The spatial spectrum is obtained by using a lens to >,>;)B@J
do Fourier transform and the far-field spectrum is recorded dU ,)TKQ
by a CCD camera positioned in its focal plane. llHc= &y#
First, we summarize our results of on-axis excitation of a \-Iny=$
single 2D gap soliton in Fig. 1. Different from previous }z%OnP
experimental observations in which either the probe beam I%}L@fZ
was launched off-axis to match the edge of the first BZ [6] %XJQ0CE<(
or its input phase or spectrum was engineered [11], we
aFRTNu/r
demonstrate on-axis excitation of a 2D gap soliton without |;A9A's
a priori phase or spectral engineering. In fact, we show Qj
6gg
