The proposed research will explore the properties of new photonic bandgap materials, called hyperuniform disordered solids, for novel isotropic photonic devices such as isolators and waveguides.
Intellectual Merit: The emphasis in this program will optimize computational tools to tailor this novel material for specific applications in photonic devices, manufacture and characterize sample materials displaying photonic band gap in all directions and polarizations, then fabricate waveguides with arbitrary bending angles and explore novel optical functionalities. The merit of this approach lies in the fundamentally novel devices and functionalities that can be obtained from this material, thus contributing to advancing the field of photonic devices.
Broader Impact: Disordered materials with a complete photonic bandgap may open up a range of novel photonic functionalities, due to their advantageous properties, with applications in optical telecommunications, energy harvesting and non-linear optics. Laying the groundwork for the first photonic components may also unlock broader applications in electronics and phononics. This research will support a research scholar with early interest in this area, and research dissemination will be provided through publications in leading journals, international conferences and collaborative visits. If successful, the project has the potential to contribute to the understanding and development of a new material for next generation concepts for advanced photonic devices. Overall, the project will create new material and knowledge for teaching and instruction in Photonics.
The goal of the research project was to develop a revolutionary type of photonic solid, a material that acts as a semiconductor for light. Just as a semiconductor blocks the conduction of electron for a finite range of energies (the range is known as the "band gap"), a photonic solid blocks the propagation of light for a finite range energies (or frequencies). Previously, it was believed that photonics solids must be crystalline (or quasicrystalline), resulting in an uneven light-blocking effect in different directions. In this project, we have shown theoretically that it is possible to have photonic solids whose effects on light are identical in all directions. The new materials, called "hyperuniform disordered solids" (HUDS), promise to greatly simplify and expand the use of photonic solids. Photonic solids are the essential base materials required to convert from technology driven by the transport of electrons (electronics) to technology driven by the transport of light or electromagnetic waves (photonics), which is desirable because light travels faster than electrons and the transmission of information by light can be more stable and compact. The transition to photonics is necessary to realize the next generation of communications and computer devices, as well as improved sensors, LEDs, display devices, and solar cells. Fiberoptic cables replace thick electronic cables for carrying light over long distances, but the channeling and manipulating light over short distances, as in photonic integrated circuits, requires photonic solids. Conventional photonic solids, also known as "photonic crystals," have been known for over twenty years. They consist of periodic arrangements of two interwoven materials with difference indices of refraction. A combination of interference and scattering from the periodic two-component medium is responsible for blocking a range of frequencies from propagating through the material and producing a band gap. However, because the interwoven materials are arranged periodically – in regularly repeating rows and layers that are aligned in certain directions – the band gap width is different in different directions, resulting in an angularly varying response that is problematic in many applications. The theoretical research under this grant explored photonic solids (HUDS) that are isotropic and has shown that they have a band gap despite the fact they are not periodic, defying the conventional wisdom that periodicity is essential. Conceptually, HUDS lie somewhere between crystal and random glass structures. They are disordered and isotropic like a glass but "hyperuniform" like a crystal. Hyperuniform means that, like a photonic crystal, the amount of the two interwoven materials found within any volume is the same except for negligibly small variations owing to how the volume’s surface cuts through the material. Our works shows that combining glass and crystal characteristics makes to possible to have isotropic band gaps. In addition to exploring the pure material, the study began the investigation of intentionally designing defects into HUDS that enable the control and manipulation of light. An example is a waveguide, a channel cut through the solid that permits light whose frequency lies within the band gap (and so should be blocked) to pass through the solid along the waveguide path. Waveguides are possible in photonic crystals, but they must be straight or bent only at certain discrete angles along the symmetry axes of the crystal. For HUDS, we showed that waveguides could have an arbitrary wiggly shape, something considered impossible previously. Since waveguides are the means of controlling the flow of light in photonic integrated circuits, this work shows that HUDS can greatly free up circuit design. We also showed that it is possible to construct cavities, local regions in the solid where material is intentionally scooped out to make places where light can be trapped. Cavities are important for sensors, improved LEDs, and the manipulation of light in photonic integrated circuits. The theoretical work under this grant led to a collaboration with experimental scientists at New York University and the San Francisco State University, who verified the theoretical predictions. A startup company (Etaphase Inc.) has been established in the last year to develop these results into practical applications.
