Abstract
A general theoretical analysis is made to determine the variation of bolometer sensitivity with thickness and heat dissipation. To a first approximation it is shown that the best response at a given modulation frequency is obtained by making the bolometer as thin as possible and then by adjusting the dissipation constant so that
where γ is the heat dissipation per unit area per unit temperature difference, a the thickness, c the heat capacity per unit volume, and ω the angular frequency of modulation. Experiments are discussed which show that this analysis is only partially correct because of the variation with thickness of the temperature coefficient of resistance. Measurements are presented of the variation of resistivity and temperature coefficient of resistance with thickness for nickel and bismuth. An interference method was used to determine the thickness. The range studied was from 190A to 760A. An investigation is also made of the variation of γ with frequency for bolometers cooled by conduction. A method is presented for predicting the general frequency response of bolometers with conductive cooling. A brief description is given of a bolometer which was built during the investigation and a comparison is made of this bolometer with several others which have been reported in the literature.© 1947 Optical Society of America
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