Pyroelectric single-element detectors for special applications

Abstract

This paper describes the set-up and the essential features of pyroelectric single-element detectors on the basis of lithium tantalate (LiTaO3). They have been developed for special applications in pyrometry, analytics and security techniques and are optimized for a maximum possible signal-to-noise ratio. Important detector characteristics (responsivity, specific detectivity) and of disturbances (acceleration sensitivity) as a function of the chopper frequency and the detector layout can be theoretically calculated on the basis of various mathematical and physical models. The latter take particular account of the thermal, electric, mechanical and optical conditions in the sensor. It is shown that the specific detectivity of the components can be essentially increased by using selected components (low-noise SFET, inert gas) for the detector and by applying various technologies for the manufacturing of the responsive element for certain chopper frequencies. For example, a specific detectivity of D* (500 K; 10 Hz; 1 Hz; τF = 1) ≥ 1.5 x 109 cmHz1/2W-1 has been obtained for LiTaO3 detectors with a responsive area of [3x3] mm2. Moreover, the acceleration sensitivity could be reduced by choosing special chip and detector layouts. As a result, this paper confirms a good correspondence between the measured and calculated values of the detector characteristics. This paper also presents innovative detector designs (integrated optics, three-dimensionally structured LiTaO3 chips) and their basic properties.