A team of researchers from the TDK Corporation in Japan has developed a groundbreaking RGB multiplexer based on thin-film lithium niobate (TFLN), significantly enhancing the efficiency and speed of laser beam scanning (LBS) technology. Published in Advanced Photonics Nexus on July 28, 2025, this innovation could propel numerous applications, from barcode scanning to sophisticated light displays.
LBS systems have come to the forefront of photonic technologies, utilizing laser beams to scan, sense, and display information rapidly. Traditionally, these systems relied on direct modulation of red, green, and blue (RGB) lasers, a method that proved to be slow and energy-consuming. The newly developed TFLN-based multiplexer promises a more efficient alternative by employing electric fields to manipulate light propagation, thereby achieving higher modulation speeds with reduced power usage.
Atsushi Shimura, the corresponding author of the study, emphasized the importance of this development: “A TFLN-based RGB multiplexer is essential for LBS with lower power consumption and higher resolution; however, this had never been demonstrated.” This breakthrough addresses the limitations of conventional glass-based photonic integrated circuits, which have hindered advancements in the field.
Innovative Design and Fabrication Techniques
The compact multiplexer measures just 2.3 millimeters in length and was fabricated using a physical vapor deposition technique, often referred to as “sputter” deposition. This method allows for the deposition of the lithium niobate film without the complex bonding processes typically required for bulk materials, thus paving the way for scalable production of these advanced optical devices.
The waveguide structure was meticulously designed, featuring a trapezoidal cross-section that minimizes signal loss. The researchers optimized the lengths of the combined sections to enhance performance for each color channel. During testing, the RGB multiplexer successfully combined laser beams of red (638 nm), green (520 nm), and blue (473 nm) through its waveguides. By adjusting the intensity of each laser, the team generated a spectrum of colors, including cyan, magenta, yellow, and even white light.
This precise color control is crucial for applications in LBS-based displays, as it enhances visual quality and improves the overall user experience.
Challenges and Future Directions
Despite the promising results, the research highlights significant challenges that must be addressed. One major concern is the lower crystal quality of sputter-deposited TFLN compared to traditional bulk lithium niobate, which can negatively impact performance, particularly at shorter wavelengths. For instance, at the blue light wavelength of 473 nm, optical loss was measured between 7 and 10 dB, considerably higher than the predicted value of 3.1 dB. This discrepancy is attributed to surface roughness in the waveguides, which causes light scattering and diminishes efficiency.
Shimura acknowledged the need for improvements: “Optimizing fabrication processes to produce smoother surfaces is a key step toward realizing TFLN’s potential in visible-light photonics and applications.”
The findings from this study lay the groundwork for the future development of faster, energy-efficient multiplexers for visible-light LBS systems. As Shimura points out, “This work demonstrates the feasibility of a passive RGB multiplexer as a first step toward developing active photonic integrated circuits.”
As the demand for efficient and high-quality laser technologies continues to grow, advancements like these could significantly impact various sectors, streamlining processes and enhancing technological capabilities.
