A Photonic Transformer Processor: Thermal-Optical Screening with Direct CMOS Detection

We present a photonic Transformer attention processor based on athermal-optical screening architecture with direct CMOS photodetection.Unlike silicon-photonic MZI mesh approaches, our design uses free-spaceoptical paths where light passes through thermo-optic phase shiftersencoding query vectors, is attenuated by electro-optic modulatorsencoding key vectors, and is directly detected by a CMOS Ge-on-Siphotodetector array. Bipolar differential detection provides intrinsiccommon-mode noise rejection. We verify 25 validation items spanningdevice physics, algorithm robustness, thermal-field simulation,electro-optic bandwidth, temperature drift, detector physics, opticallink budget, and full-system Monte Carlo. At D=128, bipolar dot-productSpearman rho=0.9971, and complete Transformer attention achievesrho>=0.995 across all configurations.