Hi,

I use HeCd laser to do holography with two-beam interference.  The
wavelength is 446nm.  My sample is PR1805/SiO2/GaAs.  The period is
1.5um.  The sample is exposed twice to form a crossed grating.  After
exposure and development, I can always see the non-uniformity on the
sample surface: some area has good exposure, some area has
under-exposure, and some area has over-exposure.  Because the time for
a single exposure is only ~ 3s and the development is also only ~ 3s,
I suspect that this is caused by the very short development time.  (I
cannot use long development time for my present conditions.  Otherwise
all the patterns will be lost.)  Can anybody give me some hints for
that?  Thanks.

Best regards,

Tao