Optical autocorrelation

In <a href="/facts/Optics/p0vq4S1T">optics</a>, various <a href="/facts/Autocorrelation/dm4MqK0A">autocorrelation</a> functions can be experimentally realized. The field autocorrelation may be used to calculate the spectrum of a source of light, while the intensity autocorrelation and the interferometric autocorrelation are commonly used to estimate the duration of <a href="/facts/Ultrashort_pulse/V8joGdvF">ultrashort pulses</a> produced by <a href="/facts/Modelocking/7p9MjBjT">modelocked</a> <a href="/facts/Laser/jk6PTvvT">lasers</a>. The laser pulse duration cannot be easily measured by <a href="/facts/Optoelectronic/0SCr9px0">optoelectronic</a> methods, since the response time of <a href="/facts/Photodiode/152Rpk06">photodiodes</a> and <a href="/facts/Oscilloscope/HMdD8XVk">oscilloscopes</a> are at best of the order of 200 <a href="/facts/Femtosecond/vaVXTVyR">femtoseconds</a>, yet laser pulses can be made as short as a few <a href="/facts/Femtosecond/vaVXTVyR">femtoseconds</a>.
In the following examples, the autocorrelation signal is generated by the nonlinear process of <a href="/facts/Second-harmonic_generation/NzWSrT3J">second-harmonic generation</a> (SHG). Other techniques based on <a href="/facts/Two-photon_absorption/BaEbrAKj">two-photon absorption</a> may also be used in autocorrelation measurements, as well as higher-order nonlinear optical processes such as third-harmonic generation, in which case the mathematical expressions of the signal will be slightly modified, but the basic interpretation of an autocorrelation trace remains the same. A detailed discussion on interferometric autocorrelation is given in several well-known textbooks.

Optical autocorrelation open-in-new

Optical autocorrelation