Pulse Burst Multiwavelength Terahertz-Wave Spectroscopic Measurement Using Parametric Wavelength Conversion

In this study, we developed a multiwavelength spectroscopic measurement system using a pulse burst-pumped injection-seeded terahertz (THz)-wave parametric generator (is-TPG). Real-time spectroscopy using multiwavelength simultaneous generation has been demonstrated; however, the ability to make quantitative measurements with this method has been limited by the gain competition between wavelengths. In this study, we divided the pump beam into multiple paths and created pulse bursts with nanosecond intervals via spatial delays. Quasi-multiwavelength simultaneous generation was achieved by generating different THz wavelengths with each pulse; in principle, this is equal to repetitive single-wavelength generation. The gain competition between multi-wavelengths was suppressed compared to the multiwavelength is-TPG pumped by a single-pump pulse. Pulse-burst pumping improved the “quantitativeness” of real-time spectroscopic measurements using an is-TPG and is expected to expand the scope of THz wave applications.