 
Summary: to confirm our structure's predicted negative
refraction, using the interfaces of the
photonic crystal in the M direction. The
electric field was kept parallel to the rods
for all measurements and calculations; the
horn antenna was orientated so that the
incident waves make an angle of 45 with
the normal of the M interface. Our
structure exhibits the maximum angular
range of negative refraction at an operating
frequency of 13.7 gigahertz (GHz). In
simulations using the finitedifference
timedomain method (FDTD), the incident
gaussian beam width was set at 6 cm, which
is equal to the width of the horn antenna.
The centre of the outgoing gaussian
beam is shifted to the left of the centre of
the incident gaussian beam (Fig. 1c), which
corresponds to negative refraction7
. The
