The Evolution of DUV Laser Technology: A New Era of Precision and Efficiency

The Evolution of DUV Laser Technology: A New Era of Precision and Efficiency

In the realm of science and technology, harnessing coherent light sources in the deep ultraviolet (DUV) region is critical for various applications such as lithography, defect inspection, metrology, and spectroscopy. Traditionally, high-power 193-nanometer (nm) lasers have played a crucial role in lithography, enabling precise patterning. However, the limitations in coherence associated with conventional ArF excimer lasers have hindered their effectiveness in applications requiring high-resolution patterns, like interference lithography. The introduction of the “hybrid ArF excimer laser” has revolutionized this space by integrating a narrow linewidth solid-state 193-nm laser seed in place of the ArF oscillator, resulting in enhanced coherence and improved performance in high-throughput interference lithography. This innovation not only enhances pattern precision but also accelerates lithography speed, making it a game-changer in the field.

To achieve optimal performance in an ArF amplifier, the linewidth of the 193-nm seed laser must be meticulously controlled, ideally below 4 gigahertz (GHz). This specification determines the coherence length crucial for interference, a requirement that is easily met through solid-state laser technologies. A recent breakthrough by researchers at the Chinese Academy of Sciences showcases a remarkable 60-milliwatt (mW) solid-state DUV laser at 193 nm with a narrow linewidth. This achievement was made possible through a sophisticated two-stage sum frequency generation process utilizing LBO crystals, involving pump lasers at 258 and 1553 nm derived from a Yb-hybrid laser and an Er-doped fiber laser, respectively. The impressive results of this setup, which includes a 2mm×2mm×30mm Yb:YAG bulk crystal for power scaling, highlight the significant advancements in DUV laser technology.

The generated DUV laser, in conjunction with its 221-nm counterpart, demonstrates an average power of 60 mW, a pulse duration of 4.6 nanoseconds (ns), and a repetition rate of 6 kilohertz (kHz), with a linewidth of approximately 640 megahertz (MHz). This breakthrough marks the highest power output for both 193- and 221-nm lasers generated by an LBO crystal, showcasing the narrowest linewidth reported for a 193-nm laser. The exceptional conversion efficiency achieved – 27% for 221 to 193 nm and 3% for 258 to 193 nm – sets new benchmarks in efficiency values and highlights the potential of LBO crystals in generating DUV lasers at varying power levels.

This groundbreaking research not only pushes the boundaries of DUV laser technology but also holds promise for revolutionizing applications in scientific and industrial domains. According to Prof. Hongwen Xuan, the corresponding author for the work, the findings demonstrate the feasibility of pumping LBO with solid-state lasers to generate a reliable and effective narrow-linewidth laser at 193 nm. This research not only showcases the potential of LBO crystals but also presents a cost-effective way to develop high-power DUV laser systems. The advancements in DUV laser technology are poised to have a significant impact on various fields, opening up avenues for exploring other DUV laser wavelengths and pushing the boundaries of precision and efficiency in laser technology.


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