7th September 2022: PICS Today Webinar #10

Abstract: The concept of programmable photonic circuits has been studied and developed extensively in the last few years. It has shown great potential in cutting-edge applications, including machine learning, quantum computing, radio frequency (RF) signal processing, and hardware accelerators. This concept, so-called field-programmable photonic gate array (FPPGA), can evolve into a truly general-purpose photonic circuit if we successfully implement it on a large scale. However, there are several hurdles for scaling, including a large footprint, high power consumption, and high optical loss. These issues mainly originate from the low efficient tuning mechanisms of photonic circuits. Thermo-optics, the most commonly used method, constantly dissipate heat to the surrounding area, and therefore it consumes large power even when the circuits are at static states. In addition, thermal crosstalk between the elements prevents increasing their integration density. On the other hand, the MEMS-based tuning mechanism has shown its potential to implement large-scale photonic circuits by demonstrating large-scale photonic switches. The large scalability of the technology originates from its tuning mechanism that allows moving optical building blocks using an extremely small amount of power. By moving optical elements, large index contrast can be created, and therefore large optical effect follows. The electrostatic actuator creating the movements is just a simple variable capacitor that consumes electrical power only when the state of the elements is changing. Our team has been developing various MEMS-tunable photonic components for power-efficient and low-loss photonic circuits. We have demonstrated programmable photonic processors directly applicable to classical and quantum photonics applications using the MEMS-tunable elements. In this talk, we will show our recent progress on MEMS-based programmable photonic circuits and their perspective on large-scale photonic systems on a chip.


3rd August 2022: PICS Today Webinar #09

Abstract: Currently available commercial transmission systems operate at symbol rates of just over 50 Gbaud in short range and 90 Gbaud in long-reach scenarios. If historical trends were to continue, we'd expect a doubling of symbol rates roughly every 5 years, bringing 200+ Gbaud systems to the market in ~6-7 years. With Moore's Law soon to be given its last rites, the industry faces a seemingly insurmountable hurdle in the quest to make future ultra-high baudrate systems a commercial reality. Modern, low-power transceivers based on CMOS technology are reaching its limits in terms of both bandwidth and performance. New emerging bandwidth expanding solution based on SiGe BiCMOS or InP HBT hybrid integrated with silicon photonics devices could provide 200Gbaud symbol rate. What are the technological and system level challenges associated with high symbol rates? The total aggregated optical link power consumption constrain may lead to trade-offs between the modulation speed and other solutions allowing extend aggregated bandwidth such as wavelength-division multiplexing (WDM). WDM is an attractive approach for enabling high aggregate transceiver bandwidth without increasing symbol rate or parallelizing optical link however it may lead to extensive thermal tuning and decreasing overall link efficiency. Integration of a light source as well as signal integrity-preserving assembly and fiber packaging solutions will strongly influence the development of terabit/s optical transceivers.


6th July 2022: PICS Today Webinar #08

Abstract: Integrated photonics, particularly silicon-based photonic circuits, has revolutionised optical signal processing applications in communication, sensing, and computing. Building on scalable and flexible fabrication technology, monolithic and heterogeneous integration has mitigated the limitations in the silicon photonics platform. In this talk, I will share our exploration of exploiting passive silicon technology developed at IISc for communication, RF signal processing and sensing. Integration of electro-optic and phase-change materials is key to extending the functionality and application space of traditional silicon photonics platforms. We shall discuss schemes that will help to realise energy-efficient neuromorphic photonic circuits. While telecom wavelengths dominate PIC developments, lower wavelengths play a key role in extending the application space to spectroscopy and biosensing. I will present some compelling reasons for developing circuits operating in lower wavelengths and some demonstrations of circuits with integrated WDM and on-chip detectors. Furthermore, photonic circuits could be used to enable and enhance signal transduction. By integrating photonic with micro-mechanics, we were able to demonstrate state-of-the-art displacement detection down to the picometer scale. While there are a plethora of disruptive technologies that photonic circuits could enable, having scalable and reliable fabrication technology is essential. In this talk, all the demonstrations will be based on the indigenous process and material developed at the Indian Institute of Science, Bangalore.


1st June 2022: PICS Today Webinar #07

Abstract: The exponential increase in the use of AI/ML based applications coupled with increased adoption of 5G & IoT has motivated the need for rethinking and optimizing data center network architectures. Some of these implementations include a drive towards composable, scale up and scale out architectures with resource pooling and memory disaggregation. Such an implementation would require scalable interconnect (I/O) architecture that would support >1Tb/s bandwidth (BW) between various AI, server and memory clusters that are within 50m radial distance . Within the constraints of the data center network architecture, there is also a need to optimize the I/O for low power and cost. The relevant I/O FoM (Tbps/mm / pj/bit) for data center interconnects would thus involve the product of I/O escape bandwidth density (Tbps/mm) and energy efficiency (1/pj/bit). The legacy front panel pluggable (FPP) architectures result in significant power, scale and cost inefficiencies as BW go up. Co-packaged optics (CPO) architecture enable extremely high escape BW density (> 1Tbps/mm) at low power (< 2 pj/bit) by converting electrical signals into optical signals in the same package as that of signal generating silicon (SoC/ASIC) thereby improving the I/O FoM . This talk will provide an overview of the CPO.


4th May 2022: PICS Today Webinar #06

Abstract: Over the past decade, the development of CMOS-compatible silicon technology has provided a novel platform for integrated nonlinear photonics, offering a path towards chip-scale devices for applications including spectroscopy, communications, and optical computing. Recent advances in silicon nitride (SiN) fabrication technology have enabled efficient nonlinear photonics in integrated microresonators. This is enabled by the low linear losses, large effective nonlinearities due to the high optical confinement in the nanowaveguide structure, and the ability to tailor the group-velocity dispersion (GVD) of the device, which is essential for phase-matched parametric nonlinear interactions such as four-wave mixing (FWM). The development of such high-Q SiN microresonators has led to the realization of highly-compact Kerr optical frequency comb sources based on FWM parametric oscillation. Here, we discuss progress in Kerr comb technology, including all-optical synchronization between Kerr combs and high-power normal GVD combs for wavelength-division multiplexing.


6th April 2022: PICS Today Webinar #05

Abstract: Digital electronics is a technological cornerstone in our modern society which has covered the increasing demand in computing power during the last decades thanks to a periodic doubling of transistor density and power efficiency in integrated circuits. Currently, such scaling laws are reaching their fundamental limits, leading to the emergence of a large gamut of computing applications that cannot be exclusively supported by digital electronics. In this context, an analog computing approach implemented in a real-time reconfigurable non-electronic hardware such as programmable integrated photonics (PIP) can be more efficient than digital electronics to perform these emerging applications. In this talk I will present the foundations of a new computation theory, termed Analog Programmable-Photonic Computation, explicitly designed to unleash the full potential of PIP technology.


2nd March 2022: PICS Today Webinar #04

Abstract: Quantum technologies promise a change of paradigm for many fields of application, for example in communication systems, in high-performance computing and simulation of quantum systems, as well as in sensor technology. They can shift the boundaries of todays systems and devices beyond classical limits and seemingly fundamental limitations. The use of complex photonic systems, which comprise multiple optical modes as well as non-classical light, has been proposed for various quantum applications over the last decades and illustrate the versatility of photonic systems. However, their implementation often requires advanced setups of high complexity, which poses considerable challenges on the experimental side. Here we present three differing approaches to advance current experimental approaches for multi-dimensional photonic quantum systems: non-linear integrated quantum optics, pulsed temporal modes and time-multiplexing. Non-linear integrated quantum devices with multiple channels enable the combinations of different functionalities, such as sources and fast electro-optic modulations, on a single compact monolithic structure. Pulsed photon temporal modes are defined as field orthogonal superposition states and can constitute a high dimensional quantum system. They occupy only a single spatial mode and thus they can be efficiently used in single-mode fibre communication networks. Finally, time-multiplexed quantum walks are a versatile tool for the implementation of a highly flexible simulation platform with many modes and dynamic control of the underlying graph structures and coherence properties of the quantum network.


2nd February 2022: PICS Today Webinar #03

Abstract: In this presentation I will discuss the use of micro transfer printing technology for the realization of III-V/Si(N) photonic integrated circuits. The technology allows for throughput integration of III-V opto electronic components such as semiconductor optical amplifiers, lasers, modulators and photodiodes on a Si(N) platform, completing the toolkit for next generation photonic systems-on-chip.


5th January 2022: PICS Today Webinar #02

Abstract: A fault-tolerant quantum computer hardware architecture demands integrating several qubits with optimized signal routing and control electronics without sacrificing the quantum coherence. However, the monolithic integration of such devices is challenging due to the material and thermodynamic incompatibilities of multiple quantum components and their increased parasitic modes. Therefore, a heterogeneously integrated scalable interposer packaging architecture is of great importance to merge and interconnect different functionalities within a sophisticated chip while maintaining qubit coherence. This talk shall discuss a novel Quantum Chip Optoelectronics Interposer Packaging (QuIP) with heterogeneously integrated electrical and optical quantum components, interconnected using electrical (superconducting microstrip), electromagnetic (inductive or capacitive), and integrated optical interconnects on silicon interposers. The proposed QuIP scheme is a scalable and high-volume manufacturable solution that improves the size, speed, power, mechanical and thermal robustness at cryogenic temperatures.


1st December 2021: PICS Today Webinar #01

Abstract: Programmable integrated photonics circuits have evolved in complexity during the last 10 years. As an alternative to custom design circuits, multipurpose programmable circuits were recently presented with the promise of achieving arbitrary functionality and dynamic system operation. In this talk we review the fundaments of programmable photonics, with special focus on programming methods, performance, and its applications. These devices are called to revolutionize the PIC industry by providing flexible, multi functional operation with an unprecedented level of customization.


1st October 2021: IRIS Webinar on "Photonic Integrated Circuits"

IRIS Webinar on "Photonic Integrated Circuits" from IoE IIT Madras showcased the invaluable insight on Silicon Photonics research and fabrication facilities as well as state-of-the-art global R&D scenarios. Prof. Wim Bogaerts (Ghent University, Belgium), one of the pioneers in Silicon Photonics gave his valuable talk on this field along with Prof. Bijoy Krishna Das and Prof. Enakshi Bhattacharya. We are thankful to Prof. Shayan Mookherjea (University of California, San Diego, USA) for being the moderator of this webinar.


18th August 2021: Riddhi's PhD Defence

We are proud to announce that our research scholar Ms. Riddhi Nandi has successfully defended her PhD thesis entitled, "Electrical Control of Optical Bistability in Silicon Microring Resonators". She has already started her professional career in Global Foundries Bangalore (Silicon Photonics Group). Congratulations Dr. Riddhi Nandi.


30th December 2020: Fund Sanctioned for CoE-CPPICS

The Centre of Excellence CPPICS @ IIT Madras has been jointly sponsored by MeitY, Govt. of India and Si2 Microsystems, Bengaluru (www.si2microsystems.com ). Total project value is Rs. 2990.80 Lakhs (~ 4.1 Million USD) and for a duration of five years starting from 1st January, 2021.