“Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) claims the highest side-mode suppression ratio (SMSR) for indium gallium nitride (InGaN) distributed feedback (DFB) laser diodes (LDs) so far [Jorge A. Holguín-Lerma et al, Appl. Phys. Express, vol12, p042007, 2019]. The highest SMSR achieved in the KAUST work was 36.9dB. The researchers' comment: “This could enable immediate implementation of narrow-line green laser diodes on various applications, such as atom cooling, spectroscopy, and optical communications.”
“Narrow-line emissions usually require external, complex and bulky filtering techniques to reduce the presence of side-modes relative to the main peak. An attractive alternative is the monolithic integration of DFB gratings into the structure of the laser diode. Such an approach is already common in laser diodes constructed in other compound semiconductor systems serving wavelengths in the infrared and red parts of the electromagnetic spectrum. Also, DFBs have been applied to blue and ultraviolet InGaN devices, but with lower SMSR values.”
