An optical de-MUX includes a sub-wavelength grating that magnifies an input optical signal. In particular, along a direction perpendicular to a propagation direction of the optical signal, the sub-wavelength grating has a spatially varying effective index of refraction that is larger at a center of the sub-wavelength grating than at an edge of the sub-wavelength grating. Moreover, the optical de-MUX includes an optical device that images and diffracts the optical signal using a reflective geometry, and which provides different diffraction orders to output ports. For example, the optical device may include an echelle grating.