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.
Highlights
The light input to a semiconductor optical modulator can constitute an electrical energy supply through the photovoltaic effect, which is unexploited in conventional modulators
As we will discuss in detail below, our scheme achieves electrical gain, resulting in a reduction of the necessary input voltage Vin and reduced energy dissipation
The total electrical energy dissipation in our device is provided by the external electrical driver but includes the energy generated by the photovoltaic effect
Summary
The light input to a semiconductor optical modulator can constitute an electrical energy supply through the photovoltaic effect, which is unexploited in conventional modulators. Since these applications are mostly targeted for electrophysiological sensing, only moderate data rates on the order of 10–100 MHz are necessary. Numerous high-performance integrated silicon modulators have been reported in the literature (Fig. 2a, Supplementary Table 1), but to date, their electrical energy consumption has been limited to values near or above 1 fJ/bit, dominated by the need for large driving voltages (>500 mVpp) due to the relatively weak electrooptic effect in silicon
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