Latest Issue
Volume 4 ， Issue 3 ， 2024
- Abstract：Ultrafast imaging is key for the real-time visualization of many transient events in physics, chemistry, and biology. The past decade has witnessed the blossom of new theories and technologies that have substantially propelled ultrafast imaging. The newly developed ultrafast imaging systems, in turn, have enabled unprecedented applications in both fundamental and applied sciences that unveil many new scientific discoveries ranging from carrier dynamics to brain functions. To date, ultrafast imaging marks an active frontier in both research and innovation.16|1|0Updated：2024-10-22
Editorial
- Abstract：Singlet fission (SF) is a spin-conserving process converting 1 singlet exciton into 2 triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley–Queisser limit. However, it remains unclear how intermolecular coupling, which is subject to the aggregation extent in thin-film morphology, controls SF pathways and dynamics. The prototype molecule 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) has been extensively studied to investigate SF mechanisms. However, previous literature reports have presented divergent SF mechanisms and pathways in TIPS-pentacene films. In this study, solvent vapor annealing treatment is used to deliberately adjust the aggregation extent in TIPS-pentacene films. This enables us to reproduce various SF pathways reported in the literature under the same experimental conditions, with the only variation being the level of aggregation. These results shed light on the crucial role that molecular aggregation plays in modulating both the SF mechanism and pathway and reconciles the previously contentious SF mechanisms and pathways reported in TIPS-pentacene films. Our study offers substantial insights into the understanding of the SF mechanism and provides a potential avenue for future control of SF pathways in accordance with specific application requirements.11|2|0Updated：2024-10-22
- Abstract：Dynamic phenomena occurring on the ultrafast time scales are inherently difficult to image. While pump–probe techniques have been used for decades, probing nonrepeatable phenomena precludes this form of imaging. Additionally, many ultrafast phenomena, such as electron dynamics, exhibit low amplitude contrast in the optical wavelength range and thus require quantitative phase imaging. To better understand the underlying physics involved in a plethora of ultrafast phenomena, advanced imaging techniques must be developed to observe single events at an ultrafast time scale. Here, we present, to the best of our knowledge, the first ptychographic imaging system capable of observing ultrafast dynamics from a single event. We demonstrate ultrafast dynamic imaging by observing the conduction band electron population from a 2-photon absorption event in ZnSe pumped by a single femtosecond pulse. We verify experimental observations by comparing them to numeric solutions of a nonlinear envelope equation. Our imaging method represents a major step forward in ultrafast imaging, bringing the capabilities of ptychography to the ultrafast regime.11|0|0Updated：2024-10-22
- Abstract：Soliton molecules in optical resonators have attracted remarkable attention in nonlinear dynamics, driven by their compelling analogies with matter molecules. So far, while extensive research has been conducted on their generation, pulsations, and dissociation behaviors, the investigation of their quasi-periodic dynamics has been relatively limited. Here, we present a systematic exploration of the quasi-periodic dynamics of soliton molecules using advanced balanced optical cross-correlation techniques. The incommensurable quasi-period bifurcations constituted of cascaded Hopf bifurcations are found, providing an unambiguous pathway toward chaotic soliton molecules. The chaotic intramolecular dynamics are analyzed by time series, radio frequency spectra, phase portraits, and Lyapunov exponent analysis. In addition, we reveal an intrinsic frequency entrainment phenomenon experimentally. Such frequency entrainment provides a novel perspective on synchronization in optical resonators, encompassing the competition and interaction of oscillations across multiple temporal scales. Our experimental findings offer clear proof that the gain dynamics serve as the origin of the binding forces between solitons within the molecule, which are well supported by the numerical simulations. By advancing the understanding of sub-femtosecond resolved quasi-period dynamics of optical soliton molecules, this study contributes to the broader field of complex nonlinear dynamics, paving the way for future explorations into the intricate behaviors of solitons within optical resonators and relevant fields.6|0|0Updated：2024-10-22
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Two-Dimensional Control of Rydberg Fragment Emission in Dissociative Frustrated Ionization of Oxygen
Abstract：Advances in producing tailored ultrashort laser pulses have enabled the generation and control of molecular dissociative Rydberg excitation along the polarization axis of the laser field. Here, we exploit the orthogonally polarized two-color femtosecond laser fields and achieve an unprecedented two-dimensional control of Rydberg fragment emission in the dissociative frustrated single ionization of oxygen. The Rydberg fragments are collected over the 4π solid angle, whose momentum distribution is manifested in a characteristic four-lobe pattern. Through precise scanning of the relative phase of the orthogonal two-color laser fields, we demonstrate control over asymmetric directional emission of the Rydberg fragments. Our experimental findings are well supported by classical trajectory Monte Carlo simulations, which suggest an efficient emission control achieved through the manipulation of charge localization upon ionization.6|0|0Updated：2024-10-22
Research
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