Terahertz Technology
Many products use electromagnetic radiation to improve our everyday lives and commercial products exist for almost every portion of the electromagnetic spectrum (from x-rays to radio waves). However, products that use terahertz (THz) radiation are lacking; even though there are many THz applications such as non-destructive testing, illicit substance detection, high-speed wireless communication, and chemical recognition. The reason for this is a lack of THz technology. Recently significant progress has been made in the development of THz time-domain spectroscopy (TDS) which enables THz fields to be measured in time using femtosecond lasers. TDS has permitted the development of niche commercial THz applications such as pharmaceutical drug encapsulation testing where costs are not critical. However, TDS systems often require an expensive regenerative amplified laser system in order to generate a sufficient THz signal. As a result potential TDS applications are often limited to the laboratory and not economical. In an attempt to address these problems, we recently introduced an amplifier for THz waves based on a THz quantum cascade laser (QCL). Our goal is to perform TDS by amplifying THz waves generated from extremely low-power femtosecond fiber lasers. Furthermore, by locking the QCL frequency to the repetition rate of a femtosecond laser, we demonstrated that the emission from QCLs could be detected coherently in the time domain.