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For different pulse shapes, the minimum duration-bandwidth product is different. The duration-bandwidth product is minimal for zero phase-modulation. For example, s e c h 2 {\displaystyle \mathrm {sech^{2}} } pulses have a minimum duration-bandwidth product of 0.315 while gaussian pulses have a minimum value of 0.441.
Classification of the different kinds of optical autocorrelation. In optics, various autocorrelation 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 ultrashort pulses produced by modelocked lasers.
For ultrashort-pulse lasers, a hyperbolic-secant-squared (sech 2) pulse shape is often assumed, giving a time–bandwidth product of 0.315. Using this equation, the minimum pulse duration can be calculated consistent with the measured laser spectral width.
A mode-locked laser is capable of emitting extremely short pulses on the order of tens of picoseconds down to less than 10 femtoseconds.These pulses will repeat at the round trip time, that is, the time that it takes light to complete one round trip between the mirrors comprising the resonator.
FROG is currently the standard technique for measuring ultrashort laser pulses replacing an older method called autocorrelation, which only gave a rough estimate for the pulse length. FROG is simply a spectrally resolved autocorrelation, which allows the use of a phase-retrieval algorithm to retrieve the precise pulse intensity and phase vs. time.
The optimal parameters are 4 degrees of noncollinearity, β-barium borate (BBO) as the material, a 400-nm pump wavelength, and signal around 800 nm (and can be tunable in the range 605-750 nm with sub-10 fs pulse width which allows exploring the ultrafast dynamics of large molecules [1]) This generates a bandwidth 3 times as large of that of a ...
Multiphoton intrapulse interference phase scan (MIIPS) is a method used in ultrashort laser technology that simultaneously measures (phase characterization), and compensates (phase correction) femtosecond laser pulses using an adaptive pulse shaper. When an ultrashort laser pulse reaches a duration of less than a few hundred femtosecond, it ...
FWHM is applied to such phenomena as the duration of pulse waveforms and the spectral width of sources used for optical communications and the resolution of spectrometers. The convention of "width" meaning "half maximum" is also widely used in signal processing to define bandwidth as "width of frequency range where less than half the signal's ...