Browsing by Author "Hsiao, Yu-Hao"

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Circular Polarized Lasing Characteristics in Metal/GaN Double-Spiral Nanowire Cavity
(2017-01-01)
Yu, Cheng-Li
;
Liao, Shu-Wei
;
Hsiao, Yu-Hao
;
Kuo, Hao-Chung
;
Shih, Min-Hsiung
Room temperature highly circular polarized laser was demonstrated with a compact metal/GaN double-spiral nanowire cavity. The lasing action was observed with a UV wavelength of 363 nm and a high dissymmetry factor of +1.05.
Circularly-polarized lasing of ultraviolet plasmonic gammadion nanocavity
(2019-01-01)
Cheng, Pi-Ju
;
Lai, Ming-Sheng
;
Hsiao, Yu-Hao
;
Yu, Cheng-Li
;
Chang, Chiao-Yun
In this work, we present the model of plasmonic chrial nanolasers composed of aluminum-coated gallium-nitride (GaN) gammadions, which may lase with a high degree of circular polarization at room temperatures. Using the finite-element method, we examine resonant modes of the four-fold rotationally symmetric cavities of gammadions whose resonant frequencies lie in the gain spectrum of GaN. We find a degenerate doublet of resonant modes which can couple to plane waves in the far-field zone above gammadions. Their near-field profiles exhibit localized distribution in the arms of gammadions and a Fabry-Perot standing-wave pattern along the post. In practice, fabrication imperfections would inevitably spoil the four-fold rotation symmetry of gammadions. Typical perturbation could lift the degeneracy of doublet and leads to mixing of the two degenerate modes which may still output signals with observable handedness above gammadions. Considering a gammadion cavity with a single elongated arm, we show that the magnitude of dissymmetry factor of its resonant mode can be larger than unity. Our calculations are consistent with the experimental results, indicating that the right-handed gammadion cavities lase with a magnitude of dissymmetry factors near 1 at a wavelength of 364 nm. The dimensionless effective mode volume scaled by the cube of effective wavelength is 2.62, reflecting a modal distribution remarkably confined in the plasmonic structures and the capability of enhancing the spontaneous-emission rate noticeably. These chiral nanolasers with an ultrasmall footprint could be potentially utilized as future circularly-polarized photon source at the chip level.
High Circular Polarized Nanolaser with Chiral Gammadion Metal Cavity
(2020-05-12)
Yu, Cheng-Li
;
Hsiao, Yu-Hao
;
Chang, Chiao-Yun
;
Cheng, Pi-Ju
;
Lin, Hsiang-Ting
We demonstrate a circularly polarized laser with the metal-gallium-nitride gammadion nanocavities. The ultraviolet lasing signal was observed with the high circular dichroism at room temperature under pulsed optical pump conditions. Without external magnetism which breaks the time-reversal symmetry to favor optical transitions of a chosen handedness, the coherent outputs of these chiral nanolasers show a dissymmetry factor as high as 1.1. The small footprint of these lasers are advantageous for applications related to circularly polarized photons in future integrated systems, in contrast to the bulky setup of linearly-polarized lasers and quarter-wave plates.
Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature
(2016-05-25)
Liao, Wei-Chun
;
Liao, Shu-Wei
;
Chen, Kuo-Ju
;
Hsiao, Yu-Hao
;
Chang, Shu-Wei
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.
Planar Metal-GaN Spiral Nanowire Cavities for High Circular Dichroism Lasing Action
(2016)
Hsiao, Yu-Hao
;
Kao, Tsung Sheng
;
Liao, Shu-Wei
;
Liao, Wei-Chun
;
Chen, Kuo-Lu
The compact and energy-efficient planar metal-GaN spiral nanowire cavity lasing device has been demonstrated with high circularly polarized UV laser light at 364 nm and the circular dichroism performance enhanced to dissymmetry factor of + 1.4.