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(a) Schematic of a PGe Bragg reflector made of a repeated pattern constituted by alternating a layer of low porosity (refractive index nLP and thickness eLP) and a layer of high porosity (refractive index nHP and thickness eHP). In this case, the pattern is repeated twice (N = 2). (b) Calculated reflectance spectrum of the corresponding PGe Bragg reflector, with values of 60% and 80% for the low and the high porosities, respectively.
