Jinsong Xia

Photonic integrated circuits have driven advances in optical interconnects, wireless communications, seamless sensing. Electro-optic modulators, which bridge the electronic and optical domains, act as the cornerstone of these systems. To address the ultra-broadband demands of next-generation information systems while enabling heterogeneous integration with other functional components, here we present a high-performance thin-film lithium tantalate-on-silicon nitride heterogeneous Mach-Zehnder modulator fabricated via micro-transfer printing. The device shows an insertion loss of 1.0 dB, an electro-optic bandwidth exceeding 110 GHz, and a power drift of ~0.3 dB over 72 h at quadrature bias. We employ the modulator for three typical scenarios in the applications of optical communications, fully photonic terahertz wireless communications, and radar sensing. It achieves optical data transmission rates beyond 375 Gbps, a record rate of 148 Gbps for wireless communications in the D-Band, and a range resolution of 1.2 cm with measured errors below 2 mm in the W-Band. These results pave the way for scalable, high-performance, cross-domain photonic chips for next-generation information networks.

The rapid growth of artificial-intelligence computing demands high-bandwidth and energy-efficient data-center interconnects. Although self-homodyne coherent (SHC) transmission reduces digital signal-processing complexity, its practical deployment is limited by ultrafast state-of-polarization (SOP) fluctuations that destabilize coherent reception. Here we show an ultrafast adaptive polarization controller (APC) based on thin-film lithium tantalate, enabled by the co-design of a photonic chip, a finite-boundary gradient-descent (FBGD) algorithm, and a low-latency real-time control system. The FBGD algorithm incorporates the finite phase boundary directly into the control strategy, enabling reset-free continuous SOP tracking. The implemented APC is validated through both standalone polarization-tracking measurements and a dual-polarization 16-QAM SHC 400-Gbps transmission system. Stable reset-free operation under continuous polarization disturbances is maintained up to 1 Mrad·s⁻¹. These results establish a previously inaccessible operating regime for integrated polarization control and provide a practical route toward ultrafast and reset-free polarization control in coherent optical interconnects and other polarization-sensitive photonic systems.

Thin-film lithium tantalate (TFLT) is an emerging electro-optic material with properties comparable to lithium niobate and promising applications in communications, sensing, and computing. With advances in wafer fabrication and low-loss dry-etched waveguides, TFLT has gained increasing attention. However, efficient fiber-to-chip coupling remains critical, especially for large-NA fibers that complicate mode conversion. Here, we demonstrate a TFLT large-mode-size edge coupler fabricated by standard semiconductor processes. Coupling to a high-NA fiber (MFD ∼6.5 μm) exhibits losses below 0.5 dB/facet in the O-band, below 0.37 dB/facet in the C-band, and 0.22 dB/facet at 1482 nm. The coupler maintains <1.3 dB/facet across 1200–2400 nm, with high misalignment tolerance and power stability.

Integrated lithium niobate electro-optic modulators are emerging for applications in next-generation optical fiber communication networks. In this work, we demonstrate a polarization-insensitive Michelson interferometer modulator based on a thin-film lithium niobate on insulator platform. By leveraging a mode-conversion-based architecture, the device achieves polarization-insensitive operation while maintaining a low voltage-length product and optical insertion loss. Experimental results show a polarization-dependent loss of 0.36 dB, insertion loss below 0.9 dB, and a half-wave voltage of 11.2 V, corresponding to a voltage-length product of 1.12 V·cm, with an electro-optic bandwidth of ∼21.8 GHz. These performance metrics establish the proposed modulator as a promising candidate for next-generation optical communication systems utilizing standard single-mode fibers, ensuring robust performance in polarization-diverse environments.

Emerging demands for dynamic wavefront modulation in holographic displays, augmented/virtual reality, and light detection and ranging require spatial light modulators (SLMs) with high pixel density and fast refresh rates. However, key parameters of existing liquid-crystal and metasurface-based SLMs, such as spatiotemporal product density, field of view and refresh rate, remain far below application requirements. Here we report an optically addressed metasurface SLM composed of independently tunable meta-atom supercells with a 756 nm pitch. This device reduces SLM pixel size to the submicrometre scale while achieving a spatiotemporal product density of 2.3 × 10¹² pixels s⁻¹ cm⁻², thereby meeting the critical threshold for true holography. It enables real-time complex-amplitude holography, three-dimensional focusing and beam steering over a ±20.6° field of view in the visible spectrum.

Photonic integrated circuits (PICs) have driven advances in optical interconnect, wireless communications, seamless sensing, etc. Among various components of PICs, electro-optic modulators serve as the critical bridge between the electronic and optical domains, acting as the cornerstone of these systems. To address the ultra-broadband demands of next-generation information systems while enabling heterogeneous integration with other functional components, we present a high-performance thin-film lithium tantalate-on-silicon nitride heterogeneous Mach-Zehnder modulator (MZM), fabricated via micro-transfer printing. The MZMs show an insertion loss of 1.0 dB, an electro-optic bandwidth exceeding 110 GHz, and a power drift of ~0.3 dB over 72 h at quadrature bias. We employ the modulator for three typical scenarios in the applications of optical communications, full photonic terahertz wireless communication, and radar sensing. Using the MZM, we achieve optical data transmission rates beyond 375 Gbps, a record of 148 Gbps for wireless communications in the D-Band, and a range resolution of 1.2 cm with measured errors below 2 mm in the W-Band. These results pave the way for scalable, high-performance, cross-domain photonic chips for next-generation information networks.

The escalating capacity limitations of conventional near-infrared telecommunication bands have spurred urgent investigations into wide-band optical communication systems spanning from the near-infrared to mid-infrared regimes. This has motivated the development of optical components combining broadband bandwidth with high-speed operation. The state-of-the-art modulators face challenges in achieving broad operational bandwidth due to waveguide dispersion and velocity mismatch. Here we demonstrate a thin-film lithium niobate (TFLN) electro-optic (EO) modulator with an unprecedented 800-nm operational bandwidth, covering the full O-U telecom bands and extending into the 2-μm regime. The TFLN modulator exhibits >67 GHz EO bandwidth across O-U bands (~100 GHz at O-/S-/C-/L-bands) and >50 GHz at 2-μm band. It enables single-lane exceeding 240 Gbps PAM-4 transmission across O-U bands and a record 170 Gbps PAM-4 transmission at 2-μm band. This breakthrough establishes TFLN as a compelling platform for multispectral photonics, bridging conventional telecom infrastructure with emerging 2-μm technologies for next-generation optical communications.

The rapid escalation of computing power driven by large-scale artificial intelligence is placing unprecedented demands on the bandwidth, latency, and energy efficiency of data-center interconnects (DCIs). Self-homodyne coherent (SHC) transmission is a promising architecture because it preserves the spectral efficiency of coherent detection while greatly simplifying digital signal processing, but its practical deployment is critically limited by random and often ultrafast state-of-polarization (SOP) fluctuations that induce carrier fading and destabilize coherent reception. Here we report the first integrated polarization controller based on thin-film lithium tantalate (TFLT), enabling reset-free polarization tracking at Mrad/s speeds. The four-stage electro-optic device exhibits polarization-dependent loss (PDL) below 0.3 dB, a half-wave voltage below 2.5 V, high modulation bandwidth, and negligible DC drift. To accommodate the finite tuning range of integrated phase shifters, we develop a finite-boundary gradient-descent (FBGD) control algorithm that ensures reset-free SOP evolution with no phase jump. The implemented adaptive polarization controller (APC) is validated through both standalone polarization-tracking measurements and a dual-polarization 16-QAM SHC 400-Gbps transmission system. Transient polarization disturbances can be tracked at speeds up to 2 Mrad/s, while stable reset-free operation under continuous polarization disturbances is maintained up to 1 Mrad/s. This reset-free performance represents more than doubling the state of the art, while the pre-FEC bit-error rates remain below the HD-FEC threshold under realistic DCI conditions and lightning-scale polarization disturbances. These results establish TFLT as a new platform for ultrafast, low-power, reset-free, and drift-free polarization control in coherent optical interconnects and beyond.

Emerging demands for dynamic wavefront modulation in holographic displays, augmented/virtual reality, and light detection and ranging (LiDAR) require spatial light modulators (SLMs) with high pixel density and fast refresh rates. However, key parameters of existing liquid-crystal and metasurface-based SLMs, such as spatiotemporal product density (STPD), field of view (FOV), and refresh rate, remain far below application requirements. Here, we report an optically addressed metasurface spatial light modulator (OA-MSLM), composed of independently tunable meta-atom supercells with a 756 nm pixel pitch. This device represents the first demonstration of submicron-scale 2D addressing with an STPD of 2.3 × 10¹² pixels/(s·cm²), thereby meeting the critical threshold for true holography. It enables real-time complex-amplitude holography, three-dimensional focusing, and beam steering over a ±20.6° FOV in the visible spectrum. This work establishes a scalable platform for dynamic wavefront control, paving the way for next-generation 3D display, photodetection, optical communication, and laser manufacturing technologies.