Ultra wideband pulse compression grating for single cycle Ava laser implemented by Shanghai Institute of Optics and Mechanics

Recently, Shao Jianda, a researcher of Shanghai Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Jin Yunxia, a researcher team, and Li Chaoyang, a researcher of Zhangjiang Laboratory, have made breakthroughs in the field of ultra wideband pulse compression gratings.

The research team has successfully developed a ultra 400 nm broadband gold grating for single cycle pulse compression needs. Its diffraction efficiency is greater than 90% in the wavelength range of 750-1150 nm, which is nearly twice the bandwidth of the current gold grating. Moreover, its development aperture can be further pushed to the meter level. The related achievements were published in the journal Nature Communications under the title of "400nm ultra wideband gradients for near single cycle 100 Petawatt lasers".

The compression of pulse width from 10-20 cycles to a single cycle (3.3 fs), combined with high-energy loading, is considered the future of realizing Ava lasers. The research team has long been deeply involved in the field of broadband high threshold pulse compression gratings. In the progress of this work, a breakthrough has been made in the simulation design of ultra wideband gold gratings, introducing azimuth angle to expand the design and application degrees of freedom; We have mastered the evolution law of grating groove shape in experiments, invented the technology of large bottom width and small sharp angle gold grating (patent number: CN114879293B), and successfully developed 1443 g/mm and 1527 g/mm ultra 400 nm broadband gold gratings (Figure 1).

The ultra wideband grating with such broadband and high threshold (better than 0.3J/cm2) will play a crucial role in the wide angle non collinear optical parametric chirped pulse amplification system [WNOPCPA, Laser Photonics Rev 172100705 (2022). https://doi. org/10.1002/lpor. 202100705]. Theoretical calculations have shown that it is sufficient to support 4 fs pulse compression and can reduce the grating aperture required to achieve 100 beat watts from the meter level to the half meter level.

Figure 1 400 nm ultra wideband gold grating
Chirped pulse amplification (CPA) and its derivative technologies have driven the peak laser power from terawatts to the 10PW level, and pulse compressors have become the core module of high-power, ultra strong, and ultra short laser devices. Due to the single channel load capacity of large aperture, wide spectrum, and high threshold compressed gratings, countries such as China, Europe, the United States, Russia, and South Korea have deployed multi channel coherent synthesis of 100 PW or even Ava level laser facilities. In addition, single cycle (3.3fs) pulses are also an important strategy for generating Aiwa level lasers.

In recent years, technologies such as WNOPCPA have been able to expand the bandwidth of gain media to 400 nm in engineering, thereby supporting 3-6 fs of Fourier transform limit pulses. The ultra wideband grating that supports single cycle pulse broadening and compression is a core technical challenge in achieving single cycle Ava laser. At present, the team is pushing the caliber of ultra wideband gratings to the meter level and applying them to the principle prototype of a single cycle Ava laser.

The research work has received support from the National Key R&D Plan, National Natural Science Foundation of China, Ministry of Science and Technology, and Shanghai Strategic Emerging Industry Project.

Figure 2 illustrates the concept of ultra wideband compression, where the bandwidth, efficiency, and threshold of the compressed grating determine the width and peak power of the compressed pulse

Source: Shanghai Institute of Optics and Precision Machinery