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For a one-dimensional (1D) periodic system with inherent mirror symmetry, the value of the geometric "Zak" phase in a bulk band is related to the sign of reflection phase for wavelengths inside the bandgaps sandwiching the bulk band. Here, we designed an interference setup which allows us to measure the reflection phase of 1D phonic crystal fabricated for the optical range; this, in turn, enabled us to determine the Zak phases of the bands. We then found interface states whose existence can be traced to the topological properties of the bandgaps and the geometric phases of the bulk bands.

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We report on the fabrication of double-layer gold crossed-gratings consisting of a convoluted top gold grating superposed on a bottom gold grating by using an e-beam direct write technique together with a lift-off process. The crossed-gratings exhibit, in the visible range, strong circular dichroism which is dependent upon the incident direction due to the convoluted top gold grating and also the substrate. Resonance dips in the transmittance of circularly polarized light are also observed. The experimental results are explained qualitatively by simulations using a finite-integration technique. The simulations confirm that the dips in the transmittance are electromagnetic resonances corresponding to parallel and anti-parallel current flows in the crossed-gratings.

Optical coherence tomography (OCT) is employed in the diagnosis of skin cancer. Particularly, quantitative image features extracted from OCT images might be used as indicators to classify the skin tumors. In the present paper, we investigated intensity-based, texture-based and fractalbased features for automatically classifying the melanomas, basal cell carcinomas and pigment nevi. Generalized estimating equations were used to test for di®erences between the skin tumors. A modi¯ed p value of < 0.001 was considered statistically signi¯cant. Signi¯cant increase of mean and median of intensity and signi¯cant decrease of mean and median of absolute gradient were observed in basal cell carcinomas and pigment nevi as compared with melanomas. Signi¯cant decrease of contrast, entropy and fractal dimension was also observed in basal cell carcinomas and pigment nevi as compared with melanomas. Our results suggest that the selected quantitative image features of OCT images could provide useful information to di®erentiate basal cell carcinomas and pigment nevi from the melanomas. Further research is warranted to determine how this approach may be used to improve the classi¯cation of skin tumors.

OCT is usually employed for the measurement of retinal thickness. However, coherent reflected light carries more information characterizing the optical properties of tissue. Therefore, optical property changes may provide further information regarding cellular layers and early damage in ocular diseases. We investigated the possibility of OCT in detecting changes in the optical backscattered signal from layered retinal structures. OCT images were obtained from diabetic patients without retinopathy (DM, n = 38 eyes) or mild diabetic retinopathy (MDR, n = 43 eyes) and normal healthy subjects (n = 74 eyes). The thickness and reflectivity of various layered structures were assessed using a custom-built algorithm. In addition, we evaluated the usefulness of quantifying the reflectivity of layered structures in the detection of retinal damage. Generalized estimating equations considering within-subject inter-eye relations were used to test for differences between the groups. A modified p value of <0.001 was considered statistically significant. Receiver operating characteristic (ROC) curves were constructed to describe the ability of each parameter to discriminate between the eyes of DM, MDR and healthy eyes. Thickness values of the GCL + IPL and OPL showed a significant decrease in the MDR eyes compared to controls. Significant decreases of total reflectance average values were observed in all layers in the MDR eyes compared with controls. The highest AUROC values estimated for the total reflectance were observed for the GCL+IPL, OPL and OS when comparing MDR eyes with controls. Total reflectance showed a better discriminating power between the MDR eyes and healthy eyes compared to thickness values. Our results suggest that the optical properties of the intraretinal layers may provide useful information to differentiate pathological from healthy eyes. Further research is warranted to determine how this approach may be used to improve diagnosis of early retinal neurodegeneration