Abstract
We theoretically analyze plasmonic gap-mode nanocavities covered by a thick cladding layer at telecommunication wavelengths. In the presence of high-index cladding materials such as semiconductors, the first-order hybrid gap mode becomes more promising for lasing than the fundamental one. Still, the significant mirror loss remains the main challenge to lasing. Using silver coatings within a decent thickness range at two end facets, we show that the reflectivity is substantially enhanced above 95 %. At a coating thickness of 50 nm and cavity length of 1.51 μm, the quality factor is about 150, and the threshold gain is lower than 1500 cm(-1).
Highlights
There has been significant progress in miniaturized semiconductor lasers beyond the diffraction limit [1,2,3]
Russell et al have demonstrated a gap-mode plasmonic nanocavity consisting of a metallic nanowire and dielectric/metal planar structure [18, 19]
Metallic nanowires introduce the higher absorption than dielectric counterparts do, the experiment indicates that the cavity quality (Q) factor and threshold gain of this type of cavities are mainly limited by the mirror loss at end facets rather than the propagation loss from metallic components [19]
Summary
There has been significant progress in miniaturized semiconductor lasers beyond the diffraction limit [1,2,3]. Rather than the fundamental guided mode which is usually the focus in typical FP cavities, we look into the first-order mode in the presence of high-index cladding materials such as semiconductors.
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