23 July 2012
The first violet nonpolar vertical-cavity surface-emitting lasers (VCSELs) based on m-plane gallium nitride semiconductors have been developed and could lead to higher optical efficiency lasers at reduced manufacturing costs for lighting, displays and sensor applications.
VCSELS offer advantages over conventional edge-emitting laser technology for some applications; e.g., on-wafer testing of VCSEL arrays during manufacture could save costs compared with edge-emitting lasers that require additional steps before they can be tested. VCSELS exhibit low threshold currents, and circular and low divergence output beams and are easily integrated into two-dimensional arrays.
The discovery, by LED pioneer Shuji Nakamura and his research team at the University of California, Santa Barbara, has opened the door for new products and applications such as pico projectors for smartphones, mobile cinema and automotive lighting, said Steven DenBaars, co-director of the university’s Solid State Lighting and Energy Center.
“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,” said 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 polarization 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.”
The electrically injected nonpolar m-plane nitride VCSEL platform lases at room temperature and provides high optical gain, which helps to increase optical efficiency of devices. The device is naturally polarization-locked along the crystallographic a-direction of the wurtzite crystal, a contrast to the majority of VCSELS, which are typically randomly polarized, said Dr. Daniel Feezell, a project scientist with Nakamura’s lab.
“The enhanced laser performance and prospects for significantly improved cost-effectiveness demonstrated is likely to have important impact on future generations of flat panel displays, mobile phones and lighting,” said Rod Alferness, dean of the College of Engineering at UCSB.
The findings have been submitted for publication.