Liu Jiaxi, Ru Guangzhe, Jiang Xunya
Opt Express. 2019 Oct 28;27(22):32823-32834. doi: 10.1364/OE.27.032823.
We investigate the beam propagation behavior in the photonic crystal (PhC) of the local super-collimation (LSC) regions both theoretically and numerically. A theory based on the cubic dispersion model in the LSC regions is established, which is a powerful tool to predict the beam evolution after a long propagation distance. The numerical experiments are also implemented, whose results agree well with those from our theory. Both the theoretical and simulation results show the new phenomenon of the asymmetric beam broadening for beams in the LSC regions, which is quite different from the traditional symmetric broadening. Physical reasons of such asymmetric broadening are explained by the cubic dispersion model and the solution to suppress the asymmetric broadening is proposed. Since the LSC beams could be widely used in photonic devices, such as hypersensitive spectrometers and demultiplexers, the deep insights of the beam propagation behavior in the LSC regions can help us to optimize our designs, such as choosing the proper beam width and the proper working range in the phase space.
我们从理论和数值两方面研究了光子晶体（PhC）中局部超准直（LSC）区域的光束传播行为。建立了基于LSC区域三次方色散模型的理论，这是预测光束在长传播距离后演化的有力工具。同时进行了数值实验，其结果与我们的理论结果吻合良好。理论和模拟结果均表明，LSC区域光束存在不对称光束展宽的新现象，这与传统的对称展宽有很大不同。利用三次方色散模型解释了这种不对称展宽的物理原因，并提出了抑制不对称展宽的解决方案。由于LSC光束可广泛应用于光子器件，如高灵敏度光谱仪和解复用器，深入了解LSC区域的光束传播行为有助于我们优化设计，如在相空间中选择合适的光束宽度和合适的工作范围。
