Kiyotaka Hammura
Hitachi
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Publication
Featured researches published by Kiyotaka Hammura.
Applied Physics Letters | 2007
Xiulai Xu; Ian Toft; R. T. Phillips; J. D. Mar; Kiyotaka Hammura; D. A. Williams
The authors report a “plug and play” source of single photons, with full integration to a single-mode optical fiber. One end of the fiber is attached to the top of an InGaAs∕GaAs quantum dot wafer. The other end is connected via a wavelength-division multiplexing system to two separate fibers: one for carrying excitation light and the other for emitted light. A Hanbury-Brown and Twiss [Nature (London) 77, 27 (1956)] measurement was performed on the emission from single excitons recombining in the quantum dots. A second-order correlation function at zero time delay of approximately 0.01 indicates a nearly ideal source of single photons. The maximum variation of peak position over 24days is less than 0.1nm.
Applied Physics Letters | 2008
Xiulai Xu; Frederic S. F. Brossard; Kiyotaka Hammura; D. A. Williams; B Alloing; Lianhe Li; Andrea Fiore
We report a “plug and play” single photon source, fully integrated with an optical fiber, emitting at 1.3μm. Micropillars were patterned on a single layer InAs quantum dot wafer to guarantee a single pillar per fiber core. The single exciton peak filtered with a tunable optical filter was fed to a Hanbury Brown and Twiss interferometer, and the second order correlation function at zero delay was less than 0.5, indicating single photon emission. The measured decay dynamics under double-pulse excitation show that the single photon device can be operated at speeds greater than 0.5GHz.
Journal of Optics | 2009
Kiyotaka Hammura; D. A. Williams
The detection sensitivity (DS) of a commercial single-photon receiver based on an InGaAs gate-mode avalanche photodiode is estimated. The installation of a digital-blanking system (DBS) to reduce dark current differentiates between the DS, which is the efficiency of the detector during its open-gate/active state, and the total/overall detection efficiency (DE). Using numerical simulations it is found that the average number of light-pulses blanked by DBS following a registered pulse is 0.333. The DS is estimated at 0.216, which can be used for estimating the DE for an arbitrary photon arrival rate and gating frequency of the receiver.
Archive | 2006
Tatsuya Tomaru; Shinya Sasaki; Kiyotaka Hammura
Journal of Physics: Conference Series | 2007
Xiulai Xu; Ian Toft; J. D. Mar; Kiyotaka Hammura; R. T. Phillips; D. A. Williams
Bulletin of the American Physical Society | 2014
Kiyotaka Hammura; Haruhiko Udono; Tomosuke Aono
Physica Status Solidi (c) | 2013
Kiyotaka Hammura; Haruhiko Udono; Tomosuke Aono
Bulletin of the American Physical Society | 2013
Kiyotaka Hammura; Haruhiko Udono; Tomosuke Aono
Bulletin of the American Physical Society | 2012
Kiyotaka Hammura; Haruhiko Udono; Tomosuke Aono
Thin Solid Films | 2011
Kiyotaka Hammura; Haruhiko Udono; Isao J. Ohsugi; Tomoyuki Aono; E. De Ranieri