Determination of optical cross sections by the measurement of saturation flux using laser-pumped laser oscillators

A new method is reported which measures transition cross sections independent of active atom concentration and extrinsic loss using a laser-pumped cw laser oscillator. Extrapolation of the linear input-output characteristic of a cw oscillator to null pumping rate will yield the saturation power from which is determined the saturation flux and laser cross section. For Nd3+ in YAG and YVO4 the measured saturation fluxes were 2.07 and 3.24 kW/cm2, respectively, and the laser cross sections were 3.92 and 7.78 × 10−19 cm2, respectively.