Dear Friends,
  I did prism coupling in waveguides (formed by ion exchange in glass slides)
The dimension of the glass slides were L=75 mm, width=25 mm, thickness= 1mm. In
this i could successfully couple light and was able to excite modes in it. Later
on i tied to form a waveguide by spin coating PMMA (Refractive index=1.49 at 633
nm) over quartz block (Refractive index=1.457 at 633 nm)with dimension L= 3 cm,
width= 1.5 cm, thickness= 1 cm. I spin coated a 20 % w/v of PMMA in
chlorobenzene at spin speed of 1000, 1500 rmp, and baked at 110 degree celsius
for 40 minutes.. In this film i was unable to excite any modes.
  What can be the reasons, and how can i get M-lines in this setup (I'm doing
the experiment at He-Ne wavelength).
  Any help will be heartly appreciated.

regards
Aashish Singh