The spatial spectrum is obtained by using a lens to mkgGX|k;
do Fourier transform and the far-field spectrum is recorded Go~bQ2*'(/
by a CCD camera positioned in its focal plane. Ot}fGiio
First, we summarize our results of on-axis excitation of a A tl`J.;G
single 2D gap soliton in Fig. 1. Different from previous IN=pki |.
experimental observations in which either the probe beam pm$2*!1F(
was launched off-axis to match the edge of the first BZ [6] n@n608
or its input phase or spectrum was engineered [11], we ,K9\;{C
demonstrate on-axis excitation of a 2D gap soliton without 2{;&c
a priori phase or spectral engineering. In fact, we show 9rXbv4{
