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

[slap babies]

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

 

[Dr Lots-o'watts]

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.

 

[slap babies]

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.