There is also discussion on how PSN is suppressed over the years in spite of facing challenges in the execution of suppression techniques. This chapter even concludes on the suitable ways for mitigating PSN in the contemporary era of delivering complex on-chip features

Developing large-scale field-programmable analog arrays for rapid prototyping

Field-programmable analog arrays (FPAAs) provide a method for rapidly prototyping analog systems. While currently available FPAAs vary in architecture and interconnect design, they are often limited in size and flexibility. For FPAAs to be as useful and marketable as modern digital reconfigurable devices, new technologies must be explored to provide area efficient, accurately programmable analog circuitry that can be easily integrated into a larger digital/mixed signal system. By leveraging recent advances in floating gate transistors, a new generation of FPAAs are achievable that will dramatically advance the current state of the art in terms of size, functionality, and flexibility

Proceedings of the Cold Electronics Workshop

The benefits and problems of the use of cold semiconductor electronics and the research and development effort required to bring cold electronics into more widespread use were examined

Programmable photonics : an opportunity for an accessible large-volume PIC ecosystem

We look at the opportunities presented by the new concepts of generic programmable photonic integrated circuits (PIC) to deploy photonics on a larger scale. Programmable PICs consist of waveguide meshes of tunable couplers and phase shifters that can be reconfigured in software to define diverse functions and arbitrary connectivity between the input and output ports. Off-the-shelf programmable PICs can dramatically shorten the development time and deployment costs of new photonic products, as they bypass the design-fabrication cycle of a custom PIC. These chips, which actually consist of an entire technology stack of photonics, electronics packaging and software, can potentially be manufactured cheaper and in larger volumes than application-specific PICs. We look into the technology requirements of these generic programmable PICs and discuss the economy of scale. Finally, we make a qualitative analysis of the possible application spaces where generic programmable PICs can play an enabling role, especially to companies who do not have an in-depth background in PIC technology

Built-in-self-test of RF front-end circuitry

Fuelled by the ever increasing demand for wireless products and the advent of deep submicron CMOS, RF ICs have become fairly commonplace in the semiconductor market. This has given rise to a new breed of Systems-On-Chip (SOCs) with RF front-ends tightly integrated along with digital, analog and mixed signal circuitry. However, the reliability of the integrated RF front-end continues to be a matter of significant concern and considerable research. A major challenge to the reliability of RF ICs is the fact that their performance is also severely degraded by wide tolerances in on-chip passives and package parasitics, in addition to process related faults. Due to the absence of contact based testing solutions in embedded RF SOCs (because the very act of probing may affect the performance of the RF circuit), coupled with the presence of very few test access nodes, a Built In Self Test approach (BiST) may prove to be the most efficient test scheme. However due to the associated challenges, a comprehensive and low-overhead BiST methodology for on-chip testing of RF ICs has not yet been reported in literature. In the current work, an approach to RF self-test that has hitherto been unexplored both in literature and in the commercial arena is proposed. A sensitive current monitor has been used to extract variations in the supply current drawn by the circuit-under-test (CUT). These variations are then processed in time and frequency domain to develop signatures. The acquired signatures can then be mapped to specific behavioral anomalies and the locations of these anomalies. The CUT is first excited by simple test inputs that can be generated on-chip. The current monitor extracts the corresponding variations in the supply current of the CUT, thereby creating signatures that map to various performance metrics of the circuit. These signatures can then be post-processed by low overhead on-chip circuitry and converted into an accessible form. To be successful in the RF domain any BIST architecture must be minimally invasive, reliable, offer good fault coverage and present low real estate and power overheads. The current-based self-test approach successfully addresses all these concerns. The technique has been applied to RF Low Noise Amplifiers, Mixers and Voltage Controlled Oscillators. The circuitry and post-processing techniques have also been demonstrated in silicon (using the IBM 0.25 micron RF CMOS process). The entire self-test of the RF front-end can be accomplished with a total test time of approximately 30µs, which is several orders of magnitude better than existing commercial test schemes