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Waveguide-coupled metal-clad cavity with integrated feedback stub
摘要： We propose a wavelength-scale metal-clad III–V semiconductor cavity coupled to silicon-on-insulator (SOI) waveguide with integrated feedback stub for external tuning of the Q factor. We consider a typical wavelength-scale metal-clad InP/InGaAs cavity integrated on a SOI waveguide and demonstrate more than 5-fold Q-factor improvement in agreement with that predicted by the coupled-mode theory. From additional thermal analysis, we prove that improved heat dissipation can be realized by engineering the layer thicknesses without sacrificing much of the optical performance.
关键词： metal-clad cavity,waveguide-coupled,thermal analysis,feedback stub,Q-factor tuning
更新于2025-09-12 10:27:22
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Folded chaotic whispering-gallery modes in nonconvex, waveguide-coupled planar optical microresonators
摘要： Chaotic whispering-gallery modes have significance both for optical applications and for our understanding of the interplay between wave phenomena and the classical ray limit in the presence of chaotic dynamics and openness. In strongly nonconvex geometries, a theorem by Mather rules out the existence of invariant curves in phase space corresponding to rays circulating in whispering-gallery patterns, so that no corresponding modes of this type are expected. Here, we discuss numerical computations of the electromagnetic fields in planar dielectric cavities that are strongly nonconvex because they are coupled to waveguides. We find a family of special states which retains many features of the chaotic whispering-gallery modes known from convex shapes: An intensity pattern corresponding to near-grazing incidence along extended parts of the boundary, and comparatively high-cavity Q factors. The modes are folded into a figure-eight pattern, so overlap with the boundary is reduced in the region of self-intersection. The modes combine the phenomenology of chaotic whispering-gallery modes with an important technological advantage: The ability to directly attach waveguides without spoiling the Q factor of the folded mode. Using both a boundary-integral method and the finite-difference time-domain technique, we explore the dependence of the phenomenon on wavelength in relation to cavity size, refractive-index contrast to the surrounding medium, and the degree of shape deformation. A feature that distinguishes folded from regular whispering-gallery modes is that a given shape will support high-Q folded chaotic whispering-gallery modes only in certain wavelength windows.
关键词： chaotic whispering-gallery modes,finite-difference time-domain technique,nonconvex geometries,waveguide-coupled planar optical microresonators,boundary-integral method
更新于2025-09-12 10:27:22
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Surface Plasmon Field-Enhanced Raman Scattering Based on Evanescent Field Excitation of Waveguide-Coupled Surface Plasmon Resonance Configuration
摘要： We propose a bimetallic waveguide-coupled surface plasmon resonance (WCSPR) configuration to enhance Raman scattering with an evanescent field excited using surface plasmons. The WCSPR configuration is a five-phase Kretschmann resonance setup composed of a K9 prism/inner Ag film/MgF2 film/outer Ag film/water structure. Incident angle-dependent SERS spectra were measured in the evanescent field on this WCSPR configuration using an in-house-built angle-dependent SPR-SERS microspectrometer. The SERS signal obtained under evanescent field excitation at the SPR angle was 20× higher than that collected using the conventional SPR configuration. The experimental results also proved that the waveguide-coupled surface plasmons in this evanescent field-enhanced SERS spectroscopy setup had electric field penetration depth of at least 500 nm, which is longer than the penetration depth for conventional surface plasmons. High quality SERS signals can still be obtained after adding a 500nm MgF2 film to the WCSPR configuration due to the deeper penetration depth. This advantage makes it possible to use Ag with a stronger electric field enhancement capability instead of an inert noble metal such as Au in the experiment without worrying about the oxidation of Ag. The enhancement factor of this WCSPR configuration was 6.2×107. The lowest detectable concentration for the SERS signal of 4- mercaptopyridine reaching to 1.0 ×10?10 M using the WCSPR configuration. The WCSPR configuration has great potential for label-free sensing and detections of macromolecules and biomolecules.
关键词： SERS,Evanescent Field,Surface Plasmon Resonance,Waveguide-Coupled,Raman Scattering
更新于2025-09-11 14:15:04
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Theoretical and Experimental Investigation of an All-Fiber Waveguide Coupled Surface Plasmon Resonance Sensor With Au–ZnO–Au Sandwich Structure
摘要： In this paper, we proposed an all-fiber waveguide coupled surface Plasmon resonance (SPR) sensor which was designed and fabricated with Au-ZnO-Au sandwich multi-layer structure. Based on the transfer matrix method (TMM), the theoretical modeling of the proposed sensor structure was investigated. The influence of the layer thickness on the transmission spectrum of the sensor was studied numerically, in order to optimize each layer thickness, leading to sensitivity enhancement in the infrared spectral range. Meanwhile, an experimental testbed for the refractive index measurement was implemented based on the proposed all-fiber waveguide coupled SPR sensor. Using this waveguide coupled SPR sensor, the refractive index sensing was realized with a sensitivity enhancement of 7%—131% compared with conventional SPR sensors.
关键词： refractive index sensing,optical fiber,Surface plasmon resonance,waveguide coupled,sensitivity
更新于2025-09-11 14:15:04