[Cytometry] Optical pathways: mirrors or fibre optics?

Marty Bigos bigos at stanford.edu
Sat Feb 14 19:02:47 EST 2009


There are two types of fiber optics used in the BD instruments, single-mode to bring the laser light to the flow cell, and multi-mode, which brings the light from the fluorescence collection objective to the PMTs. The multi-mode fibers have low light loss ( < 10% ) and last quite a while; the single-mode fibers have wavelength dependent light loss (shorter, the lossier) and become unusable with UV light. For 405 violet solid state lasers the loss is about 30%. However the single mode fiber preserves beam shape, which is important for excitation in a cytometer - the multi-mode doesn't, but that has no affect on the sensitivity of the measurements. The SORP instruments gain sensitivity by using mirrors ("air launched") to direct the laser beams. However, this can lead to greater problems with alignment drift of the input beams than with fibers, and more difficulties in configuring multi-laser systems.

Power transmitted through the fiber is limited by wavelength and heating of the fiber. The fibers BD uses do not have heat problems with the 405 50 mW violet; I would not be surprised if they are OK for the 150mW 532 as well.

Marty

                                                                           
             "Helen Ferry"                                                 
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                                       [Cytometry] Optical pathways:       
             02/10/2009 10:11          mirrors or fibre optics?            
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Hi FLOWers

Is there any reason why fibre optics shouldn’t be used with high powered
lasers e.g. 150mW, 532nm or 100mW, 488nm? If not, then why are some BD
SORP instruments fitted with mirrors to direct the laser beam to the
flow cell instead of fibre optics, as in the standard machines?

I have searched the mailing list archive and other literature, but
haven’t been able to find an answer. Hopefully somebody out there
will know the answer and care to share.

Thanks!

Helen

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