K. Kawashima, M. Hosoda, and K. Fujiwara, "Optical tri-state switching through a metastable state using short pulse excitation," Appl. Phys. Lett. 62,  184-186 (1993).
K. Kawashima, T. Yamamoto, K. Kobayashi, and K. Fujiwara, "Stark-ladder transitions and their oscillator strengths in GaAs/AlAs superlattices," Phys. Rev. B 47,  9921-9924 (1993).
K. Kawashima, M. Takata, K. Fujiwara, T. Kagawa, Tadanaga, and H. Iwamura, Photocurrent spectra and Wannier-Stark localization of In0.53Ga0.47As/InP superlattices with different barrier thicknesses, Microelectronic Engineering vol. 51-52, 143-150 (2000).