TOKYO, June 21, 2012 — The first green wavelength (530 nm) semiconductor laser diode with an optical output power of more than 100 mW is twice as bright as conventional gallium nitride (GaN) based diodes, Sumitomo Electric Industries Ltd. and Sony Corp. announced Thursday. The diode will significantly improve the quality of images reproduced by laser projectors and other display devices.
Red and blue laser diodes have been commercially available among the primary red-green-blue (RGB) colors, but there has been greater need for high-output green laser diodes for high-performance laser projectors and display devices, the companies said. Currently, green lasers are generated by converting the wavelength of infrared laser light from a light source using optical materials, but the light source is large and expensive. In addition, conventional GaN-based green lasers have difficulties achieving sufficient luminosity, as their performance is limited to an output power of several tens of milliwatts at a wavelength of 520 nm or less.
Schematic illustration of true-green laser diode and structural device. (Images: Sony)
Sony and Sumitomo said they overcame these challenges by using a semi-polar GaN substrate and improving the production process. A semi-polar GaN substrate plane is tilted 75° 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 successful growth of a high-quality light-emitting layer.
Sumitomo Electric and Sony said they reduced the laser's operating current and voltage by optimizing its structure, controlling impurities in the crystal, and minimizing electrode resistance.
"This true-green semiconductor laser diode is highly reliable, as it realizes wall-plug efficiency of over 8 percent," the companies said in a statement. "The new laser diode features twice the luminosity compared with conventional gallium nitride (GaN) green laser diodes and a color gamut broadened by 182 percent based on the NTSC standard."
The resulting diode will "significantly improve the performance of laser projectors and other display devices to reproduce vibrant video and images," they said.
Sumitomo Electric and Sony said they will continue work to boost the diode's output power, efficiency and laser quality even higher.
For more information, visit: www.sony.net