The spatial spectrum is obtained by using a lens to $ # @G!
do Fourier transform and the far-field spectrum is recorded 3`J?as @^8
by a CCD camera positioned in its focal plane. {.z2n>1J{T
First, we summarize our results of on-axis excitation of a TvAA
single 2D gap soliton in Fig. 1. Different from previous _$0<]O$
experimental observations in which either the probe beam H]Q Z4(
was launched off-axis to match the edge of the first BZ [6] 8[ 1D4d
or its input phase or spectrum was engineered [11], we `Te n2(D
demonstrate on-axis excitation of a 2D gap soliton without RP7e)?5$s
a priori phase or spectral engineering. In fact, we show gCgMmD=AZ
