Sasikanth Manipatruni | |
---|---|
Born | 1984 |
Nationality | American |
Alma mater | Cornell University ETH Zurich IIT Delhi Indian Institute of Science Jawahar Navodaya Vidyalaya |
Known for | Beyond CMOS Magneto-Electric Spin-Orbit Silicon photonics Spintronics In-memory processing Quantum materials Artificial intelligence |
Awards | IEEE/ACM Young Innovator Award, [1] National Academy of Engineering Frontiers award, [2] SRC Mahboob Khan Award [3] |
Scientific career | |
Institutions | Intel General Electric Research Laboratory Cornell University ETH Zurich Indian Institute of Science Inter-University Centre for Astronomy and Astrophysics |
Thesis | Scaling silicon nanophotonic interconnects : silicon electrooptic modulators, slowlight & optomechanical devices (2010) |
Doctoral advisor | Michal Lipson Alexander Gaeta |
Other academic advisors | Ajoy Ghatak Manfred Morari Christopher J. Hardy Keren Bergman |
Sasikanth Manipatruni is an American engineer and inventor in the fields of Computer engineering, Integrated circuit technology, Materials Engineering and semiconductor device fabrication. [4] Manipatruni contributed to developments in silicon photonics, spintronics and quantum materials. [5] [6] [7]
Manipatruni is a co-author of 50 research papers and ~400 patents [8] (cited about 7500 times [4] ) in the areas of electro-optic modulators, [9] [10] Cavity optomechanics, [11] [12] nanophotonics & optical interconnects, [13] [14] spintronics, [15] [16] and new logic devices for extension of Moore's law. [17] [18] His work has appeared in Nature, Nature Physics, Nature communications, Science advances and Physical Review Letters.
Manipatruni received a bachelor's degree in Electrical Engineering and Physics from IIT Delhi in 2005 where he graduated with the institute silver medal. [19] He also completed research under the Kishore Vaigyanik Protsahan Yojana [20] at Indian Institute of Science working at Inter-University Centre for Astronomy and Astrophysics and in optimal control [21] at Swiss Federal Institute of Technology at Zurich.
Manipatruni received his Ph.D. in Electrical Engineering with minor in applied engineering physics from Cornell University. [22] The title of his thesis was "Scaling silicon nanophotonic interconnects : silicon electrooptic modulators, slowlight & optomechanical devices". [22] His thesis advisors were Michal Lipson and Alexander Gaeta at Cornell University. He has co-authored academic research with Michal Lipson, Alexander Gaeta, Keren Bergman, Ramamoorthy Ramesh, Lane W. Martin, Naresh Shanbhag, [23] Jian-Ping Wang, [24] Paul McEuen, Christopher J. Hardy, Felix Casanova, [25] Ehsan Afshari, Alyssa Apsel, Jacob T. Robinson, [26] fr:Manuel Bibes spanning Condensed matter physics, Electronics and devices, Photonics, Circuit theory, Computer architecture and hardware for Artificial intelligence areas.
Manipatruni's PhD thesis was focused on developing the then nascent field of silicon photonics by progressively scaling the speed of electro-optic modulation from 1 GHz [27] to 12.5 Gbit/s, [28] 18 Gbit/s [29] and 50 Gbit/s [30] on a single physical optical channel driven by a silicon photonic component. The significance of silicon for optical uses can be understood as follows: nearly 95% of modern Integrated circuit technology is based on silicon-based semiconductors which have high productivity in Semiconductor device fabrication due to the use of large single crystal wafers and extraordinary control of the quality of the interfaces. However, Photonic integrated circuits are still majorly manufactured using III-V compound semiconductor materials and II-VI semiconductor compound materials, whose engineering lags silicon industry by several decades (judged by number of wafers and devices produced per year). By showing that silicon can be used as a material to turn light signal on and off, silicon electro-optic modulators allow for use of high-quality engineering developed for the electronics industry to be adopted for photonics/optics industry. This the foundational argument used by silicon electro-optics researchers. [31] This work was paralleled closely at leading industrial research groups at Intel, [32] IBM [33] and Luxtera [34] during 2005–2010 with industry adopting and improving various methods developed at academic research labs. Manipatruni's work showed that it is practically possible to develop free carrier injection modulators (in contrast to carrier depletion modulators) to reach high speed modulation by engineering injection of free carriers via pre-amplification and back-to-back connected injection mode devices. [35]
In combination with Keren Bergman at Columbia University, micro-ring modulator research led to demonstration of a number of firsts in long-distance uses of silicon photonics utilizing silicon based injection mode electro-optic modulators including first demonstration of long-haul transmission using silicon microring modulators [36] first Error-free transmission of microring-modulated BPSK, [37] First Demonstration of 80-km Long-Haul Transmission of 12.5-Gb/s Data Using Silicon Microring Resonator Electro-Optic Modulator, [38] First Experimental Bit-Error-Rate Validation of 12.5-Gb/s Silicon Modulator Enabling Photonic Networks-on-Chip. [39] These academic results have been applied into products widely deployed at Cisco, [40] Intel. [41]
Manipatruni, Lipson and collaborators at Intel [42] have projected a roadmap that required the use of Silicon micro-ring modulators to meet the bandwidth, linear bandwidth density (bandwidth/cross section length) and area bandwidth density (bandwidth/area) of on-die communication links. While originally considered thermally unstable, [43] by early 2020's micro-ring modulators have received wide adoption for computing needs at Intel [44] [45] Ayar Labs, [46] Global foundries [47] and varied optical interconnect usages.
The optimal energy of an on-die optical link is written [42] as : where is the optimal detector voltage (maintaining the bit error rate), detector capacitance, is the modulator drive voltage, are the electrooptic volume of the optical cavity being stabilized, refractive index change to carrier concentration and spectral sensitivity of the device to refractive index change is the change in optical transmission, B is the bandwidth of the link, Ptune the power to keep the resonator operational and B the bandwidth of the link at F frequency of the data being serialized.
Manipatruni and Christopher J. Hardy applied integrated photonic links to the Magnetic resonance imaging to improve the signal collection rate from the MRI machines via the signal collection coils [48] while working at the General Electric's GE Global Research facility. The use of optical transduction of the MRI signals [49] can allow significantly higher signal collection arrays within the MRI system increasing the signal throughput, reducing the time to collect the image and overall reduction of the weight of the coils and cost of MRI imaging by reducing the imaging time. [50]
Manipatruni proposed the first observation that optical radiation pressure leads to non-reciprocity in micro cavity opto-mechanics in 2009 [51] [12] in the classical electro-magnetic domain without the use of magnetic isolators. In classical Newtonian optics, [52] [53] it was understood that light rays must be able to retrace their path through a given combination of optical media. However, once the momentum of light is taken into account inside a movable media this need not be true in all cases. This work [51] [12] proposed that breaking of the reciprocity (i.e. properties of media for forward and backward moving light can be violated) is observable in microscale optomechanical systems due to their small mass, low mechanical losses and high amplification of light due to long confinement times.
Later work has established the breaking of reciprocity in a number of nanophotonic conditions including time modulation and parametric effects in cavities. [54] [55] [56] [57] [58] [59] Manipatruni and Lipson have also applied the nascent devices in silicon photonics to optical synchronization [60] [11] and generation of non-classical beams of light using optical non-linearities. [61] [62]
Manipatruni worked on Spintronics for the development of logic computing devices for computational nodes beyond the existing limits to silicon-based transistors. He developed an extended modified nodal analysis that uses vector circuit theory [63] for spin-based currents and voltages using modified nodal analysis which allows the use of spin components inside VLSI designs used widely in the industry. [64] [65] The circuit modeling is based on theoretical work [66] by Supriyo Datta [67] [68] and Gerrit E. W. Bauer. [69] Manipatruni's spin circuit models were extensively applied for development of spin logic circuits, [70] [71] [72] spin interconnects, [73] domain wall interconnects [74] and benchmarking logic [75] and memory devices utilizing spin and magnetic circuits. [76] [77]
In 2011, utilizing the discovery of Spin Hall effect and Spin–orbit interaction in heavy metals from Robert Buhrman, [78] Daniel Ralph [79] and Ioan Miron [80] in Period 6 element transition metals [81] [80] Manipatruni proposed an integrated spin-hall effect memory [82] (Later named Spin-Orbit Memory to comprehend the complex interplay of interface and bulk components of the spin current generation [83] ) combined with modern Fin field-effect transistor transistors [84] to address the growing difficulty with embedded Static random-access memory in modern Semiconductor process technology. SOT-MRAM for SRAM replacement spurred significant research and development leading to successful demonstration of SOT-MRAM combined with Fin field-effect transistors in 22 nm process and 14 nm process at various foundries. [85] [86] [87]
Working with Jian-Ping Wang, [88] Manipatruni and collaborators were able to show evidence of a 4th elemental ferro-magnet. [89] [90] [91] Given the rarity of ferro-magnetic materials in elemental form at room temperature, use of a less rare element can help with the adoption of permanent magnet based driven systems for electric vehicles.
In 2016, Manipatruni and collaborators proposed a number of changes to the new logic device development by identifying the core criterion for the logic devices for utilization beyond the 2 nm process. [17] The continued slow down the Moore's law as evidenced by slow down of the voltage scaling, [92] [93] lithographic node scaling and increasing cost per wafer and complexity of the fabs indicated that Moore's law as it existed in the 2000-2010 era has changed to a less aggressive scaling paradigm.
Manipatruni proposed [17] that spintronic and multiferroic systems are leading candidates for achieving attojoule-class logic gates for computing, thereby enabling the continuation of Moore's law for transistor scaling. However, shifting the materials focus of computing towards oxides and topological materials requires a holistic approach addressing energy, stochasticity and complexity.
The Manipatruni-Nikonov-Young Figure-of-Merit for computational quantum materials is defined as the ratio of " energy to switch a device at room temperature" to " energy of thermodynamic stability of the materials compared to vacuum energy, where is the reversal of the order parameter such as ferro-electric polarization or magnetization of the material"
This ratio is universally optimal for a ferro-electric material and compared favorably to spintronic and CMOS switching elements such as MOS transistors and BJTs. The framework (adopted by SIA decadal plan [94] ) describes a unified computing framework that uses physical scaling (physics-based improvement in device energy and density), mathematical scaling (using information theoretic improvements to allow higher error rate as devices scale to thermodynamic limits) and complexity scaling (architectural scaling that moves from distinct memory & logic units to AI based architectures). Combining Shannon inspired computing allows the physical stochastic errors inherent in highly scaled devices to be mitigated by information theoretic techniques. [95] [96]
Ian A. Young, Nikonov, and Manipatruni have provided a list of 10 outstanding problems in quantum materials as they pertain to computational devices. These problems have been subsequently addressed in numerous research works leading to various improved device properties for a future computer technology Beyond CMOS. The top problems listed as milestones and challenges for logic are as follows:
Problems of magnetic/ferro-electric/multiferroic switching
Magneto-electric spin-orbit logic is a design using this methodology for a new logical component that couples magneto-electric effect and spin orbit effects. Compared to CMOS, MESO circuits could potentially require less energy for switching, lower operating voltage, and a higher integration density. [18]
An optical neural network is a physical implementation of an artificial neural network with optical components. Early optical neural networks used a photorefractive Volume hologram to interconnect arrays of input neurons to arrays of output with synaptic weights in proportion to the multiplexed hologram's strength. Volume holograms were further multiplexed using spectral hole burning to add one dimension of wavelength to space to achieve four dimensional interconnects of two dimensional arrays of neural inputs and outputs. This research led to extensive research on alternative methods using the strength of the optical interconnect for implementing neuronal communications.
Optical computing or photonic computing uses light waves produced by lasers or incoherent sources for data processing, data storage or data communication for computing. For decades, photons have shown promise to enable a higher bandwidth than the electrons used in conventional computers.
Nanophotonics or nano-optics is the study of the behavior of light on the nanometer scale, and of the interaction of nanometer-scale objects with light. It is a branch of optics, optical engineering, electrical engineering, and nanotechnology. It often involves dielectric structures such as nanoantennas, or metallic components, which can transport and focus light via surface plasmon polaritons.
An optical circulator is a three- or four-port optical device designed such that light entering any port exits from the next. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3. This is analogous to the operation of an electronic circulator. Fiber-optic circulators are used to separate optical signals that travel in opposite directions in an optical fiber, for example to achieve bi-directional transmission over a single fiber. Because of their high isolation of the input and reflected optical powers and their low insertion loss, optical circulators are widely used in advanced fiber-optic communications and fiber-optic sensor applications.
A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components that form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated circuits use photons as opposed to electrons that are used by electronic integrated circuits. The major difference between the two is that a photonic integrated circuit provides functions for information signals imposed on optical wavelengths typically in the visible spectrum or near-infrared (850–1650 nm).
Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. The silicon is usually patterned with sub-micrometre precision, into microphotonic components. These operate in the infrared, most commonly at the 1.55 micrometre wavelength used by most fiber optic telecommunication systems. The silicon typically lies on top of a layer of silica in what is known as silicon on insulator (SOI).
William James Dally is an American computer scientist and educator. He is the chief scientist and senior vice president at Nvidia and was previously a professor of Electrical Engineering and Computer Science at Stanford University and MIT. Since 2021, he has been a member of the President's Council of Advisors on Science and Technology (PCAST).
A slot-waveguide is an optical waveguide that guides strongly confined light in a subwavelength-scale low refractive index region by total internal reflection.
A subwavelength-diameter optical fibre is an optical fibre whose diameter is less than the wavelength of the light being propagated through it. An SDF usually consists of long thick parts at both ends, transition regions (tapers) where the fibre diameter gradually decreases down to the subwavelength value, and a subwavelength-diameter waist, which is the main acting part. Due to such a strong geometrical confinement, the guided electromagnetic field in an SDF is restricted to a single mode called fundamental. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically.
Michal Lipson is an American physicist known for her work on silicon photonics. A member of the National Academy of Sciences since 2019, Lipson was named a 2010 MacArthur Fellow for contributions to silicon photonics especially towards enabling GHz silicon active devices. Until 2014, she was the Given Foundation Professor of Engineering at Cornell University in the school of electrical and computer engineering and a member of the Kavli Institute for Nanoscience at Cornell. She is now the Eugene Higgins Professor of Electrical Engineering at Columbia University. In 2009 she co-founded the company PicoLuz, which develops and commercializes silicon nanophotonics technologies. In 2019, she co-founded Voyant Photonics, which develops next generation lidar technology based on silicon photonics. In 2022, Lipson was a co-founder of Xscape photonics to accelerate AI, ML, and simulation hardware. In 2020 Lipson was elected the 2021 vice president of Optica, and she served as the Optica president in 2023.
Silicon Photonics Link is a silicon-based optical data connection developed by Intel Corporation which uses silicon photonics and hybrid silicon laser, it provides 50 Gbit/s bandwidth. Intel expected the technology to be in products by 2015.
Ian A. Young is an Intel engineer. Young is a co-author of 50 research papers, and has 71 patents in switched capacitor circuits, DRAM, SRAM, BiCMOS, x86 clocking, Photonics and spintronics.
Plasmonics or nanoplasmonics refers to the generation, detection, and manipulation of signals at optical frequencies along metal-dielectric interfaces in the nanometer scale. Inspired by photonics, plasmonics follows the trend of miniaturizing optical devices, and finds applications in sensing, microscopy, optical communications, and bio-photonics.
Beyond CMOS refers to the possible future digital logic technologies beyond the scaling limits of CMOS technology. which limits device density and speeds due to heating effects.
Juerg Leuthold is a full professor at ETH Zurich, Switzerland.
Keren Bergman is an American electrical engineer who is the Charles Batchelor Professor at Columbia University. She also serves as the director of the Lightwave Research Laboratory, a silicon photonics research group at Columbia University. Her research focuses on nano-photonics and particularly optical interconnects for low power, high bandwidth computing applications.
Andrew Marc Weiner OSA NAE NAI was an American electrical engineer, educator and researcher known for contributions to the fields of ultrafast optics and optical signal processing. He was the Scifres Family Distinguished Professor of Electrical and Computer Engineering at Purdue University.
Joyce Poon is Professor of Electrical and Computer Engineering at the University of Toronto and Director of the Max Planck Institute of Microstructure Physics, where her research focuses on developing new optical devices for applications in neurotechnology. She is also an honorary professor at the Technische Universität Berlin. She is a Fellow of Optica, and has been serving as a Director-At-Large for the society since January 2021.
Niels Quack is a Swiss and German engineer specialized in optical micro engineering. He is a SNSF professor at EPFL and director of the Photonic Micro- and Nanosystems Laboratory at its school of engineering.
Amy Carole Foster is an American engineer who is an associate professor in the Department of Electrical and Computer Engineering at Johns Hopkins University. Her work considers nonlinear optics and silicon-based photonic devices.