Hi,
I am working on a planar optical wave guide. I have a laser (He-Ne, 635 nm) and I need to excite the TE mode of a planar wave guide. How can I determine if my laser is in TE mode or TM mode?
I have tried a linear polarizer (as an analyzer) in front of the laser.
The poalrization axis (mark on linear polarizer) perpendicular to planar wave guide gives max. intensity. (Please see attached pics.)
The polarization axis when parallel to planar waveguide almost blocks all light.
Does it prove that my laser is TM polarized (parallel to plane of incidence)?
If the planar waveguide is placed horizontally (this follows from your explanation but cannot be seen on the picture), then the incident light is TM polarized and you will excite TM modes
You can use a simple glass plate and check whether you have to rotate it around the vertical or the horizontal axis to find the Brewster angle where no light will be reflected. P-polarised light, i.e. the electric field is in the same plane as the incident beam and the surface normal, will not be reflected @ Brewster angle.
Result:
I checked the laser for brewster angle, it worked as P-polarized light (intensity nearly zero at ~60° rotation of a glass slide) then I rotated the laser to 90° and repeat the glass slide rotation and it behaved as TE polarized light (No significant intensity drop at any angle).
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