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

46
is measured as a function of translation distance. For a quartz wedge with a 1 0
angle
excited by an 800 nm Ti:AI 2 0 3 pulse, the damped Maker fringe has a period of
2.4 mm. In other words, translating the quartz wedge by 2.4 mm results in one ~Iaker
fringe. Fourth, a value for ~w is assumed and the Maker fringe damping parameter,
17, is calculated from the measured SHG intensity as a function of position, the quartz
thickness, the wavelength of the incident light, and the quartz wedge angle. Fifth.
the measured 17 is compared with the calculated 17.
If the measured T/ is greater than
the calculated 17, then T/ is recalculated assuming a smaller ~w.
Conversely. if the
measured 17 is smaller than the calculated T/, then 17
is recalculated assuming a larger
~w. This procedure is repeated until the calculated T/ equals the measured 17. This
procedure determines ~w.
vVe define ~w as full width at which the intensity of the pulse falls to 1/ e 2 of
its max:imum value. Assuming the pulse is Fourier transform limited, the angular
frequency bandwidth is related to the time width of the pulse as
8
TFWI = ---
~ ~WFW 1
~
(2.70)
Conventionally, pulse widths are reported in terms of the full width at half ma.'dmum.
TFW H AI rather than T FW!:r. These quantities are related as
e
ln2
TFWHM = -T FW
1
2 ~
(2.71)
vVe discuss typical values of TFWHM and ~w for our Ti:Ah03 laser system in section
3.9.
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