The spatial spectrum is obtained by using a lens to bX:ARe
O
do Fourier transform and the far-field spectrum is recorded n(gw%w+\7
by a CCD camera positioned in its focal plane. j 6~#_t[
First, we summarize our results of on-axis excitation of a 8S>T1st
single 2D gap soliton in Fig. 1. Different from previous Gv!*
Qk4
experimental observations in which either the probe beam M<, E[2op
was launched off-axis to match the edge of the first BZ [6] ~ (xIG
or its input phase or spectrum was engineered [11], we uOqWMRsoi
demonstrate on-axis excitation of a 2D gap soliton without ,?+rM ;
a priori phase or spectral engineering. In fact, we show XQu ~/{A=
