Sharp developed a blue-violet semiconductor laser powerful enough to burn on triple- and quadruple-layer Blu-ray discs.
Since beginning mass production of the industry's first infrared laser diode for use in CD players in 1982, Sharp has been an industry leader in this field. The Japanese company announced its latest developments related to semiconductior laser diodes at the 70th Autumn Meeting of the Japan Society of Applied Physics, which place from Sept 8 to 11, 2009, in Toyama Prefecture, Japan.
The new semiconductor laser has an oscillation wavelength of 405nm and is optical output reaches the 500mW (pulsed operation), which is high enough to write at 8x speed on triple- and quadruple-layer Blu-ray discs.
Sharp managed to dramatically increase the optical output of the new laser 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.
Until now, 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.
The new 405nm diode is offering a reliability of more than 1,000 hours under the temperature of 80 degrees C with a pulse width of 30ns and an output of 500mW, according to the company.
Mass production of the new diode has not been decided, since 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.
The company has already started volume production of a blue-violet semiconductor laser with 320mW pulsed output in June 2009. These diodes are able to burn single and dual layer Blu-ray discs at 8x.