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Researchers demonstrate thin-film lithium tantalate (LT) waveguides and electro-optic modulators operating at 532 nm, achieving propagation losses at the dB/cm scale and a flat frequency response up to approximately 50 GHz. Unlike thin-film lithium niobate (LN) counterparts, the LT modulators exhibit stable operation when delivering 5 dBm of modulated optical power over one hour, suggesting superior photorefractive resistance in the blue-green band. Using these devices in an integrated external modulator configuration, the team validates underwater optical wireless communication (UWOC) at 112 Gb/s over 3 meters and 64 Gb/s over 9 meters, marking the first demonstration of an integrated external modulator-based UWOC system.
Why it matters
High-speed, stable visible-light modulators in the blue-green band address a critical bottleneck for underwater optical communications, where seawater transmission windows align with this wavelength range, enabling potential applications in submarine data links, marine robotics, and ocean monitoring systems.
arXiv:2603.14346v2 Announce Type: replace
Abstract: Visible-light integrated photonics enables compact platforms for sensing, precision metrology, and free-space data links at visible wavelengths. However, many applications remain limited by the lack of high-speed and robust modulators in the blue-green band. Here we report, both operating at 532 nm, thin-film lithium tantalate waveguides of propagation losses of dB/cm scale and modulators with a flat frequency response to ~50 GHz. The modulator remains stable when delivering 5 dBm modulated optical power for an hour, which cannot be achieved by thin-film lithium niobate based counterparts under similar conditions and structures. System-level underwater optical wireless communication (UWOC) is validated with 112-Gb/s transmission over 3-m and 64-Gb/s transmission over 9-m underwater links. This represents the first integrated external modulator based UWOC system, overcoming the bandwidth-power-chirp trade-offs of traditional directly modulated laser-based systems. We further demonstrate dual-drive modulators for optical single-sideband and electro-optic frequency-comb generations in the green-wavelength band. These results provide a foundation for complex, robust, and active visible-light photonic integrated circuits for underwater optical applications.