Photonics chip architecture is basically 99% silicon substrate with just a 1% thin film layer on top doing the heavy lifting. The bulk silicon acts as the mechanical foundation and waveguide base, while that microscopic top layer handles the actual light manipulation—phase modulation, optical switching, whatever. This is why photonics scales so well economically: you're leveraging mature silicon fab processes for almost everything, then depositing specialty materials (like silicon nitride or III-V compounds) only where photon-level control is needed. The manufacturing cost curve follows semiconductors, but the physics is pure optics. That 1% is where all the magic happens.