News
Karl K. Berggren selected as the Julius A. Stratton Professor in Electrical Engineering and Physics
Congratulations to Karl! He has been selected as the Julius A. Stratton Professor in Electrical Engineering and Physics for a five-year renewable term beginning July 1, 2025.
This chair was established in the late 1970s by William R. Hewlett, a founder of the Hewlett-Packard Company, in honor of Prof. Stratton, the first provost and the eleventh president of MIT. Prof. Stratton had deep interests in both electrical engineering and physics; thus, the Stratton Chair is held by faculty members in EECS and Physics or those studying related fields.
Congrats to John Simonaitis and Owen Medeiros on their successful Theses Defenses!
In May 2025, we congratulates Drs. John Simonaitis and Dr. Owen Medeiros on their thesis defenses!
Owen Medeiros successfully defended his PhD thesis entitled “Superconducting Nanowire Integrated Circuits for Scalable Cryogenic Memory” on May 13, 2025.
The talk was recorded and can be found here.
Abstract:
Superconducting nanowire integrated circuits (SNICs) are a promising class of cryogenic electronics that harness the zero resistance, high kinetic inductance, and nanoscale geometry of ultrathin superconducting wires to implement logic, memory, amplification, and sensing with minimal energy dissipation. Unlike Josephson-junction-based circuits, SNICs support compact, planar layouts compatible with single-layer fabrication and operation in unshielded cryogenic environments.
This thesis develops superconducting nanowire memory (SNM) as a scalable implementation of SNICs. A modular cell architecture is introduced, exploiting hysteretic switching and inductive asymmetry to enable nonvolatile digital state storage with zero static power consumption. A hierarchical design framework is established, combining automated layout generation, electrothermal simulation in LTspice, and microscopic modeling using the time-dependent Ginzburg–Landau (TDGL) formalism.
John Simonaitis successfully defended his PhD thesis entitled “Low-energy Electron-Photon Interactions in a Scanning Electron Microscope” on May 12, 2025.
Abstract:
The interaction of free-electrons with matter and light is among the most fundamental of processes in nature. From the use of free-electrons for atomic imaging, to their use in the generation of high-intensity, tunable light in synchrotrons, the physics of unconfined electrons has wide application. In recent years, there has been a new focus on looking more closely at the quantum nature of individual electrons in electron microscopes to enable further improvements in these technologies. This work takes advantage of developments in ultrafast optics, electron spectroscopy, quantum optics, and nanofabrication to explore various electron-electron, electron-photon, and electron-material interactions. In this thesis, we construct a low-energy, ultrafast scanning electron microscope, using it to explore quantum coherent interactions between electrons, light, and matter.
New Publication: Bandwidth of Lightwave-Driven Electronic Response from Metallic Nanoantennas
A new publication written by the group was just published in Nano Letters.
Matthew Yeung, Lu-Ting Chou, Felix Ritzkowsky, Marco Turchetti, Karl K. Berggren, Shih-Hsuan Chih, Philip D. Keathley, “: Bandwidth of Lightwave-Driven Electronic Response from Metallic Nanoantennas,” Nano Letters, 25, 13, pp. 5250–525, May 2025.
Abstract
Lightwave electronics offer transformative field-level precision and control at high optical frequencies. While recent advances show that lightwave-driven electron emission from nanoantennas enables time-domain, field-resolved analysis of optical waveforms through a small-signal analysis, the effect of the gate waveform on the measurement transfer function remains unexplored. By generating electrons with a 10-cycle pulse in the optical tunneling regime and perturbing the response with a 1.5-cycle pulse, we experimentally measure the bandwidth limitations imposed by the electron emission process. By comparing these measurements with TDSE simulations and analytical models, we reveal the temporal properties of the electronic response and its impact on the small-signal transfer function. Our results test and confirm the accuracy of the Fowler–Nordheim model in estimating the lightwave electronic response from noble metals. We envision extending these techniques to multi-octave-spanning signals for precise characterization of sub-cycle electronic responses through harmonic frequency mixing.
New Publication: A superconducting full-wave bridge rectifier
A new publication written by the group on a superconducting diode was just published in Nature Electronics.
Matteo Castellani, Owen Medeiros, Alessandro Buzzi, Reed A. Foster, Marco Colangelo and Karl K. Berggren.
M. Castellani, O. Medeiros, A. Buzzi, R. A. Foster, M. Colangelo, and K. K. Berggren, “A superconducting full-wave bridge rectifier,” Nat Electron, pp. 1–9, May 2025.
Abstract
Superconducting thin-film electronics can offer low power consumption, fast operating speeds and interfacing capabilities with cryogenic systems such as single-photon detector arrays and quantum computing devices. However, the lack of a reliable superconducting two-terminal asymmetric device, analogous to a semiconducting diode, limits the development of power-handling circuits, which are fundamental for scaling up such technology. Here we report a robust superconducting diode with tunable polarity using the asymmetric vortex surface barrier in niobium nitride micro-bridges. The diode offers a 43% peak rectification efficiency and half-wave rectification up to 120 MHz. We also integrate several of the diodes to create a bridge rectifier circuit on a single microchip that can perform continuous full-wave rectification at up to 3 MHz and alternating to direct current conversion of a 50 MHz signal in periodic bursts with an estimated peak power efficiency of 50%.
Dr Keathley’s Talk on Nanoscale Petahertz Electronics now available
Dr. Donnie Keathley’s talk on Nanoscale Patahertz Electronics is now available on Optica’s website here. The talk took place during the Frontiers in Optics 2024 conference.
Abstract
This talk overviews developments in nanoscale petahertz electronics, including our work in the area using metallic nanoantennas. It will focus on how we are leveraging insights and tools from the electronics community in device development.