We propose a novel plasmonic waveguide structure, which is referred to as a circular hybrid plasmonic waveguide (HPW) and consists of a metal wire covered with low- and high-index dielectric layers. The circular HPW exhibits two distinctly different modes, namely, the strongly localized mode and the extremely low-loss mode. Our numerical calculation demonstrates that the strongly localized mode exhibits 10-4 order scale in normalized mode area and can be performed even in tens of nanometer sizes of waveguide geometry. In the extremely low-loss mode, the HPW exhibits ultra-long propagation distance of more than 103μm that can be achieved by forming the dipole-like hybrid mode and properly adjusting the radius of the metal wire. It is also shown that, even with this long-range propagation, the mode area of the dipole-like hybrid mode can be maintained at subwavelength scale. The simultaneous achievement of a small mode area and ultra-long propagation distance contributes to the ultra-high propagation distance to mode size ratio of the waveguide. The HPW results are very helpful for plasmonic device applications in the fields of low-threshold nanolasers, ultrafast modulators, and optical switches.
We propose a high-performance, graphene-based optical modulator with a surface plasmon resonance (SPR) at 1550 nm. In the proposed device, a graphene layer is embedded in a hybrid plasmonic waveguide to enhance the light-graphene interaction. The adjustment of the permittivity of the graphene causes a significant modulation of the absorption in the SPR through a variation of the field confinement in the graphene layer, in addition to a resonant angle shift. With an optimal thickness of a metal (Ag) film and the properly chosen operation point of the Fermi level of graphene, a modulation depth of ∼100% was achieved. As the number of graphene layers in the proposed device increases, the insertion loss decreases. With five-layer graphene, a 6% insertion loss was achieved.
Objectives
We estimated volume changes in the posterior bony wall of the sphenoid sinus, as well as alterations in nasal function (including olfactory function and subjective symptoms), after sphenoid mucosal repositioning using the endoscopic endonasal transsphenoidal approach (EETSA).
Methods
During 2010 and 2021, 13 patients underwent sphenoid mucosal repositioning during EETSA, while 24 patients (the control group) did not. Pre‐ and postoperative paranasal sinus computed tomography and the Mimics program were used to evaluate three‐dimensional changes in the posterior wall of the sphenoid sinus. All patients underwent the Connecticut Chemosensory Clinical Research Center (CCCRC) test, the Cross‐Cultural Smell Identification Test (CCSIT), Nasal Obstruction Symptoms Evaluation (NOSE), the Sino‐Nasal Outcome Test‐20 (SNOT‐20), and visual analog scale (VAS) evaluation.
Results
The increase in the volume of the posterior wall of the sphenoid sinus after surgery was objectively smaller in the sphenoid mucosal repositioning group than in the control group (P = .046). However, this did not affect olfactory function (as revealed by the CCCRC test or the CCSIT) or subjective symptoms (as revealed by the NOSE, SNOT‐20, and VAS scores) (all P > .05).
Conclusion
Surgical closure via sphenoid mucosal repositioning during EETSA reduces the volume of the posterior wall of the sphenoid sinus and facilitates re‐operation. We suggest that sphenoid mucosal repositioning is appropriate during EETSA.
Level of Evidence
4 Laryngoscope, 132:965–972, 2022
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