BEGIN:VCALENDAR VERSION:2.0 PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4// BEGIN:VEVENT UID:20260522T015200EDT-8376PN5C52@132.216.98.100 DTSTAMP:20260522T055200Z DESCRIPTION:Abstract\n\nSurface-emitting (SE) semiconductor lasers have bec ome one of the most important building blocks in modern photonic technolog ies. Currently\, SE semiconductor laser technologies are predominantly bas ed on the vertical cavity surface-emitting laser (VCSEL) architecture. Whi le VCSELs have been successful in the near-infrared (NIR) region\, they ha ve lagged severely at shorter wavelengths\, especially the ultraviolet (UV ) spectral range. A breakthrough in the SE UV laser development is pivotal \, given their potential applications related to our everyday life includi ng disinfection\, medical diagnostics\, and more. In this context\, III-ni tride nanowires have attracted significant interest for the SE laser devel opment\, leveraging the unique physical properties of III-nitrides includi ng widely tunable bandgap energies\, as well as the merits of semiconducto r nanowires such as the large surface-to-volume ratio. In fact\, to date I II-nitrides are the only known material system suitable for all-semiconduc tor UV photonics.\n In this thesis study\, we fulfill the technological nee d for SE lasers with III-nitride-based epitaxial nanowire photonic crystal s (epi-NPCs). Such lasers exploit the slow-light modes near the Gamma-poin t in the photonic band structure of nanowire photonic crystals. This is ma de possible thanks to the improved epitaxial growth using low-substrate te mperature\, i.e.\, low-temperature selective area epitaxy (LT-SAE) by mole cular beam epitaxy (MBE). In contrast to conventional SAE at high temperat ures\, LT-SAE enables precise control over the nanowire growth and morphol ogy. Using GaN epi-NPC grown by LT-SAE\, ultralow threshold optically pump ed SE UV lasing at 367 nm is demonstrated\, with a threshold of merely 7 k W/cm2 —more than two orders of magnitude reduction compared to the previou sly reported conventional III-nitride-based UV VCSELs at similar lasing wa velengths. Moreover\, by changing the III-nitride epi-NPC material composi tion (e.g.\, InGaN epi-NPCs) and further engineering the photonic crystal bands\, ultralow threshold optically pumped SE UVlasers at various UV wave lengths are achieved.\n This thesis work further demonstrates the electrica lly injected SE UVlaser. By employing transferred graphene as the top p-co ntact of the epi-NPC\, SE UV lasing at 383 nm under a direct electrical cu rrent injection is successfully achieved. This thesis work not only repres ents an important step in the journey of the SE UV laser development\, but more importantly\, it lays the foundation for the wavelength-tunable SE l asers broadly from the NIR to UV spectral range.\n DTSTART:20250805T130000Z DTEND:20250805T150000Z LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H 3A 0E9\, 3480 rue University SUMMARY:PhD defence of Mohammadfazel Vafadar – Epitaxial III-Nitride Nanowi re Photonic Crystals for Surface-Emitting Lasers by Molecular Beam Epitaxy URL:/ece/channels/event/phd-defence-mohammadfazel-vafa dar-epitaxial-iii-nitride-nanowire-photonic-crystals-surface-emitting-3662 31 END:VEVENT END:VCALENDAR