光梯度力驱动的纳米硅基光开关

A nano-silicon-photonic switch driven by an optical gradient force

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标,然而,由于硅材料的光学非线性较弱,在硅材料上实现开关的全光控制难以实现.因此本文提出了一种由光梯度力驱动的纳米硅基光开关,实现了硅基光开关的全光控制.该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成,当通入一道控制光时,悬空的微环谐振器在光梯度力的作用下发生弯曲,微环谐振器的谐振波长随之发生变化,从而实现光信号的传输路线发生改变.该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造,实验数据得出其最小消光比为10.67 d B,最大串扰为-11.01 d B,开关时间分别为180 ns和170 ns.该光开关具有尺寸小,响应速度快,低损耗和可拓展等优点,在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.

Using light to dynamically and stably redirect the flow of another beam of light is a long-term goal for photonicintegrated circuits. However, it is challenging to realize a practically all-optical switching device in silicon owing to its weak optical nonlinearity. Major published work on all-optical switches were using single-photon absorption and twophoton absorption, which requires ultrahigh switching energy. This paper presents a nano-silicon-photonic all-optical switch driven by an optical gradient force, in which a fast switching speed with low power consumption is obtained. Each switching element is composed of a waveguide crossing connection and a micro-ring resonator. The ring resonator is side-coupled to a double-etched waveguide crossing, while the micro-ring resonator is partially released from the substrate and becomes free-standing. When the ＂drop＂ port is in ＂OFF＂ state, the wavelength of the signal light from the ＂input＂port does not satisfy the resonant condition in the micro-ring. Therefore, light is mainly transmitted to the ＂thru＂ port without control light. When a control light is loaded to the ＂add＂ port, of which the wavelength satisfies the resonance condition in the micro-ring, a strong optical gradient force is generated by the induced evanescent optical field. The freestanding arc of the ring is then bent down to the substrate, leading to a cavity resonance wavelength shift. As a result, the signal light is diverted to the ＂drop＂ port and the corresponding transmission state is switched to the ＂ON＂state. The optical switch is fabricated by nano-photonic fabrication processes using standard silicon-on-insulator（SOI）wafer. The waveguide structures have a width of 450 nm and a height of 220 nm for a single mode transmission; the outer radius of the ring in the switching element is 15 μm; the coupling gap between the ring and the nano-waveguide is200 nm; the system is fabricated through two-step lithography and plasma dry etching processes while the free-standing arc is released by undercutting the buried oxide layer.A switching time of 180 ns（rise） and 170 ns（fall） is experimentally demonstrated, which is much faster than that of conventional optical switches. The present optical switch can reach a high extinction ratio（10.67 d B） and a low crosstalk（-11.01 d B）. In addition, the proposed switch has the advantages of compact size and low power consumption.Potential applications of this optical switch include photonic integrated circuits, signal processing, and high speed optical communication networks.