Researchers develop violet non-polar m-plane VCSELs

A team at the University of California, Santa Barbara (UCSB) says it has developed the first violet non-polar vertical-cavity surface-emitting lasers (VCSELs) based on m-plane gallium nitride semiconductors.

This recent discovery by Shuji Nakamura and his research team at UCSB is claimed to be an achievement in VCSEL technology that opens doors for higher-optical-efficiency lasers at greatly reduced manufacturing costs for a variety of applications.

‘We have demonstrated working, electrically injected non-polar 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,’ said Dr Daniel Feezell, project scientist with Nakamura’s lab. ‘This is in contrast to the majority of VCSELs, which are typically randomly polarised.’

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. Their findings have been submitted for publication.

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

According to a statement, the non-polar VCSEL platform also provides high optical gain, which helps to increase the optical efficiency of devices.

‘The non-polar VCSEL could enable new products and applications, such as pico-projectors for smartphones, mobile cinemas or even automotive lighting,’ said DenBaars, professor of materials.