DAST crystal based terahertz generation and recording of time resolved photoacoustic spectra of N2O gas at 0.5 and 1.5 THz bands

• Tunable femto-seconds OPA based efficient THz generation from indigenously grown DAST crystal.
• The efficient THz radiation is generated at 1.3 μm of conversion efficiency (η) of 0.0161%.
• Time resolved PA spectra of N2O is recorded at 0.5 and 1.5 THz bands for the first time.
• Two important rotational lines J = 19 and 58 are theoretically identified for recording of PA spectra.

We report the THz generation using optical rectification process in an indigenously grown organic salt 4-N, N-dimethylamino-4′-N′-methyl-stilbazoliumtoyslate (DAST). A 60 fs, 1 kHz optical parametric amplifier, tunable between 0.8 and 1.6 μm range was employed to generate THz radiation. It is observed that the THz signal is accompanied with weak second harmonic signal of pump wavelength. The conversion efficiency (η) of generated THz is 0.0161%. The radiation generated from DAST crystal is only THz signal, which is confirmed theoretically by choosing the crystal thickness is equivalent to be its optimum coherence length. In addition, we have selected two rotational lines i.e. J = 19, 58 of pure N2O gas by using 0.5 and 1.5 THz band pass filters for recording the time resolved photoacoustic (PA) spectra at 1 atm pressure for the first time.