There is provided a high performance optical waveguide type optical modulator with excellent long term reliability, in which contamination of the buffer layer in a forming process of a signal field adjustment region on the buffer layer by a lift-off method or an etching method, is prevented and DC drift thus suppressed. The cap is arranged in operable combination with the housing and includes a movable first member or spring seat and a movable second member or top cap carried by the first member. This invention provides a solution to these problems. 25 micron and is defined as equal to one-half of minimum pitch, with minimum pitch being defined as equal to the smallest distance of a line width plus width of a space immediately adjacent said line on one side of said line between said line and a next adjacent line in a repeated pattern within the array. The thermal switch is switchable between an open position wherein the system circuit is electrically isolated from the power supply and receives no power therefrom and a closed position wherein the system circuit is electrically connected to the power supply and receives power therefrom. The gate layer has atomically smooth major surfaces, and perfectly bonded onto the substrate to bridge a gap between the two semiconductor pockets.