CLEO '99 Postdeadline: Optically Pumped VCSEL Produces Blue Output
Gallium-nitride-based vertical-cavity surface-emitting laser generates 399-nm output at room temperature.
By: Kristin Lewotsky
BALTIMORE, MD—Indium gallium nitride (InGaN) has been making headlines in the past three years, with the commercial release of blue InGaAs-based light-emitting diodes, and more recently, blue diode lasers. Now it appears that vertical-cavity surface-emitting lasers (VCSELs) are next on the list, as researchers announced the room temperature operation of InGaN-based devices in at blue wavelengths. Takao Someya and collaborators at the University of Tokyo (Tokyo, Japan) and the Universität Würzburg (Würzburg, Germany) reported on the work in the postdeadline paper sessions at the Conference on Electro-Optics and Lasers (CLEO '99; May 23-28).1
Grown on a sapphire substrate using atmospheric-pressure metal organic chemical vapor deposition, the devices consist of a 26-layer InGaN multiple quantum well structure sandwiched between distributed Bragg reflector structures. The lower Bragg reflectors incorporate 43 pairs of aluminum gallium nitride/gallium nitride (Al0.34Ga0.66N/GaN) layers for 98% reflectivity, while the upper Bragg reflectors contain 15 pairs of silicon dioxide/zirconium dioxide (SiO2/ZrO2) layers for 99.5% reflectivity. The researchers fabricated a two-dimensional array 18-µm devices on 22-µm centers.
The group optically pumped the single-post devices at 367 nm, using a dye laser pumped by a nitrogen laser (see Figure 1). At a threshold of 10 mJ/cm2, the device produced 399-nm pulses with spectral widths on the order of 0.1 nm.
References
1. Takao Someya, et. al., "Room temperature operation of blue InGaN VCSELs by optical pumping," postdeadline paper #CPD15, Conference on Lasers and Electro-Optics (CLEO '99; Baltimore, MD), 1999.