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UCSB researchers tout blue laser diode breakthrough

Posted: 31 Jan 2007 ?? ?Print Version ?Bookmark and Share

Keywords:laser diode? blue-violet laser diode? DVD format? UCSB? University of California-Santa Barbara?

A team of University of California-Santa Barbara (UCSB) researchers, led by Shuji Nakamura, have created a new type of blue-violet laser diode that they say could replace the c-plane violet laser diodes used for competing next-generatation DVD formats, the university said Jan. 29.

UCSB said the team has achieved lasing operation in nonpolar gallium nitride (GaN) semiconductors and demonstrated what it touts as world's first nonpolar blue-violet laser diodes. The nonpolar blue-violet laser diodes have numerous commercial applications, including high-density optical data storage for high definition displays and video, optical sensing and medical applications, according to USSB. Because of the shorter wavelength of emission in these devices, they can accommodate higher densities of optical storage than conventional red-laser based systems.

Nakamura, a UCSB professor who is best known as a pioneering developer of volume-manufacturing technology for GaN-based LEDs and lasers, led a team of two UCSB faculty colleagues and two graduate students in fabricating the new nonpolar blue-violet laser diodes. The professors were Steven BenBaars and James Speck, and the students were Mathew Schmidt and Kwang Choong Kim.

"Our initial results of the first violet nonpolar laser diodes with a low threshold current density demonstrate a high possibility that current c-plane violet laser diodes used for HD-DVD and Blue Ray DVD could soon be replaced with nonpolar violet laser diodes, which require lower operating power and have longer lifetimes," Nakamura said through a statement.

UCSB said the new blue-violet laser diodes displayed threshold current densities as low as 7.5kA/cm2, clear far-field pattern and a lasing wavelength of 405nm under pulsed operation. The GaN-based laser diode is based on novel nonpolar orientations of GaN that were pioneered at UCSB, according to the university. Devices based on nonpolar GaN semiconductors are expected to yield lower threshold current than the commercially available c-plane devices, and the new orientations of GaN will result in laser diodes with lower operating power and longer lifetimes, UCSB said.

"This is a groundbreaking advancement in laser diodes and a major step in solid-state lighting technology," said UCSB Chancellor Henry Yang. "The blue-violet laser will improve high density optical data storage for high definition TV, video discs, and optical sensors, and will also have applications in and long-term benefits for the communication, entertainment, medical, and environmental areas."

Fabrication of blue-violet laser diodes, which are essential to competing next-generation HD DVD and Blu-ray Disc formats, has been a tricky issue. Sony Corp.'s 2006 roll out of the PlayStation 3 gaming console, which incorporates a Blu-ray drive, was dramatically impacted by ongoing blue-laser diode manufacturing problems at the company. Sony says it has since corrected the problem.

- Dylan McGrath
EE Times

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