Fast and sensitive bolometric terahertz detection at room temperature through thermomechanical transduction

Abstract

Terahertz (THz) electromagnetic spectrum draws wide attention for nondestructive and/or biocompatible sensing. In order to be widely applicable to the THz sensing, it is of prime importance to develop THz sensors that can be operated at room temperature and have high sensitivity and fast operation speed. However, conventional room-temperature THz thermal sensors fall short of expectations in these characteristics required in various applications of THz sensing, including THz cameras. Utilizing a thermomechanical transduction scheme, we have developed an uncooled, sensitive, and fast THz bolometer by using a doubly clamped GaAs microelectromechanical system (MEMS) beam resonator as a sensitive thermistor. Owing to its ultrahigh temperature sensitivity (the noise equivalent temperature difference of ∼1 μK/√Hz), the present bolometer achieves not only high sensitivity but also an operation bandwidth of several kHz, which is more than 100 times faster than other uncooled THz thermal sensors. The obtained electrical noise equivalent power is as low as ∼90 pW/√Hz, which is close to the limit set by the thermal fluctuation noise. The MEMS bolometers are fabricated by the standard semiconductor fabrication processes and are well suited for making detector arrays for realizing THz cameras.