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Semiconductor Laser for Triple, Quadruple-layer Blu-ray Discs – Sharp

Sharp Corp developed a blue-violet semiconductor laser whose optical output is as high as 500mW under pulsed operation for use in Blu-ray Disc (BD) recorders.

It has an oscillation wavelength of 405nm and a capability of writing at 8x speed on triple- and quadruple-layer Blu-ray discs. The company started volume production of a blue-violet semiconductor laser with 320mW pulsed output in June 2009.

Sharp has not decided when to mass-produce the new blue-violet semiconductor laser because the specifications of triple or more layer Blu-ray disc have not been determined yet. However, the company claimed that it is now ready to commercialize the laser.

Sharp enhanced the optical output by using a new method of processing the edge face of a resonator. Normally, the edge face of a crystal in a semiconductor laser is protected by a dielectric film. This time, the company formed an aluminum oxynitride (AlON) film between the edge face of the semiconductor laser and the dielectric film by a sputtering method and realized an epitaxial growth where the growth axis of the laser’s crystal corresponds to that of the AlON crystal.

In the past, the crystal of a semiconductor laser was just covered by a noncrystalline dielectric film. Therefore, the edge face of the crystal had a surface state and absorbed laser light, and the crystal was degraded by the heat and stopped oscillation.

Sharp has already verified the reliability of the new blue-violet semiconductor laser. It confirmed that the laser operated for more than 1,000 hours under the temperature of 80°C with a pulse width of 30ns and an output of 500mW.