Hot filament infrared radiators and pyroelectric single-element detectors for analytical application

摘要

The infrared source and detector are essential components of infrared analysers. They basically determine the system's resolution, its size, energy demand and price. This paper describes the schematic set-up and the basic characteristics of radiators and pyroelectric single-element detectors that have been developed for the efficient application in the wavelength range 2...15 μm On the one hand, the infrared sources are housed in a transistor package (TO-39, TO-8), electrical input power <10 watts and, on the other hand, in a glass bulb with a fitted infrared window, electrical input power 15...30 watts. They are based on tungsten filaments. It is shown that the radiators are optimised for high radiation power and a direct modulation capability with a sufficient modulation depth (50%) of up to 30 Hz. Calcium fluoride and zinc selenide were chosen as window materials. In particular for analytical applications, pyroelectric infrared sensors with small responsive elements have been developed, which are characterised by high responsivity, high specific detectivity and an optimised spectral responsivity. As a result, responsivity values S_V of (500 K; 10 Hz; 25 °C; τ_F = 1) ≥ 6,000 VW~(-1) and a specific detectivity D~* (500 K; 10 Hz; 1 Hz; 25 °C) ≥ 4 * 10~8 cm Hz~(1/2)W~(-1) have been obtained for LiTaO_3 sensors with a responsive area of O 0.5 mm.