Femto is not always necessarily better.   You can safely use more 
average power with picosecond compared to femtosecond to go deep into 
brain or muscle tissue.  I have found that picosecond is /sometimes/ 
better than femtosecond, even for SHG.  Femtosecond will give more 
initial signal but picosecond signal will stay constant, longer, at the 
same power, in tissue.  Also, for our confocal core's speciality: CARS 
microscopy, picosecond is far superior in that it matches the 
vibrational linewidths and doesn't dump a lot of energy in a broad 
spectral region like femtosecond pulses.  Dispersion is far less of a 
problem with pico and not as much need to pre-comp, but I do believe for 
THG, and if you have very weak 2-photon signal you would have to used 
pre-chirped compressed femtosecond pulses, with SHG on collagen, 
2-photon with more average power, and CARS you're ok with pico, 
otherwise you need femto.

Best,
Evangelos

Advanced Biological Imaging Scientist
Harvard Center for Nanoscale Systems
11 Oxford Street
Cambridge, MA 02138

Manja Schubert wrote:
> Dear Confocal list members,
>
> I have a question to multiphoton technology - femto second IR laser 
> versus pico second IR laser.
> We run in following problem. We have a femto second laser but because 
> of patent law we can use it only with attenuation filter and a pulse 
> stretcher meaning in the end we scanning with a pico second IR laser.
>
> Has anyone experienced how that effect the scanning outcome? For 
> example, the possible deepness of the scan. Any thoughts are highly 
> appreciated.
>
> Many thanks in advance!
>
> Cheers,
> Manja
>
> Dr. Manja Schubert
> University of Bergen
> Department of Biomedicine
> Jonas Lies  vei 91
> 5009 Bergen
> Norway
> Tel:+47-55 58 67 15