Theory of optical heterodyne detection using the pyroelectric effect

Up to this time, thermal detectors have been limited to a minimum detectable power of 10(-10) W Hz(-(1/2)) at very low frequencies. It is shown theoretically in this paper that by using the pyroelectric effect in a heterodyne detection mode of operation, a factor of 10(7) improvement is possible in the minimum detectable power and that 1-GHz frequencies are attainable with sacrifice in sensitivity. The detector is quantum and temperature noise limited for large local oscillator power. These theoretical limits in the minimum detectable power do not seem to be practically attainable at present. The room temperature pyroelectric detector in the heterodyne mode of operation described in the paper would be very useful for special communication and ir radar applications.