In a laser guided through a fiber, the beam is divergent upon exit. What normally is done is to put the fiber on the focus of a lens in order to achieve a collimated beam. This beam is then guided through focusing optics. The spot of the resulting beam after the focusing optics depends on the focal length of the collimating optics and the focusing optics. What I am trying to achieve is the possibility to have multiple spots without having to physically change the lenses. My idea is to put a beam expander between the collimating and focusing optics, which receives a collimated beam of a certain size and outputs another collimated beam of a larger size, simulating the use of a collimation optics of larger focal length. Such beam expanders are available for purchase
Is this idea feasible or am I forgetting something?