The realm of science and technology has been exploring the potential of harnessing coherent light sources in the deep ultraviolet (DUV) region for various applications. One of the key areas where DUV lasers have shown immense significance is in lithography, defect inspection, metrology, and spectroscopy. However, traditional high-power 193-nanometer (nm) lasers, such as ArF excimer lasers, have been facing coherence limitations that hinder their effectiveness in applications requiring high-resolution patterns. This article delves into the concept of hybrid ArF excimer lasers and the recent breakthrough in solid-state DUV laser technology.
In applications like interference lithography, where high-resolution patterns are crucial, the coherence limitations of conventional ArF excimer lasers become a bottleneck. To address this challenge, researchers have introduced the concept of hybrid ArF excimer lasers. By integrating a narrow linewidth solid-state 193-nm laser seed in place of the ArF oscillator, these hybrid lasers achieve enhanced coherence and narrow linewidth, improving performance in high-throughput interference lithography. The precise control of the laser linewidth below 4 gigahertz (GHz) is essential for optimizing seeding in an ArF amplifier.
A recent breakthrough in solid-state DUV laser technology by researchers at the Chinese Academy of Sciences has propelled the field forward. Using a sophisticated two-stage sum frequency generation process with LBO crystals, the researchers have achieved a remarkable 60-milliwatt (mW) solid-state DUV laser at 193 nm with a narrow linewidth. The process involves pump lasers at 258 and 1553 nm, derived from a Yb-hybrid laser and an Er-doped fiber laser, respectively. The setup culminates in a 2mm×2mm×30mm Yb:YAG bulk crystal for power scaling, yielding impressive results in terms of power output, pulse duration, repetition rate, and linewidth.
The advancements in solid-state DUV laser technology not only push the boundaries of DUV laser technology but also hold promise for revolutionizing myriad applications across scientific and industrial domains. The generated DUV laser, along with its 221-nm counterpart, opens up possibilities for direct processing of various materials with minimal thermal impact. The outstanding conversion efficiency achieved in this research sets new benchmarks for efficiency values, paving the way for exploring other DUV laser wavelengths.
The recent breakthrough in solid-state DUV laser technology represents a significant advancement in the field. The reported research showcases the viability of pumping LBO with solid-state lasers for generating narrow-linewidth lasers at 193 nm. This breakthrough not only enhances the performance of hybrid ArF excimer lasers but also expands the potential applications of DUV lasers in diverse fields. The future looks promising for DUV laser technology, with continued research and innovation driving further advancements in this exciting field.
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