The spatial spectrum is obtained by using a lens to p6W|4_a?
do Fourier transform and the far-field spectrum is recorded J0 x)NnWJ
by a CCD camera positioned in its focal plane. 2umgF
First, we summarize our results of on-axis excitation of a >du|DZq
single 2D gap soliton in Fig. 1. Different from previous 8{4jlL;"`?
experimental observations in which either the probe beam W 33MYw
was launched off-axis to match the edge of the first BZ [6] TKZ[H$Z
or its input phase or spectrum was engineered [11], we PFPZ]XI%F
demonstrate on-axis excitation of a 2D gap soliton without h_K!ch }
a priori phase or spectral engineering. In fact, we show z[0 B"f
