Hybrid Plasmonic Devices Research Articles

Observation of Multi-Directional Energy Transfer in a Hybrid Plasmonic-Excitonic Nanostructure.

Hybrid plasmonic devices involve a nanostructured metal supporting localized surface plasmons to amplify light-matter interaction, and a non-plasmonic material to functionalize charge excitations. Application-relevant epitaxial heterostructures, however, give rise to ballistic ultrafast dynamics that challenge the conventional semiclassical understanding of unidirectional nanometal-to-substrate energy transfer. Epitaxial Au nanoislands are studied on WSe2 with time- and angle-resolved photoemission spectroscopy and femtosecond electron diffraction: this combination of techniques resolves material, energy, and momentum of charge-carriers and phonons excited in the heterostructure. A strong non-linear plasmon-exciton interaction that transfers the energy of sub-bandgap photons very efficiently to the semiconductor is observed, leaving the metal cold until non-radiative exciton recombination heats the nanoparticles on hundreds of femtoseconds timescales. The results resolve a multi-directional energy exchange on timescales shorter than the electronic thermalization of the nanometal. Electron-phonon coupling and diffusive charge-transfer determine the subsequent energy flow. This complex dynamics opens perspectives for optoelectronic and photocatalytic applications, while providing a constraining experimental testbed for state-of-the-artmodelling.

Experimental confirmation of self-imaging effect between guided light and surface plasmon polaritons in hybrid plasmonic waveguides

We fabricated a hybrid plasmonic device using self-imaging effect between guided light and surface plasmon polaritons in the hybrid plasmonic waveguide. The hybrid plasmonic device was fabricated by evaporating gold on the part of the silicon waveguide. Self-imaging was generated at the gold-covered section in the waveguide. Self-imaging of guided light and surface plasmon polaritons in hybrid plasmonic waveguides affect the output intensity of the hybrid plasmonic waveguide. The length of the hybrid plasmonic waveguide changes self-imaging conditions. We confirmed that the output intensity was affected by the length of the hybrid plasmonic waveguide. These findings contribute to the development of hybrid plasmonic devices and potentially improve integration density of hybrid photonic integrated circuits.

Sub-femtojoule optical modulation based on hybrid plasmonic devices

Optical modulation is an essential process in the telecommunication technology. A sub-femtojoule optical modulation based on low loss hybrid plasmonic waveguide which integrates silicon, metal, and electro-optic material is demonstrated. Modulation is achieved through applying modulating voltage across the electro-optic layers. Firstly, a directional coupler modulator is designed and simulated, it showed a modulation depth of 26 dB, and energy consumption of 0.8 fJ/bit. Secondly, a Mach Zender interferometer circuit based modulator is designed and analyzed, with a modulation depth of 32 dB, and energy consumption of 0.8 fJ/bit.

Remote Dual-Cavity Enhanced Second Harmonic Generation in a Hybrid Plasmonic Waveguide.

On-chip nanoscale optical platforms capable of efficient second harmonic generation (SHG) are highly desired for optical sensing, subwavelength coherent sources, and quantum photonic devices. Here, we develop a remotely excited dual cavity resonance scheme to achieve significantly enhanced SHG in a CdSe nanobelt on Au film hybrid waveguide system. The SHG emission with superior efficiency originates from counter-propagating plasmonic modes interference in a horizontal Fabry-Pérot (FP) cavity enabled by remote excitation of propagating surface plasmons, which is further enhanced through a vertical FP cavity. With this effective cooperation of hybrid plasmon modes and FP cavity modes, 2 orders of magnitude enhancement of the conversion efficiency (3.5 × 10-4 W-1) is achieved compared to the off-resonance case. Our design provides new insight into the development of a multifunctional hybrid plasmonic device toward on-chip nonlinear nanophotonic applications.

Direct visualization of phase-matched efficient second harmonic and broadband sum frequency generation in hybrid plasmonic nanostructures

Second harmonic generation and sum frequency generation (SHG and SFG) provide effective means to realize coherent light at desired frequencies when lasing is not easily achievable. They have found applications from sensing to quantum optics and are of particular interest for integrated photonics at communication wavelengths. Decreasing the footprints of nonlinear components while maintaining their high up-conversion efficiency remains a challenge in the miniaturization of integrated photonics. Here we explore lithographically defined AlGaInP nano(micro)structures/Al2O3/Ag as a versatile platform to achieve efficient SHG/SFG in both waveguide and resonant cavity configurations in both narrow- and broadband infrared (IR) wavelength regimes (1300–1600 nm). The effective excitation of highly confined hybrid plasmonic modes at fundamental wavelengths allows efficient SHG/SFG to be achieved in a waveguide of a cross-section of 113 nm × 250 nm, with a mode area on the deep subwavelength scale (λ2/135) at fundamental wavelengths. Remarkably, we demonstrate direct visualization of SHG/SFG phase-matching evolution in the waveguides. This together with mode analysis highlights the origin of the improved SHG/SFG efficiency. We also demonstrate strongly enhanced SFG with a broadband IR source by exploiting multiple coherent SFG processes on 1 µm diameter AlGaInP disks/Al2O3/Ag with a conversion efficiency of 14.8% MW−1 which is five times the SHG value using the narrowband IR source. In both configurations, the hybrid plasmonic structures exhibit >1000 enhancement in the nonlinear conversion efficiency compared to their photonic counterparts. Our results manifest the potential of developing such nanoscale hybrid plasmonic devices for state-of-the-art on-chip nonlinear optics applications.

Hybrid Loss‐Compensated Plasmonic Device

AbstractHere it is studied how the active medium affects the Rabi‐analog splitting when an active plasmonic microcavity mode is coupled to a surface plasmon polariton mode. The incorporation of Rubrene‐like molecules in the plasmonic microcavity results in stronger modal coupling. Anticrossing is observed with a large Rabi‐analog splitting energy of 280 meV in the strong coupling regime. The active medium contributes to the split enhancement through channeling more energy toward the coupling. The variation of photoluminescence emission and exciton‐cavity mode coupling from the hybrid plasmonic microcavity are also measured. This work shows that by introducing an active medium in the microcavity, mode coupling between microcavity and surface plasmon polariton can be enhanced and the hybrid plasmonic device exhibits parity–time symmetry characteristics.

Tuneable strong optical absorption in a graphene-insulator-metal hybrid plasmonic device

An optical device configuration allowing efficient electrical tuning of near total optical absorption in monolayer graphene is reported. This is achieved by combining a two-dimensional gold coated diffraction grating with a transparent spacer and a suspended graphene layer to form a doubly resonant plasmonic structure. Electrical tuneability is achieved with the inclusion of an ionic gel layer which plays the role of the gate dielectric. The underlying grating comprises a 2-dimensional array of inverted pyramids with a triple layer coating consisting of a reflective gold layer and two transparent dielectric spacers, also forming a vertical micro-cavity known as a Salisbury screen. Resonant coupling of plasmons between the gold grating and graphene result in strong enhancement of plasmon excitations in the atomic monolayer. Plasmon excitations can be dynamically switched off by lowering the chemical potential of graphene. Very high absorption values for an atomic monolayer and large tuning range, extremely large electrostatically induced changes in absorption over very small shifts in chemical potential are possible thus allowing for very sharp transitions in the optical behavior of the device. Overall this leads to the possibility of making electrically tunable plasmonic switches and optical memory elements by exploiting slow modes.

Strong coupling of diffraction coupled plasmons and optical waveguide modes in gold stripe-dielectric nanostructures at telecom wavelengths

We propose a hybrid plasmonic device consisting of a planar dielectric waveguide covering a gold nanostripe array fabricated on a gold film and investigate its guiding properties at telecom wavelengths. The fundamental modes of a hybrid device and their dependence on the key geometric parameters are studied. A communication length of 250 μm was achieved for both the TM and TE guided modes at telecom wavelengths. Due to the difference between the TM and TE light propagation associated with the diffractive plasmon excitation, our waveguides provide polarization separation. Our results suggest a practical way of fabricating metal-nanostripes-dielectric waveguides that can be used as essential elements in optoelectronic circuits.

Entangled light from bimodal optical nanoantennas

We suggest a hybrid plasmonic device consisting of a bimodal metallic nanoantenna coupled to an incoherently pumped quantum emitter. This hybrid device emits light into the two modes entangled in the number of photons. The process is a prime example where losses are turned from a nuisance into something beneficial, since, even though counterintuitively, the entanglement is enabled by strong incoherent processes, i.e. dominant scattering and absorption rates of the nanoantenna. Both, the high emission rate and the degree of entanglement of the emitted light are insensitive with respect to imperfections in the nanoantenna geometry, rendering the scheme feasible for an implementation.

Plasmonic nanoantenna based triggered single-photon source

Highly integrated single photon sources are key components in future quantum-optical circuits. Whereas the probabilistic generation of single photons can routinely be done by now, their triggered generation is a much greater challenge. Here, we describe the triggered generation of single photons in a hybrid plasmonic device. It consists of a lambda-type quantum emitter coupled to a multimode optical nanoantenna. For moderate interaction strengths between the subsystems, the description of the quantum optical evolution can be simplified by an adiabatic elimination of the electromagnetic fields of the nanoantenna modes. This leads to an insightful analysis of the emitter's dynamics, entails the opportunity to understand the physics of the device, and to identify parameter regimes for a desired operation. Even though the approach presented in this work is general, we consider a simple exemplary design of a plasmonic nanoantenna, made of two silver nanorods, suitable for triggered generation of single photons.

All-Optical Switching Using a Hybrid Plasmonic Donut Resonator With Photothermal Absorber

A novel hybrid plasmonic (HP) donut resonator integrated with a photothermal plasmonic absorber has been developed, which can be used as a compact all-optical switch or modulator. The radius of the fabricated HP donut resonator is 1.8 $\mu \text{m}$ , with a resonant wavelength around 1550 nm and a quality factor ( ${Q}$ factor) around 600. The photothermal plasmonic absorber is directly integrated above the HP device, which can absorb as much as 75% of impinging optical power at 1064 nm wavelength. Since the absorber is in tight contact to the Si ridge of the HP waveguide, the absorbed optical power can efficiently heat up the Si ridge, and hence change the resonant wavelength of the HP donut resonator by Si thermal expansion effect. Experimental results show that the power used for 15 dB amplitude switch is only 10 mW, with rise and fall response times around 18 and 14 $\mu \text{s}$ , respectively.