• Bidirectional pump-controlled SSPP waveguide enables dynamic switching between perfect absorption and perfect transmission.
• Nonlinear varactor diodes and voltage-tuned dispersion engineering achieve degenerate phase matching and three-wave mixing.
• Experimental results show signal gain tunability from −69.50 to +1.04 dB (forward pumping) and −70.49 to +1.45 dB (backward pumping).
• Offers new design paradigms for reconfigurable electromagnetic devices in adaptive energy harvesting and high-speed signal processing.