Diploma thesis

or z-polarization, and we are left with three different processes:
Py = d242EyEz, (4.1)
Pz = d32E 2 y, (4.2)
Pz = d33E 2 z . (4.3)
Consequently, we should be able to identify three different conversion processes
(Ep1Ep2 → ESHG) [14]:
EyEy → Ez, (4.4)
EyEz → Ey, (4.5)
EzEz → Ez. (4.6)
A schematic representation of our setup can be seen in figure 4.12. As a pulsed
laser source, we used an optical parametric amplifier (OPA) that can generate pulsed
laser light from 1000 to 1700 nm with a FWHM around 15 nm. A small sample of
this beam has been split out to monitor the frequency, the main part has been
coupled into our waveguide. A half-wave plate in front of the crystal has been used
to change the polarisation of the incoming beam. After the crystal, we applied a
polarisation filter to test the polarization of the SHG light, whose frequency was
monitored by another spectrometer. The short-wave pass frequency filter, after the
waveguide, served the purpose to filter remaining pump light. Otherwise, the pump
light might damage the second spectrometer.
Figure 4.12: Setup to detect the different SHG processes
Into the waveguide, depicted in Figure 3.16, we sent z-polarised, y-polarised and
yz-polarized light. After the crystal we tested the SHG light for y- and z-polarisation.
This measurement has been performed multiple times at different pump wavelengths
ranging from 1200 to 1600 nm.
Our results for chip BCT0703-B12 can be seen in Figure 4.13 (all measurements
are listed in Appendix A.4.1). We where able to measure all SHG processes predicted
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