The realm of science and technology has witnessed a groundbreaking advancement with the introduction of a new deep ultraviolet (DUV) laser. This innovative light source is pivotal for a myriad of applications, such as lithography, defect inspection, metrology, and spectroscopy. The 193-nanometer (nm) lasers, known for their high power, have been instrumental in lithography, enabling precise patterning in manufacturing processes.

However, the traditional ArF excimer lasers faced limitations due to their coherence constraints, which affected their performance in high-resolution patterning tasks like interference lithography.

193-nm DUV laser generated by cascaded LBO crystals. Image Credit: H. Xuan (GBA branch of Aerospace Information Research Institute, Chinese Academy of Sciences)

Enter the “hybrid ArF excimer laser,” a game-changer in the field. This laser integrates a small linewidth solid-state 193-nm laser seed in place of the conventional ArF oscillator. The result is a laser with enhanced coherence and a narrower linewidth, which significantly boosts the performance of interference lithography, particularly in high-throughput scenarios. This translates to faster lithography speeds and heightened precision in patterning.

The hybrid ArF excimer laser’s superior photon intensity and coherence enable it to process a diverse array of materials, including solids and carbon compounds, without inducing thermal damage. This versatility underscores its potential to revolutionize industries such as laser machining and lithography.

For optimal performance, the 193 nm seed laser’s linewidth must be meticulously controlled to remain under 4 GHz. This requirement is crucial for achieving the necessary coherence length for interference, a feat readily attainable by solid-state laser technologies.

Pioneering researchers at the Chinese Academy of Sciences have propelled this technology forward. They employed a sophisticated two-stage sum-frequency generation method utilizing LBO crystals to create a remarkable 60 mW solid-state DUV laser at 193 nm with a minimal linewidth, as reported in Advanced Photonics Nexus.

The process involves pump lasers at 258 nm and 1553 nm, derived from Yb-hybrid and Er-doped fiber lasers, respectively. These pump lasers interact within a specially designed 2 mm × 2 mm × 30 mm Yb:YAG bulk crystal, facilitating power scaling. The resulting DUV laser, along with its 221 nm counterpart, boasts a linewidth of approximately 640 MHz, an average power output of 60 mW, a pulse duration of 4.6 nanoseconds, and a repetition rate of 6 kHz. Notably, this represents the highest power output and the narrowest linewidth for 193 nm lasers produced using an LBO crystal to date.

The conversion efficiencies are particularly impressive, with 27% for the 221 nm to 193 nm transition and 3% for the 258 nm to 193 nm transition, setting new benchmarks for efficiency. This research not only pushes the boundaries of DUV laser technology but also opens up exciting new avenues for exploring various DUV laser wavelengths. The potential of LBO crystals in generating DUV lasers with power levels ranging from hundreds of milliwatts to watts is now more tangible than ever. These technological strides are not merely extending the capabilities of DUV lasers; they are poised to fundamentally transform numerous scientific and industrial domains.

Bijing-optics is proud to present this cutting-edge development in DUV laser technology, marking a significant stride in the journey towards unparalleled precision and efficiency in various applications. Stay tuned for more updates on how these innovations will shape the future of our industries.

Reference:

‌Zhang, Z., et al. (2024) High-power, narrow linewidth solid-state deep ultraviolet laser generation at 193 nm by frequency mixing in LBO crystals. Advanced Photonics. doi.org/10.1117/1.APN.3.2.026012