Is co-packaged optics made of photoresist Why

Co-packaged optics are not made of photoresist; photoresist is only used during fabrication for lithography, while the main materials are glass, silicon, and silicon nitride.Core MaterialsCo-packaged optics (CPO) integrate optical and electronic components within a single package to reduce electrical path lengths and improve bandwidth and energy efficiency . The primary materials used in CPO include:Glass substrates: Provide a stable platform for optical waveguides and electrical redistribution layers, enabling precise alignment and low-loss optical routing .Silicon and silicon nitride: Used for photonic integrated circuits (PICs) and waveguides, allowing high-density optical interconnects and integration with electronic ICs .Organic or ceramic packaging materials: Sometimes used for mounting optical engine chiplets around ASICs to manage thermal and mechanical constraints .Role of PhotoresistPhotoresist is not a structural material in CPO. Instead, it is used during lithography and microfabrication to pattern features on glass or silicon wafers. For example, a positive-acting MicroSpray™ photoresist can be applied to a glass wafer to define cavities and bonding pads, which are later etched and integrated with optical waveguides . After the lithography step, the photoresist is removed, leaving the functional optical and electrical structures intact.SummaryWhile photoresist is essential in the manufacturing process of co-packaged optics, it does not constitute the final device. The functional CPO package is primarily composed of glass, silicon, and silicon nitride, with photoresist serving only as a temporary patterning tool during fabrication . This distinction is important for understanding both the material properties and the performance characteristics of CPO devices.