Nonreciprocal light transport is of great importance due to its potential applications in optical communication. We investigate theoretically the unidirectional reflectionlessness behaviors of single photons in a waveguide system coupled with whispering-gallery-mode microresonators. Numerical results show that multi-band unidirectional reflectionlessness can be effectively implemented at the exceptional points by adjusting asymmetric intermode backscatterings of the coupled resonators, and reflectionless frequency-band number increased by multiplication with coupled resonators is also predicted. This suggests a novel multi-band device to effectively perform single-photon unidirectional reflectionlessness, which provides possible applications in quantum communication for designing high-efficiency optical filters, diodes, and so on.

不可逆的光传输由于其在光通信中的潜在应用而非常重要。我们在理论上研究了与耳语画廊模式微谐振器耦合的波导系统中单光子的单向无反射行为。数值结果表明，通过调节耦合谐振器的非对称模间反向散射，可以在异常点处有效地实现多频带单向无反射，并且还预测了通过与耦合谐振器相乘而增加的无反射频带数。这表明一种新颖的多频带器件可以有效地实现单光子单向无反射，这为量子通信中设计高效光学滤波器，二极管等提供了可能的应用。