Compressing all the energy of a laser pulse into a spatiotemporal focal cube edged by the laser center wavelength will realize the highest intensity of an ultra-intense ultrashort laser, which is called the λ³ regime or the λ³ laser. Herein, we introduced a rotational hyperbolic mirror—an important rotational conic section mirror with two foci—that is used as a secondary focusing mirror after a rotational parabolic mirror to reduce the focal spot size from several wavelengths to a single wavelength by significantly increasing the focusing angular aperture. Compared with the rotational ellipsoidal mirror, the first focal spot with a high intensity, as well as some unwanted strong-field effects, is avoided. The optimal focusing condition of this method is presented and the enhanced tight focusing for a femtosecond petawatt laser and the λ³ laser is numerically simulated, which can enhance the focused intensities of ultra-intense ultrashort lasers for laser physics.

The characteristics of plasmas play an important role in femtosecond laser filament-based applications. Spectroscopic analysis is used to experimentally investigate the plasma density and its temperature of the air filament under different pulse repetition rates. In our experiments, the measured average plasma density of the filament is 1.54×1017cm-3 and the temperature of the plasma is about 5100 K under 100 Hz pulse repetition rate. The plasma density decreases to 1.43×1017cm-3 and the temperature increases to 6230 K as the pulse repetition rate increases to 1000 Hz. The experimental observation agrees with the numerical simulation by solving the nonlinear Schrödinger equations with repetition rate related “low density hole” correction.

极紫外(Extreme ultra-violet, EUV)光刻机光源主要采用激光产生等离子体技术, 用高功率激光轰击锡液滴靶产生13.5 nm波长的EUV光。其中, 基于逆压电效应的压电式高温锡液滴喷射元件是获取高重频高温锡液滴靶的关键部件。本项工作突破了耐250 ℃高温微细压电陶瓷管的组成设计和精细制备, 以及高温锡液滴喷射元件的结构设计和封装等关键技术, 成功研制了压电式高温液滴喷射元件。并通过自主搭建高温锡液滴靶光学检测平台, 基于此高温液滴喷射元件实现了重复频率20 kHz, 直径~100 μm的高温锡液滴靶的稳定输出。

After reaching a world record of 10 PW, the peak power development of the titanium-sapphire (Ti:sapphire) PW ultraintense lasers has hit a bottleneck, and it seems to be difficult to continue increasing due to the difficulty of manufacturing larger Ti:sapphire crystals and the limitation of parasitic lasing that can consume stored pump energy. Unlike coherent beam combining, coherent Ti:sapphire tiling is a viable solution for expanding Ti:sapphire crystal sizes, truncating transverse amplified spontaneous emission, suppressing parasitic lasing, and, importantly, not requiring complex space-time tiling control. A theoretical analysis of the above features and an experimental demonstration of high-quality laser amplification are reported. The results show that the addition of a 2 × 2 tiled Ti:sapphire amplifier to today’s 10 PW ultraintense laser is a viable technique to break the 10 PW limit and directly increase the highest peak power recorded by a factor of 4, further approaching the exawatt class.

With the development of high-volume manufacturing for very-large-scale integrated circuits, the purity of the light source in the extreme ultraviolet lithography (EUVL) system needs to fulfil extreme requirements in order to avoid thermal effect, optical distortion and critical dimension errors caused by out-of-band radiations. This paper reviews the key technologies and developments of the spectral purity systems for both a free-standing system and a built-in system integrated with the collector. The main challenges and developing trends are also discussed, with a view towards practical applications for further improvement. Designing and manufacturing spectral purity systems for EUVL is not a single task; rather, it requires systematic considerations for all relevant modules. Moreover, the requirement of spectral purity filters drives the innovation in filtering technologies, optical micromachining and advanced metrology.