Keywords: graphene, 2D materials, photonics; optoelectronics, neuromorphic photonics.
Our research interests are mainly focused on optical characterizations of 2D materials, more specifically, the light-matter interactions in the forms of nonlinear light absorption, light modulation (amplitude, phase and polarisation), photo-electrical conversion, wave-guiding and polaritonic manipulation. This talk will give an overview of photonic and optoelectronic device applications based on these optical phenomena in 2D materials [1-4]. First, to overcome the limit light absorption in graphene and obtain large nonlinear optical modulation depth, we developed a serial of new saturable absorbers based on graphene heterostructures and other 2D materials, including graphene/Bi2Te3 , black phosphorus  and self-doped plasmonic 2D Cu3-xP nanosheets  as well as 2D halide perovskite . Second, in order to fabricate improved graphene photodetectors working in different spectral ranges, we integrated graphene with other 2D materials with variant electronic structures, for example, graphene/perovskite for visible light detection , graphene/MoTe2  and graphene/black phosphorus for near infrared light detection , and graphene-Bi2Te3 for broadband infrared light detection . By fine tuning or aligning the electronic structure, we are able to engineer the photo-gating effect  and depletion width in 2D material heterostructures [14-16], so as to achieve higher quantum efficiency and large photo-active area. Third, the THz light modulations associated with plasmonic excitation in graphene/Bi2Te3, topological insulator Bi2Te3, graphene nanoribbon and 3D graphene were investigated using both spectroscopic and real space imaging techniques [17-20]. We developed a surface plasmon resonance (SPR) sensor using 2D antimonene nanosheets, and demonstrated 10,000 times improvement in sensitivity.  Last, we update our recent progress on the observation of anisotropic and ultra-low-loss polariton propagation along the natural vdW material α-MoO3. We will also present how the hyperbolic polaritons in α-MoO3 thin slabs are delicately manipulated by controlling the interlayer twist angle. We experimentally observed tunable topological transitions from open (hyperbolic) to closed (elliptical) dispersion contours in twisted α-MoO3 bilayers at a photonic magic twist angle. We further demonstrated the manipulation and steering of the hyperbolic polaritons in this exotic material by chemical intercalation  and edge orientation , an important step for building polaritonic circuitry. In summary, we have performed intensive researches on 2D materials integrated photonic and optoelectronic devices ranging from pulse lasers, waveguide, modulators to photodetectors, which are essential building blocks for constructing next generation integrated photonic circuitries and neuromorphic photonic processors.
 Adv. Funct. Mater., 2017, 27: 1603918.
 Adv. Sci., 2017, 4: 1600305.
 Small, 2018, 14: 1800682.
 Appl. Phys. Rev., 2018, 5: 041105.
 ACS Photon., 2015, 2: 832–841.
 Adv. Opt. Mater., 2015, 3: 1447-1453.
 Adv. Mater., 2016, 28: 3535.
 ACS Appl. Mater. Inter., 2017, 9: 12759.
 Adv. Opt. Mater., 2015, 3: 1389.
 Small, 2017, 13: 1700268.
 ACS Appl. Mater. Inter. 2017, 9, 36137.
 ACS Nano, 2015, 9: 1886.
 Adv. Mater., 2017, 29: 1606370.
 ACS Nano, 2016, 10: 573.
 2D Mater., 2016, 3: 041001.
 Adv. Mater., 2018, 30, 1870102.
 Light: Sci. App., 2017, 6: e16204.
 ACS Photon., 2017, 4 : 3055.
 Nat. Commun., 2019, 10:28.
 Nature, 2018, 562: 557.
 Nature, 2020, 582: 209.
 Nat. Commun., 2020,11 :2646.
 Nat. Commun., 2020,11:6086