Fig. 3

FWM in PT symmetry coupled microresonator. a Optical microscope image of a fabricated PT symmetry coupled dual-microresonators. b Typical transmission spectrum of the PT symmetry structure supporting the high-speed signal operation. In this particular case, \({\gamma }_{c}=289\) GHz, \(g=120\) GHz forming signal and idler resonances with synthetic linewidths of about 40 GHz. c FWM spectrum measured at the output of the bus waveguide by scanning the frequency of the signal light. Colored lines and a black line show the optical spectra when the signal is on resonance and off-resonance, respectively. Colored circles indicate the wavelengths of the signal and the corresponding idler wave. The conversion efficiency is obtained by subtracting the power of the off-resonance signal from the generated idler. The inset shows the zoomed-in spectrum of the generated idler with a black arrow indicating the signal bandwidth. d Analytical (lines) and experimental (circles) conversion efficiency plotted as a function of the signal bandwidth at a pump power of 1 mW