A slanted grating coupler for coupling a radiation beam between a waveguide lying substantially in a plane on a substrate and an optical element outside that plane is provided, whereby the slanted grating coupler has a good coupling efficiency for medium or low index contrast material systems. Furthermore, a method for manufacturing the slanted grating coupler is provided. The slanted grating coupler comprises a plurality of slanted slots extending through the waveguide core and being arranged successively in the propagation direction of the waveguide. In at least part of the coupling region, the size of the slanted slots in a lateral direction, being a direction within the waveguide plane and perpendicular to the propagation direction of the waveguide, is smaller than the lateral size of the waveguide core. Successive slots are displaced with respect to each other in the lateral direction. Radiation incident from the waveguide on a slanted slot of the slanted segmented coupler is partly reflected upwards at the interface with air. Part of the radiation is transmitted in between or around the slots and propagates further, until it reaches another slot.