Practical question- anyone w. experience w. BBO crystals?

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SUMMARY

The discussion centers on the challenges faced when inserting BBO (Beta Barium Borate) crystals into the optical path of Ti-Sapphire (TiSaph) femtosecond lasers. Users report achieving strong second harmonic generation (SHG) output but experiencing severe spatial distortion of the pulse shape, resulting in a transition from a circular input to a line-shaped output. This issue has been observed with two separate crystals across different laser systems, raising concerns about potential surface defects affecting SHG efficiency.

PREREQUISITES
  • Understanding of Ti-Sapphire laser operation
  • Knowledge of second harmonic generation (SHG) principles
  • Familiarity with BBO crystal properties and applications
  • Experience in optical pulse characterization techniques
NEXT STEPS
  • Investigate BBO crystal surface quality and its impact on SHG efficiency
  • Learn about optimizing pulse shape in Ti-Sapphire laser systems
  • Research techniques for characterizing optical pulse distortion
  • Explore alternative nonlinear optical materials for SHG applications
USEFUL FOR

Optical physicists, laser engineers, and researchers working with nonlinear optics and pulse shaping in laser systems.

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hi all-

having a strange (perhaps expected?) problem inserting a BBO into the optical path of a TiSaph fs laser.

the issue is that i can achieve strong SHG output, but only with *severe* spatial distortion of the pulse shape.

has anyone had experience/encountered this issue in an optics lab? if so i can go into more details.

tia

slaps
 
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I've used BBO with Ti-Sapphire, and I've used cameras to characterize pulse shape. But I haven't specifically seen the wave front of a TiSaph pulse that went through a BBO.

Interested in the problem and more details though. I might have time to look it up.
 
well, i suspect its less of a 'physicsy' problem than one might hope.

generally, when things are working well the output SHG more or less matches the input pulse shape with some extra chirp and/or dispersion which can often be disregarded.

in our case, we see this 'good' output shape, but as you try and optimize the SHG signal, a second component is introduced which is 1-2 orders of magnitude more intense and is distorted into the shape of a line. thus, you have a circular input and a line output. moreover, if you proceed to optimize the output of this line-shaped SHG output, the crystal ends up at an extremely cockeyed angle.

to make matters worse, its happening w/ two separate crystals on two separate laser systems. in the past (two years) i don't recall this problem. I'm curious if there may be enhanced SHG off a surface defect, but the problem persists even if you move the crystal surface laterally.
 

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