A novel waveguide loop mirror consisting of a 3-dB coupler and a loop waveguide is proposed. This is a useful component for configuring catoptric high-density integrated planar lightwave circuits (PLC). The silica loop mirrors were designed and fabricated using a locally enhanced optical confinement structure to reduce the minimum bend radius of the waveguides. A small sized-helical reflective arrayed-waveguide grating (R-AWG) is also proposed, as an application of the loop mirrors.