Progress and Prospects in Optical Ultrafast Microscopy in the Visible Spectral Region: Transient Absorption and Two-Dimensional Microscopy

Abstract

Ultrafast optical microscopy, generally employed by incorporating ultrafast laser pulses into microscopes, can provide spatially resolved mechanistic insight into scientific problems ranging from hot carrier dynamics to biological imaging. This Review discusses the progress in different ultrafast microscopy techniques, with a focus on transient absorption and twodimensional microscopy. We review the underlying principles of these techniques and discuss their respective advantages and applicability to different scientific questions. We also examine in detail how instrument parameters such as sensitivity, laser power, and temporal and spatial resolution must be addressed. Finally, we comment on future developments and emerging opportunities in the field of ultrafast microscopy.

Synthesis of Self-Supporting Gold Microplates on Soft Substrates through Infiltration Growth Mechanism

“…The experimental setup has been widely applied and discussed earlier . A Coherent Mira 900 Ti:sapphire oscillator combined with a Coherent Mira optical parametric oscillator (OPO) laser system is used for the Au MP acoustic vibration measurements.…”

Coherent Acoustic Vibrational Spectrum of Single and Coupled Nanoresonators

“…An improvement in ultrafast spectroscopy measurements is the recording of the vibrational dynamics of single nanoresonators, which removes inhomogeneous broadening effects from the distribution of particle sizes and shapes in ensemble studies. , There have also been significant efforts to develop techniques that are capable of high spatial resolution in probing coherent phonons. These techniques include X-ray diffraction imaging, , ultrafast electron diffraction imaging, − four-dimensional electron energy-loss spectroscopy, and nanoscale coherent phonon spectroscopy. , The advantages and disadvantages of which are well discussed in refs and .…”

On-Chip Lock-In Detection for Ultrafast Spectroscopy of Single Particles

“…Beyond the steady-state regime, time-resolved studies are vital to understanding the underlying mechanisms that govern the optical properties of these nanomaterials. − By tracking the optical behavior down to the femtosecond time scale after initial photoexcitation, time-resolved methods can resolve the ultrafast dynamics of photoexcited charge carriers, like their equilibration and diffusion, as well as subsequent mechanical and thermal effects. , Often employed time-resolved methods such as transient absorption/extinction spectroscopy and 2D ultrafast spectroscopy use laser pulses to pump and probe samples with adjustable time delays between them . On the ensemble level, these techniques have provided a wealth of information on systems ranging from biological materials to organic crystals and nanoparticles. , However, measurements of single particles are required to fully resolve their photoexcited dynamics if the material’s properties are affected by heterogeneity in particle morphology or local environment.…”