The use of coherent light sources in the deep ultraviolet (DUV) region has always been crucial in various fields such as lithography, defect inspection, metrology, and spectroscopy. However, traditional high-power 193-nanometer (nm) lasers have faced coherence limitations, especially in applications requiring high-resolution patterns like interference lithography. This has led to the development of the hybrid ArF excimer laser, which integrates a narrow linewidth solid-state 193-nm laser seed in place of the ArF oscillator, enhancing coherence and narrow linewidth.
The hybrid ArF excimer laser offers improved performance in high-throughput interference lithography, boosting pattern precision and accelerating lithography speed. Its heightened photon energy and coherence allow for direct processing of various materials with minimal thermal impact, making it versatile across different fields from lithography to laser machining. To optimize seeding for an ArF amplifier, the linewidth of the 193-nm seed laser must be controlled below 4 gigahertz (GHz), a criterion easily met through solid-state laser technologies.
A recent breakthrough by researchers at the Chinese Academy of Sciences has propelled DUV laser technology forward. They have successfully achieved a 60-milliwatt (mW) solid-state DUV laser at 193 nm with a narrow linewidth using a sophisticated two-stage sum frequency generation process employing LBO crystals. The process involves pump lasers at 258 and 1553 nm, leading to impressive results in terms of power output, pulse duration, repetition rate, and linewidth.
This breakthrough marks the highest power output for both 193- and 221-nm lasers generated by an LBO crystal, along with the narrowest linewidth reported for a 193-nm laser. The outstanding conversion efficiency achieved sets new benchmarks in efficiency values, demonstrating the immense potential of LBO crystals in generating DUV lasers at varying power levels. Prof. Hongwen Xuan notes that this research paves the way for cost-effective, high-power DUV laser systems, revolutionizing applications across scientific and industrial domains.
The advancements in DUV laser technology, particularly with the hybrid ArF excimer laser and breakthroughs in solid-state DUV laser generation using LBO crystals, showcase the potential for transforming various applications in science and industry. The enhanced coherence, narrow linewidth, and high power output of these advancements open up new possibilities for precision lithography, materials processing, and other fields. As researchers continue to push the boundaries of DUV laser technology, the future looks bright for harnessing coherent light sources in the DUV region.
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