We report on a high-energy, few-ps, continuous-wave pumped Ho:YLF regenerative amplifier (RA) operating in a chirped-pulse amplification arrangement. A three-stage optical parametric amplifier serves as versatile seed source emitting broadband pulses centered at 2050 nm. It provides seed pulses with 4 µJ energy within the Ho:YLF amplification bandwidth centered at 2051 nm. Thanks to the high seed pulse energy, bifurcation instabilities are mitigated and gain narrowing is reduced for such a high-gain Ho-doped RA operating at few kHz repetition rate. At 1 kHz the Ho:YLF RA emits 22.5 mJ energy pulses with a compressed pulse duration of 2.0 ps in the stable single-pulse regime. The water cooled RA features a high extraction efficiency of 31% and exhibits a remarkable stability of 0.11% rms. Doubling the repetition rate to 2 kHz, RA pulse energy reaches 15 mJ. The demonstrated 10 GW peak power at 1 kHz and the 30 W average power at 2 kHz are the highest values reported to date for few-ps RAs operating at 2 µm wavelength.
Dynamic resistance exercise (RE) produces sinusoidal fluctuations in blood pressure, with hypotension and cerebral hypoperfusion commonly observed immediately following RE. Whether the cerebral vasculature adapts to these regular blood pressure challenges is unclear. This study examined the cerebrovascular response to post-dynamic RE orthostasis.
Harvard Medical School, Boston, MA 02114, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Cardiology, Erasmus Medical Center, Rotterdam GD3015, The Netherlands; Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
Photoacoustic microscopy (PAM) is a high-resolution and non-invasive imaging modality that provides optical absorption contrast. By employing dual- or multiple-wavelength excitation, PAM extends its capabilities to offer valuable spectroscopic information. To achieve efficient multispectral PAM imaging, an essential requirement is a light source characterized by a high repetition rate and switching rate, a ≈microjoule pulse energy, and a ≈nanosecond pulse duration.
We report on continuous high-harmonic generation (HHG) at 1 kHz repetition rate from a liquid-sheet plasma mirror driven by relativistic-intensity near-single-cycle light transients. Through precise control of both the surface plasma density gradient and the driving light waveform, we can produce highly stable and reproducible extreme ultraviolet spectral quasi-continua, expected to correspond to the generation of stable kHz-trains of isolated attosecond pulses in the time domain. This confirms the exciting potential of liquid-sheet targets as one of the building blocks of future high-power attosecond lasers.
Transverse mode instability (TMI) significantly limits the power scaling of ytterbium-doped fiber lasers. In this Letter, what we believe to be a novel TMI mitigation strategy is proposed and demonstrated in a bidirectional output fiber laser. On the basis of the continuous wave (CW) pump, integrating a quasi-continuous wave (QCW) pump can effectively improve the TMI threshold of the system.
Resonant inelastic X-ray scattering (RIXS) is an ideal X-ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core-hole lifetime energy broadening. Also, in pump-probe experiments the interaction time is made very short by the same core-hole lifetime. RIXS is very photon hungry so it takes great advantage from high-repetition-rate pulsed X-ray sources like the European XFEL.
