Frequency-resolved optical gating

The English term frequency -resolved optical gating ( FROG, dt as " frequency-resolved optical connection " ) refers to a method of measurement of the ultrafast physics. It is used for complete characterization of ultrashort light pulses, eg from a femtosecond laser, which can be dissolved even by very rapid electronic components no longer.

Operation

The construction of a FROG similar to an autocorrelator. A beam splitter of the pulse to be analyzed is split into two parts. The same two pulses create different long distances ( the difference being precisely adjustable) and are in a nonlinear crystal superimposed on again ( for example, for sum-frequency generation ). However, instead of only the intensity of the autocorrelation spectrometer is used to measure that examines the newly generated in the crystal fraction. Thus, for many spectra for different large temporal overlap of the pulse with itself, or more precisely: the spectrally resolved autocorrelation ( second order ) of the pulse, shown graphically also called FROG trace. From this data, the duration and the temporal and spectral phase of the pulse can be numerically reconstructed by means of an algorithm.

There are numerous variants of the process in each of various non -linear effects are exploited.