A precision, double prism attenuator for CO2 lasers, calibrated by its gap capacitance, was constructed to evaluate its possible use as a standard for attenuation measurements. It was found that the accuracy was about 0.1 dB with a dynamic range of about 40 dB.
T. Oseki and S. Saito, "A Precision Variable, Double Prism Attenuator for CO2 Lasers," Appl. Opt. 10, 144-149 (1971)