Date: 27/06/2012

100 mW at 530 nm true green semiconductor laser diode

Sumitomo Electric Industries, Ltd. and Sony Corporation have successfully developed the first semiconductor laser diode with an optical output power of over 100 mW in the true green region at a wavelength of 530 nm. This laser diode can be mounted on laser projectors and other display devices. The new laser diode features increased luminosity compared with conventional gallium nitride (GaN) green laser diodes, and a broadened color gamut based on the NTSC standard (CIE 1976 color gamut).

The challenges faced by the conventional red, blue and green laser diodes are successfully overcome by the joint collaboration of Sumitomo Electric and Sony in the development of a true green semiconductor laser for practical use. To mention about the challenges, red and blue laser diodes are commercially available among the primary RGB colors but lack the high output green lasers. However, GaN-based green lasers are limited to an output of few tens of milliwatt at a wavelength of 520nm or less.

The joint development represents Sumitomo Electric’s semi-polar GaN substrate, crystal growth, and wafer processing technologies, as well as Sony’s GaN-based laser technology, acquired through the Blu-ray development. By introducing new techniques and improving the entire semiconductor laser production process, including structural design, crystal growth, wafer processing, and electrode configuration, Sumitomo Electric and Sony were able to successfully develop true green semiconductor laser with an optical output power of more than 100 mW at a wavelength of 530 nm. This true green semiconductor laser diode is reliable as it realizes wall-plug efficiency of over 8%.

With this development, the three basic colors of the RGB laser light sources are completed. Sumitomo Electric and Sony expect a variety of applications for this technology such as incorporation into advanced laser projectors with high luminosity and broad color gamut, as well as compact, light, energy-efficient laser projectors.

Sumitomo Electric and Sony continue to jointly develop true green semiconductor laser diode to achieve higher output power, efficiency, and laser quality.

Main features of the development
Sumitomo Electric and Sony have developed the first true green semiconductor laser diode that has an output power of over 100 mW at 530 nm by using a semi-polar GaN substrate and improving the production techniques.

High quality active layer
A semi-polar {2021} GaN substrate plane is tilted 75 degrees compared to the conventional GaN crystal c-plane. The semi-polar GaN substrate enables the sustainable production of homogenous indium-based active layers, leading to the growth of a high quality light-emitting layer.

Wall-plug efficiency of more than 8%
The luminous efficiency in the GaN-based green light-emitting devices declines in the green region due to the internal field effects resulting from distortion in the crystal structure and the resultant internal polarization. Sumitomo Electric and Sony have succeeded in reducing the operating current and voltage in the laser through the optimization of the laser structure, impurity control in crystal, and minimization of electrode resistance.

Source: Sony