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

Abstract

The infrared source and detector are essential components of infrared analyzers. 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 micrometers . On the one hand, the infrared sources are housed in a transistor package (TO-39, TO-8), electrical input power less than 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 optimized 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 characterized by high responsivity, high specific detectivity and an optimized spectral responsivity. As a result, responsivity values S<SUB>v</SUB> of (500 K; 10 Hz; 25 degree(s)C; (tau) <SUB>F</SUB> equals 1)&gt;=6,000 VW<SUP>-1</SUP> and a specific detectivity D*(500 K; 10 Hz; 1Hz; 25 degree(s)C)&gt;=4 x 10<SUP>8</SUP> cm Hz<SUP>1/2</SUP>W<SUP>-1</SUP> have been obtained for LiTaO<SUB>3</SUB> sensors with a responsive area of 0.5 mm.