The spatial spectrum is obtained by using a lens to lE k@I"
do Fourier transform and the far-field spectrum is recorded COw"6czX/
by a CCD camera positioned in its focal plane. w~@"r#-
First, we summarize our results of on-axis excitation of a |0[Buh[_:c
single 2D gap soliton in Fig. 1. Different from previous ${T/ b(NM
experimental observations in which either the probe beam h4]^~st I
was launched off-axis to match the edge of the first BZ [6] `\( ?^]WLa
or its input phase or spectrum was engineered [11], we 2F2Hl
demonstrate on-axis excitation of a 2D gap soliton without 0=>$J
WF
a priori phase or spectral engineering. In fact, we show /S]$Hu|
