Large enhancement of interface second-harmonic generation near the zero-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mover accent="true"><mml:mi>n</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:math>gap of a negative-index Bragg grating
Physical review. E, Statistical, nonlinear and soft matter physics