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UCSB reports a promising laser development

23 July 2012

In what has been described as a 'leap forward' for laser technology, a team at University of California, Santa Barbara (UCSB) has developed the first violet nonpolar vertical-cavity surface-emitting lasers (VCSELs).

Shuji Nakamura and his research group at UCSB demonstrate the first nonpolar m-plane VCSEL based on gallium nitride
Shuji Nakamura and his research group at UCSB demonstrate the first nonpolar m-plane VCSEL based on gallium nitride

Based on m-plane gallium nitride semiconductors, this recent discovery by LED pioneer Shuji Nakamura and his research team at UCSB could open doors for higher optical efficiency lasers at greatly reduced manufacturing costs for a variety of applications.

“We have demonstrated working, electrically-injected nonpolar m-plane nitride VCSELs lasing at room temperature, and have shown that such devices are naturally polarisation-locked along the crystallographic a-direction of the wurtzite crystal. This is in contrast to the majority of VCSELs, which are typically randomly polarised,” said Dr. Daniel Feezell, project scientist with Nakamura’s lab. Feezell directed the research effort with Nakamura and Steven DenBaars , co-directors of the Solid State Lighting and Energy Center at UCSB , and graduate student Casey Holder.  

“This is the first report of a nonpolar VCSEL, which we believe to be one of the biggest breakthroughs in the field of laser diode technology,” explained Nakamura, a professor of Materials at UCSB . “The nonpolar VCSEL has a lot of advantages in comparison with conventional c-plane devices. One major advantage is that the light polarisation is locked to one direction. This device could be used for a variety of applications, such as lighting, displays, sensors, and technology that requires energy efficiency and small form-factor.”

VCSELs offer advantages over conventional edge-emitting laser technology for some applications. On-wafer testing of VCSEL arrays during the manufacturing process, for example, can save costs compared to edge-emitting lasers that require additional steps before they can be tested. VCSELs exhibit low threshold currents, circular and low divergence output beams, and are easily integrated into two-dimensional arrays.

The nonpolar VCSEL platform also provides high optical gain, which helps to increase optical efficiency of devices. According to DenBaars , the nonpolar VCSEL could enable new products and applications, such as pico-projectors for smartphones, mobile cinema, or even automotive lighting.

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