Waveguide Surface Roughness Reduction via Cyclic Oxidation-Etching

The patent applies periodic action by implementing a cyclic oxidation-etching process where oxidation and etching steps are alternately repeated multiple times. Each cycle reduces surface roughness progressively, achieving ultra-low roughness values (Rrms < 1 nm) that would be impossible with a single etching step. This periodic alternation between oxidation (which smooths surfaces) and etching (which defines patterns) resolves the contradiction between precision and complexity.

The conventional single-step etching process is segmented into multiple discrete cycles of oxidation followed by etching. Each cycle is a separate, controllable step that contributes incrementally to the final surface quality. This segmentation allows precise control over surface roughness by adjusting the number of cycles, oxidation time, and etching parameters, thereby achieving high precision without excessive overall complexity.

The patent employs parameter changes by systematically adjusting oxidation temperature, oxidation time, etching power, and etching time across different cycles. By optimizing these parameters, the process achieves ultra-low surface roughness (Rrms < 1 nm) that minimizes light scattering loss. The parameter optimization ensures that each cycle contributes maximally to roughness reduction while minimizing cycle time, thus reducing total manufacturing time despite multiple cycles.

The cyclic oxidation-etching process maintains continuous useful action by ensuring that each cycle immediately follows the previous one without unnecessary interruptions. The oxidation step continuously smooths the surface while the subsequent etching step continuously refines the pattern, creating an unbroken sequence of beneficial actions. This continuity maximizes efficiency and reduces total processing time compared to interrupted or batch-wise approaches.