Diploma thesis
Diploma thesis
Diploma thesis
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1.90<br />
1.85<br />
1.80<br />
1.84<br />
1.82<br />
1.80<br />
1.78<br />
1.76<br />
neff<br />
neff<br />
Modelling<br />
advanced<br />
2.5 3.0 3.5 4.0 4.5 5.0 Ω�PHz�<br />
Figure 3.13: Comparison between neff for bulk crystal, slab waveguide<br />
and the model considering evanescences<br />
3 4 5 6 Ω�PHz�<br />
Figure 3.14: neff in waveguides<br />
�0,0�<br />
�0,1�<br />
�1,1�<br />
0.010<br />
0.008<br />
0.006<br />
0.004<br />
�neff<br />
bulk<br />
simple<br />
�0,0���0,1�<br />
�0,0���1,1�<br />
3 4 5 6 Ω�PHz�<br />
Figure 3.15: neff difference in waveguides<br />
shifted phasematching contours (Figure 3.18). The differences in effective refraction<br />
index increase significantly for lower frequencies (Figure 3.15). For PDC this has<br />
higher influence on the signal and idler modes than on the pump modes (Figure<br />
3.15).<br />
With the expansion of our model to higher order spatial modes, modal overlap<br />
between signal, idler and pump modes has to be taken into account. It will limit the<br />
efficiency of this ”higher order” phasematching. The transverse spatial dimensions<br />
of the electric fields have been neglected in the prior derivation of PDC (Eq. 3.23).<br />
15
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