Abstract
In this report, we investigate a photonic crystal circular-shaped microcavity (removing seven air holes) sustaining whispering-gallery mode (WGM) by shifting the 12 nearest air holes according to the concept of cavity-shaping in micro-disk and micro-gear lasers. The WGM modal characteristics are investigated by three-dimensional (3D) finite-difference time-domain (FDTD) simulations. From well-fabricated devices and simulated results, we obtain and identify WGM single-mode lasing with low threshold and high measured quality factor. By inserting additional waveguides, we also investigate its uniform coupling behaviors in different waveguide-cavity-waveguide geometries in both FDTD simulations and experiments.
Highlights
Over the past two decades, micro-disk lasers with high quality (Q) factor whispering-gallery modes (WGM) have become key components in constructing various optical applications
Because the field distribution of WGM resonance concentrates in the region of cavity-edge, it is very suitable for integration with other optical components by coupling effect in photonic integrated circuits (PICs) on-chip and optical logic applications [1,2,3]
The micro and nanocavities formed by photonic crystal (PC) with photonic band gap (PBG) have successfully overcome above performance degradations and show excellent performances including high Q-factor and low threshold when minimizing the cavity size [4,5,6]
Summary
Over the past two decades, micro-disk lasers with high quality (Q) factor whispering-gallery modes (WGM) have become key components in constructing various optical applications. Several groups have investigated and demonstrated WGM lasing in microcavities formed by various qausiperiodic photonic crystal (QPC) lattices [7,8,9,10]. All of them show WGM single-mode lasing with high Q-factors and low thresholds. This kind of QPC microcavity is difficult to integrate with the present PC-based passive optical system due to its spatial non-periodic lattice structure. It is possible to realize photonic integrated circuits by QPC lattice system, many further investigations are still needed To overcome this difficult situation, one realistic approach is to enhance or welllocalize WGM in PC microcavity by some modifications, for example, the air-hole shifting reported by H. In our previous report [10], we have shown a strong WGM mode dependence on the boundary geometry of 12-fold QPC microcavity (positions of 12 nearest air holes) and this provide us a design direction to enhance WGM in PC microcavity
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