Towards efficient broadband parametric conversion in ultra-long Si 3 N 4 waveguides.

Broadband continuous-wave parametric gain and efficient wavelength conversion is an important functionality to bring on-chip. Recently, meter-long silicon nitride waveguides have been utilized to obtain continuous-traveling-wave parametric gain, establishing the great potential of photonic-integrated-circuit-based parametric amplifiers. However, the effect of spiral structure on the performance and achievable bandwidth of such devices have not yet been studied. In this work, we investigate the efficiency-bandwidth performance in up to 2 meter-long waveguides engineered for broadband operation. Moreover, we analyze the conversion efficiency fluctuations that have been observed in meter-long Si ₃ N ₄ waveguides and study the use of temperature control to limit the fluctuations.