Overview of Quantum Optics and Optical Materials Research

Yoshiro Hirayama
Physical Science Laboratory

 In the fields of quantum optics and optical materials we pursue the development of core-technologies that will innovate optical communications and optical signal processing and seek fundamental scientific progress.

Quantum Optical State Control Research Group
(1)Quantum communication and information processing (quantum cryptography/protocols, entanglement, and computing).
(2)Atom optics (Bose-Einstein condensation of alkali atoms).

Ultrafast Optical Physics Research Group
(1)High-irradiance, short-pulse soft X-ray generation from femtosecond laser-produced plasma and its application to materials science.
(2)Ultrafast laser pulse induced terahertz radiation and its application.

Optical Device Physics Research Group
(1) Optical properties in nitride-semiconductors and their device applications.
(2) Coherent control of excitonic and spin states in quantum dots.

Photonic Nanostructure Research Group
(1) Photonic crystal optical circuits (2D SOI photonic crystals, organic photonic crystals, and higher-dimensional structures).
(2) Interaction between photonic nanostructures and materials (negative refraction, extremely-large group velocity dispersion, and photonic quasicrystal lasers)
(3) Direct nanoprinting lithography

 Major results obtained fiscal year 2002 are reported in the following pages.
 We have carried out quantum key distribution experiments using a single-photon source in collaboration with a Stanford group. A single photon source, which emits exactly one photon per pulse, is essential to completely prevent the eavesdrop action by a beam splitter.
 We have demonstrated a change in the spectral shape of high-order surface harmonics at an extreme ultraviolet wavelength by varying the spectral shape of a pump laser. We have also observed a drastic increase in solid-surface harmonic intensity for glass targets. These results show that active control of solid-surface harmonics is possible through pump and target control, which will become important for single attosecond pulse generation.
 We proposed a novel structural design for an InGaN/GaN laser using a deeply etched semiconductor/air DBR mirrors. The optimum design for practical DBR mirrors with tilted sidewalls is different from the conventional design using λ/(4n) semiconductor and λ/4 air. We achieved a mirror reflectivity of 62% using the properly designed DBR structure.
 We realized spot-size converters for photonic-crystal optical circuits, which enable us to efficiently couple light from conventional single-mode fibers to photonic-crystal waveguides. This overcomes one of main obstacles for photonic-crystal circuits. We also proposed and demonstrated novel nano-electrode lithography technique, which will be applied for various nanostructured devices.

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