Spatial Characterization Of Two-Photon States - GAP-Optique
Spatial Characterization Of Two-Photon States - GAP-Optique
Spatial Characterization Of Two-Photon States - GAP-Optique
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Before<br />
the crystal<br />
4.3. Effect of the Poynting vector walk-off on the OAM transfer<br />
After<br />
the crystal<br />
Polarization Optical axis<br />
Figure 4.11: The images obtained with a ccd camera show that before the crystal,<br />
the pump beam has a circular shape, and that after passing the crystal part of the<br />
beam gets displaced in the direction of the optical axis of the crystal. The displaced<br />
part corresponds to the portion of the beam polarized orthogonal to the crystal axis.<br />
In the case of the last image almost all the beam is displaced. The values of the<br />
experimental parameters are listed in table 4.3.<br />
every rotation, the tilt of the crystal was adjusted to achieve the generation of<br />
photons at the same noncollinear angle in all cases.<br />
The bottom row of figure 4.12 presents a sample of images taken at different<br />
azimuthal sections of the cone, while the upper row shows the expected shape<br />
predicted by the theory. Each column shows the coincidence rate for different<br />
angles, α = 0 ◦ , 90 ◦ , 180 ◦ and 270 ◦ . Each point of these images corresponds to<br />
the recording of a 10 seconds measurement. The typical maximum number of<br />
coincidences is around 10 coincidences per second. Each image is 10 × 10 mm,<br />
and its resolution is 50 × 50 points.<br />
Theory<br />
Experiment<br />
0º 90º 180º 270º<br />
Figure 4.12: The coincidence measurements of the mode function, as well as the<br />
theoretical calculations, show that the ellipticity of the mode function changes for<br />
different positions on the cone. The ellipticity is minimal for α = 90 ◦ . The values of<br />
the experimental parameters are listed in table 4.3.<br />
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