A coupling apparatus for coupling light from a source to optical or optoelectronic components on a photonic chip (100,500), comprising: the photonic chip (100, 500); an optical coupler (108, 200), wherein the optical coupler comprises: a beam splitter having an input port, a first output port and a second output port, the beam splitter configured to receive an incident beam of light from the source at the input port and output a first beam of light (214,460) with substantially transverse-magnetic polarization from the first output port and output a second beam of light (212,410) with substantially transverse-electric polarization from the second output port; and a first grating coupler (218,452) formed on the chip (100,500), including a first horn section, the first horn section including a first grating with a first plurality of arc-shaped grating lines, wherein the first plurality of arc-shaped grating lines are substantially asymmetric about the longitudinal axis of the first horn section; a second grating coupler (216,402) for coupling light from the source to optical or optoelectronic components formed on the photonic chip (100,500), including a second horn section, the second horn section including a second grating with a second plurality of arc-shaped grating lines, characterized in that a first prism or reflector is positioned to reflect the first beam of light (214,460) onto the first grating coupler (218,452) such that a first plane of incidence of the first beam of light (214,460) is substantially normal to the longitudinal axis of the first horn section (218,452), the direction of TM polarization is within the first plane of incidence, and the first beam of light (214,460) is incident on the first grating at a first non-zero angle with respect to a normal to the plane of the first grating coupler (218,452); a second prism or reflector positioned to reflect the second beam of light (212,410) onto the second grating coupler (216,402) such that a second plane of incidence of the second beam of light (212,410) is substantially parallel to the longitudinal axis of the second horn section, the direction of TE polarization is substantially normal to the second plane of incidence, and the second beam of light (212,410) is incident on the second grating at a second non-zero angle with respect to a normal to the plane of the second grating coupler (216,402). the photonic chip (100, 500); an optical coupler (108, 200), wherein the optical coupler comprises: a beam splitter having an input port, a first output port and a second output port, the beam splitter configured to receive an incident beam of light from the source at the input port and output a first beam of light (214,460) with substantially transverse-magnetic polarization from the first output port and output a second beam of light (212,410) with substantially transverse-electric polarization from the second output port; and a beam splitter having an input port, a first output port and a second output port, the beam splitter configured to receive an incident beam of light from the source at the input port and output a first beam of light (214,460) with substantially transverse-magnetic polarization from the first output port and output a second beam of light (212,410) with substantially transverse-electric polarization from the second output port; and a first grating coupler (218,452) formed on the chip (100,500), including a first horn section, the first horn section including a first grating with a first plurality of arc-shaped grating lines, wherein the first plurality of arc-shaped grating lines are substantially asymmetric about the longitudinal axis of the first horn section; a second grating coupler (216,402) for coupling light from the source to optical or optoelectronic components formed on the photonic chip (100,500), including a second horn section, the second horn section including a second grating with a second plurality of arc-shaped grating lines, characterized in that a first prism or reflector is positioned to reflect the first beam of light (214,460) onto the first grating coupler (218,452) such that a first plane of incidence of the first beam of light (214,460) is substantially normal to the longitudinal axis of the first horn section (218,452), the direction of TM polarization is within the first plane of incidence, and the first beam of light (214,460) is incident on the first grating at a first non-zero angle with respect to a normal to the plane of the first grating coupler (218,452); a second prism or reflector positioned to reflect the second beam of light (212,410) onto the second grating coupler (216,402) such that a second plane of incidence of the second beam of light (212,410) is substantially parallel to the longitudinal axis of the second horn section, the direction of TE polarization is substantially normal to the second plane of incidence, and the second beam of light (212,410) is incident on the second grating at a second non-zero angle with respect to a normal to the plane of the second grating coupler (216,402).