Ultrafast optical microscopy, generally employed by incorporating ultrafast laser pulses into
microscopes, can provide spatially resolved mechanistic insight into scientific problems …

We visualized negative refraction of phonon polaritons, which occurs at the interface
between two natural crystals. The polaritons—hybrids of infrared photons and lattice …

Semiconductor interfaces are at the heart of the functionality of many devices for opto-
electronic applications. At these interfaces, the importance of ultrafast dynamics–processes …

Electric-field-driven scanning tunneling microscopy (STM) that uses carrier envelope phase-
controlled pulses in the THz region (THz-STM) has been attracting considerable attention …

The coupling of terahertz optical techniques to scattering-type scanning near-field
microscopy (s-SNOM) has recently emerged as a valuable new paradigm for probing the …

Carrier distribution and dynamics in semiconductor materials often govern their physical
properties that are critical to functionalities and performance in industrial applications. The …

Many photonic and electronic molecular properties, as well as chemical and biochemical
reactivities are controlled by fast intramolecular vibrational energy redistribution (IVR). This …

In high fluence applications of lead halide perovskites for light-emitting diodes and lasers,
multi-polaron interactions and associated Auger recombination limit the device performance …

Accessing the low-energy non-equilibrium dynamics of materials and their polaritons with
simultaneous high spatial and temporal resolution has been a bold frontier of electron …

We investigate heterostructures composed of monolayer WSe2 stacked on α-RuCl3 using a
combination of Terahertz (THz) and infrared (IR) nanospectroscopy and imaging, scanning …