Abstract: An optical switch mechanism for reflecting an input light beam from an input port to a reflection output port in a first state and for transmitting an input light beam to a transmission output port in a second state is disclosed. The switch mechanism comprises a block made of a light transmissive substrate. The block contains a cavity, which is divided by a light transmissive diaphragm into a reflective portion and a transmissive portion. At the input port a light beam is coupled into the block such that the light beam encounters a reflective surface at an angle greater than a critical angle determined by the refractive indices of the substrate and a reflective fluid retained in the reflective portion of the cavity. When the reflective fluid is in contact with the reflective surface the light beam is totally reflected to a reflection output port.