Refractive index of the gas-discharge medium in a CO2 laser

The alternating component of the refractive index of the gas-discharge medium of a CO₂ laser (λ = 10.6 μ) was determined during the modulation of the discharge current. At a modulation frequency of 0–2 kHz, the alternating component was governed by the periodic expulsion of the neutral gas into a ballast chamber, whereas at frequencies exceeding 2 kHz it was due to variations in the free-electron density.