1. Department of Applied Science for Integrated System Engineering, Kyushu Institute of Technology, 1-1 Senshuimachi, Tobata, Kitakyushu, Fukuoka 804-8550, Japan
2. Department of Electrical and Electronic Engineering, Kitakyushu National College of Technology, 5-20-1 shii, Kokuraminami, Kitakyushu, Fukuoka 802-0985, Japan
3. Department of Physics, Kyushu Institute of Technology, 1-1 Senshuimachi, Tobata, Kitakyushu, Fukuoka 804-8550, Japan