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30 January 2007


First nonpolar blue-violet laser diodes demonstrated by UCSB

A research team at the Solid State Lighting and Display Center (SSLDC) in the University of California, Santa Barbara's College of Engineering has achieved lasing operation in nonpolar gallium nitride (GaN) and demonstrated the first nonpolar blue-violet laser diodes, which could be used in high-density optical data storage for high-definition displays and video, optical sensing, and medical applications.

The team is led by blue laser diode inventor and Department of Materials professor Shuji Nakamura (winner of the 2006 Millennium Technology Prize) together with faculty professors Steven DenBaars and James Speck. The lasers were fabricated by graduate students 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 [which are based on polar GaN material] could soon be replaced with nonpolar violet laser diodes, which require lower operating power and have longer lifetimes,” says Nakamura.

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 (the wavelength used in high-definition optical data storage applications such as HD-DVD and Blue Ray DVD), but only under pulsed operation so far (not the continuous-wave operation needed for commercial application).

The laser is based on novel nonpolar orientations of GaN that were pioneered at UCSB. Devices based on nonpolar GaN are expected to yield lower threshold current than the commercially available c-plane devices. These new orientations of GaN will result in laser diodes with lower operating power and longer lifetimes, which are necessary for high-performance operation.

Funding for the latest research was provided jointly by the SSLDC and the Japan Science & Technology Agency's Exploratory Research for Advanced Technology (JST ERATO) program. Such funding also led in December to the team reporting record-efficiency LEDs based on both nonpolar and semipolar GaN.

The latest results have now been submitted for publication. A public demonstration of the nonpolar blue-violet laser at UCSB is planned for early February.

See related item:

Record efficiency nonpolar and semipolar GaN LEDs