SPIDER is a technique to measure the electric field (in amplitude and phase) of ultrashort laser pulses. SPIDER is an acronym for Spectral Phase Interferometry for Direct Electric Field Reconstruction.
SPIDER employs spectral interferometry to measure the gradient of the spectral phase of the unknown laser pulse. Spectral interferometry is a linear optical technique to measure the phase difference:
Using a non-linear optical process (e.g. sum-frequency mixing) two copies of the unknown pulse are generated with a small frequency shear. This way the phase difference (above) is turned into a gradient.
This gradient of the unknown pulse phase can be integrated to reconstruct the original spectral phase. Together with a measurement of the spectrum (which can also be obtained from the SPIDER interferogram) the electric field in the time domain can be calculated via a Fourier transform.
Below is an overview of the experimental implementation of SPIDER:
Example MATLAB code:
External Links:
The SPIDER wikipedia page: https://en.wikipedia.org/wiki/Spectral_phase_interferometry_for_direct_electric-field_reconstruction
The SPIDER website at Oxford: http://www2.physics.ox.ac.uk/research/ultrafast-quantum-optics-and-optical-metrology/ultrafast-metrology/spider
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