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|Title:||Structural tailoring of nanoporous anodic alumina optical microcavities for enhanced resonant recirculation of light|
|Citation:||Nanoscale, 2018; 10(29):14139-14152|
|Publisher:||Royal Society of Chemistry|
|Cheryl Suwen Law, Siew Yee Lim, Andrew D. Abell, Lluís F. Marsal and Abel Santos|
|Abstract:||A comprehensive study about the structural engineering of high quality nanoporous anodic alumina optical microcavities (NAA-μCVs) fabricated by rationally designed anodisation strategies to enhance the light-confining capabilities of these photonic crystal (PC) structures is presented. Two types of NAA-μCV architectures are produced: (i) GIF-NAA-μCVs composed of a cavity layer featuring straight nanopores that is sandwiched between two gradient-index filters (GIFs) with sinusoidally modulated porosity in depth, and (ii) DBR-NAA-μCVs formed by sandwiching a cavity layer with straight nanopores between two distributed Bragg reflectors (DBRs), in which the porosity is engineered in a stepwise fashion. The geometric features of GIF-NAA-μCVs and DBR-NAA-μCVs are engineered and optimised through a systematic modification of the anodisation parameters (i.e. cavity anodisation time, cavity anodisation current density, anodisation period and number of anodisation pulses, and pore widening time). This methodology enables fine-tuning of the optical properties of GIF-NAA-μCVs and DBR-NAA-μCVs, such as quality factor and position and width of resonance band, to generate NAA-μCVs with unprecedented quality factors (i.e. 170 ± 8 and 206 ± 10 for the first and second order resonance bands – threefold and fourfold quality enhancement as compared to previous studies). Our results demonstrate that an optimal design of the geometric features and the nanoporous architecture of NAA-μCVs can significantly enhance resonant recirculation of light within these PC structures, creating new opportunities to develop ultrasensitive optical platforms, highly selective optical filters, and other photonic devices.|
|Rights:||© The Royal Society of Chemistry 2018|
|Appears in Collections:||Chemical Engineering publications|
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