Dispersion measurement of inert gases and gas mixtures at 800 nm.

ABSTRACT

Dispersion of femtosecond laser pulses propagating in Ar, He, Kr, N(2), Ne, Xe, and their mixtures is measured by spectrally and spatially resolved interferometry. By varying the gas pressure in a 4.5 m long tube between 0.05 mbar and ambient pressure, the first, second, and third order phase derivatives of broadband laser pulses are determined at 800 nm under standard conditions. The dispersion of gases and gas mixtures obeys the Lorentz-Lorenz formula with an accuracy of 0.7%. Based on the measured pressure dependent dispersion values in the near infrared and the refractive indices available from the literature for the ultraviolet and visible, a pressure dependent Sellmeier-type formula is fitted for each gas. These common form, two-term dispersion equations provide an accuracy between 4.1x10(-9) (Ne) and 4.3x10(-7) (Xe) for the refractive indices, from UV to near IR.