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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.
For a Gaussian time profile, the autocorrelation width is longer than the width of the intensity, and it is 1.54 longer in the case of a hyperbolic secant squared (sech 2) pulse. This numerical factor, which depends on the shape of the pulse, is sometimes called the deconvolution factor. If this factor is known, or assumed, the time duration ...
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.
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.
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 ...
The bandwidth of pulses generated by optical rectification is limited by the laser pulse duration, terahertz absorption in the crystal material, the thickness of the crystal, and a mismatch between the propagation speed of the laser pulse and the terahertz pulse inside the crystal. Typically, a thicker crystal will generate higher intensities ...
Pulse duration using 50% peak amplitude. DECT phone pulduration measurement (100 Hz / 10 mS) on channel 8. In signal processing and telecommunications, pulse duration is the interval between the time, during the first transition, that the amplitude of the pulse reaches a specified fraction (level) of its final amplitude, and the time the pulse amplitude drops, on the last transition, to the ...