[OpenSPIM] Cobolt lasers in OpenSPIM?

[Veli-Pekka Ronkainen]

Thanks Jan for your comprehensive reply!

This helps a lot and gives many aspects to think about. What is the operating software you are using? µManager or something else, and how well these lasers integrate with the software? 

Regards,
Veli-Pekka 

-----Original Message-----
From: Jan Krieger [mailto:j.krieger at dkfz-heidelberg.de] 
Sent: 19. joulukuuta 2013 14:11
To: Veli-Pekka Ronkainen; openspim at openspim.org
Subject: Re: [OpenSPIM] Cobolt lasers in OpenSPIM?

Hi!

we are using Cobolt DPSS lasers in a dual-color SPIM setup (not an openSPIM, but a comparable design: 
http://www.dkfz.de/Macromol/research/spim.html and a new publication to appear in a few days/weeks: Krieger, Singh etal. (2013): "Dual-Color Fluorescence Cross-Correlation Spectroscopy on a Single Plane Illumination Microscope (SPIM-FCCS)", OPtics Express, accepted). The lasers are generally good, but you should care for a few things:

1. As most DPSS lasers they are stable at the specified output power, but might get instable if you go below 10% of that power (our 25mW lasers typically show a TEM20 or TEM10 mode, when driven at 1mW output power instead of 25mW, where they have a nice TEM00) ... but thats generally true for all DPSS lasers, so in oder to reduce the laser power, you should use neutral-density filters or waveplate+ polarizer cube.

2. The Cobolt 491nm laser is good, but has a little green light coming out of the cavity (a few microwatt @ ~530nm), so I would strongly advice a cleanup-filter. On the 561nm laser I haven't noticed anything yet.

3. A general thing on two-color illumination on a SPIM: We had some problems, when combining the two beams immediately behind the lasers. 
The focal points of the lasers were not overlapping (distance ~10µm), but then we have a very thin lightsheet (~1.5µm FWHM, i.e. NA0.3
overilluminated) and accordingly small depth of focus. Depending on your application that may not be that much of a problem. Anyways we're using two beam expanders and combine the expanded beams. This also allows us to independently move the focal points along the lightsheet axis. I'm attatching a sketch of the setup (5x-beam expanders, 100mm/300mm relais telescope, 100mm cylindrical lens, 10x/NA0.3 Nikon air objective).

4. As we just replaced a ArKr laser by two DPSS lasers, I talked to a lot of different companies ... all the DPSS lasers are more or less comparable. Some are maybe spectrally a bit cleaner or slightly more stable, but Cobolt offers good value for the price and we are very happy with those guys ;-)

5. About the beam-combiner I would also have second thoughts: On the one hand see point 3 above and the other problem is that you can realign the beamcombiner (it's glued internally, so if it's missaligned at some point, you cannot do much), so I would simply buy a dichroic and a second mirror. Then you can use these two to fully align the second laser beam:

+---------+                \
| LASER 2 |-----------------\ mirror
+---------+                 |\
                             |
                             |
+---------+                \| dichroic
| LASER 1 |-----------------\==============> SPIM
+---------+                  \

Here you can align the SPIM first with laser 1 and then use the mirror and dichroic (both on kinematic mirror mounts) to align the second laser.

Hope that helps,
JAN



Am 19.12.2013 11:17, schrieb Veli-Pekka Ronkainen:
> Hi all,
>
> Has anyone used Cobolt DPSS lasers in OpenSPIM? There is a nice 
> selection of lasers with different wavelengths and output powers 
> listed on their catalogue. Moreover, micro-manager seems to have 
> device support for Cobolts (Cobolt Laser Controller by name). We’d be 
> interested especially in Cobolt Dual Combiner, which allows a 
> permanently aligned combination of any 2 wavelengths to one single 
> output. That would be very handy in multi-color imaging. So, can 
> anyone comment on the Cobolts and the functionality in OpenSPIM?
>
> Regards,
>
> Veli-Pekka Ronkainen
>
> Biocenter Oulu, Finland
>