Offset frequency stabilization of RF excited waveguide CO2 laser arrays

A close-packed array of waveguide lasers provides an offset frequency which is inherently more stable than that from independent devices, and permits difference frequency tuning based on the tilting of a common resonator mirror. Examples are given for two- and three-channel arrays. Passive stability of the beat frequencies between channels generated by this tuning method is shown to be good, and for two channel arrays was further enhanced by using an electronic stabilization loop. A simple model of the control loop is formulated to express the relationship between the loop parameters and resultant improvement in frequency stability. The model parameters are compared to experimental results through Allan variance measurements. An Allan variance minimum of 20 Hz has been achieved for the two-channel system and areas for further improvements are considered