Design and optimization of a highly sensitive clamped optical waveguide cantilever sensor with 3-μm coupling gap and...

Optical waveguide microcantilever (OWC) sensors are attracting increasing attention due to their high integration density. Achieving low coupling loss and high sensitivity at larger lithographic critical dimension (CD) is a key challenge in the development of OWC sensors. This study demonstrates a proof of concept for an improved OWC sensor with a clamped structure, achieving low coupling loss, high sensitivity detection with a 3 μm minimum lithographic CD. Compared with double coupling regions of the traditional OWC sensor, this design reduces coupling loss and enhances optical sensitivity by employing single coupling structure. The improved OWC sensor achieves optical sensitivities of 0.57 μm^-1 in air and 0.43 μm^-1 in water, about 8-fold and 6-fold higher than the traditional OWC sensor, respectively. Furthermore, its deflection noise density (DND) is in air and 29.42fm/Hz in water, about 4-fold and 3-fold improvement compared with the traditional OWC sensor. In a water environment, the deflection interval with optical sensitivity exceeding 0.02μm^-1 is further broadened, indicating a satisfactory tolerance to the initial displacement and a wide dynamic range for sample detection. Furthermore, based on 3D FDTD simulation, the proposed sensor exhibits high optical stability against variations in process accuracy, which is crucial for practical manufacturing.