Optimizing semiconductor optical amplifier Mach–Zehnder interferometer-based NOT logic gate at 80 Gb/s using continuous wave probe signal

The all-optical NOT gate is a fundamental building block for ultra-high-speed photonic computing. We demonstrate that the waveform of an auxiliary probe injected into the interferometer’s middle port critically determines NOT gate performance at 80 Gb/s in semiconductor optical amplifier-based Mach-Zehnder interferometer (SOA-MZI) configurations. Three configurations are compared—no probe (baseline), additional clock (pulsed), and continuous wave (CW) probe. Baseline quality factor (QF) = 5.75 (below threshold). Additional clock yields QF = 6.16 (7% improvement). CW probe achieves QF = 20.92, a 264% improvement over baseline and 240% over additional clock. Both add identical optical power; the sole difference is waveform, yet CW outperforms by 3.4×, revealing that probe waveform is the dominant performance determinant. CW power optimization shows monotonic QF improvement from 7.92 at 1 mW to 20.92 at 10 mW (164% increase). Scalability analysis demonstrates error-free operation from 20 Gb/s (QF = 37.51) to 100 Gb/s (QF = 11.83), with degradation below threshold at 120 Gb/s (QF = 5.46). Noise analysis reveals a critical spontaneous emission factor of N_sp ≈ 7.2, with QF = 20.92 at N_sp = 2 confirming robust performance within commercial SOA ranges (N_sp = 2–5). CW injection fundamentally alters the SOA operating point by maintaining constant stimulated recombination, reducing carrier density modulation from 38% to < 2% and suppressing pattern effects by 78%. CW-assisted probing is a transformative yet simple technique for ultra-high-speed optical logic without exotic materials, with similar improvements anticipated for other photonic logic functions.