We propose an approach to separate the contributions of transient solid-state processes to the ultrafast optical response of multiresonant metasurfaces. The resonant modes of a hybrid metal–dielectric metasurface based on gold nanospheres embedded in a layer of bismuth-substituted yttrium–iron garnet exhibit complex relaxation dynamics involving bulk gold, garnet, and their interface processes. Analysis of the evolution of these resonant modes makes it possible to separate the contributions of bulk and interface processes, thereby revealing the otherwise elusive plasmon-induced hot-electron transfer across the Au-Bi:YIG interface.
The phase spectrum encodes spatial translations of fine structural features in images, offering unique physical insights distinct from conventional amplitude-based measurements. Here, we propose a novel technique, transient image phase spectroscopy (TIPS), integrating phase-resolved image analysis with ultrafast spectroscopy to extract carrier diffusion coefficients by tracking phase evolution across a time series of images. Unlike amplitude spectrum, the phase spectra of the time-resolved carrier dynamic images exhibit intrinsic immunity to overall intensity change arising from carrier recombination. Moreover, the dynamic features of the phase spectrum can be leveraged to effectively distinguish and suppress system noise. These 2 types of fundamental robustness enable reliable diffusion characterization under low signal-to-noise conditions where traditional amplitude-based methods fail. Through numerical simulations and experimental validation, we demonstrate the superior performance of TIPS, including the successful determination of high hot-carrier diffusion coefficients (~130 cm 2 s −1 ) in a rough-surface boron arsenide (BAs). For TIPS decouples spatial dynamics from amplitude decay and fluctuations, we anticipate that this phase-based paradigm will advance innovation in optical and optoelectronic measurement.
Since the first generation of attosecond pulses, observing electron dynamics on their intrinsic time scale became possible, which enabled breakthroughs across various fields, such as the revisit of tunneling time after long debate. Attosecond strong-field physics employing terawatt attosecond pulse represents another vital research front, analogous to how the advent of intense femtosecond lasers enabled the discovery of unprecedented phenomena 40 years ago. However, generation of attosecond pulses with terawatt peak power is extremely challenging, hindering the development of strong-field laser physics. In this work, we theoretically propose and design a tabletop 10-TW-class attosecond light transient in the visible regime, employing an inline spectral–temporal optical parametric amplification scheme that combines C(NH2)3BF4 (GFB) and BaB2O4 crystals. Building upon the experimentally obtained nearly 3-octave seed spanning 0.35 to 2.5 μm, our simulations yield a 524-as-duration light field transient with 7.7-mJ pulse energy and 14.7-TW peak power at 1 kHz. Furthermore, we show flexible waveform manipulation by precisely controlling the phase and spectral shape in the parametric amplification process, enabling tailored attosecond electric fields such as double-peaked, π-shifted, sawtooth-like, and square-like waveforms. The tabletop design first extends GFB-based optical parametric amplification to the attosecond regime and introduces ultraviolet amplification across 350 to 450 nm. Such a high-power attosecond light transient covering the ultraviolet–visible–near-infrared spectrum will advance attosecond nonlinear and strong-field physics and offer a potential tool for applications in biomolecules, quantum materials, and cold atomic systems.
