A Polarization-Actuated Plasmonic Circulator

Coherent control of enhanced second-harmonic generation in a plasmonic nanocircuit using a transition metal dichalcogenide monolayer

Nonlinear nanophotonic circuits, renowned for their compact form and integration capabilities, hold potential for advancing high-capacity optical signal processing. However, limited practicality arises from low nonlinear conversion efficiency. Transition metal dichalcogenides (TMDs) could present a promising avenue to address this challenge, given their superior optical nonlinear characteristics and compatibility with diverse device platforms. Nevertheless, this potential remains largely unexplored, with current endeavors predominantly focusing on the demonstration of TMDs' coherent nonlinear signals via free-space excitation and collection. In this work, we perform direct integration of TMDs onto a plasmonic nanocircuitry. By controlling the polarization angle of the input laser, we show selective routing of second-harmonic generation (SHG) signals from a MoSe2 monolayer within the plasmonic circuit. Routing extinction ratios of 14.86 dB are achieved, demonstrating good coherence preservation in this hybrid nanocircuit. Additionally, our characterization indicates that the integration of TMDs leads to a 13.8-fold SHG enhancement, compared with the pristine nonlinear plasmonic nanocircuitry. These distinct features-efficient SHG generation, coupling, and controllable routing-suggest that our hybrid TMD-plasmonic nanocircuitry could find immediate applications including on-chip optical frequency conversion, selective routing, switching, logic operations, as well as quantum operations.

Near-Field Photodetection in Direction Tunable Surface Plasmon Polaritons Waveguides Embedded with Graphene

2D materials have manifested themselves as key components toward compact integrated circuits. Because of their capability to circumvent the diffraction limit, light manipulation using surface plasmon polaritons (SPPs) is highly-valued. In this study, plasmonic photodetection using graphene as a 2D material is investigated. Non-scattering near-field detection of SPPs is implemented via monolayer graphene stacked under an SPP waveguide with a symmetric antenna. Energy conversion between radiation power and electrical signals is utilized for the photovoltaic and photoconductive processes of the gold-graphene interface and biased electrodes, measuring a maximum photoresponsivity of 29.2 mA W-1 . The generated photocurrent is altered under the polarization state of the input light, producing a 400% contrast between the maximum and minimum signals. This result is universally applicable to all on-chip optoelectronic circuits.

Enhancing on/off ratio of a dielectric-loaded plasmonic logic gate with an amplitude modulator

Plasmonic waveguides allow focusing, guiding, and manipulating light at the nanoscale and promise the miniaturization of functional optical nanocircuits. Dielectric-loaded plasmonic (DLP) waveguides and logic gates have drawn attention because of their relatively low loss, easy fabrication, and good compatibility with gain and active tunable materials. However, the rather low on/off ratio of DLP logic gates remains the main challenge. Here, we introduce an amplitude modulator and theoretically demonstrate an enhanced on/off ratio of a DLP logic gate for XNOR operation. Multimode interference (MMI) in DLP waveguide is precisely calculated for the design of the logic gate. Multiplexing and power splitting at arbitrary multimode numbers have been theoretically analyzed with respect to the size of the amplitude modulator. An enhanced on/off ratio of 11.26 dB has been achieved. The proposed amplitude modulator can also be used to optimize the performance of other logic gates or MMI-based plasmonic functional devices.

Nonscattering Photodetection in the Propagation of Unidirectional Surface Plasmon Polaritons Embedded with Graphene

Recently, nanoscale light manipulation using surface plasmon polaritons (SPPs) has received considerable research attention. The conventional method of detecting SPPs is through light scattering or using bulky Si or Ge photodetectors. However, these bulky systems limit the application of nanophotonic circuits. In this study, the light-matter interaction between graphene and SPP was investigated. For realizing an improved integration in nanocircuits, single-layer graphene was added to asymmetric SPP nanoantenna arrays for nonscattering detection in the near field. The developed device is capable of detecting the controlled propagation of SPPs with a photoresponsivity of 15 mA/W, which paves the way for the new-generation on-chip optical communication.

Non-reciprocal population dynamics in a quantum trimer

We study a quantum trimer of coupled two-level systems beyond the single-excitation sector, where the coherent coupling constants are ornamented by a complex phase. Accounting for losses and gain in an open quantum systems approach, we show how the mean populations of the states in the system crucially depend on the accumulated phase in the trimer. Namely, for non-trivial accumulated phases, the population dynamics and the steady states display remarkable non-reciprocal behaviour in both the singly and doubly excited manifolds. Furthermore, while the directionality of the resultant chiral current is primarily determined by the accumulated phase in the loop, the sign of the flow may also change depending on the coupling strength and the amount of gain in the system. This directionality paves the way for experimental studies of chiral currents at the nanoscale, where the phases of the complex hopping parameters are modulated by magnetic or synthetic magnetic fields.