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Hu, X., Dauler, E. A., Molnar, R. J., & Berggren, K. K. (2011). Superconducting nanowire single-photon detectors integrated with optical nano-antennae. Opt. Express, 19(1), 17–31.
Abstract: Optical nano-antennae have been integrated with semiconductor lasers to intensify light at the nanoscale and photodiodes to enhance photocurrent. In quantum optics, plasmonic metal structures have been used to enhance nonclassical light emission from single quantum dots. Absorption and detection of single photons from free space could also be enhanced by nanometallic antennae, but this has not previously been demonstrated. Here, we use nano-optical transmission effects in a one-dimensional gold structure, combined with optical cavity resonance, to form optical nano-antennae, which are further used to couple single photons from free space into a 80-nm-wide superconducting nanowire. This antenna-assisted coupling enables a superconducting nanowire single-photon detector with 47% device efficiency at the wavelength of 1550 nm and 9-μm-by-9-μm active area while maintaining a reset time of only 5 ns. We demonstrate nanoscale antenna-like structures to achieve exceptional efficiency and speed in single-photon detection.
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Huang, K. C. Y., Jun, Y. C., Seo, M. - K., & Brongersma, M. L. (2011). Power flow from a dipole emitter near an optical antenna. Opt. Express, 19(20), 19084–19092.
Abstract: Current methods to calculate the emission enhancement of a quantum emitter coupled to an optical antenna of arbitrary geometry rely on analyzing the total Poynting vector power flow out of the emitter or the dyadic Green functions from full-field numerical simulations. Unfortunately, these methods do not provide information regarding the nature of the dominant energy decay pathways. We present a new approach that allows for a rigorous separation, quantification, and visualization of the emitter output power flow captured by an antenna and the subsequent reradiation power flow to the far field. Such analysis reveals unprecedented details of the emitter/antenna coupling mechanisms and thus opens up new design strategies for strongly interacting emitter/antenna systems used in sensing, active plasmonics and metamaterials, and quantum optics.
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Ikuta, R., Kusaka, Y., Kitano, suyoshi, Kato, H., Yamamoto, T., Koashi, M., et al. (2011). Wide-band quantum interface for visible-totelecommunication wavelength conversion. Nat. Comm., 2, 5.
Abstract: Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversion from visible to telecommunication bands while keeping the quantum states is thus required for bridging such wavelength gaps. Here we report demonstration of a quantum interface of frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal, which has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieved the conversion of a picosecond visible photon at 780 nm to a 1,522-nm photon, and observed that the conversion process retained entanglement between the down-converted photon and another photon.
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Kawakami, A., Saito, S., & Hyodo, M. (2011). Fabrication of nano-antennas for superconducting Infrared detectors. IEEE Trans. Appl. Supercond., 21(3), 632–635.
Abstract: To improve the response performance of superconducting infrared detectors, we have developed a fabrication process for nano-antennas. A nano-antenna consists of a dipole antenna, and a superconducting thin film strip placed in the antenna's center. By measuring the transition temperature of the superconducting strips, we confirmed that their superconductivity maintained a good condition after the nano-antenna fabrication process. We also evaluated nano-antenna characteristics using Fourier transform infrared spectroscopy. The evaluated antenna length and width were respectively set at around 2400 nm and 400 nm, and the antennas were placed at intervals of several micrometers around the area of 1 mm2 . In an evaluation of spectral transmission characteristics, clear absorption caused by antenna effects was observed at around 1400 cm-1. High polarization dependencies were also observed.
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Kono, J. (2011). Coherent terahertz control. Nat. Photon., 5, 5–6.
Abstract: Spin and charge terahertz excitations in solids are promising for implementing future technologies such as spintronics and quantum computation, but coherently controlling them has been a significant challenge. Researchers have now manipulated coherent spin waves in an antiferromagnet using the intense magnetic field of ultrashort terahertz pulses.
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