Bob, I actually showed that it would be vertical. The reason is that the dipole moment of the atoms in the mirror are vertical and so the E vector is also vertical.BobH wrote: I strongly disagree with this. Dinesh my friend, sometimes a mathematical analysis can go very wrong and this is one case if it led you to that conclusion. There is no way the polarization of the beam coming off the top mirror in the drawing referred to above is "horizontal" if the mirror itself is in the "vertical" direction with respect to the plane of incidence defined by the beamsplitter cube. No way. A page of argument won't change that, and only confuses anyone reading this topic.
My point is not whether or not it's vertical, my point is: why? I repeat, in case it's been missed again: Why is it vertical? - there must be a reason besides, "Because I'm an 'expert' and I say it is". No one seems to be able to give a reason. If it's as "obvious" and as "simple", then surely it's not very difficult to explain why. Otherwise, I'm simply expected to understand this as a matter of faith or "belief", and I ain't too good in both the faith department and blind unquestioning belief in "experts" department. If I accepted faith and blind belief as criteria for understanding natural law, I'd have become a priest and not a physicist! (Not that I'm demeaning priests, I simply have a different weltanscauung) I need some sort of proof. If people simply accept facts and speculation on some sort of faith basis, how do you find anything new? With no clue about a reason for something, the phenomena is not understood, it's simply accepted. In such a situation (My gawd, I'm beginning to sound like Thomas Jannsen!) there can be no creativity because there's no understanding! As I've said many times, if gawd almighty told me it was vertical, I'd ask why and examine the proof. Kaveh flat out told me he couldn't tell me why
So, why (besides the dipole moment argument). Does anyone have an alternate reason?kaveh1000 wrote: I don't know how to answer your question.
The point you make about the fact that the polarisation must be vertical because the mirror is "vertical" is presumably meant to mean that the mirror is tilted to the right of the beamsplitter and is presented with a horizontal polarisation (along the x in my coord system) that's in the direction of tilt. However, had it been presented with a horizontal polarisation along the z - the other horizontal polarisation - would the beam still be vertical? Since the beam is going "up", it can have two horizontal polarisations; if it had the other horizontal polarisation - the z direction in my system - the dipole moment would be along the z direction and so would the polarisation.