William Angerer - Department of Physics and Astronomy - University ...

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Let us compare the light transmitted through a birefringent thin film with the s-
polarized SHG light from a GaN sample excited by a p-polarized fundamental beam.
The nonlinear polarization is
p~12) = 1 (2 (2) (2) (2) ') (2) 'J
_ 2 Xxxz - X.:xx - Xzzz + -Xxxz COS_Q
(E.12)
to lowest order in Q.
Equations (E.ll) and (E.12) have azimuthal dependences of sin cP.
For p-polarized
excitation, the GaN film generates second-harmonic light in the p-polarized direction
and a small fraction of light in the s-polarized direction. which is due to the miscut.
The birefringence of the sapphire film rotates '"'-'.5% of the p-polarized light into the
s-direction. The SHG light that is generated in the p-polarized direction is rotated by
the linear optical properties of sapphire and dominates the the CaN miscut induced
SHC light. Because the azimuthal dependences are similar. the miscut of the Ga~
film cannot be accurately measured in the p-in/s-out geometry. This argument applies
to the s-in/s-out measurements as well. Note that this effect is insignificant for both
the p-in/p-out and s-in/p-out measurements.
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