Fast modulation of a long-wave infrared laser based on the two-photon absorption of CO2

In this work, we report a long-wave infrared (LWIR) modulator based on the two-photon absorption of CO2 gas. The effect of gas pressure and laser power on the modulation under different wavelengths is discussed. A maximum modulation depth of 21.5% with a rise time (full time) less than 20 ns for a 9.36 μm laser was achieved. The gaseous modulator, which adopts a 2.75 μm laser as the pumping source, is capable of converting the pulse characteristics of the pump light into the modulation of the long-wave infrared light. It demonstrates promising potential for applications in the rapid optical modulation of LWIR lasers.