CO2-Laser—Beam Absorption by a Dense Plasma

We study the absorption of a ${\mathrm{CO}}_2$-laser beam by an independently produced plasma at approximately the critical density. The measured fractional absorption coefficient agrees with that associated with inverse breamsstrahlung for incident laser intensities below ${10}^{10}$ ${\mathrm{W}/\mathrm{c}\mathrm{m}}^2$. Above this value, an abrupt increase in absorption is observed.