A method of forming an optical bench includes forming a reflector layer over a sloping side of a substrate. The method includes depositing a redistribution layer over the substrate. The method includes disposing an under bump metallization (UBM) layer over the redistribution layer. The method includes forming a passivation layer over the redistribution layer and surrounding sidewalls of the UBM layer. The method includes mounting a first optical component over an uppermost portion of the substrate, wherein the reflector layer is configured to reflect an electromagnetic wave from the first optical component, and the first optical component is mounted outside the trench.