Abstract
Silicon nitride waveguides have emerged as an excellent platform for photonic applications, including nonlinear optical signal processing, owing to their relatively high Kerr nonlinearity, negligible two photon absorption, and wide transparent bandwidth. In this paper, we propose an effective approach using 3D finite element method to optimize the dispersion characteristics of silicon nitride waveguides for four-wave mixing (FWM) applications. Numerical studies show that a flat and low dispersion profile can be achieved in a silicon nitride waveguide with the optimized dimensions. Near-zero dispersion of 1.16 ps/km/nm and 0.97 ps/km/nm at a wavelength of 1550 nm are obtained for plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD) silicon nitride waveguides, respectively. The fabricated micro-ring resonator with the optimized dimensions exhibits near-zero dispersion of −0.04 to −0.1 ps/m/nm over a wavelength range of 130 nm which agrees with the numerical simulation results. FWM results show that near-zero phase mismatch and high conversion efficiencies larger than −12 dB using a low pump power of 0.5 W in a 13-cm long silicon nitride waveguide are achieved.
Highlights
Accepted: 10 May 2021With the rapid development of the modern optical communication, the technology of integrated photonic devices is continuously developing
Due to the different deposition temperature and gas ratio, there is a relatively large difference between refractive indices of silicon nitride films prepared by plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD) [21,22]
If the dispersion is optimized for TM mode in silicon matching for four-wave mixing (FWM), in which the thickness is in the range of 700 nm to 800 nm and the nitride waveguide, a larger waveguide thickness (>1 μm) will be required because of the width is in the range of 1100 nm to between
Summary
With the rapid development of the modern optical communication, the technology of integrated photonic devices is continuously developing. Four-wave mixing (FWM), as an important third-order nonlinear optical process, can be used for wavelength conversion and optical signal processing in integrated waveguides, and has received intense investigations on different platform [1]. Near-zero dispersion over a wavelength range is required to achieve phase matching for high FWM conversion efficiencies [18,19]. Note that other third-order nonlinear applications, such as optical frequency combs, broadband supercontinuum generation, self-phase modulation, and cross-phase modulation require dispersion engineering for phase matching. Both the material dispersion and waveguide dispersion contribute to the total dispersion. FWM results show that the optimized silicon nitride waveguide exhibits a high conversion efficiency larger than −12 dB
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