结合物理光学原理和表面等离子体共振(SPR)角度传感器，提出了可以突破衍射极限的纳米间距检测方法。在理论上建立起纳米间距和位相改变量之间的函数关系，借助于SPR角度传感器的高灵敏性，提出通过检测出射光束振动方向的p分量和s分量的位相差值来实现纳米间距的实时检测。模拟结果显示：纳米间距改变量从-05~05 μm变化时，位相改变量可实现-150°~150°的变化，检测灵敏度＞1 nm。该检测方法能够实现10 nm以下间距的灵敏检测，且具有结构简单，易于操作，实时检测的特点。

An optical method for the nanogap measurement beyond the optical diffraction limit was reported. The function relationship between the nanogap width and the phase difference was built. Based on the high sensitivity of a surface plasmon resonance(SPR) sensor, the nanogap width between a light transmitting mirror and a reflector could be measured by detecting the phase difference between p- and s- polarizations of the light. Numerical simulation shows that the phase difference shifts from 150° to -150° by changing the nanogap width from -05 to 05 μm and the measured sensitivity of nanogap width is better than 1 nm. This nanogap measurement method can realize the measurement for the smallest gap below 10 nm and provides a simple and real-time operation beyond the physical diffraction limit.