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

Sep 11, 2009
Mayuko Uno, Nikkei Electronics
A cross-sectional image of the semiconductor laser with an aluminum oxynitride film
A cross-sectional image of the semiconductor laser with an aluminum oxynitride film
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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.

Sharp announced those findings at the 70th Autumn Meeting of the Japan Society of Applied Physics, which is taking place from Sept 8 to 11, 2009, in Toyama Prefecture, Japan (lecture number: 11p-X-8).