Chuangtang Wang

Northeastern University

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Lei Bi

Bohai University

Longjiang Deng

University of Electronic Science and Technology of China

Yan Zhang

University of Chinese Academy of Sciences

Juejun Hu

Massachusetts Institute of Technology

Qingyang Du

Massachusetts Institute of Technology

Jun Qin

National Engineering Research Center of Electromagnetic Radiation Control Materials

Caroline A. Ross

Massachusetts Institute of Technology

Bo Peng

National Engineering Research Center of Electromagnetic Radiation Control Materials

Shuyuan Liu

Sichuan University

Paolo Pintus

University of California, Santa Barbara

Cooperative Institutions

University of Electronic Science and Technology of China

National Engineering Research Center of Electromagnetic Radiation Control Materials

Chinese Academy of Sciences

State Key Laboratory of Electronic Thin Films and Integrated Devices

University of Chinese Academy of Sciences

Tsinghua University

Northeastern University

Universidad del Noreste

Georgia Institute of Technology

Massachusetts Institute of Technology

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Oxygen vacancies of YIG influence on the MPE in Au/YIG heterostructures

Xiao Liang Fei Huang Chuangtang Wang Yupeng Zhu Yan Zhang

The oxygen vacancies of Y 3 Fe 5 O 12 (YIG) influence on the magnetic proximity effect (MPE) in Au/YIG heterostructures has been studied by first principles calculations based on the density functional theory (DFT).The results show that one oxygen vacancies can reduce the two neighbor Fe 3+ to Fe 2+ and MPE in Au/YIG is strongly depended on the valence states of Fe ion.The induced magnetism in Au atoms is found to increase with the increasing concentration of Fe 2+ .In oxygen vacancy free case (Fe 3+ state), weak electron states hybridization of Fe(3d) and Au(5d) is found form the projected electron density of states distribution, while after introduce the oxygen vacancy (Fe 2+ state), the states of Fe(3d) are generally move to higher energy states and hybridize with the Au(5d) states.Moreover, more states of Fe 2+ at tetrahedral sites are hybridize with the Au(5d) states compare with that of Fe 2+ at octahedral sites, therefore a net magnetic moment induced Au atoms is found and the direction of spin polarization of Au atoms is paralleled to Fe ion at tetrahedral sites.

10.2991/icmmita-16.2016.74

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Monolithic integration of broadband optical isolators for polarization-diverse silicon photonics

Optica (2019)

Yan Zhang Qingyang Du Chuangtang Wang Takian Fakhrul Shuyuan Liu

Integrated optical isolators have been a longstanding challenge for photonic integrated circuits (PICs).An ideal integrated optical isolator for a PIC should be made by a monolithic process, have a small footprint, exhibit broadband and polarization-diverse operation, and be compatible with multiple materials platforms.Despite significant progress, the optical isolators reported so far do not meet all of these requirements.In this paper we present monolithically integrated broadband magneto-optical isolators on silicon and silicon nitride (SiN) platforms operating for both TE and TM modes with record-high performances, fulfilling all the essential characteristics for PIC applications.In particular, we demonstrate fully TE broadband isolators by depositing high-quality magneto-optical garnet thin films on the sidewalls of Si and SiN waveguides, a critical result for applications in TE-polarized on-chip lasers and amplifiers.This work demonstrates monolithic integration of high-performance optical isolators on-chip for polarization-diverse silicon photonic systems, enabling new pathways to impart nonreciprocal photonic functionality to a variety of integrated photonic devices.

Optical Isolator

Isolator

10.1364/optica.6.000473

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Monolithic On-chip Magneto-optical Isolator with 3 dB Insertion Loss and 40 dB Isolation Ratio

ACS Photonics (2018)

Qingyang Du Chuangtang Wang Yifei Zhang Yan Zhang Takian Fakhrul

On-chip optical isolators constitute an essential building block for photonic integrated circuits (PICs). Here, we experimentally demonstrated a magneto-optical isolator monolithically integrated on silicon featuring 3 dB insertion loss and 40 dB isolation ratio, both of which represent significant improvements over state-of-the-art. The isolator is also fully passive and operates under a simple unidirectional magnetization scheme. Such superior performance is enabled through a three-way combination of a strip-loaded waveguide design, a compositionally optimized chalcogenide glass as the light guiding medium, and low-loss taper structures created via gray -scale lithographic processing. The device represents an important step toward a practical solution for on-chip isolation in PICs.

Optical Isolator

Isolator

Waveguide

10.1021/acsphotonics.8b01257

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Dysprosium substituted Ce:YIG thin films with perpendicular magnetic anisotropy for silicon integrated optical isolator applications

APL Materials (2019)

Yan Zhang Qingyang Du Chuangtang Wang Wei Yan Longjiang Deng

In this report, dysprosium substituted Ce1Y2Fe5O12 (Ce:YIG) thin films (Dy:CeYIG) with perpendicular magnetic anisotropy (PMA) are successfully deposited on silicon and silicon-on-insulator waveguides by pulsed laser deposition. The structural, magnetic, and magneto-optical properties of Dy:CeYIG films are investigated. We find that increasing dysprosium concentration leads to a decreased out-of-plane magnetic saturation field. Dy2Ce1Fe5O12 and Dy2Ce1Al0.4Fe4.6O12 thin films show PMA dominated by magnetoelastic effects due to thermal mismatch strain. These films further exhibit high Faraday rotation and low optical loss. Our work demonstrates that Dy substitution is an effective way to induce PMA in Ce:YIG thin films without compromising their magneto-optical figure of merit, making this material promising for self-biased transverse electric mode optical isolator applications.

Dysprosium

Optical Isolator

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10.1063/1.5112827

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Filling in the missing link: monolithic optical isolators on silicon with high performance, broadband operation, and polarization diversity

Juejun Hu Yan Zhang Qingyang Du Chuangtang Wang Takian Fukhrul

On-chip optical isolators constitute an essential building block for photonic integrated circuits. Monolithic magnetooptical isolators on silicon, while featuring unique benefits such as scalable integration and processing, fully passive operation, large dynamic range, and simple device architecture, had been limited by their far inferior performances compared to their bulk counterparts. Here we discuss our recent work combining garnet material development and isolator device design innovation, which leads to a monolithic optical isolator with an unprecedented low insertion loss of 3 dB and an isolation ratio up to 40 dB. To further overcome the bandwidth and polarization limitations, we demonstrated broadband optical isolators capable of operating for both TM and TE modes. These results open up exciting opportunities for scalable integration of nonreciprocal optical devices with chip-scale photonic circuits.

Optical Isolator

Isolator

10.1117/12.2553949

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Photon Energy‐Dependent Optical Spin‐Orbit Torque in Heavy Metal–Ferromagnet Bilayers

Advanced Functional Materials (2023)

Chuangtang Wang Yihao Xu Yongmin Liu

Abstract The manipulation of magnetization through optically generated ultrafast spin currents is a fascinating area that needs a thorough understanding for its potential future applications. In this work, a comprehensive investigation of helicity‐driven optical spin‐orbit torque in heavy metal/ferromagnetic metal heterostructures is presented, specifically cobalt capped with gold or platinum, subject to laser pumping at different wavelengths. The results demonstrate up to tenfold enhancement in optical spin‐orbit torque quantum efficiency for gold compared to platinum of the same thickness when pumped with a visible laser. Additionally, the study provides the first experimental analysis of the photon energy dependence of optical spin‐orbit torque and derives the optical spin orientation spectra for both gold/cobalt and platinum/cobalt heterostructures. A key insight gained from the study is the impact of photon energy‐dependent spin transport in the system, which suggests the use of a high photon energy pump for efficient spin transport. These findings highlight the potential of spin current generation and manipulation in gold/ferromagnet heterostructures for a wide range of applications such as all‐optical magnetization switching, spin‐wave generation and control, and spintronic terahertz emission.

Photon energy

10.1002/adfm.202307753

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Localized Surface Plasmon Resonance Enhanced Oxygen Evolution on Nickel-Based Catalysts

Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM) (2021)

Ian Kendrick Benjamin William Kaufold Sanjeev Mukerjee Yongmin Liu Chuangtang Wang

Electrochemical localized surface plasmon resonance (LSPR) is an emerging method with applications in sensing and catalysis. In terms of the latter, enhanced oxygen evolution has been demonstrated using nanostructured nickel hydroxide decorated with gold nanoparticles. However, the current state of alkaline oxygen evolution Ni-based transition metal catalysts have obviously expanded beyond monometallic Ni to include additional metals and are prepared using techniques to yield nanostructured catalysts. A variety of these nanostructures are known, with shapes and sizes that vary by synthetic method, and have been extensively studied as water splitting electrocatalysts; however, relatively few have been studied as photo electrocatalysts which make use of the hot carriers generated by LSPR. We aim to maximize the potential of Ni-based oxygen evolution catalysts as photoelectrocatalysts by applying gold nanoparticle decoration to additional types of nanostructures. Furthermore, by comparing the plasmonic enhancement observed on additional binary and ternary Ni-based catalysts, we hope to elucidate the mechanism of oxygen evolution when the LSPR phenomenon is involved. Additional work may involve the decoration of NiFeLDH nanoplates or spherical structures, as opposed to ordinary nanosheets.

Oxygen evolution

10.1149/ma2021-01381217mtgabs

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Enhanced Faraday rotation and magneto-optical figure of merit in gold grating/graphene/silicon hybrid magneto-plasmonic devices

APL Photonics (2018)

Jun Qin Shuang Xia Ke Jia Chuangtang Wang Tingting Tang

Graphene is a promising THz magneto-optical material. However, high Faraday rotation is only achievable at a low THz frequency range in single layer graphene. In this paper, we report simultaneous Faraday rotation and optical transmission enhancement in Au grating/graphene/silicon hybrid plasmonic structures across a wide frequency range from 0.43 to 24 THz using extraordinary transmission of THz spoof surface plasmons. In a broad frequency range up to 13.1 THz, the Faraday rotation and magneto-optical figure of merit in this hybrid structure can exceed the maximum value of single layer graphene at the low THz frequency range. Numerical analysis on the device dispersion relation indicates that the mechanism of simultaneous Faraday rotation and transmission enhancement is due to coupling of the TE waveguide mode with the TM hybrid waveguide-plasmon mode. Our work demonstrates the hybrid plasmonic structure as a promising candidate for THz nonreciprocal photonic device applications.

Figure of Merit

Magneto

Waveguide

Faraday cage

Optical Isolator

10.1063/1.5008775

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Citations (23)

Temperature control of spin wave propagation over 100 μm distance in 100 nm-thick YIG film

Physics Letters A (2018)

M. Shah Alam Chuangtang Wang Jilei Chen Jianyu Zhang Chuan‐Pu Liu

Yttrium Iron Garnet

Spin wave

Wave vector

10.1016/j.physleta.2018.10.016

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Ultrahigh Figure-of-Merit in Metal–Insulator–Metal Magnetoplasmonic Sensors Using Low Loss Magneto-optical Oxide Thin Films

ACS Photonics (2017)

Jun Qin Yan Zhang Xiao Liang Chuan Liu Chuangtang Wang

Achieving high figure-of-merit (defined as the ratio between refractive index sensitivity and spectral line width) in surface plasmon sensors is a fundamental quest for ultrasensitive chemical and biomedical sensing applications. Due to ohmic loss of plasmonic metal thin films, the theoretical limit of figure-of-merit is around 54 RIU–1 (refractive index unit) for Au-based plasmonic sensors at 650 nm wavelength. Here, we report a way to significantly boost the device figure-of-merit by incorporating low loss magneto-optical oxides in a novel metal–insulator–metal magnetoplasmonic sensor. Our theoretical analysis shows that a record high figure-of-merit of 39600 RIU–1 can be achieved in a simple multilayer thin film sensor device at the wavelength of 650 nm, which well exceeds that of conventional surface plasmon resonance sensors at the same wavelength. A high figure-of-merit of 964 ± 150 RIU–1 is demonstrated experimentally at 650 nm, 17.8× higher than the theoretical limit of Au surface plasmon resonance sensors at the same wavelength. The high figure-of-merit originates from strong coupling between the magneto-optical waveguide mode and the surface plasmon resonance mode causing a narrow transverse magneto-optical Kerr effect spectrum with Fano line shape at resonant excitation conditions. The limit-of-detection reaches 4.13 × 10–6 RIU, which is 16× higher compared to a standard Au SPR sensor measured on the same setup. Biomedical sensing using bovine serum albumin solutions and biotin–streptavidin interaction demonstrate excellent sensing performance and chemical stability of such metal–insulator–metal magnetoplasmonic sensors.

Figure of Merit

Localized surface plasmon

10.1021/acsphotonics.7b00091

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Citations (52)