A microelectromechanical system (MEMS) assembly includes at least one emission source; a top wafer having a plurality of side walls and a generally horizontal portion, the horizontal portion having a thickness between a first side and a directly opposed second side, at least one window in the horizontal portion extending between the first and second sides and a transmission membrane across the at least one window; and a bottom wafer having a first portion with a first substantially planar surface, an intermediate surface directly opposed to the first substantially planar surface, a second portion with a second substantially planar surface, the at least one emission source provided on the second substantially planar surface; where the top wafer bonds to the bottom wafer at the intermediate surface and encloses a cavity within the top wafer and the bottom wafer.