Nonlinear Nitrogen‐Doped Carbon‐Based All‐Optical Switch and Wavelength Converter in Mid‐Infrared Region

Abstract Exploring all‐optical devices built upon new nanomaterials and moving toward all optical signal processing has been attracted ever‐growing interest. Nitrogen‐doped carbon shows tremendous application potential in nonlinear optics due to its excellent and stable optoelectronic characteristics. Due to the reduction in scattering intensity as increasing optical wavelength, the midinfrared 2 µm band is less affected by atmospheric scattering. This study presents an experimental demonstration of a 2 µm optical Kerr switch on a microfiber, designed using nonlinear nitrogen‐doped carbon nanospheres (NCN), and combined with a highly nonlinear fiber (HNLF) to achieve cascaded four‐wave mixing (FWM) phenomena. Experimental results show that the Kerr switch exhibits an extinction ratio of approximately 12.5 dB under appropriate pump light application, indicating effective signal light control. Moreover, the maximum conversion efficiency of the first‐order cascaded FWM reaches −20.08 dB, and the second‐order efficiency reaches −39.3 dB, with a maximum wavelength spacing of 18 nm. This represents the first investigation of optical Kerr switching and cascaded FWM in the 2 µm wavelength range. This study provides new insights and approaches for developing optical signal processing technology and lays the foundation for future high‐performance photonic devices in this wavelength range.