Diploma thesis

Shg power Pump power [a.u.]
Shg power Pump power [a.u.]
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Shg spectrum
Pump spectrum
Mapping pump wavelength to shg wavelength
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Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.21: No phasematching
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Shg spectrum
Pump spectrum
Mapping pump wavelength to shg wavelength
760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.23: Shifted SHG
Shg power Pump power [a.u.]
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Shg spectrum
Pump spectrum
Mapping pump wavelength to shg wavelength
760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.22: Near phasematching
Shg power Pump power [a.u.]
90
80
70
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0
Shg spectrum
Pump spectrum
Mapping pump wavelength to shg wavelength
760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.24: Phasematching point
We can now use this error vector to correct the expected phasematching function
(see figure 4.25). In this graph we assumed ωp1 = ωp2 = ωp, and plotted the sinc
function of SHG, approximated as a Gaussian distribution.
φ(ωp) = e
L2
− (ky(ωSHG)−ky(ωp)−kz(ωp)−kΛ−kE) 2
4
(4.11)
The blue line shows the theoretically predicted phasematching point at 1300 nm,
the red line the new phasematching fitted to the experimental results.
The overall fitting constant kE is in the range of the grating vector. From
an expected phasematching point at 1300 nm, we had to adjust our model to a
phasematching at 1560 nm. Additionally, the theoretically predicted phasematching
ranges from 1550 nm to 1650 nm which is much broader than measured in the
experiment. This underlines the discrepancies between theory and experiment, and
may be solved by a better model of the waveguide geometry and hence more accurate
Sellmeier equations. The real phasematching contour will most probably exhibit a
steeper slope at the degeneracy point.
We scanned the two-dimensional phasematching plane of PDC on the +45 ◦ slope,
as plotted in Figure 4.26. The one dimensional plot in Figure 4.25 is a cut through
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