Dielectric slot-coupled half-Maxwell fisheye lens as octave-bandwidth beam expander for terahertz-range applications

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