The spatial spectrum is obtained by using a lens to 7!% cKZCY
do Fourier transform and the far-field spectrum is recorded *<UQ/)\
by a CCD camera positioned in its focal plane. [ W2p }4(
First, we summarize our results of on-axis excitation of a !At _^hSqz
single 2D gap soliton in Fig. 1. Different from previous a@7we=!
experimental observations in which either the probe beam &3JbAJ |;X
was launched off-axis to match the edge of the first BZ [6] ~/NA?E-c
or its input phase or spectrum was engineered [11], we W$3p,VTMmB
demonstrate on-axis excitation of a 2D gap soliton without +-oXW>`&
a priori phase or spectral engineering. In fact, we show p;p G@Vg
