PhD, The Australian National University, Australia (2019)
MS, Friedrich Schiller University Jena, Germany (2015)
BE, Tianjin University, China (2012)
Shanhui Fan, Postdoctoral Faculty Sponsor
METASURFACES for quantum technologies
2022; 75 (8): 38-44
View details for Web of Science ID 000847298300015
Creating boundaries along a synthetic frequency dimension.
2022; 13 (1): 3377
Synthetic dimensions have garnered widespread interest for implementing high dimensional classical and quantum dynamics on low-dimensional geometries. Synthetic frequency dimensions, in particular, have been used to experimentally realize a plethora of bulk physics effects. However, in synthetic frequency dimension there has not been a demonstration of a boundary which is of paramount importance in topological physics due to the bulk-edge correspondence. Here we construct boundaries in the frequency dimension of dynamically modulated ring resonators by strongly coupling an auxiliary ring. We explore various effects associated with such boundaries, including confinement of the spectrum of light, discretization of the band structure, and the interaction of boundaries with one-way chiral modes in a quantum Hall ladder, which exhibits topologically robust spectral transport. Our demonstration of sharp boundaries fundamentally expands the capability of exploring topological physics, and has applications in classical and quantum information processing in synthetic frequency dimensions.
View details for DOI 10.1038/s41467-022-31140-7
View details for PubMedID 35697716
- Nontrivial point-gap topology and non-Hermitian skin effect in photonic crystals PHYSICAL REVIEW B 2021; 104 (12)
Generating arbitrary topological windings of a non-Hermitian band.
Science (New York, N.Y.)
2021; 371 (6535): 1240–45
The nontrivial topological features in the energy band of non-Hermitian systems provide promising pathways to achieve robust physical behaviors in classical or quantum open systems. A key topological feature of non-Hermitian systems is the nontrivial winding of the energy band in the complex energy plane. We provide experimental demonstrations of such nontrivial winding by implementing non-Hermitian lattice Hamiltonians along a frequency synthetic dimension formed in a ring resonator undergoing simultaneous phase and amplitude modulations, and by directly characterizing the complex band structures. Moreover, we show that the topological winding can be controlled by changing the modulation waveform. Our results allow for the synthesis and characterization of topologically nontrivial phases in nonconservative systems.
View details for DOI 10.1126/science.abf6568
View details for PubMedID 33737483
Topological complex-energy braiding of non-Hermitian bands.
2021; 598 (7879): 59-64
Effects connected with the mathematical theory of knots1 emerge in many areas of science, from physics2,3 to biology4. Recent theoretical work discovered that the braid group characterizes the topology of non-Hermitian periodic systems5, where the complex band energies can braid in momentum space. However, such braids of complex-energy bands have not been realized or controlled experimentally. Here, we introduce a tight-binding lattice model that can achieve arbitrary elements in the braid group of two strands 𝔹2. We experimentally demonstrate such topological complex-energy braiding of non-Hermitian bands in a synthetic dimension6,7. Our experiments utilize frequency modes in two coupled ring resonators, one of which undergoes simultaneous phase and amplitude modulation. We observe a wide variety of two-band braiding structures that constitute representative instances of links and knots, including the unlink, the unknot, the Hopf link and the trefoil. We also show that the handedness of braids can be changed. Our results provide a direct demonstration of the braid-group characterization of non-Hermitian topology and open a pathway for designing and realizing topologically robust phases in open classical and quantum systems.
View details for DOI 10.1038/s41586-021-03848-x
View details for PubMedID 34616054
Arbitrary control and direct measurement of topological windings of a non-Hermitian band
View details for Web of Science ID 000831479801305
- Demonstration of Lossy Linear Transformations and Two-Photon Interference via Singular Value Decomposition IEEE. 2021
- Complex-Birefringent Dielectric Metasurfaces for Arbitrary Polarization-Pair Transformations ACS PHOTONICS 2020; 7 (11): 3015–22
Multidimensional synthetic chiral-tube lattices via nonlinear frequency conversion.
Light, science & applications
2020; 9 (1): 132
Geometrical dimensionality plays a fundamentally important role in the topological effects arising in discrete lattices. Although direct experiments are limited by three spatial dimensions, the research topic of synthetic dimensions implemented by the frequency degree of freedom in photonics is rapidly advancing. The manipulation of light in these artificial lattices is typically realized through electro-optic modulation; yet, their operating bandwidth imposes practical constraints on the range of interactions between different frequency components. Here we propose and experimentally realize all-optical synthetic dimensions involving specially tailored simultaneous short- and long-range interactions between discrete spectral lines mediated by frequency conversion in a nonlinear waveguide. We realize triangular chiral-tube lattices in three-dimensional space and explore their four-dimensional generalization. We implement a synthetic gauge field with nonzero magnetic flux and observe the associated multidimensional dynamics of frequency combs, all within one physical spatial port. We anticipate that our method will provide a new means for the fundamental study of high-dimensional physics and act as an important step towards using topological effects in optical devices operating in the time and frequency domains.
View details for DOI 10.1038/s41377-020-0299-7
View details for PubMedID 34282114
- Non-adiabatic dynamic-phase-free geometric phase in multiport photonic lattices JOURNAL OF OPTICS 2020; 22 (3)
- Synthetic photonic lattice for single-shot reconstruction of frequency combs APL PHOTONICS 2020; 5 (3)
- Synthesizing multi-dimensional excitation dynamics and localization transition in one-dimensional lattices NATURE PHOTONICS 2020; 14 (2): 76-+
Reversible Image Contrast Manipulation with Thermally Tunable Dielectric Metasurfaces
2019; 15 (15): e1805142
Increasing demand for higher resolution of miniaturized displays requires techniques achieving high contrast tunability of the images. Employing metasurfaces for image contrast manipulation is a new and rapidly growing field of research aiming to address this need. Here, a new technique to achieve image tuning in a reversible fashion is demonstrated by dielectric metasurfaces composed of subwavelength resonators. It is demonstrated that by controlling the temperature of a metasurface the encoded transmission pattern can be tuned. To this end, two sets of nanoresonators composed of nonconcentric silicon disks with a hole that exhibit spectrally sharp Fano resonances and forming a Yin-Yang pattern are designed and fabricated. Through exploitation of the thermo-optical properties of silicon, full control of the contrast of the Yin-Yang image is demonstrated by altering the metasurface temperature by ΔT ≈ 100 °C. This is the first demonstrated technique to control an image contrast by temperature. Importantly, the turning technique does not require manipulating the external stimulus, such as polarization or angle of the illumination and/or the refractive index of this environment. These results open many opportunities for transparent displays, optical switches, and tunable illumination systems.
View details for DOI 10.1002/smll.201805142
View details for Web of Science ID 000467418900002
View details for PubMedID 30838794
Broadband on-chip polarization mode splitters in lithium niobate integrated adiabatic couplers
2019; 27 (2): 1632–45
We report, to the best of our knowledge, the first broadband polarization mode splitter (PMS) based on the adiabatic light passage mechanism in the lithium niobate (LiNbO3) waveguide platform. A broad bandwidth of ~140 nm spanning telecom S, C, and L bands at polarization-extinction ratios (PER) of >20 dB and >18 dB for the TE and TM polarization modes, respectively, is found in a five-waveguide adiabatic coupler scheme whose structure is optimized by an adiabaticity engineering process in titanium-diffused LiNbO3 waveguides. When the five-waveguide PMS is integrated with a three-waveguide "shortcut to adiabaticity" structure, we realize a broadband, high splitting-ratio (ηc) mode splitter for spatial separation of TE- (H-) polarized pump (700-850 nm for ηc>99%), TM- (V-) polarized signal (1510-1630 nm for ηc>97%), and TE- (H-) polarized idler (1480-1650 nm for ηc>97%) modes. Such a unique integrated-optical device is of potential for facilitating the on-chip implementation of a pump-filtered, broadband tunable entangled quantum-state generator.
View details for DOI 10.1364/OE.27.001632
View details for Web of Science ID 000456326300106
View details for PubMedID 30696226
- Inline detection and reconstruction of multiphoton quantum states OPTICA 2019; 6 (1): 41–44
Quantum metasurface for multiphoton interference and state reconstruction
2018; 361 (6407): 1104–7
Metasurfaces based on resonant nanophotonic structures have enabled innovative types of flat-optics devices that often outperform the capabilities of bulk components, yet these advances remain largely unexplored for quantum applications. We show that nonclassical multiphoton interferences can be achieved at the subwavelength scale in all-dielectric metasurfaces. We simultaneously image multiple projections of quantum states with a single metasurface, enabling a robust reconstruction of amplitude, phase, coherence, and entanglement of multiphoton polarization-encoded states. One- and two-photon states are reconstructed through nonlocal photon correlation measurements with polarization-insensitive click detectors positioned after the metasurface, and the scalability to higher photon numbers is established theoretically. Our work illustrates the feasibility of ultrathin quantum metadevices for the manipulation and measurement of multiphoton quantum states, with applications in free-space quantum imaging and communications.
View details for DOI 10.1126/science.aat8196
View details for Web of Science ID 000444513300038
View details for PubMedID 30213910
Asymmetric adiabatic couplers for fully-integrated broadband quantum-polarization state preparation
2017; 7: 16841
Spontaneous parametric down-conversion (SPDC) is a widely used method to generate entangled photons, enabling a range of applications from secure communication to tests of quantum physics. Integrating SPDC on a chip provides interferometric stability, allows to reduce a physical footprint, and opens a pathway to true scalability. However, dealing with different photon polarizations and wavelengths on a chip presents a number of challenging problems. In this work, we demonstrate an on-chip polarization beam-splitter based on z-cut titanium-diffused lithium niobate asymmetric adiabatic couplers (AAC) designed for integration with a type-II SPDC source. Our experimental measurements reveal unique polarization beam-splitting regime with the ability to tune the splitting ratios based on wavelength. In particular, we measured a splitting ratio of 17 dB over broadband regions (>60 nm) for both H- and V-polarized lights and a specific 50%/50% splitting ratio for a cross-polarized photon pair from the AAC. The results show that such a system can be used for preparing different quantum polarization-path states that are controllable by changing the phase-matching conditions in the SPDC over a broad band. Furthermore, we propose a fully integrated electro-optically tunable type-II SPDC polarization-path-entangled state preparation circuit on a single lithium niobate photonic chip.
View details for DOI 10.1038/s41598-017-17094-7
View details for Web of Science ID 000417025400022
View details for PubMedID 29203841
View details for PubMedCentralID PMC5715143
- Spectral photonic lattices with complex long-range coupling OPTICA 2017; 4 (11): 1433–36
Flat-band light dynamics in Stub photonic lattices
2017; 7: 15085
We experimentally study a Stub photonic lattice and excite their localized linear states originated from an isolated Flat Band at the center of the linear spectrum. By exciting these modes in different regions of the lattice, we observe that they do not diffract across the system and remain well trapped after propagating along the crystal. By using their wave nature, we are able to combine - in phase and out of phase - two neighbor states into a coherent superposition. These observations allow us to propose a novel setup for performing three different all-optical logical operations such as OR, AND, and XOR, positioning Flat Band systems as key setups to perform all-optical operations at any level of power.
View details for DOI 10.1038/s41598-017-15441-2
View details for Web of Science ID 000414648700052
View details for PubMedID 29118387
View details for PubMedCentralID PMC5678176
Non-reciprocal geometric phase in nonlinear frequency conversion
2017; 42 (10): 1990-1993
We describe analytically and numerically the geometric phase arising from nonlinear frequency conversion and show that such a phase can be made non-reciprocal by momentum-dependent photonic transition. Such non-reciprocity is immune to the shortcomings imposed by dynamic reciprocity in Kerr and Kerr-like devices. We propose a simple and practical implementation, requiring only a single waveguide and one pump, while the geometric phase is controllable by the pump and promises robustness against fabrication errors.
View details for DOI 10.1364/OL.42.001990
View details for Web of Science ID 000401424900031
View details for PubMedID 28504731
Measuring the Aharonov-Anandan phase in multiport photonic systems
2016; 41 (8): 1889–92
Beyond the adiabatic limit, the Aharonov-Anandan phase is a generalized description of Berry's phase. In this regime, systems with time-independent Hamiltonians may also acquire observable geometric phases. Here we report on a measurement of the Aharonov-Anandan phase in photonics. Different from previous optical experiments on geometric phases, the implementation is based on light modes confined in evanescently coupled waveguides rather than polarization-like systems, thereby physical models in more than two-dimensional Hilbert spaces are achievable. In a tailored photonic lattice, we realize time-independent quantum-driven harmonic oscillators initially prepared in the vacuum state and achieve a measurement of the Aharonov-Anandan phase via integrated interferometry.
View details for DOI 10.1364/OL.41.001889
View details for Web of Science ID 000374391900051
View details for PubMedID 27082371