TERAHERTZ DETECTORS: Quantum dots enable integrated terahertz imager

摘要

A highly sensitive and frequency tunable terahertz detector based on carbon nanotube quantum dots is the main ingredient for a near-field terahertz imaging system in which all components--an aperture, a probe, and a detector--are integrated on one semiconductor chip. Technologies based on terahertz waves are currently in strong demand in many fields including biochemistry, medicine, environmental science, and security. Advantageous properties such as terahertz transmission through objects opaque to visible light are attracting much attention for spectroscopy and imaging applications (see www.laserfocusworld. com/articles/359815 and www.laserfocusworld.com/articles/338739). Terahertz measurements inevitably require a highly sensitive detector to obtain distinct spectra and images. Nevertheless, the photon energy of the terahertz wave, on the order of millielectron volts (meV), is two to three magnitudes lower than that of the visible light, making the development of a high-performance terahertz detector a difficult task. Another problem with terahertz detection is low spatial resolution of terahertz imaging, which results from the longer wavelengths of terahertz radiation compared to that of visible light. Fortunately, the application of nanoscale materials and devices is opening up new opportunities to overcome these difficulties.