Abstract

In this paper, it is shown that a suitable choice of the geometrical parameters of a silicon-wire waveguide microracetrack resonator structure can lead to a substantial improvement in the control of coupling coefficients and, hence, the design of ultracompact devices for high-performance channel add-drop filters and all-optical switching applications. On the one hand, some simple theoretical arguments and simulation results indicate that the reduction of the silicon-wire rectangular waveguide cross-section area ($\text{width}\times \text{height}$) is possible, from standard ($450\mathrm{nm}\times 220\mathrm{nm}$) to ($380\mathrm{nm}\times 200\mathrm{nm}$) on both the bus and the resonator waveguides; this action, apart from still guaranteeing a quasi-TE single-mode operation, would provide an effective improvement into scale-of-integration by a 1.30 factor per device volume. On the other hand, it will be shown by a semianalytical method (analytical calculation + numerical simulation) that achieving the waveguide-racetrack optimal coupling condition for a particular application can be reduced to a prime calculation of the main resonator geometrical parameters (bend radius, straight length, air gap and overall coupling length). In particular, the design of high-performance ultracompact waveguide-racetrack resonator structures, with pre-established $Q$ factor ($Q\ge 2000$), free spectral range ($\mathrm{FSR}\ge 15\mathrm{nm}$), full width at half-maximum ($\mathrm{FWHM}\le 5\mathrm{nm}$), finesse ($F\ge 40$) or extinction ratio signals ($\mathrm{ER}\ge 20\mathrm{dB}$) can be systematically obtained with this procedure.

© 2019 Optical Society of America

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