Shanhui Fan, Postdoctoral Faculty Sponsor
- Singular topology of scattering matrices PHYSICAL REVIEW B 2023; 108 (15)
- Roadmap on spatiotemporal light fields JOURNAL OF OPTICS 2023; 25 (9)
Majorization Theory for Unitary Control of Optical Absorption and Emission.
Physical review letters
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
- Nonreciprocal Thermal Emission Using Spatiotemporal Modulation of Graphene ACS PHOTONICS 2022
- Nondispersive Space-Time Wave Packets Propagating in Dispersive Media LASER & PHOTONICS REVIEWS 2022
Reciprocity Constraints on Reflection.
Physical review letters
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 2022; 12 (2)
- Design of Compact Meta-Crystal Slab for General Optical Convolution ACS PHOTONICS 2022; 9 (4): 1358-1365
- Internal transformations and internal symmetries in linear photonic systems PHYSICAL REVIEW A 2022; 105 (2)
- Polarization-Independent Isotropic Nonlocal Metasurfaces with Wavelength-Controlled Functionality PHYSICAL REVIEW APPLIED 2022; 17 (2)
- Nonreciprocal Thermal Emitters Using Metasurfaces with Multiple Diffraction Channels PHYSICAL REVIEW APPLIED 2021; 16 (6)
- Adaptive four-level modeling of laser cooling of solids APPLIED PHYSICS LETTERS 2021; 119 (18)
- Violating Kirchhoff's Law of Thermal Radiation in Semitransparent Structures ACS PHOTONICS 2021; 8 (8): 2417-2424
- Generation of guided space-time wave packets using multilevel indirect photonic transitions in integrated photonics PHYSICAL REVIEW RESEARCH 2021; 3 (3)
Structured 3D linear space-time light bullets by nonlocal nanophotonics.
Light, science & applications
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 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 2021; 119 (3)
Isotropic topological second-order spatial differentiator operating in transmission mode
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 2021; 12 (1): 2209
Theory for Twisted Bilayer Photonic Crystal Slabs.
Physical review letters
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 2021; 118 (13)
Topological optical differentiator.
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
View details for Web of Science ID 000831479801264
- Radiative Thermal Router Based on Tunable Magnetic Weyl Semimetals ACS PHOTONICS 2020; 7 (11): 3257–63
- Squeeze free space with nonlocal flat optics OPTICA 2020; 7 (9): 1133–38
- Theoretical constraints on reciprocal and non-reciprocal many-body radiative heat transfer PHYSICAL REVIEW B 2020; 102 (8)
- Sub-Wavelength Passive Optical Isolators Using Photonic Structures Based on Weyl Semimetals ADVANCED OPTICAL MATERIALS 2020
Meron Spin Textures in Momentum Space.
Physical review letters
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 2020; 124 (10)
- Compact Incoherent Image Differentiation with Nanophotonic Structures ACS PHOTONICS 2020; 7 (2): 338–43
Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals.
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 2019; 100 (20)
- Connection of temporal coupled-mode-theory formalisms for a resonant optical system and its time-reversal conjugate PHYSICAL REVIEW A 2019; 99 (3)
- Optical image processing using photonic crystal slab PHOTONIC CRYSTAL METASURFACE OPTOELECTRONICS 2019; 100: 93–114
- Optical Image Processing Using Photonic Crystal Slab SPIE-INT SOC OPTICAL ENGINEERING. 2019
- Isotropic wavevector domain image filters by a photonic crystal slab device JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2018; 35 (10): 1685–91
- Enhanced high-harmonic generation from an all-dielectric metasurface NATURE PHYSICS 2018; 14 (10): 1006-+
- Photonic crystal slab Laplace operator for image differentiation OPTICA 2018; 5 (3): 251–56
Enhanced Solid-State High-Harmonic Generation from a Silicon Metasurface
View details for Web of Science ID 000526031000278
A Photonic Crystal Slab Laplace Differentiator
View details for Web of Science ID 000526031000188
- Modulation-Doped Multiple Quantum Wells of Aligned Single-Wall Carbon Nanotubes ADVANCED FUNCTIONAL MATERIALS 2017; 27 (11)