The spatial spectrum is obtained by using a lens to 12KC4,C&1i
do Fourier transform and the far-field spectrum is recorded `;E/\eG"
by a CCD camera positioned in its focal plane. u] };QR
First, we summarize our results of on-axis excitation of a RhH 1nf2UR
single 2D gap soliton in Fig. 1. Different from previous Y~-y\l;Tr
experimental observations in which either the probe beam Oege ZV
was launched off-axis to match the edge of the first BZ [6] !qj[$x-ns
or its input phase or spectrum was engineered [11], we B6Vlc{c5SO
demonstrate on-axis excitation of a 2D gap soliton without M
9t 7y
a priori phase or spectral engineering. In fact, we show _XV%}Xb'
