Semiconductor lasers with ultra-low thresholds and minimal footprints are of great interest. For high-reflectivity-coated ridge-lasers, a low threshold can only be achieved by suppressing the diffraction losses arising at laser facets. We show that, counter-intuitively, opening a carefully designed aperture in a metallic facet coating can simultaneously enhance both its transmission and modal reflectivity by phase-front correction at subwavelength scale. Simulations and experimental results demonstrate a reduction of optical mirror loss by 40% while the transmission is increased by four orders of magnitude. Applying this approach to both facets of a short-cavity quantum cascade laser, we achieve laser operation at room temperature with an electrical dissipation of only 143 mW.