Reseach
Distributed Reflector (DR) laser integrated with active and passive sections
　In conventional DFB lasers, light output can be obtained from both facets. For higher efficiency maintaining low-threshold operation, the light output should be concentrated on only one facet. For this purpose, we propose and fabricate the new type of distributed reflector (DR) laser with active and passive sections.
　We propose a new method of monolithic integration by using the energy blue shift due to the lateral quantum confinement effect.
　This laser consists of an active (current injection) DFB section and a passive distributed Bragg reflector (DBR) section with quantum-wire structure as shown in the Fig. The passive DBR section works as a mirror with a high reflection for low-threshold and high efficiency operation. To realize a mirror with high reflection, the low-loss waveguide is necessary. For this purpose, we utilize the energy blue shift due to the lateral quantum confinement effect by using quantum-wire structure. Using this technique, a high reflection DBR with 97 %.can be realized.
　These two sections (active and passive) can be fabricated simultaneously by changing only the EBX pattern. Since the waveguide structure of one section is almost the same as that of the other one, the coupling loss between two sections is negligible. Moreover, the two sections can be integrated successfully maintaining the crystal quality by using low-damage dry-etching technique.
　In summary, we design and fabricate the DR laser integrated with active and passive sections by using the technique mentioned above. As a result, the DR laser with the low-threshold, high efficiency and single-mode operation can be achieved.
　
List of reports
Journal Paper
(1) K. Ohira, N. Nunoya, H. Yagi, K. Muranushi, A. Onomura, S. Tamura and S. Arai, “Distributed Reflector Laser Integrated with Active and Passive Grating Sections Using Lateral Quantum Confinement Effect,” Jpn. J. Appl. Phys., vol. 42, part 2, no. 8A, pp. L921-L923, Aug. 2003.
(2) K. Ohira, T. Murayama, H, Yagi, S. Tamura and S. Arai, “Low-Threshold Distributed Reflector Laser Consisting of Wide and Narrow Wirelike Active Regions,” IEEE Photon. Technol. Lett. to be submitted.
(3) K. Ohira, T. Murayama, M. Hirose, H. Yagi, S. Tamura and S. Arai, “Low-threshold and high-efficiency operation of 1.5 mm distributed reflector laser with DFB grating and Q-wire DBR sections,” Electron. Lett., to be submitted.
　
International Conferences

(1) K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “New Type Distributed Reflector Laser with Passive DBR Section By Using Lateral Confinement Effect,” Sixth International Symposium on Contemporary Photonics Technology (CPT2003), PDP-3, p. 3, Shinagawa (Tokyo, Japan), Jan. 2003.
(2) K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “Distributed Reflector Lasers Integrated with Passive Grating Region By Using Lateral Confinement Effect,” The 15th International Conf. on Indium Phosphide and Related Materials (IPRM2003), WB1.5, pp. 251-254, Santa Barbara (California, USA), May 2003.
(3) K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “A Novel Distributed Reflector Laser Consisting of Width Modulated Wires in Active DFB and Passive DBR Sections,” The 16th annual meeting of the IEEE Lasers & Electro-optics society (LEOS2003), TuD5, pp. 204-205, Tucson (Arizona, USA), Oct. 2003.
(4) K. Ohira, T. Murayama, M. Hirose, H. Yagi, S. Tamura, A. Haque and S. Arai, “Low-Threshold and High Efficiency Distributed Reflector Laser with Wirelike Active Regions and Quantum-Wire DBR,” The 16th International Conf. on Indium Phosphide and Related Materials (IPRM2004), WA4-6, pp. 562-563, Kagoshima (Kagoshima, Japan), May 2004.
(5) K. Ohira, T. Murayama, M. Hirose, H. Yagi, S. Tamura, A. Haque and S. Arai, “Low-Threshold Operation of Distributed Reflector Laser with Width Modulated Wirelike Active Regions,” to be presented in The 19th IEEE International Semiconductor Laser Conf. (ISLC2004) FB 5, Matsue (Shimane, Japan) Sep. 2004.
(6) S. Arai, K. Ohira and T. Murayama, “Novel Integration Technologies for Photonic Devices - Low Threshold Single-Mode Lasers by Using Lateral Quantum Size Effect,” to be presented in The 17th annual meeting of the IEEE Lasers & Electro-optics society (LEOS2004), Puerto Rico, Nov. 2004. (Invited paper)
(7) S. Arai, H. Yagi, K. Ohira, T. Maruyama and S. Tamura, “GaInAsP/InP Quantum-Wire Lasers and Distributed Reflector Lasers with Wirelike Active Regions by Lithography and Regrowth” SPIE Photonics West 2005, California (USA), Jan. 2005.
(8) H. Yagi, K. Miura, D. Plumwongrot, Y. Nishimoto, K. Ohira, T. Maruyama and S. Arai, “Low Threshold Current 1540 nm Wavelength GaInAsP/InP Quantum-Wire Distributed-Feedback Lasers,” The 17th Indium Phosphide and Related Materials Conference (IPRM2005), WP-32, Glasgow (UK), May 2005.
(9). K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “Low Threshold Current Distributed-Reflector Laser with Phase-Shifted DFB and High-Reflection DBR Sections,” The 17th Indium Phosphide and Related Materials Conference (IPRM2005), WP-41, Glasgow (UK), May 2005.
(10) H. Yagi, K. Miura, Y. Nishimoto, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “GaInAsP/InP Distributed-Feedback Lasers Consisting of Strain-Compensated Quantum-Wire Active Regions,” The 10th Optoelectronics and Communications Conference, 5F1-4, Seoul (Korea), July 2005.
(11). S M Ullah, SH Lee, R Suemitsu, K Ohira and S. Arai, “Improved performance of ,” The 18th Indium Phosphide and Related Materials Conference (IPRM2006), WP-25, Princeton, New Jersey (USA), May 2006.

　
Meeting Report

(1) K. Ohira, N. Nunoya, A. Onomura, H. Yagi, S. Tamura and S. Arai,: “Distributed Reflector (DR) Laser with Wire Structure,” 「細線構造を有する分布反射型（DR）レーザ」 Technical Report of IEICE, LQE2002-16 (2002-05), pp. 61-64, Fukui, May 2002. 電気情報通信学会技術報告会、レーザ・量子エレクトロニクス研究会（5月）、福井、2002年5月17日
(2) K. Ohira, T. Murayama, M. Hirose, H. Yagi, S. Tamura, A. Haque and S. Arai,: “Low-threshold and high efficiency operation of distributed reflector (DR) laser with wirelike active DFB and quantum-wire passive sections,” 「活性層分離型DFBと量子細線DBRを有する分布反射型レーザの低電流・高効率動作」 Technical Report of IEICE, OPE2004-19, LQE2004-17 (2004-07), pp. 7-10, Tokyo, July 2002. 電気情報通信学会技術報告会、光エレクトロニクス（7月）、東京、2004年7月2日
(3) H. Yagi, K. Miura, Y. Nishimoto, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “Low threshold current operation of 1540nm wavelength GaInAsP/InP strain-compensated quantum-wire DFB lasers,” 「1540nm波長帯GaInAsP/InP歪補償量子細線DFBレーザの低しきい値電流動作」 presented at Technical Report of IEICE, OPE2005-18/LQE2005-17 (2005-06), pp. 19-22, Tokyo (Japan), June 2005.
(4) K. Ohira, S. M. Ullah and S. Arai, “Distributed Reflector (DR) Laser with Active DFB and Passive DBR Sections”, 超高速・超省電力性能ナノデバイス・システムの創製, pp. 53, Tokyo (Japan), Oct 2005.
(5) S M Ullah, K Ohira, R Suemitsu, SH Lee and S. Arai, “Distributed Reflector (DR) laser with active DFB and passive DBR sections,”presented at 21COEシンポジウム, Tokyo (Japan), Dec 2005.
(6) S M Ullah, R Suemitsu, SH Lee, M Otake, N. Nishiyama and S. Arai, “Low threshold current DR laser integrated with wire width modulated EAM with high electrical isolation,”to be presented at Technical Report of IEICE, LQE2006, Tokyo (Japan), Dec 2006.
(7) S M Ullah, R Suemitsu, SH Lee, M Otake, N. Nishiyama and S. Arai, “Integration of low threshold Distributed Reflector laser with other photonic devices using wirewidth modulated active regions,”to be presented at 21COEシンポジウム, Tokyo (Japan), Dec 2006.
　
Domestic Conferences

(1) K. Ohira, N. Nunoya, A. Onomura, H. Yagi, T. Sano, S. Tamura and S. Arai, “Distributed Reflector Laser with Wire Structure,” 「細線構造を有する分布反射型(DR)レーザ」 The 63rd Autumn Meeting, 2002; The Japan Society of Applied Physics, 26p-A-14, Digest III -p. 997, Niigata, Sep. 2002.
(2) K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “Distributed Reflector (DR) Laser with Passive Section Using Lateral Quantum Confinement Effect,” 「横方向量子閉じ込め効果を用いた受動領域を有する分布反射型(DR)レーザ」 The 50th Spring Meeting, 2003; The Japan Society of Applied Physics and Related Societies, 28p-ZQ-14, Digest III -p. 1240, Kanagawa, Mar. 2003.
(3) T. Murayama, K. Ohira, H. Yagi, S. Tamura and S. Arai, “Reflectivity Characteristics of DBR Using Lateral Quantum Confinement Effect,” 「横方向量子閉じ込め効果を用いた高反射DBRの反射率特性評価」 The 64th Autumn Meeting, 2003; The Japan Society of Applied Physics, 30p-YB-3, Digest III -p. 1039, Fukuoka, Aug. 2003.
(4) K. Ohira, T. Murayama, H. Yagi, S. Tamura and S. Arai, “Low-threshold Operation of Distributed Reflector (DR) Laser Integrated with Active and Passive Sections,” 「活性領域と受動DBR領域を集積した分布反射型(DR)レーザの低しきい値動作」 The 64th Autumn Meeting, 2003; The Japan Society of Applied Physics, 30p-YB-4, Digest III -p. 1039, Fukuoka, Aug. 2003.
(5) T. Murayama, K. Ohira, M. Hirose, H. Yagi, S. Tamura and S. Arai, “Low-threshold Operation of Distributed Reflector (DR) Laser Using Wirelike Active Region,” 「細線状活性層を用いた分布反射型(DR)レーザの低しきい値動作」The 51st Spring Meeting, 2004; The Japan Society of Applied Physics and Related Societies, 30a-ZZ-2, Digest III -p. 1259, Tokyo, Mar. 2004.
(6) K. Ohira, T. Murayama, M. Hirose, H. Yagi, A. Haque, S. Tamura and S. Arai, “Low-threshold operation of distributed reflector laser with width modulated wirelike active regions,” 「線幅変調回折格子を有する分布反射型(DR)レーザの低しきい値動作」 to be presented in The 65th Autumn Meeting, 2004; The Japan Society of Applied Physics, 1a-ZN-8, Sendai, Sep. 2004.
(7) K. Ohira, T. Murayama, S. M. Ullah, H. Yagi, S. Tamura and S. Arai, “Integration technique by using lateral quantum confinement effect in quantum wires and its application to lasers for optical communication,” 「量子細線活性層の横方向量子閉じ込めを用いた集積法とその光通信用レーザへの応用」 The 52nd Spring Meeting, 2005; The Japan Society of Applied Physics and Related Societies, 29a-ZH-1, Digest III -p. 1297, Saitama, Mar. 2005.
(8) K. Miura, H. Yagi, Y. Nishimoto, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “Room Temperature-Continuous Wave Operation of 1540 nm Wavelength GaInAsP/InP Strain-Compensated Quantum-Wire DFB Lasers,” 「1540 nm波長帯GaInAsP/InP歪補償量子細線DFBレーザの室温連続動作」 The 52nd Spring Meeting, 2005; The Japan Society of Applied Physics and Related Societies, 29p-V-10, Digest III -p. 1552, Saitama, Mar. 2005.
(9) H. Yagi, K. Miura, Y. Nishimoto, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “Low Threshold Current Operation of GaInAsP/InP Strain-Compensated Quantum-Wire DFB Lasers,”「GaInAsP/InP歪補償量子細線DFBレーザの低しきい値電流動作」The 52nd Spring Meeting, 2005; The Japan Society of Applied Physics and Related Societies, 31p-ZH-1, Digest III -p. 1304, Saitama, Mar. 2005.
(10) T. Murayama, K. Ohira, S. M. Ullah, H. Yagi, S. Tamura and S. Arai, “Low threshold current distributed-reflector laser with phase-shifted DFB and high-reflection DBR sections,” 「位相シフトDFB領域と量子細線DBR領域を集積した分布反射型(DR)レーザの低しきい値動作」 The 52nd Spring Meeting, 2005; The Japan Society of Applied Physics and Related Societies, 31p-ZH-2, Digest III -p. 1304, Saitama, Mar. 2005.
(11) K. Miura, H. Yagi, Y. Nishimoto, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “GaInAsP/InP Strain-Compensated Quantum-Wire DFB Lasers with Low-Damage Interfaces,” 「低損傷界面を有するGaInAsP/InP歪補償量子細線DFBレーザ」 The 66th Autumn Meeting, 2005; The Japan Society of Applied Physics, 7p-ZN-14 Digest III -p. 1015, Tokushima, Sep. 2005.
(12) Y. Nishimoto, H. Yagi, K. Miura, D. Plumwongrot, K. Ohira, T. Maruyama and S. Arai, “Temperature Dependence of Threshold Current for GaInAsP/InP Strain-Compensated Quantum-Wire DFB Lasers,” 「GaInAsP/InP歪補償量子細線DFBレーザのしきい値電流の温度依存性」 The 66th Autumn Meeting, 2005; The Japan Society of Applied Physics, 7p-ZN-15 Digest III -p. 1015, Tokushima,
(13) SeungHun Lee, Saeed Mahmud Ullah, Ryo Suemitsu and Shigehisa Arai, “Threshold Current Reduction of Distributed Reflector (DR) Laser after Antireflection Coating” The 67th Autumn Meeting, 2006; The Japan Society of Applied Physics, 29a-ZT-9, Digest III -p. 1047, Kyoto, August. 2006.
(14) Saeed Mahmud Ullah, Ryo Suemitsu, SeungHun Lee and Shigehisa Arai, “A low threshold current　operation of Distributed Reflector (DR) Laser”, The 67th Autumn Meeting, 2006; The Japan Society of Applied Physics, 29a-ZT-10, Digest III -p. 1048, Kyoto, August. 2006.