We report a very simple biosensor based on the direct observation of leaky waveguide (LW) modes as exponentially decaying interference fringes in the reflectivity curve. This phenomenon was only observed when the refractive index contrast between the waveguide and sample was low (0.002-0.005) and the LW was illuminated with a range of angles of incidence simultaneously. The LW acts as a phase object in angle space, resulting in Fresnel diffraction and formation of interference fringes for each waveguide mode. We present theory, a qualitative explanation and a mathematical model governing the formation of these fringes. The binding of an analyte to recognition elements immobilised in the LW changes its refractive index and thus the angular position of the fringes, which provides the biosensing mechanism. The reported LWs comprised a film of polyacrylamide and copolymers on glass slides, and provided high sensitivity, mass manufacturability and simple instrumentation.

我们报告了一个非常简单的生物传感器，基于对泄漏波导（LW）模式的直接观察，反射率曲线中的干涉条纹呈指数衰减。仅当波导和样品之间的折射率对比度较低（0.002-0.005）并且LW同时以一定范围的入射角照明时，才能观察到此现象。LW充当角度空间中的相位对象，导致菲涅耳衍射并形成每种波导模式的干涉条纹。我们提出了理论，定性解释和控制这些条纹形成的数学模型。分析物与固定在LW中的识别元件的结合会改变其折射率，从而改变条纹的角位置，从而提供了生物传感机制。