Scientists have developed the most powerful ultraviolet laser using LBO crystals

It is reported that recently researchers from the Chinese Academy of Sciences have achieved the highest power output of 193 nm and 221 nm lasers using lithium borate (LBO) crystals. This achievement lays the foundation for the further application of the laser in deep ultraviolet (DUV) spectroscopy.
The laser in DUV spectroscopy has many applications in science and technology, such as defect detection, spectroscopy, lithography, and metrology. Traditionally, argon fluoride (ArF) lasers have been used to generate high-power 193nm lasers for applications such as lithography.
Other applications of DUV lasers include the production of microelectronic devices, semiconductor integrated circuits, and medical applications for ophthalmic surgeries. In these applications, it is commonly referred to as an excimer laser.

However, these lasers are not completely coherent and therefore cannot be used for more sensitive applications such as interferometric lithography, where fine features must be printed in the form of arrays. Such precise applications require more coherent lasers, which provides an opportunity for researchers to manufacture hybrid excimer lasers.

What is a hybrid excimer laser?
In order to achieve coherence requirements, scientists have been considering using solid-state seeds instead of gas (ArF) oscillators to make them hybrid lasers. In addition to improving coherence, this design also aims to increase the photon energy of the laser, so that it can even be used with carbon compounds with minimal thermal impact.

To achieve this goal, the linewidth of the 193nm seed laser needs to be maintained below 4 GHz. The statement states that this is the coherence length crucial for interference seen through the use of currently available solid-state laser technology.

What achievements have been made on DUV lasers?
Researchers from the Chinese Academy of Sciences have achieved the same linewidth as the 193 nm hybrid excimer laser by using LBO crystals. In their device, researchers used a complex two-stage and frequency generation process to achieve a laser output of 60 milliwatts (60 megawatts).
The device includes two lasers, one at 258 nanometers and the other at 1553 nanometers. These lasers come from ytterbium hybrid lasers and erbium-doped fiber lasers, ultimately forming 2mm x 2mm x 30mm Yb: YAG bulk crystals to provide the required laser output.

The resulting DUV laser pulse has a duration of 4.6 nanoseconds (ns), a repetition rate of 6 kHz, and a linewidth of approximately 640 MHz.
It is worth noting that the output power of the 193nm laser and its accompanying 221nm laser is 60mW, which is the highest power generated using LBO crystals.

The conversion efficiency of 221-193nm is 27%, and the conversion efficiency of 258-193nm is 3%, setting a new benchmark.
This study demonstrates the feasibility of using solid-state lasers to pump LBO, which can reliably and effectively generate 193nm narrow linewidth lasers, and opens up a new path for manufacturing cost-effective high-power DUV laser systems using LBO
Therefore, researchers believe that LBO crystals can be used to generate more DUV lasers, with output powers ranging from a few milliwatts to a few watts, opening up further avenues for these wavelengths.
This research result is published in the journal Advanced Photonic Nexus.

Source: OFweek