Currently, optics such as dielectric lenses and curved reflector dishes are commonplace in terahertz laboratories, as their functionality is of fundamental importance to the majority of applications of terahertz waves. However, such optics are typically bulky and require manual assembly and alignment. Here we seek to draw inspiration from the field of digital electronics, which underwent rapid acceleration following the advent of integrated circuits as a replacement for discrete transistors. For a comparable transition with terahertz optics, we must seek mask-oriented fabrication processes that simultaneously etch multiple interconnected integrated optics. To support this goal, terahertz beams are confined to two dimensions within a planar silicon slab, and a gradient-index half-Maxwell fisheye lens serves to launch such a slab-mode beam from a terahertz-range photonic crystal waveguide that is coupled to its focus. Both the optic and the waveguide are implemented with through-hole arrays and are fabricated in the same single-etch process. Experiments indicate that a slab-mode beam is launched with ∼86% efficiency, over a broad 3 dB bandwidth from ∼260 to ∼390 GHz, although these reported values are approximate due to obfuscation by variation that arises from reflections within the device.