Stanford Advisors

All Publications

  • Topological winding guaranteed coherent orthogonal scattering PHYSICAL REVIEW A Guo, C., Fan, S. 2024; 109 (6)
  • Light bullet generation via stimulated Brillouin scattering APL PHOTONICS Huang, D., Guo, C., Fan, S. 2024; 9 (6)

    View details for DOI 10.1063/5.0201756

    View details for Web of Science ID 001253520900001

  • Braiding topology of symmetry-protected degeneracy points in non-Hermitian systems PHYSICAL REVIEW B Li, J., Bai, K., Guo, C., Liu, T., Fang, L., Wan, D., Xiao, M. 2024; 109 (4)
  • Unitary Control of Photonic Absorption and Emission Guo, C., Fan, S., Seletskiy, D. V., Kuno, M. K., Pauzauskie, P. J. SPIE-INT SOC OPTICAL ENGINEERING. 2024

    View details for DOI 10.1117/12.3004842

    View details for Web of Science ID 001211427500003

  • Singular topology of scattering matrices PHYSICAL REVIEW B Guo, C., Li, J., Xiao, M., Fan, S. 2023; 108 (15)
  • Roadmap on spatiotemporal light fields JOURNAL OF OPTICS Shen, Y., Zhan, Q., Wright, L. G., Christodoulides, D. N., Wise, F. W., Willner, A. E., Zou, K., Zhao, Z., Porras, M. A., Chong, A., Wan, C., Bliokh, K. Y., Liao, C., Hernandez-Garcia, C., Murnane, M., Yessenov, M., Abouraddy, A. F., Wong, L., Go, M., Kumar, S., Guo, C., Fan, S., Papasimakis, N., Zheludev, N., Chen, L., Zhu, W., Agrawal, A., Mounaix, M., Fontaine, N. K., Carpenter, J., Jolly, S. W., Dorrer, C., Alonso, B., Lopez-Quintas, I., Lopez-Ripa, M., Sola, I. J., Huang, J., Zhang, H., Ruan, Z., Dorrah, A. H., Capasso, F., Forbes, A. 2023; 25 (9)
  • Majorization Theory for Unitary Control of Optical Absorption and Emission. Physical review letters Guo, C., Fan, S. 2023; 130 (14): 146202


    Unitary control changes the absorption and emission of an object by transforming the external light modes. It is widely used and underlies coherent perfect absorption. Yet two basic questions remain unanswered: For a given object under unitary control, what absorptivity α, emissivity e, and their contrast δ=e-α are attainable? How to obtain a given α, e, or δ? We answer both questions using the mathematics of majorization. We show that unitary control can achieve perfect violation or preservation of Kirchhoff's law in nonreciprocal objects, and uniform absorption or emission for any object.

    View details for DOI 10.1103/PhysRevLett.130.146202

    View details for PubMedID 37084437

  • Light control with Weyl semimetals ELIGHT Guo, C., Asadchy, V. S., Zhao, B., Fan, S. 2023; 3 (1)
  • Unitary Control of Optical Absorption and Emission Guo, C., Fan, S., IEEE IEEE. 2023
  • Nonreciprocal Thermal Emission Using Spatiotemporal Modulation of Graphene ACS PHOTONICS Ghanekar, A., Wang, J., Guo, C., Fan, S., Povinelli, M. L. 2022
  • Thermal photonics with broken symmetries ELIGHT Liu, T., Guo, C., Li, W., Fan, S. 2022; 2 (1)
  • Nondispersive Space-Time Wave Packets Propagating in Dispersive Media LASER & PHOTONICS REVIEWS He, H., Guo, C., Xiao, M. 2022
  • Reciprocity Constraints on Reflection. Physical review letters Guo, C., Fan, S. 2022; 128 (25): 256101


    Reciprocity is a fundamental symmetry of Maxwell's equations. It is known that reciprocity imposes constraints on transmission, absorption, and emission. Here, we reveal reciprocity constraints on reflection. We determine the sets of all attainable reflection coefficients of n-port scattering matrices with prescribed singular values, both with and without assuming reciprocity. Their difference establishes reciprocity constraints and nonreciprocal behaviors. As an application, we examine the conditions for all-zero reflections. Our results deepen the understanding of reciprocity in optics.

    View details for DOI 10.1103/PhysRevLett.128.256101

    View details for PubMedID 35802447

  • Adjoint Kirchhoff?s Law and General Symmetry Implications for All Thermal Emitters PHYSICAL REVIEW X Guo, C., Zhao, B., Fan, S. 2022; 12 (2)
  • Design of Compact Meta-Crystal Slab for General Optical Convolution ACS PHOTONICS Wang, H., Jin, W., Guo, C., Zhao, N., Rodrigues, S. P., Fan, S. 2022; 9 (4): 1358-1365
  • Internal transformations and internal symmetries in linear photonic systems PHYSICAL REVIEW A Guo, C., Zhao, Z., Fan, S. 2022; 105 (2)
  • Polarization-Independent Isotropic Nonlocal Metasurfaces with Wavelength-Controlled Functionality PHYSICAL REVIEW APPLIED Long, O. Y., Guo, C., Jin, W., Fan, S. 2022; 17 (2)
  • Nonreciprocal Thermal Emitters Using Metasurfaces with Multiple Diffraction Channels PHYSICAL REVIEW APPLIED Zhao, B., Wang, J., Zhao, Z., Guo, C., Yu, Z., Fan, S. 2021; 16 (6)
  • Adaptive four-level modeling of laser cooling of solids APPLIED PHYSICS LETTERS Jin, W., Guo, C., Orenstein, M., Fan, S. 2021; 119 (18)

    View details for DOI 10.1063/5.0070422

    View details for Web of Science ID 000716756400006

  • Violating Kirchhoff's Law of Thermal Radiation in Semitransparent Structures ACS PHOTONICS Park, Y., Asadchy, V. S., Zhao, B., Guo, C., Wang, J., Fan, S. 2021; 8 (8): 2417-2424
  • Generation of guided space-time wave packets using multilevel indirect photonic transitions in integrated photonics PHYSICAL REVIEW RESEARCH Guo, C., Fan, S. 2021; 3 (3)
  • Structured 3D linear space-time light bullets by nonlocal nanophotonics. Light, science & applications Guo, C., Xiao, M., Orenstein, M., Fan, S. 2021; 10 (1): 160


    We propose the generation of 3D linear light bullets propagating in free space using a single passive nonlocal optical surface. The nonlocal nanophotonics can generate space-time coupling without any need for bulky pulse-shaping and spatial modulation techniques. Our approach provides simultaneous control of various properties of the light bullets, including the external properties such as the group velocity and the propagation distance, and internal degrees of freedom such as the spin angular momentum and the orbital angular momentum.

    View details for DOI 10.1038/s41377-021-00595-6

    View details for PubMedID 34341327

  • Engineering arbitrarily oriented spatiotemporal optical vortices using transmission nodal lines OPTICA Wang, H., Guo, C., Jin, W., Song, A. Y., Fan, S. 2021; 8 (7): 966-971
  • Controllable finite ultra-narrow quality-factor peak in a perturbed Dirac-cone band structure of a photonic-crystal slab APPLIED PHYSICS LETTERS Song, A. Y., Kalapala, A., Gibson, R., Reilly, K., Rotter, T., Addamane, S., Wang, H., Guo, C., Balakrishnan, G., Bedford, R., Zhou, W., Fan, S. 2021; 119 (3)

    View details for DOI 10.1063/5.0056243

    View details for Web of Science ID 000674420200020

  • Isotropic topological second-order spatial differentiator operating in transmission mode OPTICS LETTERS Long, O. Y., Guo, C., Wang, H., Fan, S. 2021; 46 (13): 3247-3250


    Differentiation has widespread applications, particularly in image processing for edge detection. Significant advances have been made in using nanophotonic structures and metamaterials to perform such operations. In particular, a recent work demonstrated a topological differentiator in which the transfer function exhibited a topological charge, making the differentiation operation robust to variations in operating conditions. The demonstrated topological differentiator, however, operates in reflection mode at off-normal incidence and is difficult to integrate into compact imaging systems. In this work, we design a topological differentiator that operates isotropically in transmission mode at normal incidence. The device exhibits an optical transfer function with a symmetry-protected topological charge of ±2 and performs second-order differentiation. Our work points to the potential of harnessing topological concepts for optical computing applications.

    View details for DOI 10.1364/OL.430699

    View details for Web of Science ID 000668963500063

    View details for PubMedID 34197427

  • Publisher Correction: Topological optical differentiator. Nature communications Zhu, T., Guo, C., Huang, J., Wang, H., Orenstein, M., Ruan, Z., Fan, S. 2021; 12 (1): 2209

    View details for DOI 10.1038/s41467-021-22493-6

    View details for PubMedID 33828094

  • Theory for Twisted Bilayer Photonic Crystal Slabs. Physical review letters Lou, B., Zhao, N., Minkov, M., Guo, C., Orenstein, M., Fan, S. 2021; 126 (13): 136101


    We analyze scattering properties of twisted bilayer photonic crystal slabs through a high-dimensional plane wave expansion method. The method is applicable for arbitrary twist angles and does not suffer from the limitations of the commonly used supercell approximation. We show strongly tunable resonance properties of this system which can be accounted for semianalytically from a correspondence relation to a simpler structure. We also observe strongly tunable resonant chiral behavior in this system. Our work provides the theoretical foundation for predicting and understanding the rich optical physics of twisted multilayer photonic crystal systems.

    View details for DOI 10.1103/PhysRevLett.126.136101

    View details for PubMedID 33861130

  • Wide wavelength-tunable narrow-band thermal radiation from moire patterns APPLIED PHYSICS LETTERS Guo, C., Guo, Y., Lou, B., Fan, S. 2021; 118 (13)

    View details for DOI 10.1063/5.0047308

    View details for Web of Science ID 000636372600002

  • Topological optical differentiator. Nature communications Zhu, T., Guo, C., Huang, J., Wang, H., Orenstein, M., Ruan, Z., Fan, S. 2021; 12 (1): 680


    Optical computing holds significant promise of information processing with ultrahigh speed and low power consumption. Recent developments in nanophotonic structures have generated renewed interests due to the prospects of performing analog optical computing with compact devices. As one prominent example, spatial differentiation has been demonstrated with nanophotonic structures and directly applied for edge detection in image processing. However, broadband isotropic two-dimensional differentiation, which is required in most imaging processing applications, has not been experimentally demonstrated yet. Here, we establish a connection between two-dimensional optical spatial differentiation and a nontrivial topological charge in the optical transfer function. Based on this connection, we experimentally demonstrate an isotropic two-dimensional differentiation with a broad spectral bandwidth, by using the simplest photonic device, i.e. a single unpatterned interface. Our work indicates that exploiting concepts from topological photonics can lead to new opportunities in optical computing.

    View details for DOI 10.1038/s41467-021-20972-4

    View details for PubMedID 33514708

  • Photonic Meron Spin Texture in Momentum Space Guo, C., Xiao, M., Guo, Y., Yuan, L., Fan, S., IEEE IEEE. 2021
  • Radiative Thermal Router Based on Tunable Magnetic Weyl Semimetals ACS PHOTONICS Guo, C., Zhao, B., Huang, D., Fan, S. 2020; 7 (11): 3257–63
  • Squeeze free space with nonlocal flat optics OPTICA Guo, C., Wang, H., Fan, S. 2020; 7 (9): 1133–38
  • Theoretical constraints on reciprocal and non-reciprocal many-body radiative heat transfer PHYSICAL REVIEW B Guo, C., Fan, S. 2020; 102 (8)
  • Sub-Wavelength Passive Optical Isolators Using Photonic Structures Based on Weyl Semimetals ADVANCED OPTICAL MATERIALS Asadchy, V. S., Guo, C., Zhao, B., Fan, S. 2020
  • Meron Spin Textures in Momentum Space. Physical review letters Guo, C., Xiao, M., Guo, Y., Yuan, L., Fan, S. 2020; 124 (10): 106103


    We show that a momentum-space meron spin texture for electromagnetic fields in free space can be generated by controlling the interaction of light with a photonic crystal slab having a nonzero Berry curvature. These spin textures in momentum space have not been previously noted either in electronic or photonic systems. Breaking the inversion symmetry of a honeycomb photonic crystal gaps out the Dirac cones at the corners of Brillouin zone. The pseudospin textures of photonic bands near the gaps exhibit a meron or antimeron. Unlike the electronic systems, the pseudospin texture of the photonic modes manifests directly in the spin (polarization) texture of the leakage radiation, as the Dirac points can be above the light line. Such a spin texture provides a direct approach to visualize the local Berry curvature. Our work highlights the significant opportunities of using photonic structures for the exploration of topological spin textures, with potential applications towards topologically robust ways to manipulate polarizations and other modal characteristics of light.

    View details for DOI 10.1103/PhysRevLett.124.106103

    View details for PubMedID 32216415

  • Meron Spin Textures in Momentum Space PHYSICAL REVIEW LETTERS Guo, C., Xiao, M., Guo, Y., Yuan, L., Fan, S. 2020; 124 (10)
  • Compact Incoherent Image Differentiation with Nanophotonic Structures ACS PHOTONICS Wang, H., Guo, C., Zhao, Z., Fan, S. 2020; 7 (2): 338–43
  • Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals. Nano letters Zhao, B. n., Guo, C. n., Garcia, C. A., Narang, P. n., Fan, S. n. 2020


    Objects around us constantly emit and absorb thermal radiation. The emission and absorption processes are governed by two fundamental radiative properties: emissivity and absorptivity. For reciprocal systems, the emissivity and absorptivity are restricted to be equal by Kirchhoff's law of thermal radiation. This restriction limits the degree of freedom to control thermal radiation and contributes to an intrinsic loss mechanism in photonic energy harvesting systems. Existing approaches to violate Kirchhoff's law typically utilize magneto-optical effects with an external magnetic field. However, these approaches require either a strong magnetic field (∼3T) or narrow-band resonances under a moderate magnetic field (∼0.3T), because the nonreciprocity in conventional magneto-optical effects is weak in the thermal wavelength range. Here, we show that the axion electrodynamics in magnetic Weyl semimetals can be used to construct strongly nonreciprocal thermal emitters that nearly completely violate Kirchhoff's law over broad angular and frequency ranges without requiring any external magnetic field.

    View details for DOI 10.1021/acs.nanolett.9b05179

    View details for PubMedID 32073859

  • Relation between photon thermal Hall effect and persistent heat current in nonreciprocal radiative heat transfer PHYSICAL REVIEW B Guo, C., Guo, Y., Fan, S. 2019; 100 (20)
  • Connection of temporal coupled-mode-theory formalisms for a resonant optical system and its time-reversal conjugate PHYSICAL REVIEW A Zhao, Z., Guo, C., Fan, S. 2019; 99 (3)
  • Optical image processing using photonic crystal slab PHOTONIC CRYSTAL METASURFACE OPTOELECTRONICS Guo, C., Fan, S., Zhou, W., Fan, S. 2019; 100: 93–114
  • Optical Image Processing Using Photonic Crystal Slab Guo, C., Xiao, M., Minkov, M., Shi, Y., Fan, S., Adibi, A., Lin, S. Y., Scherer, A. SPIE-INT SOC OPTICAL ENGINEERING. 2019

    View details for DOI 10.1117/12.2516018

    View details for Web of Science ID 000511111900007

  • Isotropic wavevector domain image filters by a photonic crystal slab device JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION Guo, C., Xiao, M., Minkov, M., Shi, Y., Fan, S. 2018; 35 (10): 1685–91
  • Enhanced high-harmonic generation from an all-dielectric metasurface NATURE PHYSICS Liu, H., Guo, C., Vampa, G., Zhang, J., Sarmiento, T., Xiao, M., Bucksbaum, P. H., Vuckovic, J., Fan, S., Reis, D. A. 2018; 14 (10): 1006-+
  • Photonic crystal slab Laplace operator for image differentiation OPTICA Guo, C., Xiao, M., Minkov, M., Shi, Y., Fan, S. 2018; 5 (3): 251–56
  • Enhanced Solid-State High-Harmonic Generation from a Silicon Metasurface Liu, H., Guo, C., Vampa, G., Zhang, J., Sarmiento, T., Xiao, M., Bucksbaum, P. H., Vuckovic, J., Fan, S., Reis, D. A., IEEE IEEE. 2018
  • A Photonic Crystal Slab Laplace Differentiator Guo, C., Xiao, M., Minkov, M., Shi, Y., Fan, S., IEEE IEEE. 2018
  • Modulation-Doped Multiple Quantum Wells of Aligned Single-Wall Carbon Nanotubes ADVANCED FUNCTIONAL MATERIALS Komatsu, N., Gao, W., Chen, P., Guo, C., Babakhani, A., Kono, J. 2017; 27 (11)