A metal–metal waveguide quantum cascade laser with an abutted silicon hyperhemispherical lens is demonstrated at $\sim 4.1\mathrm{THz}$ . The device produced $145\mathrm{mW}$ of peak pulsed power at $5\mathrm{K}$ with a wall-plug power efficiency of 0.7%, lasing up to a maximum operating temperature of $160\mathrm{K}$ . The far-field beam pattern has a full width at half-maximum value of $\sim 4.8°$ in the H plane. The same device produced $\sim 26\mathrm{mW}$ of peak power using a Winston cone instead of a lens, lasing up to $165\mathrm{K}$ . The large increase in output power is mainly attributed to an increase in collection efficiency.