Overview of Quantum Optics and Optical Materials Research

Naoshi Uesugi
Physical Science Laboratory

In the fields of quantum optics and optical materials we pursue our studies for the development of core-technologies that will innovate optical communications and optical signal processing as well as for the scientific progress of the field. Optical State Control Research Group, Ultrafast Optical Physics Research Group and Optical Device Physics Research Group are engaged in the subjects listed below.

Quantum State Control Research Group
(1) Quantum information processing (proposal and verification of a new quantum cryptography, studies on quantum protocols and quantum computing).
(2) Soliton quantum optics (achievement of soliton quantum nondemolition measurements (QND), study of soliton squeezing).
(3) Atom optics (experimental and theoretical studies on Bose-Einstein condensation of alkali atoms, and nonlinear spectroscopy of cold atoms).
(4) Theoretical study of excitons in low-dimensional semiconductor structures (clarification of optical and electrical properties of quantum dots and dot arrays).

Ultrafast Optical Physics Research Group
(1) High-irradiance soft X-ray generation from femtosecond laser produced plasma and its application to materials science (demonstration of high-irradiance soft X-ray pulse generation and table-top soft X-ray laser, clarification of soft X-ray generation mechanism, and demonstration of time-resolved soft X-ray spectroscopy).
(2) Ultrafast coherent optical interaction (ultrafast optical nonlinearities in low-dimensional semiconductors, and coherent transient phenomenon in rare-earth doped materials).

Optical Device Physics Research Group
(1) Optical properties of low-dimensional semiconductors and their device applications (experimental study of excitonic properties of quantum disks, spin-polarized electron transport in quantum wires, and polarization control of semiconductor lasers by manipulating electron spin).
(2) Fabrication process of low-dimensional semiconductors (dry etching process for damage- free surfaces of GaAs and GaN, and study of molecular beam selective etching process).
(3) Evaluation of local optical properties of low-dimensional semiconductors on the nanometer scale (near-field optics by nanometer optical probe).
(4) Studies on nitride-semiconductor quantum well structures (optical properties of nitride quantum well, and theoretical study of energy band structure in nitride semiconductors).

Major results obtained this fiscal year 1999 are reported in the following pages. We elucidated the dynamics of evaporative cooling, which is employed to reach Bose-Einstein condensation (BEC), by a quantum-kinetic analysis that is applicable to both alkali-metal and hydrogen atoms. Time-resolved measurement of soft X-ray absorption was successfully demonstrated by means of pump-probe spectroscopy, where we employed a combination of femtosecond laser pulses and synchronized soft X-ray pulses emitted from the laser-induced plasma. It was also experimentally demonstrated that the optically spin-polarized electrons in a GaAs quantum wire can propagate more than 10 mm while maintaining a relatively high spin polarization.