Power scalable, rectangular, multi-mode, self-imaging, waveguide technologies are used with various combination of large aperture configurations, 20, 50, 80, 322, 324, 326, 328, 330, 332, 334, 336, 338, Gaussian 360 and super-Gaussian 350 beam profiles, thermal management configurations 100, flared 240 and tapered 161 waveguide shapes, axial or zig-zag light propagation paths, diffractive wall couplers 304, 306, 308, 310, 312, 314, 316, 318, 320 and phase controller 200, flexibility 210, phased arrays 450, 490, beam combiners 530, 530, and separators 344, 430, and other features to generate, transport, and deliver high power laser beams.