Re: 405 laser intensity at the objective is 0.15% of actually intensity ... is this normal?

Posted by Emmanuel Levy 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-tp7587264p7587272.html

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Dear Craig,

The numbers i gave initially do correspond to a scenario where I removed the objectives before measuring the power of each line.

Best wishes,

Emmanuel

> Try measuring the power of all three lines using a different objective
> lens. Many objectives are not designed to work below 450nm and so they
> absorb considerably for lasers shorter than the blue. Also, remove the
> objective lens and try measuring the power of the beam. You will probably
> overfill your power meter, but you will be able to compare the relative
> power between the three lines from what light does hit your sensor.
>
> Craig
>
> On Wed, Sep 6, 2017 at 1:28 PM, Emmanuel Levy <[hidden email]>
> wrote:
>
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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
>>>
>>