Theoretical limit and framework of dynamic modulation in spoof surface plasmon polariton interconnects.

Spoof-surface-plasmon-polariton (SSPP) interconnects are potential candidates for next-generation interconnects to satisfy the growing demand for high-speed, large-volume data transfer in chip-to-chip and inter-chip communication networks. As in any interconnect, the viability and efficiency of the modulation technique employed will play a crucial role in the effective utilization of SSPP interconnects. In light of the lack of a comprehensive platform for the performance analysis of SSPP signal modulation, this work presents a theoretical framework that contributes to the following: 1) predictions of the maximum attainable modulation speed, limited by geometric dispersion in SSPP waveguide, 2) quantification of the fundamental trade-off relation between modulation speed and energy-efficiency for an arbitrary design of SSPP structure, 3) extension of the analysis over a broad category of SSPP modulation technique. In conjunction, a novel SSPP signal modulation technique is introduced, involving controlled alteration of the resonant condition of the SSPP interconnect using a variable resistor. Analyzing a sample SSPP waveguide with a 7 GHz cut-off frequency, the study identifies a potential ∼28% change in its transmission-band by varying the implanted resistor from 5kΩ to 5Ω, a range of values practically attainable with gate-controlled, state-of-the-art submicron scale field-effect transistors. The assertions of the theoretical model have been independently validated by finite-element method based numerical simulations, which show that the underlying concept can be utilized to realize the digital modulation scheme of the amplitude shift keying. For a millimeter-scale SSPP channel having 2.75 GHz transmission bandwidth, up to 300 Mbps modulation speed with nominal power loss is achieved in a standard, thermal-noise limited communication system. By scaling the interconnect to micrometer dimensions, the speed can be augmented up to 10 Gbps for data transfer over 100 mm distance with ≥80% energy efficiency. Essentially, the presented theory is the first of its kind that provides the foundational design guideline for designing and optimizing diverse range of SSPP modulators.

Deep ultraviolet spontaneous emission enhanced by layer dependent black phosphorus plasmonics.

Although graphene has been the primary material of interest recently for spontaneous emission engineering through the Purcell effect, it features isotropic and thickness-independent optical properties. In contrast, the optical properties of black Phosphorus (BP) are in-plane anisotropic; which supports plasmonic modes and are thickness-dependent, offering an additional degree of freedom for control. Here we investigate how the anisotropy and thickness of BP affect spontaneous emission from a Hydrogenic emitter. We find that the spontaneous emission enhancement rate i.e. Purcell factor (PF) depends on emitter orientation, and PF at a particular frequency and distance can be controlled by BP thickness. At lower frequencies, PF increases with increasing thickness due to infrared (IR) plasmons, which then enhances visible and UV far-field spectra, even at energies greater than 10 eV. By leveraging the thickness and distance-dependent PF, deep UV emission can be switched between 103 nm or 122 nm wavelength from a Hydrogenic emitter. Additionally, we find that doping can significantly tune the PF near BP and this alteration depends on the thickness of the BP. Our work shows that BP is a promising platform for studying strong plasmon-induced light-matter interactions tunable by varying doping levels, emitter orientation, and thickness.