Boosting MIR to THz conversion with tight focusing

3D + time numerical simulations of terahertz (THz) generation in two-color femtosecond filament with the optimal phase between the optical harmonics reveal the non-monotonic dependence of the THz energy on the central wavelength of fundamental harmonic pulse. Tight focusing boosts up the conversion efficiency for the MIR pump thus making the THz energy increase monotonically with the wavelength.