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THz time-domain spectroscopy beyond 4 THz using a sub-picosecond Yb-doped fiber laser system

We performed THz pulse generation and detection beyond 4 THz by using a 1.04-μm Yb-doped fiber laser with a pulse duration of 480 fs. Owing to higher-order nonlinear processes in LiNbO3 crystals, THz pulses can be emitted with a bandwidth extending beyond the excitation pulse limitation. Emitted THz pulses are detected by using a stable sampling pulse that is temporally compressed by an optical fiber.