Fig. 4. Organic PICs based on printed microstructures.

(A) Microscopy image of a printed microring resonator coupled with a tangentially connected 1D waveguide (top) with two laser-burned termini (marked with red rectangles) for light outcoupling. (Bottom) The resonance modes generated by exciting the microring were collected by the waveguide and guided to the termini. (B) Corresponding spectrum from the laser-burned slot showing the guided ring resonance modes from the directional output in the coupled optical waveguide. (C) Schematic of an as-printed add-drop filter based on the coupling between 1D waveguides and microring resonators. When mixed light signals (white arrow) are inputted from the upper waveguide, the wavelength at resonance (red arrows) is guided into module I, whereas another wavelength goes into module II (blue arrows) on its distinct resonance modes. The signals can thus be distributed into designated ports, and the residual light would pass through the top bus (green arrow). See fig. S12 for details. (D) Microscopy image of coupled resonators obtained by printing two conjugated microrings at a distance of ~500 nm (top). (Bottom) The left ring was partially excited, and the right ring was illuminated through resonator coupling. The output spectrum was collected from the point of joining, indicated with a red square. (E) Corresponding spectrum shows enhancement of modulated resonance modes from the Vernier effect in coupled cavities. (F) Schematic of printed CROWs for optical memory based on programmable printed microring chains. The CROW structure produces a newly generated optical eigenmode (yellow) that can confine photons inside by coupling the resonance modes in each ring. This eigenmode brings isolated states to memorize light signals, similar to energy levels in atom clusters. More eigenmodes at different wavelengths can be obtained from the coupling between vertical ring chains and horizontal ring chains, which are shown in detail in fig. S13.