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

144
includes the effects of pulse propagation through the GaN film (see section 6.3). and
uses the second-order susceptibility determined by equations (6.1) and (6.3). SHC rotational
symmetry measurements in the p-in/s-out and s-in/s-out polarizations were
complicated by the sapphire birefringence and were not performed. The relationship
between the sapphire birefringence and SHG from GaN / Ah03 is discussed in
Appendix E.
Fig. 6.3 displays SHG data from our 1.020 /-Lm CaN / Ah03 sample as a function
of the angle of incidence. The maximum transmitted SHG response of GaN occurs
at an angle of incidence of f"'.J
50°. The SH response of GaN as a function of the
angle of incidence depends on three factors: the coupling of the incident fields to
the susceptibility elements: the generation of a bound wave, which has a magnitude
that depends on the propagation direction of the fields in the CaN film; and the
Fresnel coefficients. The SHG responses of all of our GaN/Ah03 samples are similar
to Fig. 6.3. The film thickness affects the overall magnitude of SHG as a function
of the angle of incidence, but does not alter the relative magnitude of the response.
i.e. the ratio of the SHG response at two angles of incidence is independent of film
thickness. This independence with respect to the film thickness arises because the
interference of the bound and free waves is insensitive to the angle of incidence.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.