Results 1994



This is an annual report on the research activities in the field of optical communications and high-speed electron devices for 1994 at Faculty of Engineering, Tokyo Institute of Technology.

These activities are initiated by Professor Y.Suematsu (emeritus, the former president), and Professor S.Arai [Group A], mainly in the field of Integrated Dynamic-Single-Mode Lasers and Laser Amplifiers, Low-dimensional Quantum-well Lasers, and also in the fabrication of ultra-fine structures;

This report consists of a brief introduction of the research activities and a collection of the research papers published in 1994.

Publication List

Group members

  • Professor Emeritus
    • Yasuharu SUEMATSU
  • Professor
    • Shigehisa ARAI Ph.D.
  • Technical Assistant
    • Shigeo TAMURA B.S.
  • Secretaries
    • Sachiko ITAI B.A. -May
    • Kyoko KASUKAWA B.A. June-
  • Visiting Researcher
    • Gerd U. BACHER(a) Ph.D. -Nov.
  • Research Student
    • Yoon Ho PARK(1) M.S. -Aug.
  • Graduate Students
    (Doctor Course)
    • Ki Chul SHIN(2) M.S. -Mar.
    • Toshiyuki TAKIZAWA M.S.
    • Munehisa TAMURA M.S.
    • Takashi KOJIMA M.S. Apr.-
    • Mothi Madhan RAJ M.S. Oct. –
  • Graduate Students
    (Master Course)
    • Eijiro KIKUNO(3) B.S. -Mar.
    • Takashi KOJIMA B.S. -Mar.
    • Shinji KURIHASHI(4) B.S. -Mar.
    • Hirotsugu KASHOU(5) B.S. -Mar.
    • Madan RAJ B.S. -Sept.
    • Naoki SERIZAWA B.S.
    • Akira UCHINO B.S.
    • Xue Ying JIA B.S.
    • Toshikazu ANDO B.S. Apr.-
    • Hiroyuki NAKAYA B.S. Apr.-
    • Kazunori NUMATA B.S. Apr.-
    • Shi PENG B.S. Apr.-
    • Takehiro SHIMIZU B.S. Apr.-
  • Undergraduate Students
    • Toshikazu ANDO -Mar.
    • Makoto ITO(6) -Mar.
    • Masataka KONDO(7) -Mar.
    • Shi PENG -Mar.
    • Tetsuyuki NUMAGUCHI Apr.-
    • Nobuhiro NUNOYA Apr.-
    • Yasushi TAKEUCHI Apr.-
    • Suguru TANAKA Apr.-

Present Address

  • (1) the Maritime University, the Republic of Korea.
  • (2) LG Cable Co., the Republic of Korea.
  • (3) Sony Music Entertainments Co.
  • (4) Mitsubishi Corp.
  • (5) Toshiba Corp.
  • (6) Prof. Araki (Bs Lab., Tokyo Inst. Tech.)
  • (7) Assoc. Prof. Munakata (Bs Lab., Tokyo Inst. Tech.

On leave from

  • (a) Brzburg Univ., Germany.


Semiconductor Lasers & Amplifiers

Staffs: S. Arai K. Komori
Students: K. Kudo S.El Yumin K.C. Shin A.Nakatani M.Tamura M.Hotta T.Kimura H. Kashou A.Katsube S.Kurihashi A.Serizawa R.Ubukata K. Saitoh

A new type of multiple-reflector micro-cavity laser was proposed and analyzed.
A linewidth property of complex coupled DFB laser was analyzed and fabricated.
A GaInAsP/InP semiconductor collimating GRIN lens was proposed and fabricated for optical coupling improvement of SLA and LD to single mode fiber.

Results obtained in this research are as follows.

(1) A new type of multiple-reflector micro-cavity laser having a 30% refractive index difference was proposed, and it was found that it is possible to operate on sub-mA current.

(2) The cavity length dependence of the linewidth property of complex coupled (CC) DFB lasers was analyzed.

(3) A 1.55 micro meter wavelength CC-DFB laser having an anti-phase structure by introducing InP depression layer was fabricated. We showed the ratio of the index-coupling coefficient to the gain-coupling coefficient can be controlled by introducing this InP depression layer.

(4) Saturation characteristics of TTW-SLA using the tensile strained quantum well active layer was demonstrated.

(5) A semiconductor collimating GRIN lens for vertical output beam divergence improvement of SLA and LD was fabricated, and integration with TTW-SLA was demonstrated.

Quantum-Film, Quantum-Wire, and Quantum-Box Lasers

Staffs: Y.Suematsu, S.Arai, M.Asada, Y.Miyamoto, S.Tamura
Students: K.Kudo, H.Hirayama, K.C.Shin, Y.Nagashima, K.Matsunaga, T.Kakinuma, M.Tamura, M.Hotta, S.Kurihashi, M.Kumazawa, H.Arima, R. Ubukata

Ga1-xInxAs/GaInAsP/InP strained-quantum-film, -wire, and -box lasers have been studied both theoretically and experimentally. By introducing tensile-strained quantum-wire (QW) structure into the active layer, room temperature CW operation of GRIN-SCH single-QW lasers with fairly low threshold current was achieved. GaInAs/GaInAsP (strained-) quantum-box (QB) structures were fabricated and obvious 0-dimensional QB size effects were observed. Temperature dependences of lasing properties were measured and compared with those of quantum-film lasers. Carrier injection process in SCH quantum-film and wire lasers was investigated.

The results obtained in this research are as follows.

(1) Temperature dependence of lasing properties of quasi-quantum-wire lasers were measured and compared with those of quantum-film lasers.

(2) By combining electron beam lithography and ECR dry etching, 20-30nm wide GaInAs/GaInAsP multi-quantum-wire and -box structures with the aspect ratio greater than 6 were realized. Moreover, low damage feature of this fabrication process was confirmed by PL observation.

(3) An emission energy level shift due to obvious 0-dimensional quantum- box effect was observed at 4K with GaInAs/GaInAsP single-layer (strained-) embedded quantum-box structures.

(4) Lasing action of Ga0.67In0.33As/GaInAsP/InP tensile-strained quantum-box laser was demonstrated for the first time. The fabricated QB size is 30nm diameter and 12nm thick with a period of 70nm. The threshold current density was 7.6KA/cm2 at 77K with pulse current injection.

(5) Carrier capture time of SCH-QW-lasers was measured by the spontaneous emission spectra above threshold. Difference between unstrained, tensile-strained, and compressive-strained lasers was obtained.

Nanometer Structure Fabrication Technology

Staffs: K.Furuya, S.Arai, Y.Miyamoto, M.Suhara, S.Tamura
Students: H.Hongo, T.Takizawa, J.Suzuki, F.Vazquez, D.Sonoda, C.Nagao, H.Tanaka, E.Kikuno

Study of nanometer structure fabrication technique is important for the realization of quantum effect devices such as quantum-wire or -box devices and ballistic electron devices based on wave characteristics of electrons.

Results obtained through this year are as follows.

(1) Ultrafine fabrication technique for hot electron interference diffraction devices was proposed using electron beam direct writing lithography and OMVPE. An alignment of 70nm pitch buried GaInAs /InP heterostructure and 70nm pitch electrodes was demonstrated for the first time.

(2) A cross-sectional multiple quantum well structure (GaInAs:3nm/ GaInAsP:8nm) was observed clearly by a scanning tunneling microscope (STM) in air. (NH4)2Sx solution was used for passivating the sample surface. In addition, the relation between the pulse voltage/time and the size of modified area was also investigated.

(3) Anodization process of InP: Anodization process of InP has been investigated with aiming at a novel fabrication technology of quality quantum-wire and quantum-box structures. As the result, a high density (space filling factor of 50%), uniformly shaped (triangle) and sized (40nm) vertical pillar structure was obtained on (111)A oriented InP substrate with a SiO2 mask by adopting an EBX direct patterning followed by the anodization with HCl acid. Very small physical damage by anodization process was established from observing strong PL intensity from 40nm size-ordered triangle pillers.

Financial Support

1. Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Grant-in-Aid for Research Center for Ultra-high Speed Electronics
Grant-in-Aid for Research Center for Quantum Effect Electronics
Grant-in-Aid for Scientific Research (A, B, C)
Grant-in-Aid for Exploratory Research
Grant-in-Aid for Encouragement of Young Scientists

2. Other Grant

Fellowship of the JSPS for Japanese Junior Scientists
Grant for “Development of Frequency Resources” from Ministry of Public Management, Home Affairs, Posts and Telecommunications
Seki Memorial Foundation for the Promotion of Science and Technology

3. Companies & Others

Fujikura Co., Ltd.
Furukawa Electric Industries Co., Ltd.
Hitachi Cable Co., Ltd.
NEC Co., Ltd.
Nippon Sanso Co., Ltd.
NTT Photonics Research Laboratories
Sumitomo Electric Industries Co., Ltd.

Nishiyama Laboratory
Quantum Nanoelectronics Research Core, Tokyo Institute of Technology

7F, S9-1, 2-12-1 O-okayama, Meguro-ku Tokyo 152-8552, Japan +81-3-5734-2555 ee.e titechnishiyama

Nishiyama lab. Student's room : South Bldg. 9 #701, #706, #707 | Measurement room : South Bldg. 9 #604, #502, #201 |
Clean room : South Bldg. 9 #202, B1F Exposure house | Research Laboratory of Ultra-High Speed Electronics