Reply to “Comment on ‘Observation of higher-order diffraction features in self-assembled photonic crystals’ ”

Abstract

In experimentally fabricated photonic crystals, especially those made using the methods of self-assembly, disorder is inevitable 4 due to factors such as the unintentional variation in the sizes of the building blocks, stacking faults, and limited domain sizes. We would like to emphasize that our paper 2 was mainly devoted to presenting and analyzing the experimental results and to establishing the fact that the photonic crystals made by the two methods of self-assembly were of superior quality. The main purpose of the paper was to identify the peaks in the experimentally observed angleresolved reflection spectra with those associated with the Van Hove singular point and other higher-order photonic stop bands. This was successfully carried out, and it was also reiterated that the high-energy features in the reflection spectrum are present even in photonic crystals of lower index contrast since they have their origin in the extent of ordering rather than in index contrast and defects. None of these results have been contested by the authors of the Comment 1. The highlight of the other works by Dorado and coworkers 3,5 was the analysis of the shape of the measured reflection spectra. The shape of the reflectance and transmittance spectra was not analyzed in our work 2, and the conclusions were based on other aspects. Both the absolute reflectance and transmittance spectra were shown in 2, without any normalization, and hence the contribution of scattering losses was obvious. The observation of higherorder photonic stop bands is known to signify the presence of good ordering in the photonic crystals, and hence the study of higher-order bands was chosen as the benchmark to ascertain the crystal quality in our work 2. We reiterate that our conclusion about the observation of high-energy optical features attributed to lesser number of disorder and defects is indeed supported by earlier works on this subject 6,7. Even in Ref. 3 it is clearly stated that the optical properties in the high-energy region are very sensitive to the presence of defects and may be used to assess the quality of the samples, which was precisely the approach of our paper 2.