Reduction of Lasing Threshold of GaN-Based Vertical-Cavity Surface-Emitting Lasers by Using Short Cavity Lengths

Ultralow lasing threshold of
$413~\mu \text{J}$
/cm
²
in GaN-based vertical-cavity surface-emitting lasers (VCSELs) was observed by reducing the cavity lengths between double-side dielectric distributed Bragg reflectors to
$6\lambda $
. To the best of our knowledge, the threshold is the lowest value ever reported in nitride optically pumped VCSEL. The spontaneous emission factor (
$\beta $
) was 0.1, and the degree of polarization was 91%. Effects of short cavity on spontaneous emission factors, gain coefficient enhancement, and absorption reduction were analyzed. In addition, effects of coupled quantum wells on the confinement factor were also discussed. We believe that our results would be meaningful for refining nitride VCSEL structure in the future.