- Quantum Cascade Laser Starter Kit Instructions Manual

Starter Kit Instruction Manual Description 22
Duty cycle calculation
UPI can be used to c alculate the duty factor as
follows:
df =
2UP I−ν
P low
ν
P high
−ν
P low
with v
P low
and v
P high
as above.
To get the real duty cycle, df must be corrected
as follows:
dc = f
LDD
df = f
LDD
2UP I−ν
P low
ν
P high
−ν
P low
to compensate for systematic errors in the LDD100.
Actual value is f
LDD
= 1.1
4.6.4 Laser peak current
The laser peak current can be calculated by the
measurement of the current through the series re-
sistor Rs. This is provided by the values ULL and
UD, which are rectifier outputs. To correct for the
duty cycle, the rectifier values have to be taken into
account with the following formula for a correc tion
factor:
p = 1 +
Rds
Rcdc
where Rds and Rc are resistors in the rectifier
circuit, dc is the duty cycle calculated as in the
preceding paragr aph. Actual values are Rds=10 kΩ
and Rc=10MΩ.
The corrected values fo r the peak laser cathode
and transistor drain voltage are then given as fol-
lows:
ULL
peak
= pULL + Uds
UD
peak
= pUD + U ds
where Uds is the voltage drop across the recti-
fier diode, actual value Uds=0.25V.
Finally, the la ser peak current is then given by:
I
peak
=
ULL
peak
−UD
peak
Rs
where Rs is the series resistor, actual value Rs
=0.85Ω.