Hard-molded 51 cm long waveguide array with a 150 GHz bandwidth for board-level optical interconnects.

We demonstrated a $51\mathrm{cm}$ long waveguide array on a poly(methyl methacrylate) sheet fabricated by silicon hard-molding technology. To reduce the silicon sidewall roughness, a wet-oxidation followed by a buffered oxidation etchant etching process is adopted, achieving a surface roughness of $1.2\mathrm{nm}$. The waveguide obtained a total insertion loss of $-15.1\mathrm{dB}$ and an adjacent channel cross talk below $-31\mathrm{dB}$. The $3\mathrm{dB}$ optical bandwidth is determined to be $150\mathrm{GHz}$ by the optical autocorrelation method.