Site: Tokyo Institute of Technology
4259 Nagatsuda-cho, Midori-ku
Yokohama 227, Japan
Date Visited: December 13, 1994
Report Author: L. Coldren
The Tokyo Institute of Technology is the largest national university in Japan for science and technology. It has about 5,300 undergraduate and 3,000 graduate students. The number of Master's degree students is about three times the number of doctoral students. This ratio is reflective of the fact that in Japan relatively few highly-qualified students continue to the doctoral level as compared to students in Europe or the United States. The Okayama campus is located in Tokyo; the Nagatsuta Campus was founded in a northern suburb of Yokohama in 1975.
Over the past several decades, the Tokyo Institute of Technology probably has had the largest impact of all Japanese universities in the area of optoelectronics. Some years ago, this was primarily due to the extensive and productive activity of Professor Yasuharu Suematsu at the Okayama Campus. His activity on lasers and optoelectronics was initiated in 1962 and was active until very recently. He was President of TIT from 1989 to 1993. Today, several of his former students have established similarly productive groups at both the Okayama (Professors Furuya, Arai, and Asada) and Nagatsuta (Professors Iga and Koyama) campuses. Others have joined the optoelectronics research effort as well. The JTEC panel's visit to the Nagatsuta campus focused on the work of Professor Iga's Precision and Intelligence Laboratory, although panelists were also able to review the work of Professors Kukimoto, Munekata, and Ohyama of the Image Science Lab and Professor Ohtsu of the Interdisciplinary Graduate School.
The JTEC team was particularly interested in the issue of technology transfer and to what extent the research at TIT was connected to industry. Also, funding sources were discussed in order to determine the level of MITI and industrial support relative to that of the Ministry of Education. In Professor Iga's case, the level of support from these other sources was higher than usual. In addition to the 5 million yen(~$50,000) that accompanies all Chairs, Iga had at the time an additional contract from the Ministry of Education amounting to 20 million yen(~$200,000). He also had a NEDO project from MITI of 10 million yen(~$100,000), and 20 million yen(~$200,000) from industry in the form of gifts. This $500,000/year of funding is quite high considering that all salaries and fees of students, professors, and researchers are taken care of separately. (Students get no salary in most cases -- they must use personal funds.)
Iga has no formal contracts with industry, but clearly he is working closely with several companies to help them develop new products. Japanese professors are presently not allowed to accept consulting fees; however, this may soon change to provide a well-deserved supplement to highly productive individuals. As near as the panel could determine, Professor Iga receives "no-strings-attached" gifts from these several companies, but gives private periodic oral reports to them on his research progress. This procedure has resulted in real products for some companies. For example, Nippon Sheet Glass has developed an ultradense microlens array that is being used in a Sharp projection TV system, the technology for which was developed at TIT. Patents are being licensed; some of the fees come back to the department of the inventor.
The review of technical work in Iga's Lab involved a poster summary of recent results on 1.55 microns, 1.3 microns, and 0.98 microns VCSELs; these results indicated 0.3 mA threshold at 77K, 14 deg. C CW operation, and 0.5 mA thresholds, respectively. Also reviewed were polarization control experiments, a GaN gain calculation, and spontaneous emission factor calculations and experiments. Associate Professor Koyama then discussed results using multiquantum barriers for better electron confinement in visible emitters (or other systems where the heterobarriers are not high enough), reactive-ion-beam etching (RIBE) of microcavity lasers, waveguide corner reflectors, and micro-optics -- such as the arrays mentioned above that are used in the Sharp TV display. The lab tours included a look at Iga's CBE system, an MOCVD, and the beginnings of a new GaN system, as well as the RIBE machine. Professor Hiroshi Kukimoto's focus in optoelectronics has been on nonlinear optics and blue lasers. The emphasis is clearly more on the fundamentals of materials rather than on devices. The effort includes work on III-Vs, II-VIs, and I-III-VI compounds. In the lab, panelists saw BE and MOCVD machines for such materials as ZnMgSe, CdZnSe, and some I-III-VIs. These scientists have constructed a novel interlocked 3-chamber MOCVD for the II-VIs. In-situ monitoring has given them relatively good material. Devices are processed in Iga's lab. In the MOVPE III-V effort, GaP/AlP and GaAs/AlAs superlattices are being pursued. The GaP has given red-green emission as a function of superlattice period, and atomic-layer epitaxy of the GaAs/AlAs has focused on high electron velocity components. A MOMBE (metal-organic MBE) system is also used for some I-III-VI compounds, such as AgGaS 2; II-VIs, such as ZnHgSe; and e-beam-assisted growth of GaAs/AlAs with a field-emission gun. A further unique capability was a system to do DLTS (deep-level transient spectroscopy) under hydrostatic pressure (using transformer oil). Professor Kukimoto is well known for his early work on DLTS.
Professor Kukimoto's funding is supplemented by a special grant from the Ministry of Education. His interactions with industry have involved a number of industrial visitors who wished to acquire the technologies developed at TIT. He did the first MOCVD in Japan, so there was a lot of interest there. Chemical companies have supported his work for some time. He also mentioned the transfer of vacuum florescence phosphor technology to Nichia.
The JTEC panelists then heard a brief presentation from a graduate student of Professor Ohyama, who is working on optical image processing. He presented a paper on optical color image correlation.
Finally, the panel toured the facilities of Professor Ohtsu, who is concerned with photon manipulation and coherence control. His work is more in the direction of basic physics. We saw experiments on sub-Doppler cooling of Rb atoms, laser frequency control, trapping of neutral atoms, quantum phenomena in Sr islands, and diode mixing to get THz signals. Also presented was work on stabilizing 1.55 microns diodes to a molecular absorption line to 200 Hz for coherent optical communication and spectroscopy, as well as on a very stable 10 W Nd:YAG laser for gravitational wave measurements.
The quality of the research being carried out at TIT-Nagatsuta is comparable to that at the best of the U.S. universities in this field. The understanding of the panel is that this is also true for a few other universities in Japan. A decade ago, this was generally less true, except for isolated instances, such as Suematsu's group in optoelectronics (of which Iga was a member). The process of technology transfer continues to be rather informal, although the infusion of MITI funding would seem to pull the work toward a practical direction. Nevertheless, it was very clear that the main focus was on highly innovative basic research.