Second Harmonic Generation (SHG) Research Papers
Tunable and efficient ultraviolet generation with periodically poled lithium niobate
Authors: Emily Hwang, Nathan Harper, Ryoto Sekine, Luis Ledezma, Alireza Marandi, and Scott Cushing
Publisher: Optica Publishing Group
Executive Summary
Compact ultraviolet (UV) light sources are essential for many emerging technologies, including quantum computing, atomic clocks, spectroscopy, high-resolution microscopy, and precision sensing. However, generating UV light efficiently on an integrated photonic chip has remained a significant technical challenge. Existing material platforms often struggle with fabrication sensitivity, optical losses, and limited nonlinear performance, preventing the development of practical, chip-scale UV photonic systems.
This research demonstrates a major advance in integrated ultraviolet photonics by achieving efficient UV light generation on a thin-film lithium niobate nanophotonic chip. Using periodically poled waveguides engineered for robust nonlinear frequency conversion, the device converts readily available near-infrared laser light into ultraviolet wavelengths through second harmonic generation. The demonstrated platform produces on-chip UV output powers of approximately 30 μW with high conversion efficiency while enabling linear wavelength tuning through temperature control.
A key innovation of this work is the waveguide design, which significantly reduces sensitivity to fabrication imperfections—a longstanding obstacle for ultraviolet integrated photonics. By utilizing larger waveguide cross-sections and longer periodic poling structures, the researchers achieved reliable first-order quasi-phase matching while maintaining efficient nonlinear conversion. This approach improves manufacturability and provides a practical path toward scalable UV photonic devices.
The research also demonstrates ultraviolet generation down to 355 nm, representing the shortest wavelength reported at the time using frequency doubling in thin-film lithium niobate. Extending integrated photonic operation into the UV spectrum greatly expands the range of applications that can be supported on a single chip while leveraging mature and cost-effective near-infrared laser technology as the optical source.
Beyond the technical achievement, this work establishes thin-film lithium niobate as one of the leading platforms for integrated ultraviolet nonlinear photonics. By combining compact device footprints, efficient frequency conversion, wavelength tunability, and compatibility with wafer-scale fabrication, the demonstrated architecture offers a scalable solution for next-generation photonic systems.
This breakthrough creates new opportunities for chip-scale ultraviolet light sources that can power advances in quantum technologies, atomic physics, spectroscopy, biomedical imaging, and precision measurement. As integrated photonic platforms continue to evolve, efficient on-chip UV generation represents an important step toward highly compact optical systems capable of spanning an increasingly broad range of wavelengths and applications.