Tight control of light beams in photonic crystals with spatially-variant lattice orientation

Abstract

Spatially-variant photonic crystals (SVPCs), in which the orientation of the unit cell changes as a function of position, are shown to be capable of abruptly controlling light beams using just low index materials and can be made to have high polarization selectivity. Multi-photon direct laser writing in the photo-polymer SU-8 was used to fabricate three-dimensional SVPCs that direct the flow of light around a 90 degree bend. The lattice spacing and fill factor were maintained nearly constant throughout the structure. The SVPCs were characterized at a wavelength of 2.94 μm by scanning the faces with optical fibers and the results were compared to electromagnetic simulations. The lattices were shown to direct infrared light of one polarization through sharp bends while the other polarization propagated straight through the SVPC. This work introduces a new scheme for controlling light that should be useful for integrated photonics.

Spatially variant periodic structures in electromagnetics

“…This device, shown in figure 2a, operated at around 15 GHz and flowed an unguided beam around a sharp 90 • bend. Soon after, an SVPC with lattice spacing of 2.0 µm was demonstrated at optical frequencies at a vacuum wavelength of 2.94 µm [55]. This device is shown in figure 2b.…”

3D Printed Terahertz Focusing Grating Couplers

“…Although there are promising results, there is still a need to further explore THz technologies to achieve a similar performance as in microwave and optical technologies. On the other hand, new advances in 2D materials [9], metasurfaces [10] and additive manufacturing [11][12][13] may boost the evolution of THz technology in the following years. This development will eventually bring up the demand for integrated devices and with them the need for effective couplers from free space to waveguides.…”

Registering functional defects into periodic holographic structures

“…The index of refraction in holographic structures can be achieved by the local filling fraction of the dielectric material in the structure [13,17]. As an alternative approach to the coordinate transformation method in transformation optics, a synthesis algorithm method [14,18,19] has been used to generate spatially variant lattices. An example of a variant lattice was designed and used to flow a light beam around a 90 deg bend [14,18,19].…”

“…As an alternative approach to the coordinate transformation method in transformation optics, a synthesis algorithm method [14,18,19] has been used to generate spatially variant lattices. An example of a variant lattice was designed and used to flow a light beam around a 90 deg bend [14,18,19]. But the designed variant lattices have not yet been registered into a periodic lattice [14,18,19].…”

“…An example of a variant lattice was designed and used to flow a light beam around a 90 deg bend [14,18,19]. But the designed variant lattices have not yet been registered into a periodic lattice [14,18,19].…”