Enhanced THz-to-IR emission from gas-surrounded metallic nanostructures by femtosecond laser irradiation

Enhanced terahertz-to-infrared (THz-to-IR) emission from gas-surrounded nanostructured metal films as a result of femtosecond laser irradiation is systematically investigated using selected gases. The dependencies of the THz-to-IR power on the gas species, gas pressure, and pump optical power are studied for Ar, N2, Ne, and He. The experimental results reveal that the power of the THz-to-IR emission is related to the thermal conductivity of the gas in question. Moreover, the THz-to-IR emission power is dramatically enhanced when the gas pressure is close to zero.