Changing the power ratio or so called modes power in the VCSEL does not necessary change the numerical values of the power coupling coefficient.
What is that?
if I excite 2 modes (LG00 and LG01) then I did the following:
-First run will divide the power ratio between those two modes equally as (0.5 0.5) and record the power coupling coefficient.
-Second run will divide the power ratio between them, but this time unequally as (0.7 0.3) and record the power coupling coefficient.
The power coupling coefficient values at the MMF of the first run and the second run is same? My question is why is that happening? Why the power coupling coefficient values are the same regardless regardless different power ratio?
There are different parameters could affect the coupling between the polarization modes of VCSEL, such as gain competition spatial hole burning as well as phase coefficient,which lead to change the coupling coefficient, please see for example these references;
(Impact of Wave guide Input Coupling on Vertical Cavity Surface Emitting Laser Diodes), (Operating Principles of VCSELs)
http://publik.tuwien.ac.at/files/PubDat_179457.pdf
https://www.uni-ulm.de/fileadmin/website_uni_ulm/iui.inst.140/Diverse/vcsel-chapter-ram_kje-d.pdf
hope that is help!
thank you very much for your prompt response. Definitely, the aforementioned parameters are going to have an effect on the coupling. My main concern is this particular parameter "modes power ratio". Changing this parameter in any design while all other parameters are constant "default values", will not have an effect on the coupling at the multimede fiber, even if you excite more than 2 or even 10 modes. The Power coupling coefficient will always be the same. I'm wondering, why?
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