Fig. 1: Photonic-heater-in-lightpath: Photon manipulation via the Opto-Thermal-Optic (O-T-O) effect.

a A platform for large-vector processing. Input vectors are wavelength-time (λ-t) encoded and accumulated simultaneously in PHIL. Leaky time integration of multiple control signals (CS) is performed across wavelengths and encoded onto a new optical carrier (probe signal, PS) at a new wavelength. b Control signals (CS, red arrow) which carry the weighted input signals, and probe signals (PS, blue arrow) are coupled to the micro ring resonator (MRR) from both directions. The clockwise and counterclockwise travelling waves produce a standing wave pattern within the ring resonator. c Fabricated photonic integrator: Scanning electron micrograph of titanium nano-heaters on a ring integrator. Absorptive (non-electrical, fully optical) photonic-heater-in-light-path (PHIL) are designed to spatially match the anti-nodes of CS while overlapping with the nodes of PS. 9 nano-heaters are deposited on both left and right side of the ring at a pitch of 308 nm. d Normalized E-field of two antiphase wavelengths at the locations of the PHIL antennas. e Normalised power absorbed per unit area by nano-heaters indicating the presence of lossy and near-lossless wavelengths. f Experimentally measured transmission spectrum of the device (inset) showing periodic lossy and low-loss resonances. The blue line is a Gaussian fit to the grating coupler spectrum, while the red line includes the loss due to the PHIL antennas on ring.