Experimental evidence of guided-resonances in photonic crystals with aperiodically ordered supercells

Abstract

We report on the first experimental evidence of guided resonances (GRs) in photonic crystal slabs based on aperiodically ordered supercells. Using Ammann-Beenker (quasiperiodic, eightfold symmetric) tiling geometry, we present our study on the fabrication, experimental characterization, and full-wave numerical simulation of two representative structures (with different filling parameters) operating at near-IR wavelengths (1300-1600 nm). Our results show a fairly good agreement between measurements and numerical predictions and pave the way for the development of new strategies (based on, e.g., the lattice symmetry breaking) for GR engineering.© [9] argued that strict periodicity is an essential requirement for the excitation of GRs. However, in some recent studies [10][11][12], we have already demonstrated by numerical analysis that GRs can be excited in PC slabs based on aperiodically ordered supercells, and we have also shown the possibility of controlling the GR excitation by introducing ad hoc point defects [12]. In spite of these first numerical results, to the best of our knowledge, the excitation of GRs in globally aperiodic photonic quasicrystals (PQC) or in PC slabs with aperiodically ordered supercells has never been experimentally observed. Starting from the periodicapproximant case, for which rigorous full-wave numerical modeling [10][11][12] is still computationally affordable, we now report the experimental evidence of GR excitation in PCs with aperiodically ordered supercells.In accordance with our previous papers [10-12], we considered a supercell based on a quasiperiodic (Ammann-Beenker, octagonal) lattice exhibiting eightfold symmetry [13] and containing 97 elements (or a fraction of them), shown in Fig. 1(a).We chose a silicon-on-insulator (SOI) wafer characterized by a top silicon layer with a nominal thickness t ¼ 220 nm, 2 μm of buried oxide, and about 750 μm of bulk silicon for the experimental realization. The PQC parameters were chosen on the basis of the design carried out in [10] but took fabrication constraints into account, e.g., leaving the buried-oxide layer underneath the guiding layer for mechanical support and making holes with a radius larger than 90 nm to guarantee that they are properly etched into the silicon slab. Based on these considerations, as a first attempt for our study, we chose a lattice constant [see Fig. 1(a)] a ¼ 300 nm and a hole radius r ¼ 95 nm, corresponding to a filling parameter r=a ¼ 0:32. Because the focus of this first study is on providing some generic experimental evidence of the GR phenomenon in PQCs, the design parameters were not optimized for a specific application.A schematic of the main steps of the fabrication process is illustrated in Fig. 1(b). The pattern was first 3946OPTICS LETTERS / Vol. 35, No. 23 /

Out-of-Plane Propagation in Photonic Quasi-Crystals: Guided Resonances

“…Starting from the periodic-approximant case, for which rigorous fullwave numerical modeling is still computationally affordable, in this Section we report the experimental evidence 44 of GR excitation in PCs with aperiodically-ordered supercells based on a quasiperiodic (Ammann-Beenker, octagonal) lattice exhibiting eight-fold symmetry 26 and containing 97 elements.…”

Nano- and Micropatterning on Optical Fibers by Bottom-Up Approach: The Importance of Being Ordered

“…Further studies demonstrated the possibility to excite otherwise uncoupled guided resonances via the judicious introduction of symmetry-breaking point-defects [31] as well as the potential for both sensing and telecommunication applications [32]. Following such theoretical and numerical studies, in 2010, Ricciardi et al provided the first experimental evidence of Fano-type guided resonances in aperiodically-ordered photonic quasicrystal slabs (Ammann-Beenker octagonal tiling) as shown in Figure 1c [33,34].…”

Lab-on-fiber technology: a new avenue for optical nanosensors

“…Although the works described in the previous sections led to all-in-fiber devices and can therefore be viewed within the lab-on-fiber concept, their main limitations rely on the impossibility to provide a fiber micro-and nano-structuring as well as a functional material definition at the sub-wavelength scale in a controlled manner. This also prevents the exploitation of many novel and intriguing phenomena that are at the forefront of the scientific optical research, involving light manipulation phenomena and excitations of guided resonances in PCs [146,147] and quasi-crystals [148][149][150][151] as well as combined plasmonic and photonic effects in hybrid metallo-dielectric structures [152]. This means that more sophisticated fabrication strategies and technologies need to be used to create the necessary technological scenario for advanced lab-on-fiber components and devices.…”