Silicon photonic platform, method for forming composite platform and method for forming silicon photonic platform

A silicon photonic platform, comprising:

• a composite substrate comprising a substrate top surface and a first photonic platform layer, the first photonic platform layer comprising a photonic platform material;
• a first signal layer covering the first photonic platform layer, having a top surface, and comprising the photonic platform material and a first signal material, wherein a photonic platform spectral signal of the photonic platform material is different from a first spectral signal of the first signal material;
• and
• a second photonic platform layer having a top surface, at least covering a portion of the top surface of the first signal layer and exposing a portion of the top surface of the first signal layer, and comprising the photonic platform material, wherein the second photonic platform layer comprises at least one ridge structure, and the second photonic platform layer forms the silicon photonic platform together with the first photonic platform layer,
• a third photonic platform layer covering the top surface of the first signal layer and comprising the photonic platform material;
• and
• a second signal layer covering the third photonic platform layer, having a top surface, and comprising the photonic platform material and a second signal material, wherein the photonic platform spectral signal of the photonic platform material is different from a second spectral signal of the second signal material,
• wherein the portion of the top surface of the first signal layer exposed from the second photonic platform layer is lower than the portion of the top surface of the first 20 signal layer covered by the second photonic platform layer.