1. M. Ohashi, H. Hamasaki, M. Kushibe, S. Nunoue, G. Hatakoshi and M. Nakamura:Tech. Dig. 10th Int. Conf. Integrated Optics and Optical Fibre Communication, 1995 (The Chinese University Press, Hong Kong, 1995) vol. 3, p. 118.
2. M. Ohashi, H. Hamasaki, M. Kushibe, S. Nunoue, G. Hatakoshi and M. Nakamura:Tech. Dig. Pacific Rim Conf. Lasers and Electro-Optics, Chiba, 1995 (IEEE, Piscataway, 1995) TuI4, p. 24.
3. C. Tombling, T. Saitoh and T. Mukai: IEEE J. Quantum Electron. 30 (1994) 2491.
4. O. Hanaizumi, K.T. Jeong, S. Kashiwada, I. Syuaib, K. Kawase and S. Kawakami: Opt. Lett. 21 (1996) 269.
5. N. Suzuki, M. Ohashi, S. Nunoue and M. Nakamura: IEEE Photon. Technol. Lett. 8 (1996) 1100.