  We generate experimentally different types of two-dimensional self-trapped
photonic lattices in a photorefractive medium and analyze the induced
refractive index change using two different methods. One method gives the first
experimental Fourier space analysis of both linear and nonlinear self-trapped
photonic lattices with periodic phase modulation using partially spatially
incoherent multi-band excitation of the lattice modes. The other method
utilizes the waveguiding properties of the lattice to achieve a real space
analysis of the induced refractive index change. The results of both methods
are compared.
