This article presents compact high-power terahertz quantum-cascade laser systems on a micro-optical bench (mQCL). A lens, evaporated wire-grid polarizer and λ/4 waveplate are all integrated directly onto the quantum cascade laser submount to significantly reduce size, reduce optical feedback effects and perform beam shaping right at the laser. An integrated immersion lens improves outcoupling efficiency for significantly increased output power. Alternatively, an aspherical lens to reduce sensitivity to optical feedback combined with the λ/4 waveplate for optical isolation makes the system better suited for spectroscopy applications.