Control of the profile of a laser output beam using an inhomogeneous interferometer

A method is proposed for controlling the intensity distribution over the cross section of a laser beam. In this method the laser exit mirror is an inhomogeneous interferometer whose transmission profile is continuously variable by varying its length over a range of λ / 2. The results are reported of a modification of the profile of an He–Ne laser beam from close to Gaussian to a beam having a dip on the axis, with almost no reduction in the laser output power. It is noted that an inhomogeneous interferometer can be used to control the phase distribution in a beam and to modify the mode structure of the laser radiation.