Xie Shangran, Tani Francesco, Travers John C, Uebel Patrick, Caillaud Celine, Troles Johann, Schmidt Markus A, Russell Philip St J
Opt Lett. 2014 Sep 1;39(17):5216-9. doi: 10.1364/OL.39.005216.
A double-nanospike As2S3-silica hybrid waveguide structure is reported. The structure comprises nanotapers at input and output ends of a step-index waveguide with a subwavelength core (1 μm in diameter), with the aim of increasing the in-coupling and out-coupling efficiency. The design of the input nanospike is numerically optimized to match both the diameter and divergence of the input beam, resulting in efficient excitation of the fundamental mode of the waveguide. The output nanospike is introduced to reduce the output beam divergence and the strong endface Fresnel reflection. The insertion loss of the waveguide is measured to be ∼2 dB at 1550 nm in the case of free-space in-coupling, which is ∼7 dB lower than the previously reported single-nanospike waveguide. By pumping a 3-mm-long waveguide at 1550 nm using a 60-fs fiber laser, an octave-spanning supercontinuum (from 0.8 to beyond 2.5 μm) is generated at 38 pJ input energy.
报道了一种双纳米尖As2S3-二氧化硅混合波导结构。该结构在具有亚波长纤芯（直径1μm）的阶跃折射率波导的输入和输出端包含纳米锥，目的是提高内耦合和外耦合效率。对输入纳米尖的设计进行了数值优化，以匹配输入光束的直径和发散角，从而有效地激发波导的基模。引入输出纳米尖以减小输出光束发散角和端面强菲涅尔反射。在自由空间内耦合的情况下，该波导在1550nm处的插入损耗测量为约2dB，比先前报道的单纳米尖波导低约7dB。通过使用60飞秒光纤激光器在1550nm处泵浦3mm长的波导，在38pJ输入能量下产生了一个倍频程跨度的超连续谱（从0.8到超过2.5μm）。
