Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants|
Applied optics/Quantum optical engineering
|Research Institution||University of Tokyo|
TADA Kunio Univ.of Tokyo, School of Engineering, Professor, 工学系研究科, 教授 (00010710)
HIRATA Takaaki Yokogawa Electric, Central Research Labs., Chief Researcher, 中研, 主任研究員
SHIMOGAKI Yukihiro Univ.of Tokyo, School of Engineering, Associate Professor, 工学系研究科, 助教授 (60192613)
NAKANO Yoshiaki Univ.of Tokyo, School of Engineering, Associate Professor, 工学系研究科, 助教授 (50183885)
|Project Period (FY)
1996 – 1997
Completed(Fiscal Year 1997)
|Budget Amount *help
¥10,800,000 (Direct Cost : ¥10,800,000)
Fiscal Year 1997 : ¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 1996 : ¥7,200,000 (Direct Cost : ¥7,200,000)
|Keywords||Distributed feedback laser / DFB laser / Gain coupling / Absorptive grating / Wavelength trimming / Laser triode / Analog modulation distortion / Quantum wire / InGaAsP / InP / 歪み多重量子井戸 / 半導体レーザ / 波長トリミング / 歪み量子井戸|
1.Development of absorptive-grating gain-coupled (GC) distributed-feedback (DFB) lasers
We fabricated and developed 1.55mum wavelength band GC DFB lasers based on absorptive grating structure. A compressively strained InGaAsP multiple quantum well was used as an active layr, and InGaAs was used as the absorptive grating layr. The device operated at room temperature in CW with threshold current of 20-30mA.We achieved high-yield single-mode lasing with 40-55dB side mode suppression without applying antireflection coating on the facets.
2.Characterization of external reflection immunity
External reflection immunity of the above lasers was characterized. Their critical feedback level was found to be improved with increasing gain coupling coefficient.
We proposed "wavelength trimming", a new concept toward wavelength division multiplexed optical communication systems, and investigated its realization. First, the wavelength trimming utilizing Photoinduced refractive index ch
ange in chalcogenide glasses was tried, and developed a new structure where the chalcogenide was loaded alongside the DFB laser active layr. By irradiating He-Ne laser beam, we demonstrated 0.14nm wavelength trimming at 1.55mum. Next, the wavelength trimming based on photo-absorption-induced disordering of quantum wells was tried, and 0.36nm trimming was accomplished by YAG laser irradiation.
4.Fabrication of GC DFB laser triode
GC DFB laser triodes have successfully been fabricated for the first time by four step metal organic vapor phase epitaxy (MOVPE). Changes of absorption coefficient in the absorptive grating and of the coupling coefficients by applying voltage to the third terminal have experimentally been demonstrated.
5.Analysis and measurement of analog modulation distortion
We analyzed analog modulation distortion in GC DFB lasers of absorptive grating type by a newly-developed numerical method. As a result, the second harmonic distortion was found to be reduced due to cancellation of gain compression in the active layr by absorption compression in the grating. A preliminary experiment was conducted to confirm the above theoretical prediction.
6.Fabrication of a GC DFB laser with quantum wire active region
By making use of MOVPE growth on V-grooved substrates, a GC DFB laser with InGaAs strained quantum wire active region has successfully been fabricated for the first time. Less