Three-dimensional photonic crystals by large-area membrane stacking
Spotlight summary: In nature, the largest energy gap for electrons is found in crystals with a diamond lattice. The quest today is to create a photonic diamond, i.e. an artificial three-dimensional (3D) crystal in the optical range (a photonic crystal) with this type of lattice. The lattice constant must be in the range of 600 nm and its features in the range of 100 nm. However, the most challenging problem when attempting to mimic the diamond lattice is that of recreating its topological structure.
The pace of science and technology is often set by material science, and when a new material platform emerges, scientists need to know how to adapt to it. Today, the technique of binding thin layers of the same or different materials has become increasingly accessible. For instance, the most promising solution for making a silicon laser is to bind a thin layer of a III-V semiconductor to silicon. Similarly, a large number of thin layers can be stacked through a technique known as mesh-stacking.
In this paper, the authors take on the challenge of designing a photonic diamond using mesh-stacking. They apply their own numerical machinery, the MIT Photonic Band (MPB), which has become the tool of the trade, to design a photonic diamond. They show that by using the mesh-staking method the complex topology of the diamond lattice can be replicated. The design is very robust to misalignment when stacking the layers.
After building the bulk of the crystal, the next step for the authors was, as in solid state physics, to add dopants: a structural defect in the shape of a line to create a waveguide. Waveguides in 3D photonic crystals, though proposed two decades ago, are still unavailable in the optical range. By contrast, their 2D version has been used extensively. 2D photonic crystals have been used, for example, to show how the speed of light pulses can be reduced significantly without pulse breakdown caused by dispersion. The authors were able to integrate this feature when designing the waveguides in their photonic diamond. These waveguides are predicted to slow down the features of a light pulse significantly more than in 2D photonic crystals.
Technical Division: Optoelectronics
ToC Category: Integrated Optics
|OCIS Codes:||(220.4241) Optical design and fabrication : Nanostructure fabrication|
|(160.5293) Materials : Photonic bandgap materials|
|(130.5296) Integrated optics : Photonic crystal waveguides|
|(050.6875) Diffraction and gratings : Three-dimensional fabrication|
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