A microfabricated sensor includes a first reflector and a second reflector in a sensor cell, separated by a cavity path segment through a sensor cavity in the sensor cell. A signal window is part of the sensor cell. A signal emitter and a signal detector are disposed outside of the sensor cavity. The signal emitter is separated from the first reflector by an emitter path segment which extends through the signal window. The second reflector is separated from the second reflector by a detector path segment which extends through the signal window.