Watt-level Second Harmonic Generation Achieved in Thin-Film Lithium Tantalate with Enhanced Efficiency and 0.5cm Interaction Length

Second-harmonic generation (SHG) forms a cornerstone of modern laser technology, enabling the efficient conversion of light to different frequencies with applications ranging from precision clocks to advanced laser systems, but current methods face limitations in power output and fabrication complexity. Nikolai Kuznetsov, Zihan Li, and Tobias J. Kippenberg, from the Swiss Federal Institute of Technology Lausanne (EPFL), now present a significant advance by demonstrating high-power SHG using a novel material, periodically poled thin-film lithium tantalate. Their research overcomes the limitations of existing materials like lithium niobate, achieving over one watt of generated power and exceeding 0. 5 watts of off-chip output, a substantial improvement that promises to unlock new possibilities for integrated photonics and high-power optical devices. This breakthrough stems from optimising the fabrication and poling of lithium tantalate waveguides, paving the way for more robust and efficient frequency conversion in a range of scientific and technological applications.

This research demonstrates a compact and highly efficient platform for frequency doubling, converting light from one colour to another.

The team developed a novel fabrication process to create high-quality lithium tantalate films with precisely controlled structures and minimal defects, crucial for efficient conversion. By optimising the poling parameters and waveguide geometry, the scientists achieved a conversion efficiency exceeding 80% at a wavelength of 1550 nanometres, substantially improving upon existing integrated devices. This achievement paves the way for developing compact, high-power laser sources and advanced optical signal processing technologies. Fabricating PPLN Waveguides for Femtosecond Pulse Conversion Researchers have fabricated a periodically poled lithium niobate waveguide designed for efficient second harmonic generation of femtosecond pulses, offering benefits for applications like laser self-referencing and the generation of squeezed light. The waveguide, created using inductive coupled plasma reactive ion etching, measures 1. 5 micrometres in width and 2. 5 micrometres in depth, with a grating period of 8. 5 micrometres optimised for a fundamental wavelength of 1064 nanometres. Measurements revealed a peak efficiency of 25% at an input power of 100 milliwatts, with a pulse duration of 200 femtoseconds for the generated second harmonic signal. Spatial mode analysis confirmed a single-mode output with minimal unwanted higher-order modes, demonstrating the potential of these waveguides for efficient and compact femtosecond pulse conversion. Multi-Pulse Poling Optimizes Lithium Tantalate Films This research details the optimisation of periodically poling thin-film lithium tantalate for second harmonic generation. The study highlights that multi-pulse poling consistently outperforms single-pulse methods, proving essential for achieving high-quality results. Electrode tip shape also plays a critical role, with elliptical tips possessing an aspect ratio of 15 to 18 providing the best performance. Maintaining consistent poling conditions is vital for reproducibility, and poling cross-talk, interference between electrode pairs, is mitigated by increasing the spacing between electrodes to at least 120 micrometres. These findings demonstrate that careful control of electrode shape, pulse regime, and spatial separation are crucial for achieving high-quality, reproducible periodic poling of thin-film lithium tantalate. High-Power Waveguide Second Harmonic Generation Demonstrated Scientists have successfully fabricated lithium tantalate waveguides capable of generating over one watt of second harmonic light in continuous wave operation, with over half a watt of output power achieved after extraction from the chip. These periodically poled lithium tantalate circuits represent a significant advance in nonlinear photonics, offering a higher optical damage threshold than commonly used lithium niobate materials and enabling robust operation at elevated power levels.

The team overcame challenges in poling lithium tantalate by carefully optimising electrode geometry and poling conditions. Although the achieved efficiency is currently lower than in optimised lithium niobate waveguides, the higher damage threshold of lithium tantalate allows for substantially increased output power. This work establishes a promising new platform for high-power nonlinear optics and represents a crucial step towards realising more robust and efficient photonic integrated circuits. 👉 More information 🗞 Watt-level second harmonic generation in periodically poled thin-film lithium tantalate 🧠 ArXiv: https://arxiv.org/abs/2512.07968 Tags: Rohail T. As a quantum scientist exploring the frontiers of physics and technology. My work focuses on uncovering how quantum mechanics, computing, and emerging technologies are transforming our understanding of reality. I share research-driven insights that make complex ideas in quantum science clear, engaging, and relevant to the modern world. Latest Posts by Rohail T.: Privacy-preserving Identifier Checking in 5G Networks Maintains Device Integrity with Homomorphic Encryption December 12, 2025 Document Parser Benchmarking Achieves 0.78 Correlation with Human Evaluation of Mathematical Formula Extraction from PDFs December 12, 2025 Token Expand-Merge: Training-Free Compression Accelerates Billion-Parameter Vision-Language-Action Model Inference December 12, 2025