  A non-resonant cavity to build up laser intensity is modeled, developed and
tested. It can be used for overlapping multiple lasers of different
wavelengths, increasing their intensities by over an order of magnitude while
maintaining good uniformity. It is simple to set up, has flexible optical
characteristics, and is robust against perturbations. The intensity buildup
requires no resonances, and the wavelength dependence of the performance is
limited only by the mirror coatings. The cavity can be used in applications
requiring a spatially-constrained intensity buildup, for example in atomic and
molecular traps.
