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Optical Chopper Experiments
Application Note #11
Single Beam Experiment Dual Beam Experiment
In this application, a single optical beam is chopped by the In this arrangement, the output from a single source is split
outer row of slots, and the reference output from the right and chopped at two different frequencies by the two rows of
BNC is used to lock the lock-in amplifier to the chop chopper slots. One beam passes through the experiment while
frequency. The inner row of slots could also be used, in which the other is used as a reference beam. The beams are
case the left BNC would be the reference output. In either recombined and sent to the same detector. Two lock-ins are
case, the REFERENCE MODE switch is in the "up" position. used to detect the signals at inner, corresponding to the
experimental signal, and outer, corresponding to the reference
beam. If the detected signal in the experimental arm is ratioed
to the detected signal in the control arm, then effects due to
changing source intensity and detector efficiency are
removed.
Aperture 0.84" (6-slot)
Aperture 0.62"
(5-slot)
4.65"
(118 mm)
Aperture 0.170" (30-slot)
5/6 slot blade
(4.04" diameter) Aperture 0.124"
(25-slot)
3.08"
(78.2 mm)
25/30 slot blade
(4.04" diameter)
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