Traditionally, green laser diodes have been difficult to construct due to the characteristics of the quantum wells that serve as their gain region. Now, however, several companies and research groups have found ways to fill this “green gap,” by mastering the epitaxy of high-indium-containing quantum wells, balancing strain and defect formation against the quantum-confined Stark effect and using optimized waveguides. Their work is driving new applications in consumer electronics, biophotonics and other areas.
by Ulrich T. Schwarz and Wolfgang G. Scheibenzuber