William Angerer - Department of Physics and Astronomy - University ...

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3 mm and with the parameters displayed in Table 2.2. Remarkably, the data is free of
~raker fringes that characterize excitation of a quartz wedge with a monochromatic
light source (see Fig. 2.4.) In addition, equation (2.66) is plotted in Fig. 2.8 as a
function of crystal length. After ",,200 J.Lm, the oscillations are damped to half of their
value for the thin film, i.e. a film in which the bound and free waves are temporally
overlapped.
Physically, the fundamental light pulse generates both a free and a bound wave
pulse at the first vacuum/quartz interface. The bound wave is coupled to the free
wave and propagates through the quartz wedge with a group velocity characteristic of
the fundamental pulse, Vb. In contrast, the free wave propagates through the quartz
wedge with a group velocity characteristic of a pulse of twice the frequency of the
fundamental pulse, vf. If the quartz wedge is thick enough. the bound wave arrives
before the free wave at the second vacuum/quartz interface, and interference does not
occur.
In section section 2.4.1, we discussed the phenomena of Maker fringes generated
from a monochromatic laser source, which are directly related to the phase velocity
mismatch of the nonlinear bound and free wave fields in the crystal. In contrast.
excitation of a dispersive medium with an ultrafast laser source produces a nonlinear
signal that depends on both phase and group velocity mismatches. The effect of
group velocity becomes more significant as the interaction length of SHG increases.
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