THORLABS OCTP Series User Manual page 32

OCTP Series Scanner Chapter 4: Installation
When not configured for a polarization-sensitive SD-OCT system, the alignment ends here.
Please continue below for adjusting the OCTP-PS.
4.3.2. Polarization Adjustment
In polarization-sensitive OCT, the polarization state of the incident light is adjusted in both the reference arm
and the sample arm. The incident light on the sample is circularly polarized light to achieve a sensitivity to all
polarization axes in the sample and to be independent on sample rotation in plane. In contrast, the light coming
from the reference arm is linearly polarized light rotated by 45° with respect to the light going into the OCTP-PS.
That way it is able to interfere with both polarization axes.
The polarization state in both arms can be adjusted by unlocking the screw of the quarter-wave plate mounts,
as shown in Figure 34. Note that the polarization state of the light of each arm is traversed twice through the
corresponding quarter-wave plate.
Please note that changing the orientation of the collimator and hence also that of the polarization maintaining
fiber, requires a readjustment of the quarter-wave plates detailed below.
Figure 34 Polarization Adjustment by Quarter-Wave Plates in OCTP-PS
ATTENTION
The quarter-wave plates are adjusted in both arms with respect to the orientation of the
polarization axis of the optical fiber (key aligned to slow axis) in the collimator. All positions are
marked in red.
In this configuration the main intensity from the sample arm is collected on Camera 0. If this is
NOT the case, please check if the CameraLink cables are interchanged.
The OCTP-PS comes prealigned and further alignment should not be necessary. Perform the following steps
only when you are certain that realignment is necessary. When using the OCTP-PS together with a Telesto™
PS-Series OCT system, the polarization adjustment can be performed by following these steps:
®
1. Start ThorImage OCT software and select the 1D Mode to display the intensity spectra of the two
cameras.
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