DazScope
manual
Chapter 3 : Software overview
Figure 3.7: Content of the ChirpScan configuration panel (simplified panel).
Pulse bandwidth (nm)
Order 2 min (fs
2
)
Order 2 max (fs
2
)
10
-20 000
+20 000
20
-5 000
+5 000
30
-3 000
+3 000
40
-2 000
+2 000
50
-2 000
+2 000
60
-2 000
+2 000
Table 3.1: Recommended minimum values for the ChirpScan algorithm as a function of the am-
plified pulse bandwidth at 800nm. A rule of thumb is to choose 2 or 3 times the square of the
FWHM duration of the corresponding Fourier-transform-limited pulse. Larger values may be used
if the spectral phase to correct for is particularly high.
around the current reference waveform
order2
(see subsection
). More precisely the scanned
second orders are given by formula
ϕ
2
,k
=
ϕ
2
,
ref
+
ϕ
2
,
min
+ (
ϕ
2
,
max
−
ϕ
2
,
min
) (
k
−
1)
/
(
N
−
1) for
k
= 1
..N
(3.1)
where
ϕ
2
,
ref
is the second order phase coefficient of the reference waveform,
ϕ
2
,
min
is the value of
the
Order2 Min
control and
ϕ
2
,
max
is the value of the
Order2 Max
control.
N
is the number of
discrete chirp values scanned over the range defined by the former second order values. Units are
in fs
2
.
Some optional settings of the ChirpScan algorithm can also be defined. The ChirpScan algo-
rithm was basically specified and designed to correct polynomial spectral phase up to the fourth
order only. However, it has, in principle, the ability to detect more complex phase aberrations.
The measured spectral phase is therefore divided into:
•
a fourth order polynomial phase
•
a residual phase
Depending on the settings of the ChirpScan algorithm, the DazScope can correct for either the
polynomial phase only or the full spectral phase.
Residual phase mode:
indicates which curves are displayed on top of the experimental data
picture and if the user is allowed to correct for the residual phase.
•
Do not correct: displays only the polynomial correction (white curve). No residual phase
correction allowed.
FASTLITE-9 september 2008
