Posted by
John Oreopoulos on
URL: http://confocal-microscopy-list.275.s1.nabble.com/405-laser-intensity-at-the-objective-is-0-15-of-actually-intensity-is-this-normal-tp7587264p7587274.html
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I took a closer look at your reported power levels along the optical train. First, recognize that most silicon-based power meters are not accurate at 405nm. There could be an error there as high as 20%. Also, as previously mentioned, these sensors are angle dependent and you might not be capturing all the light because of beam size (at the back of the objective perhaps, but probably fine at laser and fiber tip). But assuming you've taken those points into consideration and you're confident in the powers you've indicated, there's something a bit more troubling here.
You mentioned this system uses a multi-mode fiber delivery method, but the incurred losses are much higher from laser to fiber tip than I would expect, and from fiber to objective, even more so. This is a very inefficient illumination setup - at all wavelengths.
Disclaimer - I work for Andor. Andor (Spectral Applied Research) in the past manufactured the Borealis multi-mode fibre illumination upgrade for Yokogawa CSUs, and so I have some familiarity with what efficiency levels should be achievable with a multi-mode fiber delivery scheme. Here, it seems it's not much better than a single-mode fiber approach, so if I were you, I'd get this checked out with the manufacturer.
John Oreopoulos
> On Sep 6, 2017, at 3:54 PM, John Oreopoulos <
[hidden email]> wrote:
>
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>
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>
> Emmanuel,
>
> Check and make sure you don't have a filter inserted into the optical pathway that blocks the 405nm wavelength, and then check that all the other filters (dichroic and emission) actually are what you think they are. Make sure the filter wheels and linear motor positions are indexed and homing properly. Check your microscope filter turret as well.
>
> John Oreopoulos
>
>> On Sep 6, 2017, at 3:28 PM, Emmanuel Levy <
[hidden email]> wrote:
>>
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>>
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>>
>> Dear Peter,
>>
>> Thank you for this information.
>>
>> Are you running your lasers at full power?
>>
>>
>> Yes we are.
>>
>>
>>> What combiner are you using?
>>
>>
>> It is a custom made combiner, from the company that assembled the
>> microscope.
>>
>>
>>> I can't comment so much on the power you have at your objective but on
>>> your combiner side the values look low. Going into a multi-mode fibre
>>> should be like a barn door for your lasers so if we imagine a ~5% (x2) loss
>>> due to combining optics and an ~80% coupling efficiency, you should still
>>> be getting a ~72% average coupling efficiency into the fibre. It sounds to
>>> me like the setup may need to be realigned. If you still don't see an
>>> improvement then one other possibility is that the 405nm laser has degraded
>>> your fibre due to solarisation and the fibre needs replacing.
>>
>> Thanks a lot for this info, I'll discuss it with the company.
>>
>> If there are other opinions, in particular regarding the loss between te
>> fiber-output and the objective, I'd be glad to hear them.
>>
>> Best wishes,
>>
>> Emmanuel
>>
>>
>>
>>
>>
>>>
>>> I hope this helps.
>>>
>>>
>>> Kind Regards
>>>
>>> Pete Brunt
>>>