Diploma thesis

(Figure 4.17). The difference between phasematched and unphasematched SHG is
very instructive in Figure 4.18. Minimal pump power leads to SHG light at 780
nm. The conversion efficiency is much larger than at the peak to the left. For the
full data set please refer to Appendix A.4.2. Note that in Figures 4.15 to 4.18, the
Shg power Pump power [a.u.]
Shg power Pump power [a.u.]
2
1.5
1
0.5
Mapping pump wavelength to shg wavelength
Shg spectrum
Pump spectrum
0
700 720 740 760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.15: Shifted SHG
2
1.5
1
0.5
Mapping pump wavelength to shg wavelength
Shg spectrum
Pump spectrum
0
700 720 740 760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.17: Insufficient pump power
Shg power Pump power [a.u.]
2
1.5
1
0.5
Mapping pump wavelength to shg wavelength
Shg spectrum
Pump spectrum
0
700 720 740 760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.16: Phasematched SHG
Shg power Pump power [a.u.]
2
1.5
1
0.5
Mapping pump wavelength to shg wavelength
Shg spectrum
Pump spectrum
0
700 720 740 760 780 800 820 840
Shg wavelength [nm] Pump wavelength [nm/2]
Figure 4.18: Near phasematching
amplitudes of pump and SHG power have been scaled to illustrate the mappings
between SHG and pump light. Yet all plots in this measurement share the same
scaling factor.
Irregularities in the manufacturing process may lead to a different phasematching
contour for each different waveguide. Another measurement in a different waveguide
has been performed to investigate possible differences. This time no amplification
around 780 nm occurred as plotted in Figure 4.19. Furthermore at 800 nm a very
sharp peak was excited (Figure 4.20). This peak bears no resemblance to the prior
measurement and seems too narrow to result from phasematched SHG. One possible
explanation is remaining pump light from the optical amplifier that pumps the OPA.
This light around 800 nm may have seeded some SHG at this wavelength. Alternatively,
phasematched SHG may not have occurred because of insufficient pump
power. Given that we used another waveguide on the chip, it may also be possible
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