title: Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature.
abstract: Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations.
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Liao
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.
authors.forename: Shu-Wei
authors.initials: SW
authors.lastname: Liao
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.
authors.forename: Kuo-Ju
authors.initials: KJ
authors.lastname: Chen
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.
authors.forename: Yu-Hao
authors.initials: YH
authors.lastname: Hsiao
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.|Research Center for Applied Sciences (RCAS), Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Shu-Wei
authors.initials: SW
authors.lastname: Chang
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.
authors.forename: Hao-Chung
authors.initials: HC
authors.lastname: Kuo
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University (NCTU), Hsinchu 30010, Taiwan.|Research Center for Applied Sciences (RCAS), Academia Sinica, Taipei 11529, Taiwan.|Department of Photonics, National Sun Yat-sen University (NSYSU), Kaohsiung 80424, Taiwan.
authors.forename: Min-Hsiung
authors.initials: MH
authors.lastname: Shih