Guangwei Hu aims to fuse physics, material science, nanotechnology, optical engineering, computer science and other disciplines to unveil the novel nanophotonic science and technology that couples different physics and covers visible, mid-infrared, and terahertz ranges.
Hu’s work has established a systematic approach to realize atomically thin and highly compact optoelectronic nanodevices with emerging low-dimensional quantum nanomaterials. The methods can be summarized as “integration” and “structuring," which is comprehensively discussed from theoretical foundations and practical implementations.
Integration: This strategy will synergize atomically thin quantum materials with conventional nanophotonic structures. As theoretically shown, the modification of boundary condition plays the fundamental role when modelling those integrated system. Hu demonstrated the integration of linear artificial materials with two-dimensional (2D) semiconductors for nonlinear and valleytronic applications. The former conventional system controls the nonlinear dipolar excitation of 2D semiconductors via modifying the boundary conditions at the surface.
Such integration can allow optical readout of valley degree of freedoms of 2D transition-metal dichalcogenides with near-unitary efficiency at room-temperature and in free space, which can also support technologies such as nonlinear holograms, nonlinear beam steering, nonlinear phase singularity and others. This work revealed the promise of the atomically thin diffractive optical elements for simultaneous and complete manipulation of frequency, polarization, phase, spin, and orbital angular momentum of light in the free space.
Structuring: This method aims to make structures of 2D materials to design artificial atomic material to regulate the constitutive relations for solving the Maxwell equations. New concepts are developed, such as opto-twistronics and photonic magic angles via twisted stack of two structured van der Waals nanomaterials. For the first time in the community, the flat-band canalization effect is demonstrated where the light at the nanoscale can only have collimated propagation towards the fixed direction without any diffraction.
Such effect is conditioned at a topological transition which happens only for a critical angle (dubbed “photonic magic angle”) in those twisted bilayers. Firstly, it opens a new research direction called “twisted optics," also known as “Opto-twistronics." Secondly, the structuring method revealed the pathway towards guiding the wave and energy at the nanoscale in the near field, which is an essential step towards the highly integrated photonic circuits.
Via revisiting crystal optics, Hu found a new type of low-loss, highly confined and long-range propagating surface waves at the surface of optically transparent calcite, called ghost polaritons, even at room temperature. Via optical crystals with low atomic symmetry such as monoclinic and triclinic lattice, the selectively directional propagation of light at the nanoscale can be realized.
This work will allow paradigm-shifting technology for infrared nanophotonic chips based on those commercially ready platforms, which is expected to provide several immediate technologies in defense, health monitoring, chips and other applications.