Ultrafast Electron Microscopy
Transmission electron microscopy (TEM) is one of the most powerful imaging techniques, enabling imaging of three-dimensional (3D) structures at the atomic scale. However, the temporal resolution of TEM is often limited by the recording rate of the imaging device. Thus, to overcome such a limit, a pulsed laser source is applied to trigger the photoemission and, subsequently, to obtain a higher temporal resolution.
Ultrafast electron microscopy (UEM or UTEM) is, essentially, a pump-probe technique where an ultrafast laser pump pulse excites the material and a delayed probe – electron pulse – detects the response at a specific time correlated with the pump pulse. Accordingly, then the temporal resolution is no longer limited by the speed of the electron detector as it is determined by both the pump laser pulse duration and probe electron pulse. Therefore, the generation of short electron pulses is also quite important and is often carried out using a second or third harmonic of the fundamental frequency of the same ultrafast laser. Furthermore, the UEM requires the laser output with a high pulse repetition rate and high output stability to preserve a high signal-to-noise ratio (SNR).
The PHAROS and CARBIDE lasers with femtosecond pulse duration, high repetition rate, and high output stability are excellent sources for ultrafast electron microscopy, making it a promising ultrafast technology.
