Integrated target waveguide devices and optical analytical systems comprising such devices are provided. The target devices include an optical coupler that is optically coupled to an integrated waveguide and that is configured to receive optical input from an optical source through free space, particularly through a low numerical aperture interface. The devices and systems are useful in the analysis of highly multiplexed optical reactions in large numbers at high densities, including biochemical reactions, such as nucleic acid sequencing reactions. The devices provide for the efficient and reliable coupling of optical excitation energy from an optical source to the optical reactions. Optical signals emitted from the reactions can thus be measured with high sensitivity and discrimination. The devices and systems are well suited for miniaturization and high throughput.