Hybrid control method of Near-field Scanning Optical Microscope for characterization of optical waveguide devices

초록

In this study, Near-field Scanning Optical Microscope (NSOM) was used for measuring both the surface profile of an optical waveguide device and the evanescent field close to the core-cladding interface. The device has a wider measurement area and a higher step-coverage than typical samples often measured by NSOM. Therefore if the conventional method for controlling the height of NSOM probe is applied, the probe tip may be easily broken during the measurement due to the high step-coverage of the waveguide device and the long measurement time may be taken to prevent the damage of the probe. So, we proposed a hybrid method for controlling the gap distance between the sample surface and the probe tip. The method is the selective combination of the digital with the analog control methods.