Multipole-cancellation mechanism for high-Q cavities in the absence of a complete photonic band gap

Abstract

We describe and demonstrate a new mechanism for low radiation losses in structures lacking a complete band gap, and show how resonant cavities with QϾ10 3 can be achieved without sacrificing strong localization in 3d. This involves a forced cancellation in the lowest-order term͑s͒ of the multipole far-field radiation expansion. We focus on the system of photonic-crystal slabs, one-to two-dimensionally periodic dielectric structures of finite height with vertical index guiding. Simulations and analytical results in 2d and 3d are presented.

Nine Channels Wavelength Division Demultiplexer Based Upon Two Dimensional Photonic Crystal

“…The proposed structure has better quality factor values than in previous works [e.g., 9-14, 21-25]. The reduced rods will result in destructive interference between the low amplitude resonant modes, which contributes to the lower mode cancelation mechanism [26] and, as a result, creates narrow band modes and high Q-factor values. The complete specifications of the proposed demultiplexer are listed in Table 2.…”

Coupled nanopillar waveguides optical properties and applications

“…On the other hand, the spatial radiation loss profile of a mode described in Ref. [24] has a nodal line along the waveguide axis, which means poor coupling to any components coaxial with the waveguide.…”

“…Due to the absence of a complete bandgap, the breaking of translational symmetry inevitably results in radiation losses of the resonator mode, which raises the need for optimizing the Q-factor of the resonator in 1D nanopillar waveguides. There have been some proposals to decrease the losses based on either mode delocalization [23] or on the effect of multipole cancellation [24]. A delocalized mode typically suffers from a decrease of the Q-factor.…”

“…A localized change of the properties introduced in one or several nanopillars would create a point defect, which functions as a resonator [2,24]. The design of such micro-resonators on the scale of a few wavelengths is essential for integrated optics applications.…”

“…Fig. 9 Normalized energy flux of electromagnetic radiation escaping from the resonator into the terminal (solid line) and elsewhere (dashed line) for three nanopillar structures shown in the insets: a W1 with a point defect [24] (left); a W1 with Cantor-like longitudinal geometry (center) and a W3 Cantor-like CNPW (right). Here, dS = 0.5a, dL = 0.81a, r = 0.15a, ∆ = 0.75a and ε = 13.0.…”