The increasing energy demands of the world's population and the quickly diminishing fossil fuel reserves together suggest the urgent need to secure long-lasting alternative and renewable energy resources. Here, we present a THz antenna integrated with a rectifier (rectenna) for harvesting infrared energy. We demonstrate a resonant bowtie antenna that has been optimized to produce highly enhanced localized fields at the bow tip. To benefit from this enhancement, the rectifier is realized between the overlapped antenna's arms using a 0.7 nm copper oxide. The thin film diode offers low zero bias resistance of 500 Ω, thus improving the impedance matching with the antenna. In addition, the rectenna prototype demonstrates high zero bias responsivity (4 A/W), which is critical in producing DC current directly from THz signals without the application of an external electric source, particularly for energy harvesting applications.
Phonons at gigahertz frequencies interact with electrons, photons, and atomic systems in solids, and therefore have extensive applications in signal processing, sensing, and quantum technologies. Surface acoustic wave (SAW) resonators that confine surface phonons can play a crucial role in such integrated phononic systems due to small mode size, low dissipation, and efficient electrical transduction. To date, it has been challenging to achieve high quality (Q) factor and small phonon mode size for SAW resonators at gigahertz frequencies. Here, we present a methodology to design compact high-Q SAW resonators on lithium niobate operating at gigahertz frequencies. We experimentally verify out designs and demonstrate Q factors in excess of 2×10 4 at room temperature (6×10 4 at 4 Kelvin) and mode area as low as 1.87 λ 2 . This is achieved by phononic band structure engineering, which provides high confinement with low mechanical loss. The frequency-Q products (fQ) of our SAW resonators are greater than 10 13 . These high-fQ and small mode size SAW resonators could enable applications in quantum phononics and integrated hybrid systems with phonons, photons, and solid-state qubits.
New
opportunities for plasmonic applications at high temperatures
have stimulated interest in refractory plasmonic materials that show
greater stability at elevated temperatures than the more commonly
used silver and gold (Au). Titanium nitride (TiN) has been identified
as a promising refractory material, with deposition of TiN thin films
through techniques ranging from plasma-enhanced atomic laser deposition
to sputter deposition to pulsed laser deposition, on a variety of
substrates, including MgO, polymer, SiO2, and sapphire.
A variety of plasmonic devices have been evaluated, including gratings,
nanorods, and nanodisks. An implicit metric for TiN behavior has been
the comparison of its plasmonic performance to that of Au, in particular
at various elevated temperatures. This paper carries out a one-to-one
comparison of bowtie nanoantennas formed of TiN and Au (on both Si
and MgO substrates), examining the far-field characteristics, related
to the measured near-field resonances. In both cases, the optical
constants of the TiN films were used to simulate the expected plasmonic
responses and enjoyed excellent agreement with the experimental measurements.
Furthermore, we examined the consistency of the plasmonic response
and the morphological changes in the TiN and Au nanoantennas at different
temperatures up to 800 °C in the atmosphere. This comparison
of the measured plasmonic response from nanoscale resonances to the
far-field response allows for anomalies or imperfections that may
be introduced by the nanofabrication processes and provides a more
accurate comparison of TiN plasmonic behavior relative to the Au standard.
Titanium nitride (TiN) has been identified as a promising refractory material for high temperature plasmonic applications such as surface plasmon polaritons (SPPs) waveguides, lasers and light sources, and near field optics. Such SPPs are sensitive not only to the highly metallic nature of the TiN, but also to its low loss. We have formed highly metallic, low-loss TiN thin films on MgO substrates to create SPPs with resonances between 775-825 nm. Scanning near-field optical microscopy (SNOM) allowed imaging of the SPP fringes, the accurate determination of the effective wavelength of the SPP modes, and propagation lengths greater than 10 microns. Further, we show the engineering of the band structure of the plasmonic modes in TiN in the mid-IR regime and experimentally demonstrate, for the first time, the ability of TiN to support Spoof Surface Plasmon Polaritons in the mid-IR (6 microns wavelength).
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