The spectral and amplitude-frequency characteristics of a new pyroelectric detector based on thin tetraaminodiphenyl polycyclic polymer films with a thickness of <1  μm were studied in the electromagnetic radiation ranges of 0.4 to 10 and 300 to 3000  μm and at local wavelengths of 81 and 100  μm, respectively. It is shown that the volt–watt sensitivity of such a detector in the entire range is practically nonselective and is 2 to 10 times higher than the sensitivity of other pyroelectric detectors and the Golay cell. The bandwidth of the proposed pyrodetector was 330 to 500 Hz. The results showed good prospects of these sensors for fast ultrawideband spectroscopy, covering visible, infrared, terahertz, and millimeter wave ranges.