Latest Issue
Volume 4 ， Issue 2 ， 2024
- Abstract：Understanding material structural reaction to light is of utmost importance to advance processing resolution in ultrafast laser volume structuring into the nanoscale. Selective thermodynamic pathways are required to quench energy transport in the most rapid manner and to confine the process to nanometer lengths, bypassing optical resolution. Quantifying material dynamics under confinement, with in situ access to transient local temperature and density parameters, thus becomes key in understanding the process. We report in situ reconstruction of thermodynamic states over the entire matter relaxation path in bulk α-quartz irradiated by ultrafast nondiffractive laser beams using time-resolved qualitative and quantitative optical phase microscopy. Thermooptic dynamics indicate rapid spatially confined crystalline-to-amorphous transition to a hot dense fused silica form. Densification exceeds 20% and the matrix temperature rises to more than 2,000 K in the first nanosecond. This structural state relaxes in hundreds of nanoseconds. The dispersion and time design of the optical beam to picosecond durations increases the spatial confinement and triggers an extreme nanostructuring process based on nanocavitation that occurs within the amorphizing material, where the low-viscosity phase lowers the mechanical requirements for the process. Processing feature scales of less than a tenth of the optical wavelength are obtained in the volume. This allows for structural and morphological nanoscale material features under 3D confinement that can engineer optical materials.8|1|0Updated：2024-10-22
- Abstract：Quantum interference occurs frequently in the interaction of laser radiation with materials, leading to a series of fascinating effects such as lasing without inversion, electromagnetically induced transparency, Fano resonance, etc. Such quantum interference effects are mostly enabled by single-photon resonance with transitions in the matter, regardless of how many optical frequencies are involved. Here, we report on quantum interference driven by multiple photons in the emission spectroscopy of nitrogen ions that are resonantly pumped by ultrafast infrared laser pulses. In the spectral domain, Fano resonance is observed in the emission spectrum, where a laser-assisted dynamic Stark effect creates the continuum. In the time domain, the fast-evolving emission is measured, revealing the nature of free-induction decay arising from quantum radiation and molecular cooperativity. These findings clarify the mechanism of coherent emission of nitrogen ions pumped with mid-infrared pump laser and are found to be universal. The present work opens a route to explore the important role of quantum interference during the interaction of intense laser pulses with materials near multiple photon resonance.3|0|0Updated：2024-10-22
- Abstract：The field of ultrafast science is dependent on either ultrashort laser pulse technology or ultrafast passive detection. While there exists a plethora of sub-picosecond laser pulse solutions, streak cameras are singular in providing sub-picosecond passive imaging capabilities. Therefore, their use in fields ranging from medicine to physics is prevalent. Streak cameras attain such temporal resolutions by converting signal photons to electrons. However, the Coulomb repulsion force spreads these electrons spatiotemporally aggravating streak cameras’ temporal resolution and dynamic range—an effect that increases in severity in ultrafast applications where electrons are generated nearly instantaneously. While many electro-optical solutions have been proposed and successfully implemented, this issue remains as a challenge for all sub-picosecond streak camera technology. Instead of resorting to electro-optical solutions, in this work, we present an all-optical approach based on the combination of photon tagging and spatial lock-in detection with a technique called periodic shadowing—that is directly applicable to all generations of streak cameras. We have demonstrated that this accessible all-optical solution, consisting of a single externally applied optical component, results in (a) a >3× improvement in dynamic range, (b) a 25% increase in temporal resolution, and (c) a reduction of background noise levels by a factor of 50, which, when combined, allows for a markedly improved accuracy in the measurement of ultrafast signals.3|0|0Updated：2024-10-22
Research
- Abstract：Time-resolved transient absorption (TA) spectroscopy measurement technology provides detailed information into the ultrafast dynamics by tracking the transitions and deactivation processes of the excited-state carriers, which holds vast potential for investigating processes related to the luminescence and nonradiative recombination of materials. Pressure is considered a potent tool for tuning the carrier dynamic behaviors. The combination of high-pressure experimental technology and time-resolved TA spectroscopy measurement technology enables researchers to reveal the inherent relation between the structure and optical properties of materials, which is crucial for optimizing material performance and applications in the field of optoelectronics. In this review, the principles and the theoretical foundations of high-pressure time-resolved TA spectroscopy measurement technology will be introduced, and the research advancements in ultrafast dynamics processes of materials under high pressure will be summarized and discussed. In addition, we will expound on the future prospects of time-resolved TA spectroscopy measurement technology to detect the ultrafast dynamic behaviors of materials and complexes under the coregulation of temperature and pressure.4|0|0Updated：2024-10-22
- Abstract：Atomic time scale imaging, opening a new era for studying dynamics in microcosmos, is presently attracting immense research interest on the global level due to its powerful ability. On the atom level, physics, chemistry, and biology are identical for researching atom motion and atomic state change. The light possesses twoness, the information carrier and the research resource. The most fundamental principle of this imaging is that light records the event-modulated light field by itself, so-called all-optical imaging. This paper can answer what is the essential standard to develop and evaluate atomic time scale imaging, what is the optimal imaging system, and what are the typical techniques to implement this imaging, up to now. At present, the best record in the experiment, made by multistage optical parametric amplification (MOPA), is realizing 50-fs resolved optical imaging with a spatial resolution of ~83 lp/mm at an effective framing rate of 15 × 1012 fps for recording an ultrafast optical lattice with its rotating speed up to 13.5 × 1012 rad/s.3|0|0Updated：2024-10-22
Review
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