LTOI Wafe--Efficient and tunable frequency conversion using periodically poled thin-film lithium tantalate nanowaveguides

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Efficient and Tunable Frequency Conversion via Periodically Poled Thin-Film Lithium Tantalate Nanowaveguides.pdf

The paper "Efficient and Tunable Frequency Conversion Using Periodically Poled Thin-Film Lithium Tantalate Nanowaveguides" discusses the development of an ultralow-loss photonic platform based on periodically poled thin-film lithium tantalate (TFLT) nanowaveguides, aimed at achieving high-performance frequency conversion. The authors demonstrate the first functional second-harmonic generator (SHG) utilizing a z-cut TFLT waveguide. By performing quasi-phase matching (QPM) between telecom (1550 nm) and near-visible (775 nm) wavelengths, they achieve strong second-harmonic generation with a normalized efficiency of 229%/W/cm² and a maximum absolute conversion efficiency of 5.5% at a pump power of 700mW. The SHG process is also found to exhibit stable temperature tunability (-0.44 nm/°C), which is crucial for applications such as atomic clocks and quantum frequency conversion.

Key highlights of the study include:

1. Device Design and Fabrication: The TFLT waveguide is designed with a fixed width of 1 µm and a thickness of 600 nm. The poling period is optimized for efficient QPM, and the fabrication process includes electron-beam lithography, inductively coupled plasma reactive ion etching, and high-fidelity poling using nickel finger electrodes.

2. Second-Harmonic Generation: The SHG process in the waveguide successfully converts a 1550 nm pump signal into a 775 nm second harmonic with high efficiency. The experimental results match well with simulations, confirming the effectiveness of the poling process. Additionally, the power dependence of the SHG efficiency is consistent with theoretical predictions.

3. Thermal Tunability: The thermal response of the waveguide is studied, showing a blue shift of the SHG peak wavelength with increasing temperature. The thermal tunability of -0.44 nm/°C is measured, which is important for applications requiring precise frequency alignment.

4. Conclusion: The study demonstrates the potential of TFLT-based photonic devices for nonlinear applications, particularly for high-precision frequency conversion tasks. The results establish TFLT as a promising platform for integrated photonics, with potential applications in quantum communication, spectroscopy, and atomic clocks.

The paper provides significant insights into optimizing SHG performance, offering a foundation for future applications in nonlinear photonics. Further improvements could be made to enhance the quality of the poling process and reduce propagation losses, paving the way for broader applications of these devices.