Flexible waveguide probe for silicon-photonics wafer-level test

We extend our flexible probe approach to enable optical coupling into planar lightwave circuits (PLCs) in high-contrast silicon photonic platform. A flexible waveguide is used to form a variable length directional coupler that inserts/extracts light from a waveguide in the wafer to the probe. Varying the length enables optimal coupling to be achieved for a wide range of probe-to-waveguide gap, materials, widths and cladding thicknesses present on a chip. In this paper we consider simulations of two designs for coupling into silicon single mode waveguides, one based on polymer waveguide and another based on silicon waveguides. Polymer coupling into nanowire waveguides allows 75% coupling, whereas silicon probe reaches 95%. The results also indicate that this approach is ideal for characterizing PLC's as the 3dB bandwidth of the probe covers the whole 1300–1700 nm fiber-optic telecommunication range. Challenging coupling length control in the range of 5–50 μm is required.