US Patent 7573926 - Multi-wavelength quantum dot laser

http://www.freepatentsonline.com/7573926.html

Quantum dot lasers offer improvements in laser efficiency but have been limited in multi-wavelength modes important to optical communications. this patent from Industrial Technology Research Institute teaches the manufacture of a quantum dot laser capable of overcoming this limitation. Claim 1 reads:

1. A multiwavelength quantum dot laser element, comprising:

a first semiconductor layer;

a second semiconductor layer; and

an active region, disposed between the first semiconductor layer and the second semiconductor layer, having a plurality of quantum dot active regions, each of the quantum dot active regions comprising a quantum dot layer and a covering layer that covers the quantum dot layer, wherein when an applied current is larger than a start-oscillation current, the quantum dot active regions simultaneously generate a plurality of laser lights with different wavelengths, wherein at least one different parameter condition exist between the quantum dot active regions, wherein the parameter condition comprises one of thickness, material composition, and quantum dot size of the quantum dot layers, and any combination thereof, and wherein the parameter condition further comprises one of thickness of the covering layers, material composition of the covering layers, and a combination thereof.