Near-Field measurement of amplitude and phase in silicon waveguides with liquid cladding

This work demonstrates a technique that allows optical near-field characterization of devices while preserving their optical properties. To do so, a liquid overcladding is introduced to emulate the actual overcladding of the final operational device while allowing the probe to sample the evanescent field at the core cladding interface for analysis by the near-field scanning optical microscopy (NSOM). This technique enables metrology on the actual rather than duplicate device and preserves the dispersion of the optical structures to replicate the designed structure. To our best knowledge this is the only H-NSOM technique allowing characterization of photonic circuits in their final form.