Kazushige Kawasaki

High-power 980-nm ridge waveguide laser diodes including an asymmetrically expanded optical field normal to the active layer

We propose a new ridge waveguide laser diode (LD) which supports an asymmetrically expanded optical field normal to the active layer in order to increase the maximum kink-free output power and reduce the aspect ratio of output beams. The dependence of maximum kink-free output power on facet reflectivity was analyzed from the viewpoint of the total optical power in the cavity. It was clarified that the maximum kink-free output power is influenced by the facet reflectivity which affects the refractive index changes of the ridge region via the total optical power in the cavity. More than 600 mW of maximum kink-free output power and an aspect ratio of less than 2.5 were achieved in experiments with 980-nm ridge waveguide LDs by means of this proposed new structure.

A very low failure rate of COD free high power 0.98 /spl mu/m laser diode with the window structure

A very low failure rate of a 0.98 /spl mu/m laser diode is reported. COD free characteristics is realized. The cumulative failure rate 0.4% for wear-out and 5.6% for sudden failure is estimated 25 years later at 25 C-250 mW.

Wavelength stabilized 980 nm pump laser suitable for uncooled application in metro networks

Wavelength of 980nm pump lasers are stabilized not only with fiber-Bragg-grating but also without it over wide range of temperature. These are suitable for uncooled fiber amplifier application in metro networks.

High-power and highly reliable 1020-nm ridge waveguide laser diodes with small aspect ratio as a pumping source for praseodymium-doped fiber amplifiers

The structure of an asymmetrically expanded optical field normal to the active layer was applied to 1020-nm ridge waveguide laser diodes in order to increase their maximum kink-free output power and reduce the aspect ratio of the output beams. As a result, a kink-free output power of more than 400 mW and an aspect ratio of less than 2.5 were achieved by this structure. Good reliability was also obtained at an output power of 300 mW at 50/spl deg/C.

Highly reliable ridge waveguide 980 nm pump lasers suitable for submarine and metro application

Very low failure rate acquired from ridge waveguide 980 nm pump lasers with window structure is described using thermal and power dependence of random failure. This laser is suitable for both submarine and uncooled metro application.

Suppression of lasing wavelength change of 980 nm pump laser diodes by means of decreasing facet reflectivity as lengthening wavelength

We have proposed a new method of suppressing the lasing-wavelength-change by means of decreasing facet reflectivity as increasing wavelength. Less than one-third reduction of losing wavelength was realized by this method.

High power and small aspect ratio 980 nm ridge waveguide laser diodes consisted of asymmetrically expanded optical field normal to the active layer

The new ridge waveguide LD consisted of layers to support asymmetrically expanded optical field normal to the active layer has been proposed in order to satisfy the increase of kink free output power and the reduction of aspect ratio. More than 650 mW kink free output power and less than 2.5 aspect ratio have been achieved by the proposed LD. Good aging performances are also expressed in the proposed LD. It is believed that the LDs are suitable for realizing 980 nm modules with high coupling efficiency and high power EDFAs.

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).

Anomalous wavelength changes of 980-nm pump laser diodes with antireflection coatings

We have observed abrupt wavelength jumps form 980-nm pump laser diodes with an antireflection (AR) coating when the injection currents were changed. The width of the anomalous jumps becomes wider as the cavity length is shortened. It was clarified from theoretical calculations that the phenomenon is caused by narrow mirror loss distributions. It was also confirmed that wide AR coatings or a long cavity can avoid these abrupt wavelength jumps.