Single-mode Dispersion-engineered Nonlinear Integrated Waveguides for Ultra-broadband Optical Amplification and Wavelength Conversion

Four-wave mixing is a nonlinear optical phenomenon that can be utilized for wideband ultra-low-noise optical amplification as well as for wavelength conversion. This has extensively been investigated for various applications such as communications, spectroscopy, metrology, quantum computing and bio-imaging. However, there is a clear desire to implement these functionalities in a small footprint nonlinear platform, being compatible with large volume fabrication and being capable of efficient operation across a large optical bandwidth. Many such platforms, e.g., silicon, aluminum gallium arsenide, silicon nitride, nonlinear glass, etc., have been explored, but suffer from intrinsic significant performance degradation, i.e., gain and bandwidth deduction and distortion, because conventional approaches of nonlinear photonic waveguide geometry construction for dispersion engineering focus on waveguide cross section and result in always being multimode as a byproduct. Here we propose and demonstrate a methodology that utilizes not only the impact of the waveguide cross section on the modal and dispersion behavior of the waveguide but also includes the impact of the waveguide bend for cutting off high-order modes. This approach results in simultaneous single-mode operation and dispersion engineering for very broadband operation of four-wave mixing. While we implemented this in silicon nitride waveguides, which has emerged as a promising platform capable of continuous-wave optical parametric amplification, the design approach can be universally used with other platforms as well. By carefully also considering both second- and fourth-order dispersion we achieve unprecedented amplification bandwidths of approximately 300 nm in silicon nitride nonlinear waveguides of which the losses can be as record-low as 0.6 dB/m. In addition, penalty-free all-optical wavelength conversion of 100 Gbit/s data in a single optical carrier over 200 nm is realized, for the first time, without optical amplification of signal or idler waves. These single-mode hyper-dispersion-engineered nonlinear integrated waveguides can become practical building blocks in versatile nonlinear photonic devices and optical networks.