3. Laser Diodes for Blu-ray Discs

Maximum 250 mW Optical Power Output (in Pulse Drive Mode)
Even higher power levels, however, are now required by the blue-violet lasers that are used as the light source, to make higher recording densities and speeds possible in Blu-ray Disc Recorders. The newly developed laser diode minimizes reductions in reliability because of catastrophic optical damage (COD) by optimizing the laser structure and controlling the optical power density distribution in the optical region. As a result, Sony was able to create a blue-violet laser diode that is capable of a maximum optical power output of 250 mW in pulse-drive mode.

Low Power Consumption and Low Noise
The blue-violet laser diode, whose base material is gallium nitride, is a device in which, because of the physical properties of the material itself, it is extremely difficult to acquire good current-voltage characteristics. Nonetheless, by adopting optimal electrode materials and structures, and by optimizing the structure of the area around the emission point, Sony was able to achieve low power consumption. Reduction of the threshold current also made it possible to reduce the spontaneous emission component, which can cause fluctuations in the optical power output and the noise level during laser driving.

High-Temperature (80ºC) Operation Guaranteed
During recording by a Blu-ray Disc Recorder, the heat generated by both the structural components and the laser itself becomes significant. Also, since the internal areas of hardware used in IT applications can reach extremely high temperatures, high reliability in high-temperature environments is necessary in laser diodes. New structures were introduced in the optically active areas in the newly developed product, allowing this device to exhibit high resistance to temperature changes. The temperature characteristics are superlative, even when compared to the red laser diode of conventional DVD light sources, and this device can achieve stable operation even under severe environments with temperatures reaching 80ºC.