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1. Inner shell excitation by strong field laser rescattering: optimal laser conditions for high energy recollision

   https://doi.org/10.1364/JOSAB.440211  

   Kelley, L. ; Germain, Z. ; Jones, E. C. ; Milliken, D. ; Walker, Barry C. ( November 2021 , Journal of the Optical Society of America B)

   We address the challenge of finding the optimal laser intensity and wavelength to drive high-energy, strong field rescattering and report the maximum yields of K-shell and${\mathrm{L}}_{\mathrm{I}}$-shell hole creation. Surprisingly, our results show laser-driven rescattering is able to create inner shell holes in all atoms from lithium to uranium with the interaction spanning from the deep IR to x-ray free electron laser sources. The calculated peak rescattering follows a simple scaling with the atomic number and laser wavelength. The results show it is possible to describe the ideal laser intensity and wavelength for general high-energy laser rescattering processes.
2. Nanosecond Laser Annealing of NMC 811 Cathodes for Enhanced Performance

   https://doi.org/10.1149/1945-7111/acc27d  

   Khosla, Nayna ; Narayan, Jagdish ; Narayan, Roger ; Sun, Xiao-Guang ; Paranthaman, M. Parans ( March 2023 , Journal of The Electrochemical Society)

   Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi_0.8Mn_0.1Co_0.1O₂(NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li₂CO₃passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li₂CO₃layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li⁺to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions.more »As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.

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3. Wake dynamics of air filaments generated by high-energy picosecond laser pulses at 1 kHz repetition rate

   https://doi.org/10.1364/OL.439232  

   Higginson, A. ; Wang, Y. ; Chi, H. ; Goffin, A. ; Larkin, I. ; Milchberg, H. M. ; Rocca, J. J. ( October 2021 , Optics Letters)

   We investigated the filamentation in air of 7 ps laser pulses of up to 200 mJ energy from a 1.03 μm-wavelength Yb:YAG laser at repetition rates up to$f=1\mathrm{k}\mathrm{H}\mathrm{z}$. Interferograms of the wake generated show that while pulses in a train of repetition rate$f=0.1\mathrm{k}\mathrm{H}\mathrm{z}$encounter a nearly unperturbed environment, at$f=1\mathrm{k}\mathrm{H}\mathrm{z}$, a channel with an axial air density hole of$\sim <\#comment/>20\mathrm{\%<\#comment/>}$is generated and maintained at all times by the cumulative effect of preceding laser pulses. Measurements at$f=1\mathrm{k}\mathrm{H}\mathrm{z}$show that the energy deposited decreases proportional to the air channel density depletion, becoming more pronounced as the repetition rate and pulse energy increase. Numerical simulations indicate that contrary to filaments generated by shorter duration pulses, the electron avalanche is the dominant energy loss mechanism during filamentation with 7 ps pulses. The results are of interest for the atmospheric propagation of joule-level picosecond pulses from Yb:YAG lasers, of which average powers now surpass 1 kW, and for channeling other directed energy beams.
4. Radio frequency transmitter based on a laser frequency comb

   https://doi.org/10.1073/pnas.1903534116  

   Piccardo, Marco ; Tamagnone, Michele ; Schwarz, Benedikt ; Chevalier, Paul ; Rubin, Noah A. ; Wang, Yongrui ; Wang, Christine A. ; Connors, Michael K. ; McNulty, Daniel ; Belyanin, Alexey ; et al ( April 2019 , Proceedings of the National Academy of Sciences)

   Since the days of Hertz, radio transmitters have evolved from rudimentary circuits emitting around 50 MHz to modern ubiquitous Wi-Fi devices operating at gigahertz radio bands. As wireless data traffic continues to increase, there is a need for new communication technologies capable of high-frequency operation for high-speed data transfer. Here, we give a proof of concept of a compact radio frequency transmitter based on a semiconductor laser frequency comb. In this laser, the beating among the coherent modes oscillating inside the cavity generates a radio frequency current, which couples to the electrodes of the device. We show that redesigning the top contact of the laser allows one to exploit the internal oscillatory current to drive a dipole antenna, which radiates into free space. In addition, direct modulation of the laser current permits encoding a signal in the radiated radio frequency carrier. Working in the opposite direction, the antenna can receive an external radio frequency signal, couple it to the active region, and injection lock the laser. These results pave the way for applications and functionality in optical frequency combs, such as wireless radio communication and wireless synchronization to a reference source.
5. Aluminum with dispersed nanoparticles by laser additive manufacturing

   https://doi.org/10.1038/s41467-019-12047-2  

   Lin, Ting-Chiang ; Cao, Chezheng ; Sokoluk, Maximilian ; Jiang, Lin ; Wang, Xin ; Schoenung, Julie M. ; Lavernia, Enrique J. ; Li, Xiaochun ( September 2019 , Nature Communications)

   While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000 MPa, plasticity over 10%, and Young’s modulus of approximately 200 GPa, offering one of the highest specific Young’s modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400 °C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes.