Yasuhiro Kunitsugu

High-coupled-power 0.98-μm narrow-beam laser diodes

Kink-free, high coupled power of 148 mW into a single mode fiber has been realized by narrowing the vertical beam divergence in 0.98 micrometers laser diodes. It has been found that the high-refractive index GaAs layers have crucial influence on the far field patterns as well as lasing spectrum, since the GaAs is transparent to the emission wavelength of 0.98 micrometers .

Suppression of Lasing Wavelength Change of 980 nm Pump Laser Diodes for Metro Applications

High-power 980 nm laser diodes (LDs) are used as pumping sources of erbium-doped fiber amplifiers (EDFAs). Reductions of costs and power consumption in EDFAs are very important for access or metro applications. System construction without fiber Bragg gratings (FBGs) and thermal electric coolers (TECs) is strongly required. Therefore, high-power 980 nm LDs with small lasing wavelength changes under various operational conditions are highly desired in these systems. We proposed a new technique of wavelength change suppression using a facet coating for 980 nm LDs. Less than one-third reduction of lasing wavelength change was realized by this method. Moreover, the proposed LDs possess more than 350 mW output power even at 95°C and good reliability at 50°C with 700 mA automatic current control (ACC).

650-nm-band high-power and highly reliable laser diodes with a window-mirror structure

An active layer structure with 658 nm-emission at 25 degrees Celsius has been optimized in order to reduce the operating current of the laser diodes (LD) under high temperature condition. For improvement of the maximum output power and the reliability limited by mirror degradation, we have applied a zinc-diffused-type window-mirror structure which prevents the optical absorption at the mirror facet. As a result, the CW output power of 50 mW is obtained even at 80 degrees Celsius for a 650 micrometer-long window-mirror LD. In addition, the maximum light output power over 150 mW at 25 degrees Celsius has been realized without any optical mirror damage. In the aging tests, the LDs have been operating for over 2,500 - 5,000 hours under the CW condition of 30 - 50 mW at 60 degrees Celsius. The window-mirror structure also enables reliable 60 degree Celsius, 30 mW, CW operation of the LDs with 651 nm- emission at 25 degrees Celsius. Moreover, the maximum output power of around 100 mW even at 80 degrees Celsius and reliable 2,000-hour operation at 60 degrees Celsius, 70 mW have been realized for the first time by 659 nm LDs with a long cavity length of 900 micrometers.