Kenji Uchida

Wide temperature (15°C to 95°C), 80-km SMF transmission of a 1.55-μm, 10-Gbit/s InGaAlAs electroabsorption modulator integrated DFB laser

Uncooled 10-Gbit/s, 80- km SMF transmission was demonstrated for the first time using a 1.55-μm InGaAlAs EA/DFB laser. A power penalty below 2-dB was achieved over a wide temperature range from 15°C to 95°C.

1310-nm InGaAlAs short-cavity lasers for 10-Gbit/s low-power-consumption transceivers

An InGaAlAs short-cavity DBR laser enabling 1.3-μm, uncooled, 10-Gbit/s operation at lower drive currents is demonstrated. This laser consists of a short InGaAlAs-MQW active region butt-jointed to an InGaAsP-DBR region. This structure provides moderate chip power, low threshold current, and a large relaxation oscillation frequency simultaneously, because it has an optimum cavity length in the range between 10 and 100 μm, at which both VCSELs and conventional edge-emitters cannot be formed because of their difficulty of manufacture. The fabricated 75-μm short-cavity laser demonstrated 100°C, 10-Gb/s operation at a record low drive current of 14 mAp-p. Furthermore, it achieved side-mode suppression ratio of more than 37 dB at a high yield of 95%, because of the naturally high single-mode stability of its short-cavity DBR structure.

Long tail Zn diffusion in InGaAsP and InGaAlAs quaternary alloys

We investigated the Zn diffusion characteristics in InGaAsP and InGaAlAs quaternary alloys, which are commonly used as the active layers of long wavelength optical communication devices. The measured Zn diffusion profiles of InGaAsP and InGaAlAs alloys had long tails while those of InP and InAlAs alloys were quite abrupt, indicating a clearly observable difference between quaternary alloys and others. Since these tails could be well fitted by using the group-V vacancy related defect model, its mechanism seems to be closely related with group-V atomic bonds. We also found that the group-V vacancies related to Ga atoms, particularly for those originating from GaP bond, had a significant influence on this type of Zn diffusion.

LGLC Tunable Laser for Small-Form-Factor Transceiver: High Optical Power and High SMSR With Low Power Consumption

A lateral-grating-assisted lateral co-directional coupler (LGLC) type tunable laser with high optical power and low power consumption is proposed. An approach to reduce the injection current in the gain section, by means of a new laser design, provide the power consumption of the LGLC laser from 0.25 to 0.13 W. The LGLC tunable laser with new design achieved good laser characteristics, and side-mode suppression ratio of over 40-dB in the 45-nm wavelength range.

Subaru Telescope Network III (STN-III): more effective, more operation-oriented, and more inexpensive solutions for the observatory's needs

Subaru Telescope has recently replaced most equipment of Subaru Telescope Network II with the new equipment which includes 124TB of RAID system for data archive. Switching the data storage from tape to RAID enables users to access the data faster. The STN-III dropped some important components of STN-II, such as supercomputers, development & testing subsystem for Subaru Observation Control System, or data processing subsystem. On the other hand, we invested more computers to the remote operation system. Thanks to IT innovations, our LAN as well as the network between Hilo and summit were upgraded to gigabit network at the similar or even reduced cost from the previous system. As the result of the redesigning of the computer system by more focusing on the observatory operation, we greatly reduced the total cost for computer rental, purchase and maintenance.