  The local density of states and response to an incident plane wave of a
finite sized photonic crystal (PC) with nonlinear material (NLM) is analyzed.
Of particular interest is the excitation of surface wave modes at the truncated
surface of the PC, which is collocated with the NLM material. We compute the 2D
Green function of the PC with linear material and then include the Kerr NLM in
a self-consistent manner. The 2D PC consists of a square array of circular rods
where one row of the rods is semi-circular in order to move the surface wave
defect mode frequency into the band gap. Since the surface modes are resonant
at the interface, the NLM should experience at least an order of magnitude
increase in field intensity. This is a possible means of increasing the
efficiency of the PC as a frequency conversion device.
