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Broadband spontaneous parametric downconversion in reconfigurable poled linearly uncoupled resonators

OPTICS LETTERS 2024年第17期49卷 4819-4822页

作者： Stefano, Alessia Zatti, Luca Liscidini, Marco Univ Pavia Dipartimento Fis Via A Bassi 6 I-27100 Pavia Italy Univ Pavia Dipartimento Ingn Ind & Informaz Via A Ferrata 5 I-27100 Pavia Italy

In this Letter, we theoretically study spontaneous parametric downconversion (SPDC) in a periodically poled structure composed of two linearly uncoupled resonators that are nonlinearly coupled via a Mach-Zehnder interferometer. The device does not require dispersion engineering to achieve efficient doubly resonant SPDC, and, unlike the case of a single resonator, one can reconfigure the system to generate photon pairs over a bandwidth of hundreds of nm. We consider the case of SPDC pumped at 775 nm in a periodically poled lithium niobate (PPLN) device compatible with up-to-date technological platforms. We calculated pair generation rates of up to 250 MHz/mW pump power for a single resonance and integrated pair generation rates of up to 100 THz/mW pump power over 170 nm. When properly reconfigured, a single device can efficiently generate over a bandwidth of some 300 nm, covering the S, C, L, and U infrared bands. (c) nologies, are reserved.

关键词： Effective refractive index finite-difference time-domain method Frequency combs Parametric down conversion Periodically poled lithium niobate Ring resonators

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Butterfly plasmon: a plasmon capable of diverse focus modulation

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OPTICS LETTERS 2025年第1期50卷 185-188页

作者： Feng, Zien Zhang, Junxi Chen, Yanru Wu, Hailong Ruan, Zhang Liu, Yejin Fan, Zhejue Deng, Dongmei South China Normal Univ Guangdong Prov Key Lab Nanophoton Funct Mat & Devi Guangzhou 510006 Peoples R China South China Normal Univ Guangdong Basic Res Ctr Excellence Struct & Fundam Guangzhou 510006 Peoples R China South China Normal Univ Sch Informat & Optoelect Sci & Engn Guangzhou 510006 Peoples R China

In this Letter, we propose a class of plasmon that exhibits properties such as autofocusing and self-bending. In a butterfly plasmon, several new dimensions of focus modulation are introduced. By adjusting its initial phase, the position, the length, the intensity, and the bending direction of the plasmonic focus can be precisely controlled, demonstrating a high degree of tunability. Additionally, the interference of two butterfly plasmons has been explored, proposing a new method for controlling the position of the interference focal spot. finite-difference time-domain (FDTD) numerical solutions are employed to further validate the correctness of the theory. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Attenuation coefficient finite-difference time-domain method Modulation Modulation techniques Phase Surface plasmon polaritons

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Directional emission with super narrow divergence from perforated elliptical microdisk

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OPTICS EXPRESS 2024年第24期32卷 43066-43075页

作者： Wang, Yuchen Liu, Shuo Qian, Xiuxian Hou, Rui Wang, Xiuhua Qingdao Univ Technol Sch Sci Qingdao 266525 Peoples R China Qingdao Univ Technol Sch Informat & Control Engn Qingdao 266525 Peoples R China

In this work, a perforated polymeric elliptical microcavity is investigated by using the finite difference time domain (FDTD) method, highly directional laser emission with a far-field divergence angle of 2.57 degrees, which is achieved without spoiling Q much. Further simulation analyses reveal that the far-field profile is insensitive to the deformation parameter of the hole, demonstrating the device is robust. In addition, the position of the hole and deformation parameter of the elliptical microcavity is vital for optimizing the far-field profile. Our work has provided an effective way to achieve directional whispering gallery mode emission with super narrow divergence, which will be important in integrated optics, optical communication and biochemical sensing.

关键词： finite-difference time-domain method Frequency combs Optical resonators Phase matching Tapered fibers Total internal reflection

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Dual layer chessboard metasurface sandwiched by a spin-on-carbon for spectral modulation

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OPTICS EXPRESS 2024年第4期32卷 5022-5030页

作者： Tian, Shuoqiu Yuan, Wentao Guo, Jinyu Chen, Qiucheng Chen, Yifang Fudan Univ Sch Informat Sci & Technol Nanolithog & Applicat Res Grp Shanghai 200433 Peoples R China

Metasurfaces, composed by metals and dielectrics in periodical order with subwavelength pitches, are of great importance for their unique ability to abruptly manipulate optical fields. So far, all the reported metasurfaces are constructed by thermally deposited metals and dielectric films, based on semiconductor processes which are expensive and time-consuming. Inspired by the outstanding dry etch property of spin-on-carbon (SOC) as the interlayer material in CMOS technology, this paper proposes to utilize the SOC as the dielectric layer in a chessboard metasurface with dual layer of gold to form an array of local surface plasmonic resonators (localized surface plasmon resonance). finite difference and time domain (FDTD) method is used to investigate the spectral characteristics in reflectance of the metasurface in both visible and short wavelengths of infrared light. Electron beam lithography is applied to generate the nanoscale chessboard pattern on ZEP520A, followed by a conventional oxygen-based plasma etch to form high aspect ratio nanopillar arrays in SOC with the feature width under 50 nm, and ended by a thermal deposition of gold to form self-aligned dual layer local surface plasmonic resonators (LSPRs). The measured reflectance spectra agree with the simulated. A wealth of optical properties, such as coupling induced modulations of spectra by LSPRs, are revealed and analyzed. These special modes result in tunable structural colors and wavelength-selective antireflection ability. To the best of our knowledge, this is the first time that SOC is applied in the construction of metasurfaces, which has great potential for next generation nanophotonic devices.

关键词： CMOS technology Electron beam lithography finite-difference time-domain method Optical antennas Optical fields Optical properties

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Introduction to the feature issue: Advances in Optical Biosensors for Biomedical Applications

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BIOMEDICAL OPTICS EXPRESS 2024年第5期15卷 3183-3190页

作者： Kumar, Santosh Iadicicco, Agostino Kim, Seunghyun Tosi, Daniele Marques, Carlos Koneru Lakshmaiah Educ Fdn Dept Elect & Commun Engn Vaddeswaram 522302 Andhra Pradesh India Univ Naples Parthenope Dept Engn I-80143 Naples Italy Baylor Univ Dept Elect & Comp Engn Waco TX 76798 USA Nazarbayev Univ Dept Elect & Comp Engn Astana 010000 Kazakhstan Univ Aveiro Aveiro Inst Mat CICECO Phys Dept P-3810193 Aveiro Portugal

The feature issue of Biomedical Optics Express titled "Advances in Optical Biosensors for Biomedical Applications" presents a comprehensive collection of cutting -edge optical biosensor research. With the growing demand for sensitive, label -free, and real-time detection of biological analytes, optical biosensors have emerged as important devices in a wide range of biomedical applications, including medical diagnostics, bioanalysis, and personalised healthcare. This collection of 26 papers highlights recent advances and innovations in the development, design, and implementation of optical biosensors. The feature issue serves as an opportunity for disseminating ground -breaking findings, promoting new ideas, and inspiring further developments in optical biosensors for medical applications. The authors provide breakthrough technology, innovative approaches, and practical clinical applications that have the potential to revolutionize healthcare and biomedical research. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Chemical sensors Clinical applications Fiber Bragg grating sensors Fiber optic sensors finite-difference time-domain method Plastic optical fibers

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Biexcitons-plasmon coupling of Ag@Au hollow nanocube/MoS2 heterostructures based on scattering spectra

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OPTICS EXPRESS 2024年第6期32卷 9105-9115页

作者： You, Qingzhang Zhang, Congcong Wang, Yiru Bi, Xinxin Li, Ze Zhang, Lisheng Zhang, Duan Fang, Yan Wang, Peijie Capital Normal Univ Dept Phys Beijing Key Lab Nanophoton & Nanostruct Beijing 100048 Peoples R China Inner Mongolia Univ Sch Phys Sci & Technol Key Lab Semicond Photovolta Technol Inner Mongolia Hohhot 010021 Peoples R China Capital Normal Univ Elementary Educ Coll Beijing 100048 Peoples R China

The strong interaction between light and matter is one of the current research hotspots in the field of nanophotonics, and provides a suitable platform for fundamental physics research such as on nanolasers, high -precision sensing in biology, quantum communication and quantum computing. In this study, double Rabi splitting was achieved in a composite structure monolayer MoS2 and a single Ag@Au hollow nanocube (HNC) in room temperature mainly due to the two excitons in monolayer MoS2. Moreover, the tuning of the plasmon resonance peak was realized in the scattering spectrum by adjusting the thickness of the shell to ensure it matches the energy of the two excitons. Two distinct anticrossings are observed at both excitons resonances, and large double Rabi splittings (90 meV and 120 meV) are obtained successfully. The finite -difference time domain (FDTD) method was also used to simulate the scattering spectra of the nanostructures, and the simulation results were in good agreement with the experimental results. Additionally, the local electromagnetic field ability of the Ag@Au hollow HNC was proved to be stronger by calculating and comparing the mode volume of different nanoparticles. Our findings provides a good platform for the realization of strong multi -mode coupling and open up a new way to construct nanoscale photonic devices.

关键词： finite-difference time-domain method Light matter interactions Photonic devices Quantum communications Quantum computation Scanning electron microscopy

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Theoretical analysis of passively mode-locked semiconductor ring lasers

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OPTICS EXPRESS 2024年第14期32卷 24358-24371页

作者： Qin, Bisheng Zhang, Ruiying Qiu, Bocang Zhang, Ben Luo, Chanchan Univ Sci & Technol China Sch Nanotech & Nanob Hefei 230026 Peoples R China Chinese Acad Sci Suzhou Inst Nanotech & Nanob Key Lab Semicond Display Mat & Chips Suzhou 215123 Peoples R China Chinese Acad Sci Suzhou Inst Nanotech & Nanobion Nanodevices & Mat Div Suzhou 215123 Peoples R China Quanzhou Univ Informat Engn Sch Elect & Commun Engn Quanzhou 362000 Peoples R China

In this paper, the theoretical analysis of the passive mode-locked semiconductor ring lasers (PML-SRLs) is investigated based on a travelling wave model. It is found that both the optical confinement factor and the injection current make great contributions to the operation regime and the performance of PML-SRLs. All operation regimes of PML-SRLs are governed by the transient gain-loss balance. Such balance is closely associated with the relationship among the stimulated rate in the semiconductor optical amplifier (SOA), the carrier lifetime in the saturated absorber (SA), and the roundtrip time of the ring resonator. Furthermore, our investigation indicates that the mode-locked state of such PML-SRLs is independent of the passive waveguide, but the performance degrades with the increased waveguide loss or the shortened waveguide length, once the material bandwidth is wide enough. Another discovery is that it is possible to achieve the high energy pulse in the PML-SRL with shortening the passive length and narrowing the gain spectrum meanwhile. Overall, such investigations should benefit designing the required PML-SRLs and achieving the high performance.

关键词： Fiber optic communications finite-difference time-domain method Optical confinement Ring lasers Ring resonators Semiconductor lasers

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Space-time modulated loaded-wire metagratings for magnetless nonreciprocity and near-complete frequency conversion

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OPTICAL MATERIALS EXPRESS 2024年第5期14卷 1295-1308页

作者： Hadad, Yakir Sounas, Dimitrios Tel Aviv Univ Sch Elect Engn IL-69978 Tel Aviv Israel Wayne State Univ Dept Elect & Comp Engn Detroit MI 48202 USA

In recent years, significant progress has been made in the development of magnet -less nonreciprocity using space-time modulation, both in electromagnetics and acoustics. This approach has so far resulted in a plethora of non -reciprocal devices, such as isolators and circulators, over different parts of the spectrum, for guided waves. On the other hand, very little work has been performed on non -reciprocal devices for waves propagating in free space, which can also have many practical applications. For example, it was shown theoretically that non -reciprocal scattering by a metasurface can be obtained if the surface -impedance operator is continuously modulated in space and time. However, the main challenge in the realization of such a metasurface is due to the high complexity required to modulate in space and time many sub -wavelength unit -cells of which the metasurface consists. In this paper, we show that spatiotemporally modulated metagratings can lead to strong nonreciprocal responses, even though they are based on electrically -large unit cells and use only three modulation domains. We specifically focus on wire metagratings loaded with time -modulated capacitances. We use the discrete -dipole approximation and an ad -hoc generalization of the theory of polarizability for time -modulated particles and demonstrate an effective non -reciprocal anomalous reflection (diffraction) with an efficient frequency conversion. Thus, our work opens a venue for a practical design and implementation of highly non -reciprocal magnet -less metasurfaces in electromagnetics and acoustics.

关键词： Coupling efficiency Diffraction gratings finite-difference time-domain method Frequency modulation Modulation techniques Refractive index

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Ultra-fast and compact optical Galois field adder based on the LPhC structure and phase shift keying

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APPLIED OPTICS 2024年第8期63卷 1939-1946页

作者： Askarian, Asghar Parandin, Fariborz Bagheri, Nila Velez, Fernando J. Islamic Azad Univ Dept Elect Engn Arak Branch Arak Iran Islamic Azad Univ Dept Elect Engn Kermanshah Branch Kermanshah Iran Inst Telecomunicacoes P-6201001 Covilha Portugal Univ Beira Interior DEM Fac Engn P-6201001 Covilha Portugal

In this study, we propose a novel, to the best of our knowledge, all -optical Galois field (AOGF) adder that utilizes logic all -optical XOR gates. The design is founded on optical beams' constructive and destructive interference phenomenon and incorporates the phase shift keying technique within a two-dimensional linear photonic crystal (2D-LPhC) structure. The suggested AOGF adder comprises eight input ports and four output ports. We employ the finite difference time domain (FDTD) procedure to obtain the electric field distribution in this structure. The FDTD simulation results of the proposed AOGF adder demonstrate that the minimum and maximum values of the normalized power at ON and OFF states ( P 1 , min , P 0 , max ) for the output ports are 95% and 1.7%, respectively. Additionally, we obtain different functional parameters, including the ON-OFF contrast ratio, rise time, fall time, and total footprint, which are measured at 17.47 dB, 0.1 ps, 0.05 ps, and 147 mu m 2 , respectively. (c) 2024 Optica Publishing Group

关键词： finite-difference time-domain method Optical fields Optical signals Phase shift Photonic crystals Signal processing

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Ultra-compact broadband polarizing beam splitter a using tilted nano-grating-based bridge waveguide

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OPTICS EXPRESS 2024年第25期32卷 44413-44424页

作者： Liu, Haipeng Jiang, Xiaorui Zhang, Zihao Ge, Jinman Sun, Quancheng Li, Junhao Yang, Cunliang Wang, Jingjing Feng, Jijun Univ Shanghai Sci & Technol Engn Res Ctr Opt Instrument & Syst Sch Opt Elect & Comp EngnMinist Educ Shanghai Key Lab Modern Opt Syst Shanghai 200093 Peoples R China Natl Key Lab Electromagnet Space Secur Tianjin 300308 Peoples R China China Aerosp Sci & Technol Natl Key Lab Sci & Technol Space Microwave Xian 710100 Peoples R China

An ultra-compact broadband silicon polarizing beam splitter is demonstrated with the assistance of a tilted nano-grating-based bridge waveguide. By tilting the grating elements to gain polarization control over the anisotropy of the equivalent medium, a new design freedom to engineer the effective mode index and circumvent small variable duty cycles can be adopted to benefit the device fabrication. The transverse magnetic (TM) light can be resonantly coupled to the cross port, while the transverse-electric (TE) light can almost completely output from the through port. The length of the coupling region is only 13.6 mu m, which can realize an extinction ratio of 30.57 dB for TM light or 31.15 dB for TE light at a 1550-nm wavelength theoretically. The fabricated device can achieve an extinction ratio of 29.35 dB for TM or 22.6 dB for TE light with a low excess loss, and an extinction ratio of more than 20 dB can be realized in the wavelength range from 1525 to 1610 nm for both polarizations. The presented device also shows a good fabrication tolerance, which would facilitate its practical applications in commercial photonic integrated circuits.

关键词： Beam splitters Coupled mode theory Extinction ratios finite-difference time-domain method Photonic crystals Polarization control

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