Fabrication and characterization of an L3 nanocavity designed by an iterative machine-learning method

Optical nanocavities formed by defects in a two-dimensional photonic crystal (PC) slab can simultaneously realize a very small modal volume and an ultrahigh quality factor (Q). Therefore, such nanocavities are expected to be useful for the enhancement of light-matter interaction and slowdown of light in devices. In the past, it was difficult to design a PC hole pattern that makes sufficient use of the high degree of structural freedom of this type of optical nanocavity, but very recently, an iterative optimization method based on machine learning was proposed that efficiently explores a wide parameter space. Here, we fabricate and characterize an L3 nanocavity that was designed by using this method and has a theoretical Q value of 29 x 10(6) and a modal volume of 0.7 cubic wavelength in the material. The highest unloaded Q value of the fabricated cavities is 4.3 x 10(6); this value significantly exceeds those reported previously for an L3 cavity, i.e., approximate to 2.1 x 10(6). The experimental result shows that the iterative optimization method based on machine learning is effective in improving cavity Q values

Partially-disordered photonic-crystal thin films for enhanced and robust photovoltaics

We present a general framework for the design of thin-film photovoltaics based on a partially-disordered photonic crystal that has both enhanced absorption for light trapping and reduced sensitivity to the angle and polarization of incident radiation. The absorption characteristics of different lattice structures are investigated as an initial periodic structure is gradually perturbed. We find that an optimal amount of disorder controllably introduced into a multi-lattice photonic crystal causes the characteristic narrow-band, resonant peaks to be broadened resulting in a device with enhanced and robust performance ideal for typical operating conditions of photovoltaic applications.Comment: 5 pages, 4 figure

Vascular Adhesion Protein-1 Blockade Suppresses Ocular Inflammation After Retinal Laser Photocoagulation in Mice

PURPOSE. To investigate the effect of the vascular adhesion protein-1 (VAP-1) inhibitor RTU-1096 on retinal morphologic changes and ocular inflammation after retinal laser photocoagulation in mice. METHODS. C57BL/6JJcl mice were fed a diet containing RTU-1096, a specific inhibitor for VAP-1, or a control diet ad libitum for 7 days. Laser photocoagulation was performed on the peripheral retina of the animals. The semicarbazide sensitive amine oxidase (SSAO) activities in plasma and chorioretinal tissues were measured. Optical coherence tomography (OCT) images were acquired before and at 1, 3, and 7 days after laser photocoagulation, and thickness of the individual retinal layers was measured. Intravitreal leukocyte infiltration was assessed by histologic analysis. The expression level of intercellular adhesion molecule-1 (ICAM-1) in retinal tissues were examined by quantitative real-time PCR. RESULTS. One day after laser photocoagulation, the thickness of the outer nuclear layer (ONL) increased in the laser group compared with in the control group, and RTU-1096 administration abrogated the ONL thickening. Histologic analysis and OCT observation revealed that laser photocoagulation caused infiltration of inflammatory cells and the appearance of hyperreflective foci at the vitreoretinal surface, both of which were suppressed by RTU-1096 administration. In addition, systemic administration of RTU-1096 reduced upregulation of the leukocyte adhesion molecules ICAM-1 in the retina. CONCLUSIONS. The current data indicate that VAP-1/SSAO inhibition may be a potential therapeutic strategy for the prevention of macular edema secondary to scatter laser photocoagulation in patients with ischemic retinal diseases such as diabetic retinopathy

Topological unidirectional guided resonances emerged from interband coupling

Unidirectional guided resonances (UGRs) are optical modes in photonic crystal (PhC) slabs that radiate towards one side without the need for mirrors on the other, represented from a topological perspective by the merged points of paired, single-sided, half-integer topological charges. In this work, we report a mechanism to realize UGRs by tuning the interband coupling effect originating from up-down symmetry breaking. We theoretically demonstrate that a type of polarization singularity, the circular-polarized states (CPs), emerge from trivial polarization fields owing to the hybridization of two unperturbed states. By tuning structural parameters, two half-charges carried by CPs evolve in momentum space and merge to create UGRs. Our findings show that UGRs are ubiquitous in PhC slabs, and can systematically be found from our method, thus paving the way to new possibilities of light manipulation

Origins and conservation of topological polarization defects in resonant photonic-crystal diffraction

We present a continuative definition of topological charge to depict the polarization defects on any resonant diffraction orders in photonic crystal slab regardless they are radiative or evanescent. By using such a generalized definition, we investigate the origins and conservation of integer polarization defects across the whole Brollouin zone. We found that these polarization defects eventually originate from the mode degeneracy that is induced by lattice coupling as a consequence of momentum space folding, or inter-band coupling that can be either Hermitian or Non-hermitian. By counting all types of polarization defects, the total topological charge numbers in a given diffraction order is a conserved quantity across the whole Brillouin zone that is determined by lattice geometry only