The new progress of deep ultraviolet laser technology is expected to change countless applications in science and industry

Researchers have developed a 60 milliwatt solid-state DUV laser with a wavelength of 193 nanometers using LBO crystals, setting a new benchmark for efficiency values.

In the fields of science and technology, utilizing coherent light sources in deep ultraviolet (DUV) regions is of great significance for various applications such as lithography, defect detection, metrology, and spectroscopy. Traditionally, high-power 193 nanometer (nm) lasers play a crucial role in lithography technology and are an indispensable component of precise patterning systems. However, the coherence limitation of traditional ArF excimer lasers hinders their effectiveness in applications that require high-resolution patterns such as interference lithography.

193nm DUV laser generated by cascaded LBO crystals

Hybrid ArF excimer laser technology

The concept of hybrid ArF excimer laser has emerged. Integrating a narrow linewidth 193nm solid-state laser seed into an ArF oscillator enhances coherence while achieving narrow linewidth, thereby improving the performance of high-throughput interference lithography. This innovation not only improves pattern accuracy, but also accelerates lithography speed.

In addition, the enhanced photon energy and coherence of hybrid ArF excimer lasers facilitate direct processing of various materials, including carbon compounds and solids, while minimizing thermal effects. This versatility highlights its potential in various fields, from lithography to laser processing.

Progress in Solid State DUV Laser Generators
To optimize the seed laser of the ArF amplifier, it is necessary to strictly control the linewidth of the 193 nanometer seed laser, preferably below 4 GHz. This specification determines the coherence length required for interference, and solid-state laser technology can easily meet this standard.

A breakthrough recently made by researchers of the Chinese Academy of Sciences has promoted the development of this field. According to the journal Advanced Photonics Nexus, they utilized a complex two-stage sum frequency generation process using LBO crystals to achieve a 60 milliwatt (mW) solid-state DUV laser at a wavelength of 193 nanometers, with a very narrow linewidth. This process involves pump lasers with wavelengths of 258 nanometers and 1553 nanometers, respectively, from ytterbium doped hybrid lasers and erbium-doped fiber lasers. The device uses 2mm x 2mm x 30mm Yb: YAG block crystals for power expansion, achieving remarkable results.

The average power of the generated DUV laser and its 221nm corresponding laser is 60 mW, with a pulse duration of 4.6 nanoseconds (ns), a repetition frequency of 6 kHz, and a linewidth of approximately 640 MHz. It is worth noting that this marks the highest output power of 193 nm and 221 nm lasers generated by LBO crystals, as well as the narrowest linewidth of 193 nm lasers.

Of particular note is the excellent conversion efficiency achieved: the conversion efficiency from 221 nanometers to 193 nanometers is 27%, and the conversion efficiency from 258 nanometers to 193 nanometers is 3%, setting a new benchmark for efficiency values. This study emphasizes the enormous potential of LBO crystals in generating DUV lasers with power levels ranging from hundreds of milliwatts to watts, opening the way for exploring other DUV laser wavelengths.

According to Professor Hongwen Xuan, the corresponding author of this work, the research in the report demonstrates the feasibility of reliably and effectively producing 193 nanometer narrow linewidth laser by pumping LBO with a solid-state laser, and opens up a new path for manufacturing high-performance, high-power DUV laser systems using LBO.

These advances not only drive the development of DUV laser technology, but also have the potential to completely change countless applications in science and industry.

Source: Sohu