Ultrashort Laser Pulse Phenomena, 2nd Edition

466 Diagnostic Techniques

to pulse variation in frequency by displaying the pulse train on an oscilloscope,

after transmission through a spectrometer or reflection off a thin (100 µm)

etalon.

9.3. MEASUREMENT TECHNIQUES

9.3.1. Nonlinear Optical Processes for Measuring

Femtosecond Pulse Correlations

In ultrafast optics, SHG is the most widely used technique for recording

second-order correlations. Because it is a nonresonant process of electronic

origin, the nonlinearity is fast enough to measure pulses down to 10

−14

s dura-

tion. While applicable through the IR and visible spectrum, the method is limited

at short wavelength (λ<380 nm) by the UV absorption edge of optical crys-

tals. Techniques that have been used successfully for shorter wavelengths include ...