Milliwatt-level UV generation using sidewall poled lithium niobate.

Area of Science:

• Photonics
• Nonlinear Optics
• Materials Science

Background:

• Integrated coherent ultraviolet (UV) light sources are crucial for quantum computing, optical clocks, gas sensing, and microscopy.
• Frequency upconversion in integrated photonic platforms, particularly thin-film lithium niobate (TFLN), is a promising approach for UV generation.
• Existing TFLN waveguides suffer from high propagation losses and challenges in consistent poling of long waveguides with small periods, hindering progress.

Purpose of the Study:

• To overcome the limitations of TFLN waveguides for on-chip UV generation.
• To develop a novel waveguide design enabling efficient frequency upconversion.
• To demonstrate a significant increase in generated UV power for practical applications.

Main Methods:

• Introduction of a sidewall poled lithium niobate (SPLN) waveguide architecture.
• Fabrication of cm-long SPLN waveguides with precise domain inversion and optimized duty cycles.
• Characterization of propagation losses, domain inversion, and nonlinear conversion efficiency.

Main Results:

• Achieved record-low propagation losses of 2.3 dB/cm in SPLN waveguides.
• Demonstrated complete domain inversion across the waveguide cross-section with an optimal 50% duty cycle.
• Obtained a record-high normalized conversion efficiency of 5050%W⁻¹cm⁻² and 4.2 mW of on-chip UV power at 390 nm.

Conclusions:

• The SPLN waveguide approach effectively addresses the limitations of previous TFLN devices.
• This advancement establishes the TFLN platform as a viable option for high-quality on-chip UV generation.
• Enables new possibilities for integrated UV sources in advanced scientific and technological applications.