Wang Hailong, Fu Zhongxing, Ni Zhihao, Zhang Xiong, Zhao Chunliu, Jin Shangzhong, Jing Jietai
Opt Express. 2021 Mar 29;29(7):11194-11206. doi: 10.1364/OE.421217.
A nonlinear interferometer can be constructed by replacing the beam splitter in the Mach-Zehnder interferometer with four-wave mixing (FWM) process. Meanwhile, the conventional surface plasmon resonance (SPR) sensors can be extensively used to infer the information of refractive index of the sample to be measured via either angle demodulation technique or intensity demodulation technique. Combined with a single FWM process, a quantum SPR sensor has been realized, whose noise floor is reduced below standard quantum limit with sensitivity unobtainable with classical SPR sensor. Therefore, in this work we have theoretically proposed a nonlinear interferometric SPR sensor, in which a conventional SPR sensor is placed inside nonlinear interferometer, which is called as I-type nonlinear interferometric SPR sensor. We demonstrate that near resonance angle I-type nonlinear interferometric SPR sensor has the following advantages: its degree of intensity-difference squeezing, estimation precision ratio, and signal-noise-ratio are improved by the factors of 4.6 dB, 2.3 dB, and 4.6 dB respectively than that obtained with a quantum SPR sensor based on a single FWM process. In addition, the theoretical principle of this work can also be expanded to other types of sensing, such as bending, pressure, and temperature sensors based on a nonlinear interferometer.
通过用四波混频（FWM）过程取代马赫-曾德尔干涉仪中的分束器，可以构建一个非线性干涉仪。同时，传统的表面等离子体共振（SPR）传感器可以广泛用于通过角度解调技术或强度解调技术来推断待测样品的折射率信息。结合单个FWM过程，已经实现了一种量子SPR传感器，其噪声本底降低到标准量子极限以下，具有传统SPR传感器无法获得的灵敏度。因此，在这项工作中，我们从理论上提出了一种非线性干涉式SPR传感器，其中将传统的SPR传感器放置在非线性干涉仪内部，这被称为I型非线性干涉式SPR传感器。我们证明，在接近共振角时，I型非线性干涉式SPR传感器具有以下优点：其强度差压缩度、估计精度比和信噪比分别比基于单个FWM过程的量子SPR传感器提高了4.6 dB、2.3 dB和4.6 dB。此外，这项工作的理论原理还可以扩展到其他类型的传感，例如基于非线性干涉仪的弯曲、压力和温度传感器。
