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Conical refraction of optical beams with circular symmetry is often analyzed using Belsky–Khapalyuk–Berry (BKB) theory; however, for beams with noncircular symmetry, it is difficult to obtain analytical expressions for far-field diffraction patterns. We propose a method, based on fast Fourier transform (FFT), for calculating conical refraction of beams with noncircular symmetry and verify it experimentally using a quasi-plane wave passing through a square aperture and focusing lens. Excellent agreement between theoretical and experimental results has been achieved. [ABSTRACT FROM PUBLISHER]

A structure of serially coupled dumbbell microring resonator (SCDMRR) is proposed based on Vernier effects to obtain wider free spectral range (FSR), and a new kind of two-dimensional optical en/decoder is designed taking advantage of the SCDMRR. Numerical simulations are done to analyze reflection spectrum of the SCDMRR and test performance of the proposed en/decoder according to the coupled mode theory. In addition, the coupling coefficients of both ring-bus and ring-ring are optimized to suppress the spurious mode. Furthermore, a comparison is performed between the en/decoder based on SCDMRRs and the en/decoder using ordinarily coupled identical three-order-ring resonators (OCITRR). The results show that the FSR is 13 nm for SCDMRR with the ring radius of 40–30–40 μm, which is about four to five times larger than that of OCITRR. Such FSR will contain more column numbers of parallel-coupled MRR and the code cardinality generated by the proposed device is 3.43E17. For the SCDMRR-based en/decoder, the peak to wing ratio (P/W) of autocorrelation signal and peak power ratio (P/C) between the auto-/cross-correlations are 6.39 and 8.71, which have risen by approximately 33% and 8% against that of en/decoder based on OCITRR, respectively. [ABSTRACT FROM PUBLISHER]