de Cea M, Atabaki AH, Ram RJ. Energy harvesting optical modulators with sub-attojoule per bit electrical energy consumption.
Nat Commun 2021;
12:2326. [PMID:
33875653 PMCID:
PMC8055879 DOI:
10.1038/s41467-021-22460-1]
[Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 03/17/2021] [Indexed: 12/01/2022] Open
Abstract
The light input to a semiconductor optical modulator can constitute an electrical energy supply through the photovoltaic effect, which is unexploited in conventional modulators. In this work, we leverage this effect to demonstrate a silicon modulator with sub-aJ/bit electrical energy consumption at sub-GHz speeds, relevant for massively parallel input/output systems such as neural interfaces. We use the parasitic photovoltaic current to self-charge the modulator and a single transistor to modulate the stored charge. This way, the electrical driver only needs to charge the nano-scale gate of the transistor, with attojoule-scale energy dissipation. We implement this ‘photovoltaic modulator’ in a monolithic CMOS platform. This work demonstrates how close integration and co-design of electronics and photonics offers a path to optical switching with as few as 500 injected electrons and electrical energy consumption as low as 20 zJ/bit, achieved only by recovering the absorbed optical energy that is wasted in conventional modulation.
Optical modulators are a critical component for many future applications. Here the authors present a photovoltaic modulator that uses photogenerated charges and a nanoscale switch to enable low power (attojoule level), GHz-speed modulation in a CMOS-compatible platform.
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