JSAP Award Recipients
The JSAP has established three awards for outstanding research papers. Award A is for papers
published in the Japanese Journal of Applied Physics; Award B for papers published by scientists
younger than 35 years of age; Award C is for review papers published in ‘OYO BUTURI’, the JSAP
membership journal. In this issue, we feature thethree receipients of Award B for 1999.

Takashi ASANO (member) graduated from theDepartment of ElectricalEngineering and Scienceat Kyoto University in1994. He completed adoctoral course at Kyoto
University in 1998, andwas awarded a Dr. Eng. degree. He then obtained a JSPS Research fellowship at the same
university, and in 1999 was awarded a PD fellowship in Kyoto University Venture BusinessLaboratory. He has been engaged in researchon ultrafast optical phenomena and electron
relaxation process in intersubband transitions,which is aimed at the development of ultrafast
all-optical modulators. He is a member of theInstitute of Electronics, Information and Communication Engineers.
Intersubband optical transitions in quantum wells are very promising for ultrafast optical modulation or switching devices, since therelaxation times can be in the picosecond or
sub-picosecond range. We have proposed andinvestigated an unique modulation scheme
which is based on the nonlinear interaction
between the intersubband and conventional
interband transitions. The ultrafast (~1 ps) operation of the proposed scheme has been demonstrated by 2-color intersubband pump (7µm)– interband probe (800nm) measurements.
However, one problem must be resolved before this scheme can be used in practical applications, which is that the wavelength range isusually in the mid- to far-infrared regions (4 ~10 µm). In order to overcome this limitation,
we have adopted a structure based on InGaAs/ AlAs quantum wells grown coherently on aGaAs substrate, and achieved an intersubband
transition in the near-infrared, at a wavelengthof 1.90 µm.
In this work, we measured the relaxation
time of such an intersubband transition for the30

JSAPI

first time. The measurements were made using absorption saturation techniques, taking
into account the effect of homogeneous andinhomogeneous broadening. We also examined
the origins of the broadening of the absorption spectra. The measured relaxation time wasvery fast (1 ~ 10 ps), which is similar to that of
the mid-infrared intersubband transition. We
have subsequently measured the relaxation
time more accurately using the femtosecond
pump-probe method, and obtained a value ofapproximately 2.7 ps in the case of 2.5 µm
intersubband transition. This work demonstrates that the near-infrared transitions arepromising for ultrafast applications.
This work was performed under the supervision of Prof. S. Noda, Kyoto University andsupported in part by Grant-in-Aid for Scientific
Research from the Ministry of Education, Science, Sports and Culture of Japan, Asahi-Glass
Grant, and VBL Kyoto University.

Akihiko FUJII (member)
graduated from the Department of Electronic Engineering at Osaka University in 1993, and obtained a Doctor of Engineering Degree from thesame university in 1997.
He was then awarded a research fellowship ofthe Japan Society for the Promotion of Science.
In 1998, he returned to the Department of Electronic Engineering of Osaka University as a research associate. He has been engaged in research on optical and electrical devices utilizing organic materials, including dye moleculesand conducting polymers. He received a Promotion Award from the Kansai-Section Joint
Convention of Institutes of Electrical Engineering in 1996, and from the Institute of Electronics, Information and Communication Engineers
in 1997. He is a member of the Japan Societyof Applied Physics, the Institute of Electrical Engineers of Japan, the Physical Society of Japanand the Institute of Electronics, Information andCommunication Engineers.
Cylindrical microcavity structures, such as
microrings of p-conjugated conducting polymers, poly(2, 5-dialkoxy-p-phenylene vinylene)(ROPPV), were fabricated on optical fibres toform an optically pumped laser and a lightemitting diode (LED). An extremely low excitation threshold for lasing was demonstrated withthe microring structure. Microring LEDs with acylindrical geometry of Al/p-conjugated conducting polymers, ROPPV and ITO were fabricated for the first time on 125 µm optical fibers, and orange electroluminescence was observed upon application of an electric field.
These results suggest that it may be possible tofabricate an electrically pumped conducting
polymer laser diode.

Jun-ichi SHIRAKASHI(member) obtained a B.S.
degree in electrical andcomputer engineeringfrom Yokohama NationalUniversity, Kanagawa, Japan, in 1990. He thenmoved to the Tokyo Institute of Technology, where he studied electricaland electronic engineering, gaining an M.S. in
1992 and a Ph.D. in 1995. During his postgraduate work, he was engaged in researchon the MOMBE growth of III-V compound semiconductors and heterojunction bipolar transistors (HBTs) with an ultra-high carbon-dopedbase. In 1995, he joined the ElectrotechnicalLaboratory, Tsukuba, Japan, where he worked
on single electron transistors (SETs), and novel
ultra-fine nano-lithography techniques using
scanning probe microscopes (SPMs). He demonstrated the room temperature operation ofniobium (Nb)-based SETs in 1997. In this study,
the basic SET structure was fabricated by SPMbased nano-lithography and the junction area
was further reduced by thermal oxidation. In
1999, he moved to the Department of Electronics and Information Systems at Akita Prefectural University as an associate professor. His
current interests lie in novel nano-lithography
techniques and quantum nano-scale devicesand systems.
He is a member of the Japan Society ofApplied Physics, from whom he received the3rd JSAP Awards for Research Paper Presentation in 1998 and the 21st JSAP Award for theMost Promising Young Scientist (Award B) in1999.

JSAP International No.1 (January 2000)

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