Quantum dot infrared photodetectors (QDIPs) promise improved performance over existing technologies in the form of higher temperature operation and normal-incidence detection. Variation in the size of self-assembled quantum dots leads to a broadened spectral response, which is undesirable for multi-color detection. Photonic crystal slabs can filter the transmission of normally-incident light using Fano resonances, and thus may be integrated with QDIPs to create a narrowband detector. Finite-difference time-domain simulations were used to optimize such a filter for QDIPs grown by metal-organic chemical vapor deposition. The simulations predict that the integrated detector could show up to 76% decrease in the detector linewidth, with a tunable peak location. These devices were then fabricated by standard optical lithography, however the spectral width of the integrated device was similar to that of the unfiltered QDIP. This is attributed to imperfections in the filter, so alternative fabrication methods are discussed for future processing.
Photonic devices based on 2D PCs have so far been principally targeted at operation in a wave-guided configuration and at providing the basic building blocks for Photonic Integration. The problem of optical losses, which are considered as hindering the operation of 2D photonic integrated circuits based on 2D PC, can be approached from a completely different perspective: instead of attempting to confine the light entirely within waveguide structures, the 2D structures can be deliberately opened to the third space dimension by controlling the coupling between wave-guided and radiation modes. It is shown in this paper that interaction of radiative and guided modes through a photonic crystal, especially under conditions where the later correspond to extrema of the dispersion characteristics of the photonic crystal, results in resonance phenomena which can be used practically for the development of new classes of devices, e.g. combining photonic crystal and MOEMS (Micro Opto Electro Mechanical Systems) structures.
We present here the general trends for designing and fabricating PC-MOEMS structures and first experimental results on demonstrators which are now under investigations in our group.