The spatial spectrum is obtained by using a lens to :U(A;U1,
do Fourier transform and the far-field spectrum is recorded K}U-w:{
by a CCD camera positioned in its focal plane. D #/Bx[
First, we summarize our results of on-axis excitation of a a+PzI x2
single 2D gap soliton in Fig. 1. Different from previous 9!DQ~k%
experimental observations in which either the probe beam @Pzu^
was launched off-axis to match the edge of the first BZ [6] 9?3&?i2-
or its input phase or spectrum was engineered [11], we / Qk 4
demonstrate on-axis excitation of a 2D gap soliton without bNoW?8bZ
a priori phase or spectral engineering. In fact, we show )@'}\_a3[]
