In membrane photonic integration technologies, grating couplers are widely used to couple light from the photonic circuit and optical fibres. Hereby we present the design of a novel deep etched focusing subwavelength grating with a metallic reflector. This device is optimized for the InP membrane on silicon (IMOS) platform. The simulated
coupling to a fibre efficiency is as high as 76 %, with the fibre tilted 10° from the grating normal. The use of a metal reflector make the performance of the device independent of the underlying layer stack, providing flexibility to the platform.