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A transition edge sensor (TES) is one of superconducting photon detectors, which has a photon number resolving ability in light pulses. The TES device is a kind of calorimeters operated at an extremely low temperature, and the energy of the photons is measured as a resistance change in a superconducting transition region of the TES. The advantages of the TESs are an excellent energy resolution and a high quantum efficiency. However a response speed is limited due to slow thermal recovery time. To overcome this, we fabricated new TES devices which are based on a titanium superconductor. The critical temperature of our titanium films is around 410 mK, which greatly improves the thermal recovery time. The observed decay time constant of response signals to the light pulses is around several hundreds of ns, that make it possible to operate the devices at a counting rate over 1 MHz. The photon number resolving power is 0.35 eV(FWHM) for a 5 μm size device even at the high operating temperature. The system quantum efficiency is 65 % by embedding the TES films in an optical structure with a high reflection dielectric mirror and an anti-reflection coatings fabricated by an ion beam assisted sputtering method. These features are very promising for high speed photon number resolving applications in the quantum information field.

A laser manipulation technique for metal nanoparticles using an optical fiber has been developed. A micro ball lens adhered onto the flattened end of the optical fiber focuses a light beam propagated through a core. An object is trapped in the focused beam. An electromagnetic field distribution was numerically simulated for validation of the focusing lens. Calculation including an Au nanoparticle indicated that the laser trapping would be possible with this method. In the experiment, trapping of Au particles with diameter of 200nm was achieved by using a light source (Nd-YAG: 1064nm). The maximum trapping efficiency attained in the focal region was estimated to be 5.4fN/mW. Additionally, the fixation of a manipulated particle onto a glass substrate was also demonstrated. With intensifying the laser power, a laser-trapped particle is fixed on the substrate. By repetition of the procedure of laser manipulation and fixation, alignment of Au nanoparticles was achieved.