A monolithic Receiver Optical Sub-Assembly (ROSA) device is provided and a method for producing the device. The device comprises: at least one antenna configured to receive optical signals; at least one rectifier configured to rectify electrical signals being electrical representation of the received optical signals and having frequencies within an optical band range; and at least one amplifier, coupled to the rectifier and configured to amplify rectified electrical signals; and wherein the ROSA is also characterized in being a single monolithic device.