An optical coupler comprises first and second mirrors. The first mirror is positioned with respect to the second mirror so that a resonant cavity is defined between them. A waveguide structure is positioned in the resonant cavity and includes a photonic crystal coupler. A thickness of the resonant cavity is selected so that a phase matching condition is satisfied for resonance in the resonant cavity. At least one of the first and second mirrors may be formed from a structure in an optoelectronic device. Alternatively, at least one of the first and second mirrors is formed from a semiconductor layer. At least one of the first and second mirrors may be formed as a semiconductor distributed bragg reflector, or as a dielectric distributed bragg reflector. At least one of the first and second mirrors may be a mirror in a vertical cavity surface emitting laser (VCSEL) structure. The photonic crystal coupler structure may be shaped so that first order modes of light incident upon the photonic crystal coupler structure are coupled into the waveguide while zero-order modes are reflected out into the resonant cavity and reflected by the mirror.