Optical metasurfaces (OMSs) have shown unprecedented capabilities for versatile wavefront manipulations at the subwavelength scale. However, most well-established OMSs are static, featuring well-defined optical responses determined by OMS configurations set during their fabrication, whereas dynamic OMS configurations investigated so far often exhibit specific limitations and reduced reconfigurability. Here, by combining a thin-film piezoelectric microelectromechanical system (MEMS) with a gap-surface plasmon–based OMS, we develop an electrically driven dynamic MEMS-OMS platform that offers controllable phase and amplitude modulation of the reflected light by finely actuating the MEMS mirror. Using this platform, we demonstrate MEMS-OMS components for polarization-independent beam steering and two-dimensional (2D) focusing with high modulation efficiencies (~50%), broadband operation (~20% near the operating wavelength of 800 nanometers), and fast responses (<0.4 milliseconds). The developed MEMS-OMS platform offers flexible solutions for realizing complex dynamic 2D wavefront manipulations that could be used in reconfigurable and adaptive optical networks and systems.
From the onset of high-speed optical communications, lithium niobite (LN) has been the material of choice for electro-optic modulators owing to its large electro-optic response, wide transparent window, excellent thermal stability and long-term material reliability. Conventional LN electro-optic modulators while continue to be the workhorse of the optoelectronic industry become progressively too bulky, expensive and power hungry to fully serve the needs of this industry rapidly progressing towards highly integrated, cost-effective and energy efficient components and circuits. Recently developed monolithic LN nanophotonic platform enables the realization of electro-optic modulators that are significantly improved in terms of compactness, bandwidth and energy efficiency, while still demanding relatively long, on the mm-scale, interaction lengths. Here we successfully deal with this challenge and demonstrate plasmonic electro-optic directional coupler switches consisting of two closely spaced nm-thin gold nanostripes monolithically fabricated on LN substrates that guide both coupled electromagnetic modes and electrical signals influencing their coupling and thereby enabling ultra-compact switching and modulation functionalities. The extreme confinement of both slow-plasmon modes 2 and electrostatic fields created by two nanostripes along with their nearly perfect spatial overlap allowed us to achieve a 90% modulation depth with 20-µm-long switches characterized by a electro-optic modulation efficiency of 0.3 V⋅cm. Our monolithic LN plasmonic platform enables ultra-dense integration of high-performance active photonic components, enabling a wide range of cost-effective optical communication applications demanding µm-scale footprints, ultrafast operation, robust design and high environmental stability.
On-chip manipulating and controlling the temporal and spatial evolution of light is of crucial importance for information processing in future planar integrated nanophotonics. The spin and orbital angular momentum of light, which can be treated independently in classical macroscopic geometrical optics, appear to be coupled on subwavelength scales. We use spin-orbit interactions in a plasmonic achiral nano-coupler to unidirectionally excite surface plasmon polariton modes propagating in seamlessly integrated plasmonic slot waveguides. The spin-dependent flow of light in the proposed nanophotonic circuit allows on-chip electrical detection of the spin state of incident photons by integrating two germanium-based plasmonic-waveguide photodetectors. Consequently, our device serves as a compact (~ 618 m 2 ) electrical sensor for photonic spin Hall dynamics.The demonstrated configuration opens new avenues for developing highly-integrated polarizationcontrolled optical devices that would exploit the spin-degree of freedom for manipulating and controlling subwavelength optical modes in nanophotonic systems.Introduction. Light carries both the spin, an intrinsic form of angular momentum, and orbital angular momentum, which determines its polarization and spatial degree of freedom. Interaction between the spin and orbital degrees of freedom of photons has evoked intensive investigations owing to its potential to push the development of technologies, such as chiroptical spectroscopy 1,2 , communication 3 , information processing 4 , topological photonics 5,6 and quantum computing 7 , to their full potential. The limiting factor for groundbreaking developments in those fields refers to the fact that the spin-orbit interactions (SOIs) in optics are usually very weak, akin to the Planckconstant smallness of the electron SOI found in solid-state spintronics 8 . A promising way to significantly enhance spin-controlled optical phenomena is to utilize light-matter interactions on the nanoscale that are especially strong in plasmonic nanostructures. It has been shown that geometrically chiral metallic structures, which do not superimpose onto their mirror image, can strongly enhance chiroptical far-field responses as a consequence of structural chirality 9-12 .Remarkably, even achiral structures exhibit the SOI potential in the near-field due to twisted trajectories of surface plasmons at a nanosphere [13][14][15][16] . This feature enables spin-controlled local manipulation within one nanoscale coupler, which responds equally to both photonic spin states.We utilize the strong SOI in an achiral plasmonic nanostructure to demonstrate for the first time onchip detection of spin-controlled directional routing in a compact plasmonic nanocircuit. We find that a subwavelength semiring can launch gap surface plasmons supported by seamlessly integrated plasmonic slot waveguides preferentially in one direction, depending on the spin state of locally incident radiation. This spin-dependent phenomenon can thus be regarded as a manifestation ...
Topological insulators have shown great potential for future optoelectronic technology due to their extraordinary optical and electrical properties. Photodetectors, as one of the most widely used optoelectronic devices, are crucial for sensing, imaging, communication, and optical computing systems to convert optical signals to electrical signals. Here we experimentally show a novel combination of topological insulators (TIs) and transition metal chalcogenides (TMDs) based self-powered photodetectors with ultra-low dark current and high sensitivity. The photodetector formed by a MoS2/Sb2Te3 heterogeneous junction exhibits a low dark current of 2.4 pA at zero bias and 1.2 nA at 1V. It shows a high photoresponsivity of >150 mA W−1 at zero bias and rectification of 3 times at an externally applied bias voltage of 1V. The excellent performance of the proposed photodetector with its innovative material combination of TMDs and TIs paves the way for the development of novel high-performance optoelectronic devices. The TIs/TMDs transfer used to form the heterojunction is simple to incorporate into on-chip waveguide systems, enabling future applications on highly integrated photonic circuits.
Optical metasurfaces have been extensively investigated, demonstrating diverse and multiple functionalities with complete control over the transmitted and reflected fields. Most optical metasurfaces are, however, static, with only a few configurations offering (rather limited) electrical control, thereby jeopardizing their application prospects in emerging flat optics technologies. Here, we suggest an approach to realize electrically tunable optical metasurfaces, demonstrating dynamic Fresnel lens focusing. The active Fresnel lens (AFL) exploits the electro-optic Pockels effect in a 300 nm thick lithium niobate layer sandwiched between a continuous thick and a nanostructured gold film serving as electrodes. We fabricate and characterize the AFL, focusing 800−900 nm radiation at a distance of 40 μm, with the focusing efficiency of 15%, and demonstrating the modulation depth of 1.5%, with the driving voltage of ±10 V within the bandwidth of ∼6.4 MHz. We believe that the electro-optic metasurface concept introduced is useful for designing dynamic flat optics components.
Advancements in nanophotonics have raised the bar for optoelectronic devices, demanding ultra-compact size, fast speeds, high efficiency, and low energy consumption. Emerging materials hold the potential to meet these demands, enabling the creation of high-performing optoelectronic devices. We present our latest breakthroughs and demonstrate device prototypes made from various materials, pushing the boundaries of optoelectronic performance.
Nonlinear and bistable optical systems are a key enabling technology for the next generation optical networks and photonic neural systems with many potential applications in optical logic and information processing. Here, a novel bistable resonator‐free all‐optical waveguide device based on indium tin oxide as nonlinear epsilon‐near‐zero material providing a cost‐efficient and high‐performance binarity photonic platform is proposed. The salient features of the proposed device are compatibility with silicon photonics, enabling sub‐picosecond operation speeds with moderate switching power. The device can act as an optical analogue of memristor or thyristor and can become an enabling element of photonic neural networks not requiring OEO conversions.
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