Fast electron generation and transport in high-intensity laser–solid interactions induces X-ray emission and drives ion acceleration. Effective production of these sources hinges on an efficient laser absorption into the fast electron population and control of divergence as the beam propagates through the target. Nanowire targets can be employed to increase the laser absorption, but it is not yet clear how the fast electron beam properties are modified. Here we present novel measurements of the emittance of the exiting fast electron beam from irradiated solid planar and nanowire targets via a pepper-pot diagnostic. The measurements indicate a greater fast electron emittance is obtained from nanowire targets. Two-dimensional particle-in-cell simulations support this conclusion, revealing beam defocusing at the wire–substrate boundary, a higher fast electron temperature and transverse oscillatory motion around the wires.

A new method is developed for suppressing thermally induced wavefront distortions of the radiation in the active element of disk geometry. The method is based on controlling radial temperature gradients in the active element using a profiled heatsink. An active element with a zero thermal lens developed on the basis of numerical simulation was experimentally demonstrated in a disk laser head. Higher-order phase aberrations in the active element with a profiled heatsink were weaker than in the element with a flat heatsink. Using this method, a thermal-lens-free active-mirror ytterbium-doped yttrium aluminum garnet amplifier with an output energy of 54 mJ at an average pump power of 100 W and a repetition rate of 106 Hz was implemented.

Laser-driven inertial confinement fusion (ICF) diagnostics play a crucial role in understanding the complex physical processes governing ICF and enabling ignition. During the ICF process, the interaction between the high-power laser and ablation material leads to the formation of a plasma critical surface, which reflects a significant portion of the driving laser, reducing the efficiency of laser energy conversion into implosive kinetic energy. Effective diagnostic methods for the critical surface remain elusive. In this work, we propose a novel optical diagnostic approach to investigate the plasma critical surface. This method has been experimentally validated, providing new insights into the critical surface morphology and dynamics. This advancement represents a significant step forward in ICF diagnostic capabilities, with the potential to inform strategies for enhancing the uniformity of the driving laser and target surface, ultimately improving the efficiency of converting laser energy into implosion kinetic energy and enabling ignition.

We present an innovative design for a two-head, gas-cooled multi-slab high-energy, high-repetition-rate amplifier aimed at mitigating thermally induced depolarization in a wide-bandwidth neodymium-doped glass gain medium. This architecture employs two quartz rotators (QRs) with opposite-handedness, strategically positioned within each multi-slab amplifier head, to enhance depolarization compensation. Theoretical modeling of this amplifier configuration demonstrates a 20× reduction in depolarization losses for a 70 mm beam operating at the central wavelength, compared to conventional approaches that utilize a single QR positioned between the amplifier heads. In addition, for a wide bandwidth source, the integration of QRs with opposite-handedness yields a 9× improvement in depolarization losses at the spectral extremes compared to the use of two QRs exhibiting the same optical handedness in both amplifier heads.

We demonstrated a high-power, high-energy regenerative amplifier (RA) based on Yb-doped CaGdAlO4 (Yb:CALGO) crystal, which achieves a maximum average power exceeding 50 W at a repetition rate greater than 50 kHz, and a maximum pulse energy of approximately 7 mJ at a repetition rate of up to 5 kHz. After compression, 130 fs pulses with a peak power of nearly 45 GW are achieved. To the best of our knowledge, this represents the highest average power and pulse energy reported for a Yb:CALGO RA. The RA cavity is specifically designed to maintain excellent stability and output beam quality under a pumping power of 380 W, resulting in a continuous-wave output power exceeding 70 W. For the seeder, a fiber laser utilizing a nonlinear amplification process, which yields a broadband spectrum to support approximately 80 fs pulses, is employed for the high-peak-power pulse generation.

The immediate priorities for high-power delivery employing solid-core fibers are balancing the nonlinear effect and beam deterioration. Here, the scheme of tapered multimode fiber is experimentally realized. The tapered multimode fiber, featuring a 15 m (24/200 μm)–10 m (tapered region)–80 m (48/400 μm) profile, guides the laser with a weakly coupled condition. With the input power of 1035 W, the maximum output power over the 105 m delivery is 962 W, corresponding to a high efficiency of over 93% and a nonlinear suppression ratio of over 50 dB. Mode resolving results show high-order-mode contents of less than –30 dB in the whole delivery path, resulting in a high-fidelity delivery with M2 factors of 1.20 and 1.23 for the input and output lasers, respectively. Furthermore, the ultimate limits of delivery lengths for solid-core weakly coupled fibers are discussed. This work provides a valuable reference to reconsider the future boom of high-power laser delivery based on solid-core fibers.

Time-domain characterization of ultrashort pulses is essential for studying interactions between light and matter. Here, we propose and demonstrate an all-optical pulse sampling technique based on reflected four-wave mixing with perturbation on a solid surface. In this method, a weak perturbation pulse perturbs the four-wave mixing signal generated by a strong fundamental pulse. The modulation signal of the four-wave mixing, which is detected in the reflection geometry to ensure a perfect phase-matching condition, directly reflects the temporal profile of the perturbation pulse. We successfully characterized multi-cycle and few-cycle pulses using this method. The reliability of our approach was verified by comparing it to the widely employed frequency-resolved optical gating method. This technique provides a simple and robust method for characterizing ultrashort laser pulses.