Frequency and voltage response of Stark-effect modulation of CO2lasers

It is known that useful modulation of CO2laser radiation can be achieved using the Stark effect in molecular gases; however, no report of the frequency- and voltage-response characteristics of modulators using this effect has been available. This paper reports the results of an extensive experimental and theoretical study of such devices. Theoretical evidence that the frequency response of modulation depth is divided by the homogeneous absorption line width (∼ 50 MHz) into a nondispersive low-frequency region and a dispersive high-frequency region is presented. Additionally it is shown that the change in modulation depth with Stark field amplitude is divided into a linear low-field region and a non-linear high-field region. Experimental results demonstrating nondispersive linear modulation at frequencies to 30 MHz are reported.