The spatial spectrum is obtained by using a lens to 9 [wR/8Xm
do Fourier transform and the far-field spectrum is recorded NplkhgSj
by a CCD camera positioned in its focal plane. gg QI
First, we summarize our results of on-axis excitation of a /@9-D
4
single 2D gap soliton in Fig. 1. Different from previous Hv .C5mo
experimental observations in which either the probe beam z/t+t_y
was launched off-axis to match the edge of the first BZ [6] k1_3\JO"6
or its input phase or spectrum was engineered [11], we Jtl[9qe#]
demonstrate on-axis excitation of a 2D gap soliton without T^.W'
a priori phase or spectral engineering. In fact, we show &+7G|4!y