I want to excite a fabry perot filter with a white light. But the filter height is around 10-20 microns. Is it possible to couple a white light into the filter through optical fibre or a waveguide?
Dear Ali
The following article can be helpful:
F.Karim, T.Bora, M. Chaudhari, K.Habib, W. Mohammed, and J.Dutta,” Optical fiber-based sensor for in situ monitoring of cadmium sulfide thin-film growth”, Optics Letters, Vol. 38, Issue 24, pp. 5385-5388 (2013) http://dx.doi.org/10.1364/OL.38.005385.
Dear Ali
You can find the above mentioned article in my research gate website
Dear Ali,
please 'google' for ''fibre coupled broad band light sources'' or similar buzz words. You will find a lot of systems having fibre or at least fiber connector output. However they use large core fibres or even fibre bundles.
If you are able to couple an apporpriate fibre (core diameter according to your filter height?) to the connectors (simple butt joint) of these sources you should be able to get a nice running system. However the light input into your fibre will be small due to the misfit if core diameters.
Dear Ali,
very good, since you have experience with Laser light you should be able to do that task even for white light. As U. Dreher pointed out above, you have to play around with a lenses in order to do that job.
However it is not so easy compared to the Laser case.
Here (white light) you have divergent light ( NA aspect see U. Dreher) and much more extented ( and inhomogenous) light source. Please try to image part of the filament of a Halogen bulb onto your fibre core. That's it.
Good luck.
To confine maximum light into fiber you need to match the cone of focusing element with acceptance cone of the fiber. Common approach is to use lenses that focuses the image to match the NA of fiber. In order to achieve the maximum efficiency, fiber should be mounted on X-Y-Z stage.
There is one problem with coupling of the white light into the thin fibers - lenses have a chromatic effects and, therefore, the actual NA is different for different wavelengths. In turn, this will bring a big headache when you fights for a high coupling efficiency. I guess, it is better to use concave mirrors for a focusing of the white light instead of lenses to decrease a spectrum shaping during the light coupling.
But Roman,
Ali could/should use achromatic lense(s).
But you are right: coupling efficiency is a severe issue.
Hi
It depends on whether you mean single-mode fiber or multimode fiber. It is possible to launch some percentage broadband light from a lamp into a multimode fiber as long as you are careful with chromatic aberration - i.e. use an achromatic lens. Coupling efficiency is not usually high if using a single lens and more complex focusing optics would be required to get good efficiency.
It will be impossible to get good coupling efficiency from a broadband lamp into single-mode fiber due to the low spatial coherence of the light from the source. If you want to use single-mode fiber, you could use a supercontinuum fiber laser which produces spatially single-mode light over a broad spectral range.
Hi Ali
Yes, it is possible. You can use microscope objective to couple light into fiber
In the case of waveguide platform, end-face coupling arrangement can be carried out to achieve this goal. In this configuration, the light can be focused through microscope objective lens (Obj 1) and coupled into the waveguides, then the other microscope objective (Obj 2) is utilized to collect the output lasers transmitted through the waveguides.
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