New Laser Amplifier Is Launched: Breaks The Power Limit Of 10 Beat Watts!

Ultra-intense ultrashort lasers have a wide range of applications, including basic physics, national security, industrial services and healthcare. In fundamental physics, such lasers have become a powerful tool for studying strong-field laser physics, especially in laser-driven radiation sources, laser particle acceleration, and vacuum quantum electrodynamics.
From the 1-beat-watt "Nova" in 1996 to the 10-beat-watt Shanghai Experimental Ultra-intense Ultrashort Laser Facility (SULF) in 2017 and the 10-beat-watt European "Extreme Light Infrastructure-Nuclear Physics" (ELI-NP) in 2019, peak The dramatic increase in laser power is due to a shift in the gain medium of large-aperture lasers (from neodymium-doped glass to titanium:sapphire crystals). This shift reduced the pulse duration of high-energy lasers from about 500 femtoseconds (fs) to about 25 fs.
However, titanium-sapphire ultra-intense ultrashort lasers seem to rise to an upper limit of 10 beat watts. At present, for the development plan of 10 pat-watts to 100 pat-watts, researchers are generally less hopeful about the titanium sapphire chirped-pulse amplification technology, and instead aim at the optical parameter chirped-pulse amplification technology based on the deuterated potassium dihydrogen phosphate nonlinear crystal.
However, although the latter has good application prospects, its low pump-signal conversion efficiency and temporal-spectral-energy stability deficiencies bring great challenges to the realization and application of future 10-100 beat-watt lasers.
On the other hand, titanium sapphire chirped pulse amplification, a mature technology that has already built one 10 gigawatt laser in China and Europe respectively, still has great potential in the next stage of development of ultra-intense ultrashort lasers.
Titanium: Sapphire crystals are an energy-level broadband laser gain medium. During the gain process, the pump pulse is absorbed, and energy level inversion is established between the upper and lower energy levels to accomplish energy storage. As the signal pulse passes through the titanium sapphire crystal several times, the stored energy is extracted for laser signal amplification. However, in transverse parasitic lasers, the spontaneous emission noise is amplified along the crystal diameter, consuming the stored energy and reducing the signal laser amplification.
Parasitic Lasing is a type of unwanted laser operation that occurs in a laser or amplifier device. This phenomenon is usually caused by the unintentional formation of a laser cavity in some part of the device's interior, causing the laser to oscillate at an unwanted frequency or mode. The presence of parasitic lasers tends to inhibit the desired laser operation in the device, degrading the performance of the device and possibly even causing damage to the device.
Currently, the maximum aperture of titanium sapphire crystals can only support lasers of 10 beat watts. Even with larger titanium sapphire crystals, laser amplification is still not possible because strong transverse parasitic lasing grows exponentially with increasing titanium sapphire crystal size.
What is the key to the breakthrough?
To address this challenge, the researchers took an innovative approach by coherently laying multiple titanium sapphire crystals together.
According to Advanced Photonics Nexus, the method breaks through the 10-tap-watt limit of current titanium sapphire ultra-intense ultrashort lasers by effectively increasing the aperture diameter of the entire titanium sapphire tiling crystal and truncating the transverse parasitic lasing within each tiling crystal.
Yuxin Leng, corresponding author of the paper and a researcher at the Shanghai Institute of Optics and Precision Machinery, noted, "We have successfully demonstrated the amplification of tiled titanium:sapphire lasing in a 100 terawatt (i.e., 0.1 beat-watt) laser system. We used this technique to achieve near-ideal laser amplification, including high conversion efficiency, stable energy, broadband spectra, short pulses, and small focal spots."
His team reports that coherent tiled titanium:sapphire laser amplification provides a relatively simple and inexpensive method to exceed the current limit of 10 kWh. The method is expected to improve the experimental capabilities of ultra-intense ultrashort lasers in strong-field laser physics.
"By adding a 2×2 coherent tiled titanium:sapphire high-energy laser amplifier to the Shanghai Experimental Ultra-intense Ultrashort Laser Facility (SULF) or the European Union's Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, the laser power can be further increased from the current 10 beat-watts to 40 beat watts, and the focused peak intensity could be increased by a factor of nearly 10 or more."