The Advancements in Harnessing Coherent Light Sources in the Deep Ultraviolet Region

In the realm of science and technology, the use of coherent light sources in the deep ultraviolet (DUV) region is vital for a variety of applications such as lithography, defect inspection, metrology, and spectroscopy. The traditional high-power 193-nanometer (nm) lasers have been critical in lithography for precise patterning. However, the limitations in coherence associated with conventional ArF excimer lasers restrict their effectiveness in applications requiring high-resolution patterns, such as interference lithography.

The concept of the “hybrid ArF excimer laser” introduces a new way to enhance coherence and narrow linewidth in DUV lasers. By replacing the ArF oscillator with a solid-state 193-nm laser seed, better performance is achieved in high-throughput interference lithography. This innovation not only improves pattern precision but also accelerates lithography speed. The heightened photon energy and coherence of the hybrid ArF excimer laser enable direct processing of various materials with minimal thermal impact, making it a versatile tool in fields ranging from lithography to laser machining.

Researchers at the Chinese Academy of Sciences recently made a significant breakthrough in DUV laser technology by achieving a 60-milliwatt (mW) solid-state DUV laser at 193 nm with a narrow linewidth. This was made possible through a two-stage sum frequency generation process using LBO crystals. The process involved pump lasers at 258 and 1553 nm, derived from a Yb-hybrid laser and an Er-doped fiber laser, respectively. The results were impressive, with the generated DUV laser showcasing 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 not only sets new benchmarks in terms of power output and efficiency but also highlights the potential of LBO crystals in generating DUV lasers at various power levels. The advancements pave the way for exploring other DUV laser wavelengths and hold promise for revolutionizing applications across scientific and industrial domains. Prof. Hongwen Xuan, the corresponding author for the research, emphasizes the viability of pumping LBO with solid-state lasers for reliable and effective generation of narrow-linewidth lasers at 193 nm, presenting a cost-effective approach to high-power DUV laser systems.

The advancements in harnessing coherent light sources in the deep ultraviolet region represent a significant leap forward in DUV laser technology. The use of hybrid ArF excimer lasers and breakthroughs in solid-state laser technologies open up new possibilities for high-resolution patterning, direct material processing, and efficiency improvements across various applications. The implications of these advancements are far-reaching, promising a future where DUV lasers play a crucial role in advancing scientific research and industrial processes.