Crystal-Configuration Considerations for Higher-Sensitivity Picosecond-Pulse SHG FROG

We experimentally compare a thick BIBO crystal, a walk-off compensating configuration of thin BBO crystals, and a thin PPLN crystal for the use as a nonlinear medium in SHG FROG, aiming for increased sensitivity required for complete pulse characterization of low-energy (below pJ) pulses a few picos...

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Veröffentlicht in:IEEE journal of quantum electronics 2020-04, Vol.56 (2), p.1-8
Hauptverfasser: Susnjar, Peter, Jones, Travis, Trebino, Rick, Petkovsek, Rok
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Sprache:eng
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Zusammenfassung:We experimentally compare a thick BIBO crystal, a walk-off compensating configuration of thin BBO crystals, and a thin PPLN crystal for the use as a nonlinear medium in SHG FROG, aiming for increased sensitivity required for complete pulse characterization of low-energy (below pJ) pulses a few picoseconds long at wavelengths near 1030 nm. We investigate the dependence of the spectral bandwidth of the frequency-doubled input ultrashort pulse and the conversion efficiency on focal-spot size in the nonlinear crystal. Both numerical and experimental results confirm an increase of the bandwidth with tighter focusing in a thick BIBO and a more-than-threefold increase of conversion efficiency compared to a thin BIBO crystal. A PPLN crystal is found to be the most efficient among the three, but very thin (< 0.3 mm) crystals would be required to extend the measurement capabilities of SHG FROG to sub-ps pulses. A SHG FROG using a PPLN crystal for characterization of picosecond pulse is demonstrated with a sensitivity of 2\times 10^{-3} (mW) 2 .
ISSN:0018-9197
1558-1713
DOI:10.1109/JQE.2020.2971761