The spatial spectrum is obtained by using a lens to NqQ(X'W7
do Fourier transform and the far-field spectrum is recorded $@u^Jt, ?
by a CCD camera positioned in its focal plane. 5& rCNi*\
First, we summarize our results of on-axis excitation of a i"sYf9,
single 2D gap soliton in Fig. 1. Different from previous /4"S}P>f
experimental observations in which either the probe beam /K1 $_
was launched off-axis to match the edge of the first BZ [6] S\v&{
or its input phase or spectrum was engineered [11], we +4:+qGAJ{
demonstrate on-axis excitation of a 2D gap soliton without M[
~2,M&H
a priori phase or spectral engineering. In fact, we show 'a-5 U TT
