Asymmetric light transmission in PT-Symmetric microring resonators
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We propose a new type of add-drop microring resonator made of gain and loss materials. Microring resonators are compact, narrow band, and optical channel dropping filters. In such linear systems, light transmission to side-coupled signal waveguides is always symmetric. However, we prove that properly arranging a gain and loss modulation in the microring resonator provides a new functionality: asymmetric transmission; so that different resonant modes can be promoted depending on the input channel. This can be achieved when the resonator holds parity-time (PT-) symmetry, with periodic gain-loss and index modulations. PT-symmetry in optics generally requires that the index and gain-loss modulations are dephased by a quarter of the wavenumber of the modulation. Besides, we show that a simple half-gain half-loss microring also produces analogous results to a periodic PT-symmetric system. The results are numerically proved and also accounted by a simple analytical model. The effect of using complex modulated resonators with smaller periodicities is also analyzed.
CitationGiden, I., Dadashi, K., Botey, M., Herrero, R., Staliunas, K., Kurt, Hamza. Asymmetric light transmission in PT-Symmetric microring resonators. "IEEE journal on selected topics in quantum electronics", 15 Març 2016, vol. 22, núm. 5.