The mid-IR laser power was measured in the reflecting direction of dichroic mirror. A coated sapphire long-pass filter was also used before the power meter.

The incident pump power was measured before lense that couplign the pump light into the fiber and corrected by the lens and gas window transmssmions only. It represented the pump power reaching the end of hollow core fiber.

The absorbed pump power was calculated by comparing the residual pump powers passing the dichroic mirrors in on and off resonance conditions. This number was also corrected by the calculation of 3 µm laser transmitting through the dichroic mirror with pump light.  

A thermal power meter (Ophir, Vega P/N 7Z01560) was used to measure both pump and mid-IR laser powers.