Method of production of grating couplers for coupling optical fibers to semiconductor photonic integrated circuits on semiconductor-on-insulator chips, comprising the steps of: a) providing a semiconductor-on-insulator wafer comprising a substrate, a semiconductor-on-insulator layer forming an optical waveguide layer, and an insulator layer being positioned between the substrate and the semiconductor-on-insulator layer, wherein the semiconductor-on-insulator wafer has a front side and a back side, wherein the semiconductor-on-insulator layer is closer to the front side and the substrate is closer to the back side, b) producing coupler grating structures in the semiconductor-on-insulator layer, c) producing integrated optical waveguide structures in the semiconductor-on-insulator layer, wherein the integrated optical waveguide structures are optically connected to the coupler grating structures for guiding light between the coupler grating structures and the integrated optical waveguide structures, d) thinning the semiconductor-on-insulator wafer to membrane thickness from the back side at least in areas opposite to the coupler grating structures such that the back side of said insulator layer of said semiconductor-on-insulator wafer is exposed by means of etching, with the insulator layer of said semiconductor-on-insulator wafer acting as etch stop, such that this etching process stops when the insulator layer of the semiconductor-on-insulator wafer is reached, e) depositing a mirror on the back side of said insulator layer of said semiconductor-on-insulator wafer exposed in step d) from the back side at least in said areas opposite to the coupler grating structures for enhancing the coupling efficiency between the optical fibers and the grating couplers. a) providing a semiconductor-on-insulator wafer comprising a substrate, a semiconductor-on-insulator layer forming an optical waveguide layer, and an insulator layer being positioned between the substrate and the semiconductor-on-insulator layer, wherein the semiconductor-on-insulator wafer has a front side and a back side, wherein the semiconductor-on-insulator layer is closer to the front side and the substrate is closer to the back side, b) producing coupler grating structures in the semiconductor-on-insulator layer, c) producing integrated optical waveguide structures in the semiconductor-on-insulator layer, wherein the integrated optical waveguide structures are optically connected to the coupler grating structures for guiding light between the coupler grating structures and the integrated optical waveguide structures, d) thinning the semiconductor-on-insulator wafer to membrane thickness from the back side at least in areas opposite to the coupler grating structures such that the back side of said insulator layer of said semiconductor-on-insulator wafer is exposed by means of etching, with the insulator layer of said semiconductor-on-insulator wafer acting as etch stop, such that this etching process stops when the insulator layer of the semiconductor-on-insulator wafer is reached, e) depositing a mirror on the back side of said insulator layer of said semiconductor-on-insulator wafer exposed in step d) from the back side at least in said areas opposite to the coupler grating structures for enhancing the coupling efficiency between the optical fibers and the grating couplers.