Self-Assembly of Colloidal Diamond for 3-D Photonic Band Gap Materials
Abstract
The goal of this research project is to use colloidal self-assembly to construct photonic crystals that possess a full omnidirectional three-dimensional (3D) photonic band gap at near-infrared and optical frequencies and to investigate their optical properties by experiments and simulations. Three-dimensional photonic crystals are materials with a periodically varying dielectric constant in all three dimensions. Such crystals are said to have a photonic band gap if they prohibit the propagation of light in all directions over some finite range of frequencies. As such, they are the optical analog of semiconductors. Materials with a photonic band gap are interesting both for the fundamental science challenges they pose and for the new technologies they enable. They are predicted to completely suppress the spontaneous emission of light and, in the presence of modest disorder, exhibit Anderson localization of light, two phenomena that were predicted over thirty years ago but have yet to be observed. Materials with a photonic band gap are also promising materials for technology, particularly for pushing the lower size limit of microphotonic devices, including waveguides, beam splitters, filters, resonant cavities, sensors, all-optical switches, and microlasers. Late last year (2020), the self-assembly of colloidal crystals with the cubic diamond structure, suitable for photonics, was reported for the first time. The diamond crystal structure has long been predicted to be among the very best photonic structures, exhibiting a wide band gap that is robust with respect to imperfections and disorder. Because 3D structures are dicult and costly to fabricate using conventional microlithography techniques, the realization of a method to selfassemble the long-sought diamond structure in 3D represents a significant breakthrough. The research proposed in this grant application builds on that breakthrough. The first goal of this research program will be to make inverse diamond crystals from the colloidal diamond crystals, which serve as templates for the preferred inverse structure. To invert the structure and produce a 3D photonic band gap in the near infrared, silicon is used; in the visible, titanium dioxide is used. Both inverse structures have been realized in preliminary experiments. An early goal will be to demonstrate that these inverse crystals each possess a photonic band gap. While the diamond crystals fabricated thus far are of sucient quality to exhibit photonic band gaps, an intermediate goal will be to grow large single crystals that would be suitable for use in microphotonic circuits. Two broad approaches to growing large single crystals will be pursued. One involves a kind of zone refining using light-induced melting of the DNA-coated colloids that are used to self-assemble colloidal diamond. The other involves epitaxial crystal growth from a surface template fabricated using microlithography methods. A second goal will be to characterize the e ects of structural disorder in the photonic diamond crystals using coherent backscattering as a indicator of Anderson localization of light. Previous studies that sought but failed to observe Anderson localization used amorphous disordered packings of strongly scattering particles. However, there are compelling predictions that Anderson localization is more likely to occur in a system with a photonic band gap in which there is a modest degree of spatial disorder, which scatters light. This will be investigated and pursued using the newly realized inverse diamond photonic crystals.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 14, 2022
- Source ID
- W911NF2210096
Entities
People
- David J. Pine
Organizations
- Army Contracting Command
- New York University
- United States Army