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High sensitivity visualization of ultrafast carrier diffusion using a wide field holographic microscope

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2023-12-25 14:16:07
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A sketch of the imaging and holographic parts of a transient holographic microscope, including a pulse sequence, to illustrate the signal modulation method. By imaging the pinhole array at the sample position, a diffraction limited excitation spot array can be created, allowing for the simultaneous collection of transient data around 100 excitation spots.

Femtosecond transient microscopy is an important tool for studying the ultrafast transport characteristics of excited states in solid samples. Most implementations are limited to photoexcitation of a single diffraction limit point on the sample and tracking the temporal evolution of subsequent carrier distribution, thus covering a very small sample area.

Recently, scientists from Italy and Spain have demonstrated how to construct an all optical phase-locked camera by using off-axis holography, significantly increasing the field of view of ultrafast microscopes. The camera decouples the signal demodulation speed from the maximum detector frame rate.

In this original work published in the journal Ultrafast Science, researchers demonstrated simultaneous transient imaging of dozens of individual nanoobjects, with the entire field of view excitation being desirable. It is not yet clear how to apply new holographic techniques in solid-state samples that require diffraction limit excitation. Ideally, a diffraction limited excitation point array covering the entire field of view will be generated, so that multiple points in the large sample area can be detected simultaneously.

The article "High sensitivity visualization of ultrafast carrier diffusion using a wide field holographic microscope" demonstrates how to achieve this feature by imaging a pinhole array at the sample position. This not only helps to obtain statistical information about sample photophysics, but also for uniform samples, the signals of all light spots can be averaged, greatly improving the signal-to-noise ratio.

Source: Laser Net

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