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DIfferential Frequency-domain Absorption Spectrometer in the TErahertz Region (DI-FASTER) for Fast Gas Sensing

We present a differential frequency-domain absorption spectrometer in the terahertz region (DI-FASTER) for fast gas sensing applications. The system is based on an injection-seeded terahertz (THz)-wave parametric generator (is-TPG) driven by a dual-pulse self-frequency-switched microchip laser. Within a single excitation cycle of the laser, the is-Tpggenerates two THz-wave pulses with 11-GHz center frequency separation and 200-μs time interval. These pulses can be directly used to measure differential absorption signals and first-derivative spectra of gas molecules with 50-Hz data acquisition rate.