Effects of real and recalled success on learned helplessness and depression.

A high-contrast-ratio (30 dB) photonic band gap in the near-infrared transmission of hole-type GaN two-dimensional photonic crystals (PhCs) is reported. These crystals are deeply etched in a 650 nm thick GaN layer grown on sapphire. A comparison of the measured spectrum with finite difference time domain simulations gives quantitative agreement for the dielectric band and qualitative agreement for the air band. The particular behavior of the air band arises from the relatively low index contrast between the GaN layer and the sapphire substrate. Our results call for extension of the operation of GaN PhCs to the visible range. ©2008 American Institute of Physics