We describe the use of a crossed-beam irradiation system in three-dimensional femtosecond laser microprocessing to obtain three-dimensionally isotropic spatial resolution. In the crossed-beam geometry, two orthogonal objective lenses are arranged to share a common focal point. The synthesized focal spot produces an isotropic illumination volume. We demonstrate that microfluidic channels with substantially circular cross-sectional shapes can be directly fabricated inside glass by using the crossed-beam irradiation system.
Free-electron lasers (FELs), which are based on a self-amplified spontaneous emission (SASE) scheme, have attractive characters as the intense light source in short-wavelength region. However, their temporal profile and frequency-domain spectra have shot-to-shot fluctuating spikes originated from the SASE process. One of the promising approaches to these problems is a seeded FEL scheme, which is possible to realize full-coherent light pulses without shot-noise structures. We already reported the higher-order harmonic (HH) seeded FEL operation at the fundamental wavelength of 61.2 nm using a seeding source of a HH pulses from Ti:sapphire laser at the SPring-8 Compact SASE Source (SCSS) test accelerator. However, the seeded FEL pulses (intensity >4σ of SASE) were only obtained 0.3% in 3000 shots.
In recently published papers [M. J. J. Vrakking, Phys. Rev. Lett. 126, 113203 (2021); J. Phys. B 55, 134001 (2022)], Vrakking proposed an inventive scheme to control the entanglement or coherence of the vibrational states in a hydrogen molecular ion and a continuum electron, both of which were generated via the photoionization of a hydrogen molecule irradiated by a coherent pair of extreme ultraviolet (XUV) attosecond pulses and a few-femtosecond ultraviolet (UV) pulse. He clarified, for the first time to our knowledge, how the coherence of the XUV attosecond pulse pair is transferred to the molecular ion system accompanying a detached continuum electron by numerically solving a time-dependent Schr\"odinger equation (TDSE) governing the evolution of the ion and the electron in a rigorous manner. Nevertheless, it was not straightforwardly resolved how and why the specific characteristics of the resultant joint energy spectrogram emerged and how the entanglement or coherence was altered with the irradiation of the UV pulse. In this paper, we present an analytical solution of the TDSE using time-dependent perturbation theory, and we utilize the resultant solution to explain what causes the particular features in the entanglement or coherence between the electron and the ion spectra.
We demonstrate colour marking of a transparent material using laser-induced plasma-assisted ablation (LIPAA) system. After the LIPAA process, metal thin film is deposited on the surface of the ablated groove. This feature is applied to RGB (red, green and blue) colour marking by using specific metal targets. The metal targets, for instance, are Pb3O4 for red, Cr2O3 for green and [Cu(C32H15ClN8)] for blue colour marking. Additionally, adhesion of the metal thin film deposited on the processed groove by various experimental conditions is investigated.
We report optimization and characterization of a dual-chirped optical parametric amplification (DC-OPA) scheme (2011 Opt. Express 19 7190). By increasing a pump pulse energy to 100 mJ, a total (signal + idler) output energy exceeding 30 mJ was recorded with higher than 30% conversion efficiency. The feasibility of further increasing the output energy to a higher scale using the DC-OPA scheme was confirmed by a proof-of-principle experiment, in which 30%–40% conversion efficiency was observed. The signal pulse with the center wavelength of 1.4 μm was compressed to 27 fs (FWHM), which was very close to a transform-limited pulse duration of 25 fs. Since the DC-OPA scheme is efficient for generating high-energy infrared (IR) pulses with excellent scaling ability, the design parameters for obtaining hundred-mJ-level and even joule-level IR pulses are discussed and presented in detail.
We demonstrate the generation of a coherent water window x ray by extending the plateau region of high-order harmonics under a neutral-medium condition. The maximum harmonic photon energies attained are 300 and 450 eV in Ne and He, respectively. Our proposed generation scheme, combining a 1.6 microm laser driver and a neutral Ne gas medium, is efficient and scalable in output yields of the water window x ray. Thus, the precept of the design parameter for a single-shot live-cell imaging by contact microscopy is presented.
Laser-induced refractive index modification in Ag+ ion exchanged waveguides on glass substrates was observed. Waveguiding effects were measured, and an increase in refractive index of more than 2×10−3 was deduced. Refractive index profiles show that the maximum radiation-induced difference is attained 4–5 μm below the surface. Possible mechanisms for the material modification are discussed.
