High-power blue-violet laser diodes for next-generation optical disc systems

摘要

High-power and low-noise characteristics are strongly required for blue-violet laser diodes in practical application to next generation optical disc systems. We have successfully fabricated blue-violet laser diodes meeting these requirements. These laser diodes have a ridge waveguide structure with a dielectric current blocking layer. Improving the crystal quality of the grown materials on a GaN substrate and optimizing the optical confinement in the emission layer have achieved a kink level as high as 250 mW. Optimized optical confinement is also assumed to result in a good beam profile with no fringe. In addition to this, since the threading dislocation density at the emission layer below the ridge portion is reduced to less than 10~5cm~(-2), these laser diodes have been operating reliably for more than 1000 h with a light output power of 100 mW at 60°C under pulsed operation. This light output power makes it possible to realize dual layer recording systems. We have also confirmed that these laser diodes have a noise level as low as -130 dB/Hz for a light output power of 5 mW.