We study the nonlinear coupled dynamics of ultra-cold quantum gases trapped in the light field of high Q optical resonators illuminated by a transverse applied laser.  Here the optical potential is a dynamical variable itself determined by the particles positions.  Above a certain threshold illumination intensity the particles order in a regular crystalline structure, where they form ordered periodic patterns with Bragg planes optimally coupling the pump laser into the 

Interestingly such a setup can be directly generalized to include several species of particles simultaenously or a movable mirror or membrane on one side. This allows simultaneous sympathetic multispecies trapping and cooling of any sufficiently polarizable particles. In addition the tailored frequency response of the atomic sample can be used to cool the mirror even for a relatively bad cavity.

 The work was supported by the Austrian Science Fund FWF ( F4013).