The spatial spectrum is obtained by using a lens to 3_/d=ZI\
do Fourier transform and the far-field spectrum is recorded J/2p S
by a CCD camera positioned in its focal plane. e 3oIoj4o
First, we summarize our results of on-axis excitation of a K#m o+n5-;
single 2D gap soliton in Fig. 1. Different from previous a8$pc>2E
experimental observations in which either the probe beam DL{a8t1L
was launched off-axis to match the edge of the first BZ [6] 1D] wW%us
or its input phase or spectrum was engineered [11], we e|y~q0Q $
demonstrate on-axis excitation of a 2D gap soliton without QV1%Zou
a priori phase or spectral engineering. In fact, we show 2 G{KpM&
