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Ultrafast all optical modulation based on intersubband transition in semiconductor quantum wells |
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| Authors: | T. Asano S. Yoshizawa S. Noda N. Iizuka K. Kaneko N. Suzuki O. Wada |
| Affiliation: | 1. Department of Electronic Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, 606-8501, Japan 2. Corporate Research and Development Center, Toshiba Corporation, 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japan 3. FESTA Laboratories, The Femtosecond Technology Research Association, 5-5 Tokodai, Tsukuba, 300-2635, Japan |
| Abstract: | Ultrafast modulation of interband-resonant light by intersubband-resonant light in n-doped GaAs/AlGaAs and GaN/AlGaN quantum wells was investigated by femtosecond pump-probe technique. A planar-type AlGaAs/GaAs modulation device shows a modulation speed of ～1 ps at room temperature. The observed modulation efficiency indicates that 99% modulation can be achieved with a control pulse energy of ～1 pJ when a waveguide-type device structure is utilized. The feasibility of the all-optical modulation in GaN/AlGaN quantum wells is also investigated. The intersubband carrier relaxation time, which mainly determines the modulation speed, is measured and is found to be extremely fast (130–170 fs). The results indicate that the optical modulation at a bit rate of over 1 Tb/s will be possible by utilizing the intersubband transition in GaN/AlGaN quantum wells. The modulation efficiency in GaN/AlGaN quantum wells is also discussed in comparison with that in GaAs/AlGaAs quantum wells. |
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