High-gain and low-noise optical parametric amplification in PTS slot waveguides (<italic>invited</italic>)

ObjectiveLaser is used as the information carrier in laser communication. With its high bandwidth, large capacity, and strong anti-interference capability, it has become a promising technology for long-distance, high-speed, and high-fidelity communication. However, as the technical requirements for deep-space and transoceanic ultra-long-distance links continue to rise, the received signal suffers severe attenuation due to energy loss and payload constraints, which greatly increases the detection difficulty.MethodsThis work proposes a silicon-based slot waveguide structure utilizing nonlinear four-wave mixing (FWM). By leveraging the localized field enhancement of a p-toluenesulfonic-acid-filled (PTS) slot waveguide, a high-gain and low-noise phase-sensitive optical parametric amplifier (PSA) is achieved. The design is compatible with the silicon (Si) photonic integration platform and avoids performance degradation in the C-band induced by two-photon absorption in silicon.Results and Conclusions The optimized PTS slot waveguide exhibits a small effective mode area and a high nonlinear coefficient exceeding 2000 W−1·m−1 in the C-band, representing an order-of-magnitude improvement over unfilled silicon waveguides. Simulations demonstrate that with a pump power of 300 mW at 1550 nm and a waveguide length of 3 mm, a peak FWM conversion efficiency of approximately 13 dB is achieved. The corresponding phase-sensitive amplification gain exceeds 22 dB over a bandwidth greater than 100 nm within the C-band. Crucially, the noise figure (NF) of the amplifier remains below 0.8 dB across this band, significantly surpassing the 3 dB quantum limit associated with conventional phase-insensitive amplifiers. This low NF is attributed to the inherent phase-sensitive nature of the amplification process, where noise components not satisfying the phase-matching condition are suppressed. The performance metrics, including Gain and NF, compare favorably with other reported PSA implementations based on different waveguide platforms, often achieving higher gain in a shorter device length (Tab.2).ConclusionsThis work successfully demonstrates a high-gain, low-noise phase-sensitive optical parametric amplifier based on a PTS-filled silicon slot waveguide. Through strategic waveguide design and dispersion engineering, a flat anomalous dispersion profile is realized, enabling efficient and broadband four-wave mixing. The integration of the nonlinear organic material PTS not only enhances the nonlinear coefficient but also effectively suppresses two-photon absorption losses inherent to silicon in the communication band. The resulting amplifier achieves a gain over 22 dB and a noise figure below 0.8 dB in the C-band, addressing the critical need for sensitive amplification in long-distance, weak-signal detection scenarios. This study provides a viable and performance-competitive on-chip PSA solution that is fully compatible with silicon photonic integration technology. It offers a valuable reference for implementing advanced optical signal processing functions, such as amplification and wavelength conversion, on a chip, holding significant potential to propel the development of integrated silicon-based optoelectronic systems for next-generation optical communication networks.