Spectral phase interferometry for direct electric-field reconstruction of synchrotron radiation

Abstract

An undulator is a device widely used in synchrotron light sources to produce a certain quasi-monochromatic light; however, its waveform has never been recorded due to the lack of measurement techniques. Here we propose an approach to characterize the waveforms of electric fields produced by relativistic electrons using an algorithm of spectral phase interferometry for direct electric-field reconstruction, which is one of the most common methods to characterize ultrashort laser pulses. As a result, we have succeeded in retrieving a 10-cycle square enveloped electric field, which corresponds to 10 periods of permanent magnets of the undulator. This method can dramatically improve the development of synchrotron sources including x-ray free electron lasers.