Laser ablation of parallel optical interconnect waveguides

Excimer laser ablation is presented as an alternative technology to photolithography for the fabrication of board-level parallel optical interconnect waveguides. Arrays of polymer multimode waveguides with a 50×50 μm² cross section on a 125-μm pitch are fully characterized. Root mean square sidewall roughness is 35 nm; no deposition of debris is observed on scanning electron microscope images. The first conclusion out of loss spectrum measurements is a "yellowing effect" of laser ablated waveguides, leading to an increased loss at shorter wavelengths. The second important conclusion is a potential low loss at a wavelength of 850, 980, and 1310 nm. This is verified at 850 nm by cutback measurements on 10-cm-long waveguides showing an average propagation loss of 0.13 dB/cm.