Optimization of a negative index photonic crystal slab at optical wavelength

摘要

There has been an increasing interest in using photonic crystals as negative refraction index slabs for integrated nanophotonics. According to the superlensing criteria, a refractive index equal to -1 is needed to operate at an arbitrary wavelength [1-2]. The field distribution is the result of multiple propagation phenomena such as reflection, diffraction, self collimation and negative refraction. We report on the optimization of focusing properties of a triangular air hole lattice etched in a I1I-V semiconductor matrix and present the demonstration of negative refraction by FDTD 3D calculations. Under isotropy and finite length conditions, light transmission in the second band was investigated for an incident wave tilted by 0°, 2°, 7° and 15° (E Field parallel to the air holes). The advantage of our method lies in the existence of Fabry-Perot effect resulting of interferences between the front and the rear interface of the slab. From the comparison of each transmission spectrum, the filling factor was adjusted to obtain simultaneously n = -1 and a maximum of signal to operate at a wavelength of 1.55 micrometers. At least, the validity of this method to produce an intensity maximum behind the slab was checked by mapping the field with FDTD 3D simulations.