Absolute Terahertz Power Measurement of Tens of Nanowatts Using a Highly-Sensitive Calorimeter at Room Temperature

This study demonstrates a quantitative measurement of absolute terahertz power of tens of nanowatts at room temperature. A highly sensitive calorimetric measurement system is constructed using an extremely low noise amplifier and multilayer thermal insulation jackets. A vacuum insulator is used to mitigate thermal disturbance; therefore, very stable measurements are realized at room temperature. As a result, the absolute power of 26.7 nW is measured at 1 THz with the relative expanded uncertainty of 4.2% (k=2).