AI Insight
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.
Understand the Science
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.