Daiji Fukuda

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We have realized a high-detection-efficiency photon number resolving detector at an operating wavelength of about 850 nm. The detector consists of a titanium superconducting transition edge sensor in an optical cavity, which is directly coupled to an optical fiber using an approximately 300-nm gap. The gap reduces the sensitive area and heat capacity of the(More)
We experimentally demonstrated preservation of indistinguishability between two photons via mode conversions, namely, photon-to-plasmon and plasmon-to-photon conversions. A two-photon interference experiment was carried out using a broadband photon pair generated through a spontaneous parametric downconversion process. We observed the so-called(More)
The most efficient modern optical communication is known as coherent communication, and its standard quantum limit is almost reachable with current technology. Though it has been predicted for a long time that this standard quantum limit could be overcome via quantum mechanically optimized receivers, such a performance has not been experimentally realized(More)
Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a(More)
Highly sensitive spectral imaging is increasingly being demanded in bioanalysis research and industry to obtain the maximum information possible from molecules of different colors. We introduce an application of the superconducting transition-edge sensor (TES) technique to highly sensitive spectral imaging. A TES is an energy-dispersive photodetector that(More)
We have implemented the non-Gaussian operation on the pulsed squeezed vacuum at telecommunication wavelengths. The nonGaussian operation based on photon subtraction was carried out using a Titanium-based superconducting transition-edge-sensor that can resolve the photon number. We observed a dip in reconstructed Wigner functions of generated quantum states,(More)
A model describing spectral supralinearity for a silicon photodiode in the near-infrared region is presented. This theoretical model is based on the internal quantum efficiency model of the photodiode using Shockley-Read-Hall recombination, which depends on the inner structure parameters of the photodiodes. Comparing the experimental results with the(More)
Spectral supralinearity of silicon photodiodes in visible light was investigated. The experimental spectral supralinearity results were compared with the calculation results using a device simulator, PC1D that includes the front surface recombination parameters, and these comparison results were in reasonable agreement for a silicon photodiode. These(More)
The response non-uniformities of laser beam profiling cameras were investigated experimentally at near-infrared laser wavelengths. A uniform-irradiance light source with near-infrared laser wavelengths, and also a visible wavelength as comparison, was constructed for testing several different commercially available beam profiling cameras. The response(More)