Integrating multidisciplinary efforts from physics, chemistry, biology, and materials science, the field of single-molecule electronics has witnessed remarkable progress over the past two decades thanks to the development of single-molecule...

Probing charge and energy transport in molecular junctions (MJs) has not only enabled a fundamental understanding of quantum transport at the atomic and molecular scale, but it also holds significant promise for the development of molecular-scale electronic devices. Recent years have witnessed a rapidly growing interest in understanding light-matter interactions in illuminated MJs. These studies have profoundly deepened our knowledge of the structure–property relations of various molecular materials and paved critical pathways towards utilizing single molecules in future optoelectronics applications. In this article, we survey recent progress in investigating light-driven charge transport in MJs, including junctions composed of a single molecule and self-assembled monolayers (SAMs) of molecules, and new opportunities in optical sensing at the single-molecule level. We focus our attention on describing the experimental design, key phenomena, and the underlying mechanisms. Specifically, topics presented include light-assisted charge transport, photoswitch, and photoemission in MJs. Emerging Raman sensing in MJs is also discussed. Finally, outstanding challenges are explored, and future perspectives in the field are provided.

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The exceptional tunable waveguiding characteristics of graphene surface plasmons have remained unrivaled since it has inspired many electro-optical (EO) devices in terahertz (THz) and mid-infrared (MIR) photonic circuits. We propose and numerically investigate a low-loss, highly extinctive resonant EO modulator based on a suspended graphene plasmonic waveguide. Unlike other resonance-based modulators, the input power has negligible interaction with lossy resonance cavity in on-state, remarkably reducing the losses. Achieving the insertion loss (IL) of 1.3 dB and the extinction ratio (ER) of 22 dB within a footprint less than 3 µm2 substantiates the superiority of the proposed structure. The charge transport simulations are first conducted to calculate the steady-state charge distribution. The three-dimensional finite-difference time-domain (3D-FDTD) method is utilized to monitor the guided wave propagation and modulation properties. We show that the transmission spectrum is highly dependent upon geometric parameters of the structure, and the modulator can be effectively tuned to operate at the desired wavelength by applying a suitable gate voltage. Simulation results show the modulation bandwidth of 71 GHz corresponding to the total capacitance of 4.8 fF within the active area. The novel EO modulator structure has shown great potentiality and flexibility to find other applications in MIR and THz integrated circuits like controllable notch filters and switches.

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