Highly sensitive coherent detection of terahertz waves at room temperature using a parametric process

We report the experimental results of coherent detection of narrow-linewidth nanosecond terahertz radiation at room temperature using frequency conversion in a nonlinear MgO:LiNbO3 crystal. Mixing the terahertz radiation with a near-infrared intense pump pulse results in the excitation and amplification of the difference-frequency component, which is detected with an InGaAs-based photodiode. We demonstrate this method in a fast and very sensitive terahertz wave detector. The detector is capable of capturing the temporal profile of terahertz pulses with nanosecond resolution, and is at least one order more sensitive than a typical liquid-He-cooled Si bolometer for detecting nanosecond pulsed terahertz wave beams.