Abstract In this study, an optical setup for generating terahertz (THz) pulses through a two-color femtosecond laser filament was carefully designed to achieve a precise overlap of two-color laser pulses in space and time. β-barium borate (BBO), α-BBO, and a dual-wavelength plate were used to compensate the phase delay of the two-color lasers. Tilting of α-BBO could further realize the precise spatial overlap of the two beams by counteracting the walk-off effect. The maximum output THz pulse energy reached 21 μJ in argon gas when using a commercial Ti:sapphire laser with a pulse energy of 6 mJ at a 1 kHz repetition rate. The corresponding conversion efficiency exceeded 0.35%. Introduction In the present work, an optical setup for generating THz pulses by femtosecond laser filament was carefully designed to realize a precise overlapping of two-color laser pulses both spatially and temporally. By using a commercial Ti:sapphire laser with a pulse energy of 6 mJ at 1 kHz repetition rate, the maximum output THz pulse energy reached 21 μJ in argon gas. The corresponding conversion efficiency exceeded 0.35%.
Figure 3. Variation of the output THz pulse energy as a function of (a) pumping laser energy in different gases and (b) tilting angle of α-BBO (bottom axis), i.e. the time delay between the fundamental and second harmonic laser beams (upper axis) in argon. In (a): black squares – ambient air, red circles – nitrogen, and blue triangles – argon; solid lines: data fitting curves. (b) black squares: experimental data; red line: numerical simulation results.
Figure 4. (a) Autocorrelation traces and (b) spectra of various energy THz pulses in argon. See the article: https://www.oejournal.org/article/doi/10.29026/oea.2022.210065 |
