Abstract
We investigate optical microresonators consisting of either one or two coupled rectangular strips between upper and lower slab waveguides. The cavities are evanescently excited under oblique angles by thin-film guided, in-plane unguided waves supported by one of the slab waveguides. Beyond a specific incidence angle, losses are fully suppressed. The interaction between the guided mode of the cavity-strip and the incoming slab modes leads to resonant behavior for specific incidence angles and gaps. For a single cavity, at resonance, the input power is equally split among each of the four output ports, while for two cavities an add-drop filter can be realized that, at resonance, routes the incoming power completely to the forward drop waveguide via the cavity. For both applications, the strength of the interaction is controlled by the gaps between cavities and waveguides.
Highlights
Optical microresonators are used for many functionalities in integrated optics, e.g. for wavelength modulation, switching, or filtering purposes
We investigate optical microresonators consisting of either one or two coupled rectangular strips between upper and lower slab waveguides
The interaction between the guided mode of the cavity-strip and the incoming slab modes leads to resonant behavior for specific incidence angles and gaps
Summary
Optical microresonators are used for many functionalities in integrated optics, e.g. for wavelength modulation, switching, or filtering purposes Due to their compact size, wide spectral tunability and strong light confinement they gained huge interest. This work takes up our earlier results from [11], where we considered a simpler structure without the upper slab waveguide (two-port system) and only the single cavity case. Such a structure works as a system with a non-radiating bound state (the guided mode of the rectangular cavity) and a wave continuum (guided by the slab). We adopt the waveguide parameters, especially we fix the size of the cavity, for our present studies
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