  We present a paradigm for integrated photonic devices based upon broadband
slab-confined collimated beams that are launched with half-Maxwell fisheye
lenses. Although it is challenging to match to the low-index focus of the lens
whilst maintaining adequate field confinement for a well-defined point source,
integrated dielectric slot waveguides prove highly suitable, yielding
collimators of 90% efficiency and over one octave bandwidth. Terahertz
technology will benefit from such broadband slab-confined beams to replace
free-space optics, toward compact, mass-producible systems that do not require
manual optical alignment. We present two prototype systems to demonstrate the
versatility of this concept, namely a diagonally-set distributed Bragg
reflector as frequency-division diplexer for terahertz communications, and an
attenuated total reflection-based liquid sensor. Both are enabled by oblique
in-slab reflections that are collected at a location other than the originating
lens, which is not attainable using ordinary single-mode channel waveguides.
