Fig. 1
From: Parity-time symmetry enabled ultra-efficient nonlinear optical signal processing
Parity-time (PT) symmetry-based manipulation of linewidth and intensity enhancement. a Upper: schematic of the wavelength conversion, where a strong continuous-wave (CW) pump light is applied to convert a high-speed optical data stream carried by a signal wave to an idler wave. Middle and bottom: illustrations of intensity enhancement spectrum of four-wave mixing (FWM) process used for wavelength conversion operation in a single cavity (middle) and linewidth manipulated cavity (bottom) designed for the same signal bandwidth B, respectively. b, c Schematic diagram and energy ladder of the PT-symmetric coupled microresonators, respectively. d Schematic diagram of the intracavity field distribution of signal, pump, and idler wave indicated by blue, green, and red colored shades, respectively. The signal and idler wave pulses in the cavities depict high-speed data-encoded signal and idler waves; in reality, the pulse durations are longer than the cavity roundtrip time