The optical field in free electron lasers can sometimes develop sidebands and exhibit very complex behavior. The purpose of this report is to develop a two mode model of the optical field in a free electron laser in which the optical modes are coupled by the free electrons in the laser. This model may be used to study the long term stability of the optical wave and the development of sidebands in the optical field. In this report the equations of motion governing the interaction of an electron with the optical modes will be derived. Free electron lasers, Optical wave.