Guided mode resonance device for optical beam tapping and imaging without rainbows

Optical apparatus comprising:

• an optical waveguide;
• a diffraction grating disposed in proximity to the optical waveguide such that incident light on the diffraction grating can also diffractively couple to the optical waveguide;
• wherein a first diffraction process is non-resonant diffraction of the incident light by the diffraction grating without coupling to the optical waveguide;
• wherein a second diffraction process is resonant diffraction of the incident light via 1) diffractive coupling of the incident light to a guided mode of the optical waveguide to provide guided light, followed by 2) additional diffraction of the guided light into diffracted radiation;
• wherein an efficiency of the second diffraction process is substantially larger than any efficiency of the first diffraction process at a predetermined incidence angle and frequency of the incident light.