[] Chinese instrumentation network development in recent decades instrument, light energy is restricted within the range of subwavelength metal dielectric at the interface - i.e., sensing and information technology allows researchers plasmon producing countries is expected to be applied Such as the application of ultra-small devices. However, the plasmon polaritons have a fatal weakness: the tiny metallic structures necessary for photonic-electron interactions of plasmons inevitably lead to the absorption of light energy and ohmic losses. This makes designing a highly efficient and practical ultra-compact device that achieves field enhancement and rapid operation through the plasma effect, becoming a thorny problem.

At present, a joint research group composed of researchers from Switzerland and the United States has designed a micron-sized plasmonics-assisted electro-optic modulator that can solve the aforementioned loss problem. Instead of trying to minimize the plasma loss of the device, the researchers included these losses in the device design itself.
Device loss problem
In a plasma-excited device, the electronic components of the light waves that strike the surface of the metal nanostructure point can excite subwavelength-level electromagnetic waves known as surface plasmon polaritons (SPP), which propagate along the surface of the metal dielectric. By limiting and guiding light energy at the nanometer scale, isolator components can break the diffraction limit and locally enhance the relatively weak incident light field.
These advantages have found a place for plasmons in fields such as biosensors based on surface plasmon resonance detection. However, in areas such as communications and optoelectronic circuits, the wider use of plasmons is often hampered by loss problems. This is because when the surface plasmons propagate through the metal surface, the energy is inevitably absorbed by the metal and converted into heat.
Therefore, although plasmon components can provide substantial modulation effects at the micron length scale, they are also affected by the propagation loss in the order of dB/μm, while the silicon photonics propagation loss is in dB/cm. level. However, for on-chip technology, plasmon excitation components may produce more severe “insertion loss”—signal power in the circuit is reduced due to the addition of lossy plasma-excited components.
Loss reduction solution
According to a report from the Swiss-United States Joint Research Group, research teams including researchers from the Swiss Federal Institute of Technology and the University of Washington, Purdue University and Virginia Commonwealth University have found a solution to the new design loss of electro-optic modulators. An on-chip switch can be used to convert between electrical and photon energy. Researchers have solved this problem by treating the energy loss of plasmons as a feature.
The modulator consists of a gold-insulator-metal slot waveguide ring resonator with a diameter of about 3 microns and tens of nanometers thick and is filled with an organic electro-optic material for controlling the resonant state bias of the ring at the applied voltage. The ring resonator is located on a silicon dioxide substrate approximately 70 nm above the buried silicon bus waveguide.
The modulator is a well-designed notch filter that uses plasma losses in the ring to control light transmission through the underlying silicon bus waveguide. When the ring is adjusted to its resonant state - the "off" state of the switch, the surface plasmons in the ring interfere, resulting in intense plasma coupling and absorption of light through the bus waveguide, and effectively blocking light transmission. The surface plasmon in the ring destructively interferes when the ring is in the non-resonant state—the “on” position of the switch; almost all of the light in the bus waveguide escapes the plasma coupling and passes through the waveguide without obstruction .
Ultra-compact electro-optic switch
The joint research team reported that through the experimental verification of the resonator, the single chip device can reduce the on-chip optical loss, the operating frequency exceeds 100 GHz, and has high energy efficiency, small thermal drift, and small footprint. They believe that the proposed solution may have an advantage in the development of ultra-compact electro-optical switches between electronics and photonics in on-chip sensor applications for emerging hybrid chips for communications and Internet technologies.
(Original Title: Swiss United States Joint Research Team Designs Novel Low-loss Plasma Plasmonic Devices)

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