Group Research

Topological photonics: Physics and Applications [TP]

● Research fields 

        Photonic crystal & Metamaterials;

        Microwave;

        Microscopic angle-resolved spectrometer;

        Topological photonics.

● Research details

In mathematics, topology is concerned with the global properties of a geometric object that are preserved under continuous deformations. e.g. a torus is topologically equivalent to a mug, but not to a sphere. Similar ideas can also be applied to the Bloch wave functions of crystals, and we can classify the crystals into different topological types, in full electromagnetic spectrum, during microwave, optics, and nanophotonics.

Sub-research 1: Topological physics and optics [TP1]

Topological concepts have profound influence in condensed matter physics. These concepts can be applied equally to other branches of physics, including photonic systems. They have attracted much attention recently, not only because they provide powerful tools to describe and discover new phases of matter but also because of the potential to develop robust devices that cannot be disrupted by small perturbations. Based on our recent progress in this field, we will study novel photonic structures and their topological effect, mostly in microwave regime.

Spin flow of light in topological photonic crystals and microwave setup

        [1] Experimental realization of photonic topological insulator in a uniaxial metacrystal waveguide, Nat. Commun. 5, 5782 (2014).
        [2] Synthetic gauge flux and Weyl points in acoustic systems, Nat. Phys. 11, 920 (2015).
        [3] Photonic crystals possessing multiple Weyl points and the experimental observation of robust surface states, Nat. Commun. 7, 13038 (2016). 
        [4] 能谷光子晶体与拓扑光传输，《物理》第六期专题，2019年.

Sub-research 2: Measuring topological effects in nanophotonics [TP2]

Recent advances of topological physics provide a new paradigm to develop integrated nanodevices with robustly light propagation and unidirectional coupling. Based on our recent progress in this field, one of our emerging works is the precise measurement of topological effects in integrated photonic chip, by using advanced optics technology, such as microscopic angle-resolved spectrometer (mARS), a high-level facility for optical experimental measurement of topological nanophotonic effects in k space.

Microscopic angle-resolved spectrometer

       [1] Valley photonic crystals for control of spin and topology, Nat. Mat. 16, 298 (2017).
       [2] A silicon-on-insulator slab for topological valley transport, Nat. Commun. 10, 872 (2019).
       [3] “Observation of polarization vortices in momentum space.” Phys. Rev. Lett. 120, 186103 (2018).

● Required background

       TP1: Electrodynamics, Quantum mechanics, Solid state physics, Group Theory in Physics, Topological Physics.

       TP2: Basic/experienced skill in optical experiments. Interested in optics principle of microscope and spectroscope.

● Research suitability

       PhD, MPhil, Undergraduate [Position TP1 and TP2]

● Contact supervisor

       TP1:  Professor Wen-Jie Chen (博导) chenwenj5.at.SYSU,  Associate Professor Xiao-Dong Chen (硕导) chenxd67.at.SYSU

       TP2:  Professor Jian-Wen Dong (博导) dongjwen.at.SYSU

Silicon photonics: On-chip waveguide and Si-Ge photodector [SP]

● Research fields

         Photonic crystal & Metamaterials, 

         Meta-grating, 

         Ultrafast and Nonlinear optics, 

         Valley photonics.

● Research details

Silicon photonics shows outstanding ability to process light information on a single chip. Recent advances of topological physics provide a new paradigm to develop integrated nanodevices with robust light propagation and unidirectional coupling. This research is to promote the topological photonic crystal and meta-grating into the design of integrated devices, such as silicon-based waveguides and on-chip photodetector (PD). This project is supported by the National Key Research and Development Program of China. The candidates may have additional opportunity for a joint training PhD program with Europe (if you are good enough).

Sub-research 1: Design of on-chip waveguides and photodetector (PD) [SP1]

Engaging in (1) light information processing by using topological nanophotonic waveguides and (2) the design of Ge-Si photodetector based on topological optical effects. Besides of topological physics, the candidates will explore (1) the principle of optical communication in integrated photonics and (2) the basic principle of PDs, the simulations of photovoltaic effects in on-chip PDs. One may have the possibility for learning the nanofabrication techniques of semiconductor materials (e.g. Si, SiN, InP, Ge-Si).

Photonic routing based on topological waveguides

       [1] Valley photonic crystals for control of spin and topology, Nat. Mat. 16, 298 (2017).
       [2] A topological quantum optics interface, Science 359, 666 (2018).
       [3] Terahertz topological photonics for on-chip communication, arXiv:1904.04213.
       [4] Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages, Nature 562, 101 (2018).

Sub-research 2: Measuring of silicon-based waveguides [SP2]

Engaging in the transient responses and nonlinear effects in topological integrated photonics. Besides of topological physics, the candidates will explore the optical experiments of streak camera, the nanofabrication techniques of semiconductor materials (e.g. Si, SiN, Ge), as well as light-matter interaction between 2D materials and topological nanophotonic structures.

An ultrashort pulse propagating along sharp-bending topological waveguides without distortion

        [1] A silicon-on-insulator slab for topological valley transport, Nat. Commun. 10, 872 (2019).
        [2] Ultrafast optical pulse shaping using dielectric metasurfaces, Science 364, 890 (2019).
        [3] Direct Observation of Corner States in Second-Order Topological Photonic Crystal Slabs, Phys. Rev. Lett. 122, 233902 (2019).

●​ Required background

       SP1: Electromagnetism, Semiconductor physics and device, Optical communications, Advanced Optics,

       SP2: Basic/experienced skill in optical experiments. Interested in nonlinear optics and ultra-optics.

● Research suitability  

       PhD, MPhil, Undergraduate [Position SP1 and SP2]

● Contact supervisor

      SP1:  Professor Jian-Wen Dong (博导) dongjwen.at.SYSU, Doctor Xin-Tao He hext9.at.SYSU

      SP2:  Professor Fu-Li Zhao (博导) stszfl.at.SYSU, Doctor Xin-Tao He hext9.at.SYSU

Applied optics for metasurfaces [AO]

● Research fields 

       Fiber Optics,

       Micro-nano optics,

       Microscopy imaging,

       Biophotonics.

● Research details

Metasurface, an ultrathin and planar nanostructure with flexible control of the amplitude, phase, and polarization of light, has been demonstrated to excellent properties in imaging applications. This project includes the following two sub-researchs.

Sub-research 1: Fiber based endoscopy based on metasurfaces [AO1]

Fiber based endoscopy imaging has offered numerous opportunities for obtaining information from remote, hard-to-reach place in medical imaging. Such endoscopy is usually composed of complex structures and thus quite bulky. Metasurfaces with subwavelength structures, designed to change the amplitude, polarization, and phase of incident beam, provide the potential to overcome these obstacles and thus enhance the performance of endoscopy imaging.

This project combines the emerging metasurface technology with existing endoscopy imaging technology to achieve a high-quality observation of biological samples in medical imaging can be realized in a large field of view, which is expected to be applied to microscopy and the early diagnosis of cancer.

Example of Nano-optic endoscope design and fabrication

       [1] Nano-optic endoscope for high-resolution optical coherence tomography in vivo, Nature Photonics (2018).
       [2] A broadband achromatic metalens array for integral imaging in the visible, Light Sci. Appl. 8, 67 (2019).

Sub-research 2: Multicolor imaging based on metasurfaces [AO2]

Human Brain mapping is international cutting-edge science problem. As a key imaging technology of Human Brain mapping, multicolor imaging greatly enhances the investigation ability of the relationship between localization and interaction of sub-cellular structures. Thus, it is beneficial for researchers to go deep into understanding of complicated biological phenomena and processes in neural cells of brain. However, multicolor super-resolution imaging is challenging task since the use of the traditional dye filter results in the difficulties in color separation ability, spectrum cross-talk and data collection efficiency.

The starting point for this project is designing broader spectrum filter using metasurfaces and then combines metasurfaces with single-molecule localization imaging technology to achieve multicolor super-resolution imaging. Such approach is expected to enhance color separation ability, spectrum cross-talk and data collection efficiency of optical system and further can be applied to the finer human brain mapping.

● Required background 

       Advanced Optics, Fourier optics, Applied optics, Information optics, Spectroscopy, Biophysics, Introduction to Biophotonics, Programming skill (Matlab, C and so on).

● Research suitability

       PhD, MPhil, Undergraduate [Position AO1 and AO2]

● Contact supervisor

       AO1:  Professor Jian-Wen Dong (博导) dongjwen.at.SYSU      

       AO2:  Associate Professor Rui Chen (硕导) chenr229.at.SYSU

Algorithms for metalens & hologram, incl. Deep learning [DL]

● Research fields

       Imaging optics,

       Diffraction optics, 

       Micro-nano optics, 

       Deep learning.

● Research details

Metalens, an ultrathin and planar nanostructure with flexible control of the amplitude, phase, and polarization of light, has been demonstrated to replace bulky optical elements in many applications, such as imaging, spectroscopy and holography.

Typically, trial and error approaches are adopted in the metalens design where a progression of commercial software simulations that iteratively solve Maxwell’s equations. However, such full-wave simulation method is really time-consuming. On the other hand, a standard procedure of metalens design is also required for speeding up this process. This project includes the following two sub-researchs.

Sub-research 1: Deep learning enabled metalens design [DL1]

Deep learning is a class of machine learning techniques that use multilayered artificial neural networks for automated analysis of signals or data. Recently, deep neural networks, such as deep convolution neural network (CNN), have been successfully applied to solve numerous imaging-related problems including optical microscopy, computed tomography and so on.

This research is targeting for applying deep learning to design metalens for spectral and imaging device. We envision that a combination of such model with deep learning design method can expedite the metalens design with the expected performances.

A SiN mealens array for full-color integral imaging

       [1] Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging, Science 352, 1190-1194 (2016).
       [2] A broadband achromatic metalens array for integral imaging in the visible, Light Sci. Appl. 8, 67 (2019).
       [3] Deep learning for accelerated all-dielectric metasurface design, Optics Express 27, 27523-27535 (2019).

Sub-research 2: Software Development for Metalens Design and Hologram [DL2]

Computer-generated holography (CGH) is the method of digitally generating holographic interference patterns. A holographic image can be generated by illuminating the holographic interference pattern using a suitable coherent light source. Metalens is composed of subwavelength-spaced phase nanopillars at an interface, which can control the properties of light, such as amplitude, phase and polarization. Metalens focuses the light into a focal plane with subwavelength focal spot for high-resolution imaging. RCWA, FDTD and field tracing methods are frequently used to metalens design.

This task will develop your skills to write your own code in hologram and metalens design and support the software development and testing at the Metaphotonics. This research is to achieve efficient information processing and you are encouraged to bring your own ideas.

3D holographic image (left) and a metalens (right)

       [1] Viewing-angle enlar gement in holographic augumented reality using time division and spatial tiling," Optics Express 21, 12608 (2013).
       [2] Dynamic holographic imaging of real-life scene, Optics and Laser Technology 119 (2019) 105590.
       [3] Silicon Nitride Metalenses for Close-to-One Numerical Aperture and Wide-Angle Visible Imaging, Phys. Rev. Appl. 10, 014005 (2018).                                                                                                                           

● Required background

      Electrodynamics, Fourier optics, Applied optics, Information optics, Computational Physics, Programming skill (Matlab, Python and so on).

● Research suitability

       PhD, MPhil, Undergraduate [Position DL1 and DL2].

● Contact supervisor

        DL1:  Associate Professor Rui Chen (硕导) chenr229.at.SYSU

        DL2:  Professor Jian-Wen Dong (博导) dongjwen.at.SYSU