Large cross-section edge-coupled diamond waveguides

A new approach to fabricate large cross-section edge-coupled waveguides on free-standing thin diamond substrates is reported. Combining inkjet printing of photoresist multilayers with photolithographic patterning, both edge and ‘coffee stain’ effects were successfully eliminated, allowing the fabrication of well-defined, millimetre-scale uniform photoresist micro-stripes which extend to the very edge of the diamond substrate. Subsequent transfer of these micro-stripe structures into diamond by inductively coupled plasma (ICP) etching allowed long edge-coupled waveguides in diamond to be made. Guided wave propagation in these diamond waveguides was also confirmed.

Research Highlights
► This work presents a new method to fabricate mm-long edge-coupled diamond waveguides.
► The optimized inkjet printing method applied in the work provides a way to deposit uniform photoresist on small and irregular samples.
► Optical guiding verified the single mode design of large cross-section diamond waveguides.