The hermetically sealed periodically poled lithium niobate (PPLN) ridge waveguide achieves complete sealing through metal/ceramic packaging materials, effectively blocking external contaminants such as moisture, dust, and corrosive gases (e.g., sulfur dioxide). This prevents internal component oxidation and material degradation. The device is filled with inert gases (e.g., nitrogen) to suppress oxidation reactions, significantly extending its lifespan. The product undergoes rigorous helium mass spectrometry leak testing, with a leakage rate of <5×10⁻⁷ Pa·m³/s, ensuring a leak-proof seal and guaranteeing reliability in extreme environments (high temperature, high humidity, high salt fog). It is suitable for demanding field applications, including maritime operations.