KEYWORDS: Superconductors, Single photon detectors, Sensors, Single photon, Signal to noise ratio, Telecommunications, Superconducting detectors, Signal detection, Quantum efficiency, Picosecond phenomena
We report a single photon detector based on NbTiN microbridges, suitable for operation within telecommunication wavelengths. We observed an excellent signal-to-noise ratio of the readout signal while the corresponding jitter contributed by electrical noise was measured to be less than 10 ps. Routing the current through a parallel electrical connection to set the microbridge back to the superconducting state after photon absorption enabled us to overcome the hysteresis of the state transition. Our approach combines facile fabrication of fast microscale detectors with efficient current redistribution mechanism, enabling prospective applications in quantum photonics which requires accurate estimation of photon arrival events.
Despite being very weak, the chiral optical response of natural media plays a fundamental role in several areas of photonics, medicine, pharmacology, and quantum optics. Topological insulators are a class of materials in which spin-momentum locking induces a preferential response of surface electrons to circularly polarized light. However, the resulting spin-polarized photocurrents are often hindered by the strong contribution of bulk electrons. Here we show that the intrinsic circular photogalvanic effect in topological insulator BSTS (Bi1.5Sb0.5Te1.8Se1.2), probed by helicity dependent photocurrent, can be enhanced by one order of magnitude when a non-chiral metamaterial design is patterned on the crystal surface. This method can be adopted to control the polarization properties of Dirac materials beyond topological insulators by metamaterial design, opening up new opportunities for the detection of quantum light, molecular sensing, and the realization of opto-spintronic devices.
Phonon polariton resonances in the mid-infrared spectral range demonstrate properties superior to noble metal-based plasmonics, owing to smaller dissipative loss and better field confinement. However, a conventional way to excite the localized phonon resonance involves ion etching, which reduces the attainable quality factors (Q-factors) of the resonators. We show that by introducing a deep subwavelength layer of dielectric gratings on a phononic substrate, localized dipolar resonance and higher order modes with high Q-factors 96 and 195, respectively, can be excited. We further demonstrate, via experiments and simulations, that the resonant wavelength and field confinement can be controlled by coupling the localized hybrid mode with propagating surface phonon-polaritons. We also observed for the first time the coupling between a localized dipolar mode and a propagating higher-order surface phonon-polariton mode. The results will be useful in designing on-chip, low-loss, and highly integrated phononic devices in the infrared spectral domain.
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