The spatial spectrum is obtained by using a lens to IuNiEtKx
do Fourier transform and the far-field spectrum is recorded +TQ47Z c
by a CCD camera positioned in its focal plane. t=-SH^$SR
First, we summarize our results of on-axis excitation of a h\PHK C2
single 2D gap soliton in Fig. 1. Different from previous >]W)'lnO
experimental observations in which either the probe beam V\^EfQ
was launched off-axis to match the edge of the first BZ [6] L (khAmm
or its input phase or spectrum was engineered [11], we q~*t@
demonstrate on-axis excitation of a 2D gap soliton without qU#BJON]BR
a priori phase or spectral engineering. In fact, we show H
Ge0hl[n
