Due to their excellent power efficiency and small size, laser diodes coupled with SiN microresonators made from quantum well (QW) and quantum dot (QD) semiconductor materials offer tremendous possibilities. Professor Yating Wan led a study that delved into the inner workings of these composite cavity lasers, yielding important information for the advancement of laser diode technology in the future.
Quantum Dot and Quantum Well Laser Diodes: The Future of Microresonators
On-chip laser diodes made from quantum well (QW) and quantum dot (QD) semiconductor materials are now frontrunners in several fields. They’re small, lightweight, and efficient at converting power despite operating in hot environments. Despite the widespread use of QWs, QDs present a prospective alternative due to their distinctive zero-dimensional density of states and atom-like degeneracy.
Self-injection locking makes it possible for heterogeneous integration of III-V lasers with silicon nitride (SiN) microresonators, which has inherent advantages. They are more compact, can produce in larger batches, and are more stable. When compared to III-V lasers generated on native platforms, this method enables significantly better linewidth narrowing performance.
New Study Explores Quantum Well and Quantum Dot Devices
Parametric research into the active medium design of composite cavity lasers was recently published in the journal Light Science & Application. Professor Yating Wan of KAUST’s Integrated Photonics Lab, Dr. Weng W. Chow of Sandia National Laboratories in Albuquerque, New Mexico, Professor Frédéric Grillot of LTCI, Télécom Paris, Institut Polytechnique de Paris, France, and Professor John Bowers of UC Santa Barbara, California, USA, oversaw this study.
The group studied how carrier quantum confinement affected the device’s dynamic and spectral properties. When combining III-V quantum well (QW) or quantum dot (QD) distributed feedback (DFB) lasers with SiN microring resonators, they focused on reducing the linewidth of the laser’s emitted spectrum. The rationale behind the enhancement was explained by the paper’s first author, Emad Alkhazraji. “When properly tuned and locked to one or more of the microring’s whispering gallery modes, optical feedback in the form of Rayleigh backscattering can enable drastic reductions in the lasing linewidth of a laser diode to the Hz-level,” Alkhazraji said.
Findings and Implications for Future Design
Finally, a genetic algorithm was used to conduct a multi-objective design-operation optimization study of both QW and QD devices, capping off the parametric investigation. The optimal design-operation points for each optimization variable were then determined using a multi-decision method.
“These results provide guidance for more comprehensive parametric studies that can produce timely results for engineering design,” Professor Yating Wan said. The research shows that laser diode technology has room for growth and advancement.