Optical Engineering of Modal Gain in III-Nitride Laser with Nanoporous GaN

Nanoporous (NP) GaN is prepared to address the long-standing challenge in GaN edge-emitting laser diode: the lack of transverse mode confinement in conventional AlGaN/GaN-based waveguide design due to the limited index contrast and large lattice mismatch. By introducing air pores into GaN, we attain unprecedented index tunability without introducing any strain. We therefore are capable to engineer the waveguide’s modal gain by changing its design and demonstrate record high optical confinement factor (Γ ) ~ 9%, all by using NP-GaN as the cladding layer. Under optical pumping, a threshold material gain is reduced to 400 cm-1, which is more than two times lower than previously reported (> 1,000 cm^-1).