The spatial spectrum is obtained by using a lens to n0 kBLn
do Fourier transform and the far-field spectrum is recorded zo&'2I
by a CCD camera positioned in its focal plane. _* ] ~MQ=
First, we summarize our results of on-axis excitation of a 7E4=\vM
single 2D gap soliton in Fig. 1. Different from previous TGGeTtk=
experimental observations in which either the probe beam V 4}9f5FR
was launched off-axis to match the edge of the first BZ [6] l
njaHol0
or its input phase or spectrum was engineered [11], we b;O]@kBB
demonstrate on-axis excitation of a 2D gap soliton without <XX\4[wb
a priori phase or spectral engineering. In fact, we show l~wx8
,?G
