How to take a picture of a light pulse

How to take a picture of a light pulse

A new method for measuring the shape of a laser light wave with high accuracy has been developed by the MPI for Quantum Optics in Garching, the LMU Munich and the TU Wien (Vienna).

Now this can be done with a tiny crystal with a diameter of less than one millimeter instead of a large, complex experimental setup.

Previously, the common way to measure an infrared laser pulse was adding a much shorter laser pulse with a wavelength in the X-ray range. The new idea was born to measure light pulses not in a gas but in a solid.

Tiny crystals of silicon oxide with a diameter of a few hundred micrometers are used for this purpose. They are hit by two different laser pulses: The pulse which is to be investigated can have any wavelength ranging from ultraviolet light and visible colors to long-wave infrared. While this laser pulse penetrates the crystal, another infrared pulse is fired at the target.

This second pulse is so strong that non-linear effects in the material can change the energy state of the electrons so that they become mobile. This happens at a very specific point in time, which can be tuned and controlled very precisely. As soon as the electrons can move through the crystal, they are accelerated by the electric field of the first beam. This produces an electric current which is measured directly at the crystal. This signal contains precise information about the shape of the light pulse.

The paper has been published in Nature Communications. (

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