A configuration of integrated optical superconducting single photon detectors on lithium niobate substrates based on conventional titanium in-diffused waveguides with hybrid waveguide structures for enhancing the detector efficiency is proposed and analyzed. The sensing element in the form of a meander-like superconducting nanowire from niobium nitride is covered with an additional hybrid waveguide from a dielectric material with a higher refractive index than the LiNbO ₃ substrate to increase the light absorption. A special mode converter in the region free from a superconducting nanostructure is used to excite a localized mode with the maximum absorption coefficient that strongly interacts with the superconductive nanostructure. Silicon and titanium dioxide are considered and compared as suitable materials for the hybrid waveguide structures. Silicon based structures give a higher light concentration and, hence, a higher absorption coefficient. However, they are very demanding to the technological accuracy. Titanium dioxide structures potentially can be produced by the standard thin-film deposition technique and contact photolithography. The estimated absorption coefficient of 1.31 dB/μm is four orders of magnitude higher than that for the detectors with a standard titanium in-diffused waveguide, and a high transformation mode efficiency opens a way for fabrication of integrated optical superconducting single photon detectors with the efficiency comparable with other competing material platforms.

中文翻译：

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Ti:LiNbO3 波导上高效集成光学超导单光子探测器的混合波导结构设计

提出并分析了基于具有混合波导结构的传统钛扩散波导在铌酸锂衬底上集成光学超导单光子探测器的配置，以提高探测器效率。由氮化铌制成的曲折状超导纳米线形式的传感元件覆盖有由介电材料制成的额外混合波导，其折射率高于 LiNbO ₃基板以增加光吸收。在没有超导纳米结构的区域中的特殊模式转换器用于激发具有最大吸收系数的局域模式，该模式与超导纳米结构强烈相互作用。硅和二氧化钛被认为和比较作为混合波导结构的合适材料。硅基结构提供更高的光集中度，因此具有更高的吸收系数。但是，它们对技术精度的要求非常高。二氧化钛结构有可能通过标准薄膜沉积技术和接触光刻法生产。估计的吸收系数为 1.31 dB/μm，比具有标准钛扩散波导的探测器的吸收系数高四个数量级，