A direct method of thermal time constant measurement for lithium tantalate based terahertz pryroelectric detectors

Thermal time constant (τ _th ) is one of the most important parameters of pyroelectric detectors (PEDs). However, unlike other parameters such as voltage responsivity (R _v ), noise equivalent power and specific detectivity (D*), measurement of τ _th of lithium tantalate (LT) based PEDs was seldom reported in literatures. In this work, a convenient direct method for the measurement of τ _th was presented according to theoretical analysis and simulation result. Afterwards, this method was successfully applied to practical measurement of a homemade current mode terahertz (THz) LT based PED, of which τ _th was measured to be about 882 ms. To verify the measured result, τ _th was also calculated from the measured voltage-time curves according to its theoretical expression, which agrees well with the measured one. Compared with indirect measurement of τ _th through frequency response curves of PEDs, the direct method is simpler and more accurate. Furthermore, this method suggested an easy way for the measurement of pyroelectric coefficient of PEDs.