Atmospheric dispersion management in the mid-IR mode-locked oscillators

The atmospheric dispersion in the mid-infrared transparency windows presents and important albeit frequently neglected factor when developing ultra-short pulsed lasers. We show that it can amount to hundreds of fs^2 in 2-3 micron window with typical laser round-trip path lengths. Using the Cr:ZnS ultrashort-pulsed laser as a test-bed, we demonstrate the atmospheric dispersion influence on a femtosecond and chirped-pulse oscillator performance and show that the humidity fluctuations can be compensated by active dispersion control, greatly improving stability of mid-IR few-optical cycle laser sources. The approach can be readily extended to any ultrafast source in the mid-IR transparency windows.