Complex sentence: Although most details of the Excalibur concept remain classified, articles in "Nature" and "Reviews of Modern Physics" along with those in optics-related journals contain broad outlines of the underlying concepts and outline possible ways to build an Excalibur system.
Split into simpler sentences: Although most details of the Excalibur concept remain classified, it is possible to discuss the general concepts and physics behind the system. Articles in "Nature" and "Reviews of Modern Physics" along with various optics-related journals contain broad outlines of the underlying concepts and outline possible ways to build an Excalibur system.