I would like to find a laser to excite fluorophores in fluorescence microscope. However, I also need to perform interference with this laser. Due to the difficulty of aligning the system, the coherence length is better to have about a few centimeters. Usually, the longer the coherence length also means the narrower the linewidth, which will then be less efficient for fluorophores excitation. Therefore, I am asking if there is a compromised solution, or is there some ways to extend the coherence length of a semiconductor laser. I would need a laser at around 470 - 500 nm to excite green fluorescence protein (GFP).
Why you do not try to use a Superluminescent Diode (SLD) emitting at 470-500 nm?
Thanks A.B. Lobo Ribeiro. But usually the coherence length of SLD is quite short, right? I need something about a few centimeters.
One possibility to explore (need to do some calculations), although very expensive, is to use a super continuum fiber source with appropriate fiber optic filter , such a narrow FBG (
What you are asking may be hard to get - 1cm coherence length roughly corresponds to 30GHz linewidth. It is too narrow for FP laser and too broad for DFB or DBG laser. One possibility is to modulate the laser with narrow linewidth and thus extend it.
But i am not sure I understand why narrow linewidth is not good for exciting fluorescence in GFP, can you elaborate?
If narrow linewidth is not a problem, then i would recommend Crystalaser's single longitudional mode laser at 488 nm, they claim it has a coherence length of 50 m:
http://www.crystalaser.com/new/blue.html#405
Hi Gleb Shtengel,
I thought it would be more efficient if the laser can cover larger portion of the excitation bandwidth of GFP. However, after discussing with my PI and the laser providers, I understand now that the narror linewidth is not a problem.
Crystalaser will also be in our considered list.
Thanks for your answer and suggestion.
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