Yasuo Nakajima

Wavelength tunable 4-element laser array

A wavelength tunable 4-element laser array is fabricated with high performances suitable for the frequency division multiplexing (FDM) system. The array consists of four 1 .55 j.m DFB(distributed feedback) PPIBH (p-substrate partially inverted buried heterostructure) lasers with beam spacing of 125 jim. The lasing wavelength is tuned by changing the ratio of input currents to the two electrodes. The lasing frequency of the array can be allocated with a frequency interval of 10 GHz. An FM efficiency as large as 1 GHz/mA and a flat FM response with variation less than 3 dB in the modulation frequency range from 20 kHz to 1 GHz have been realized. An electrical crosstalk is less than -30 dB up to 800 MHz.

Interchangeability of optical disks

The aim of this study is to improve interchangeability to ISO standard optical disks. The compensation of the write condition and the expansion of dynamic range of servo circuits using control track data have been tried. The results were satisfactory.

High-power and highly reliable operation of all-MOCVD-grown 1.48-um diode lasers

High output power and long-term stable operation have been realized in all-MOCVD grown 1.48 micrometers buried heterostructure lasers. For the purpose of high power operation, a diode with a cavity length of 1800 micrometers was mounted junction down. This diode shows the maximum output power of 310 mW at 25 degree(s)C, cw. A preliminary aging test is being carried on at a temperature of 50 degree(s)C with a constant light output of 100 mW for the diodes with cavity length of 900 micrometers and junction up configuration. Long-term stable operation over 3000 hrs and the estimated MTTF of 2.4 X 105 hrs at 50 degree(s)C, 100 mW have been realized. As another advantage of the all-MOCVD process, the uniformity of the laser characteristics is also demonstrated. Lasers with a cavity length of 900 micrometers in junction-up configuration are assembled from a processed 2-inch wafer.