Abstract
High-Q guided resonance modes in two-dimensional photonic crystals, enable high field intensity in small volumes that can be exploited to realize high performance sensors. We show through simulations and experiments how the Q-factor of guided resonance modes varies with the size of the photonic crystal, and that this variation is due to loss caused by scattering of in-plane propagating modes at the lattice boundary and coupling of incident light to fully guided modes that exist in the homogeneous slab outside the lattice boundary. A photonic crystal with reflecting boundaries, realized by Bragg mirrors with a band gap for in-plane propagating modes, has been designed to suppress these edge effects. The new design represents a way around the fundamental limitation on Q-factors for guided resonances in finite photonic crystals. Results are presented for both simulated and fabricated structures.
Highlights
We show through simulations and experiments how the Q-factor of guided resonance modes varies with the size of the photonic crystal, and that this variation is due to loss caused by scattering of in-plane propagating modes at the lattice boundary and coupling of incident light to fully guided modes that exist in the homogeneous slab outside the lattice boundary
Periodic permittivity induced in a layer of high index material sandwiched between two lower index materials can support a group of optical modes called guided resonance modes [1,2,3,4]
Guided resonance modes are supported in structures with both 1D- and 2D-periodic permittivity in the plane, and are qualitatively well understood by temporal coupled mode theory [12,13]: When incoming light hits the surface of a photonic crystal (PC), it sees a combination of a homogeneous slab and an optical resonator
Summary
Periodic permittivity induced in a layer of high index material sandwiched between two lower index materials can support a group of optical modes called guided resonance modes [1,2,3,4]. If the group velocity is small for all the plane wave components of the beam, incident light will tend not to travel far away from where it enters the slab, but be locally confined and lead to limited edge losses Such approaches are especially useful for high-contrast gratings, where the band diagram of the infinite lattice yields the transmission spectrum for a PC with a limited number of periods in the lattice. Incident light cannot couple to fully guided modes outside the boundaries of the lattice, making the PC work as if it was much larger than its physical size In this way, a fundamental problem with high-Q guided resonance modes in PCs is solved, enabling performance predicted by simulations on infinite structures to be realized in finite structures. We present simulations of our Bragg mirror PC structure, and show how simulated results can be reproduced in fabricated devices
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