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Ultra-high extinction ratio polarization beam splitter using an antisymmetric grating-assisted multimode waveguide

APPLIED OPTICS 2024年第22期63卷 5911-5916页

作者： Xu, ZhengYing Tu, Bin Liu, Hao Jiangsu Univ Sci & Technol Sch Sci Dept Optoelect Informat Sci & Engn Zhenjiang 212100 Peoples R China Chinese Acad Sci Purple Mt Observ Nanjing 210023 Peoples R China

We have proposed and demonstrated a polarization beam splitter (PBS) with an ultra-high extinction ratio (ER) utilizing an antisymmetric grating-assisted multimode waveguide (AGMW) and an asymmetric directional coupler (ADC) on a silicon-on-insulator (SOI) platform. The AGMW structure is designed to facilitate the conversion of the forward TE0 mode into the backward TE1 mode. Upon injection of the TE0 mode, it transforms into the backward TE1 mode, subsequently undergoing conversion back to a TE0 mode through the ADC and ultimately dropping out from the designated port. In contrast, the injected TM0 mode traverses the device with minimal impact. The simulation results indicate that, for the TE0 mode, a bandwidth of 70 nm with an insertion loss (IL) below 0.65 dB and an ER over 40 dB is achieved. Similarly, for the TM0 mode, the bandwidth with the IL below 0.13 dB and an ER over 40 dB is 90 nm. Experimental validation confirms that, within the measured wavelength range from 1500 to 1580 nm, the bandwidth with an ER exceeding 30 dB is 61 nm for the TE0 mode and 78 nm for the TM0 mode. (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： Beam splitters Extinction ratios finite-difference time-domain method Lithium niobate Optical directional couplers Subwavelength structures

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Optical properties of nanoparticles in blood : considering blood absorption

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APPLIED OPTICS 2024年第35期63卷 8959-8964页

作者： Cheng, Ning Li, Xingcai Wang, Juan Ma, Xin Lanzhou Univ Coll Civil Engn & Mech Key Lab Mech Disaster & Environm Western China Minist Educ China Lanzhou 730000 Peoples R China Ningxia Univ Sch Phys Yinchuan 750021 Peoples R China Ningxia Univ Xinhua Coll Yinchuan 750021 Peoples R China Ningxia Univ Sch Elect & Elect Engn Yinchuan 750021 Peoples R China

Nanomedicine is emerging as a crucial avenue for exploring new therapeutic and diagnostic techniques in the medical field. Effective monitoring of the dispersion concentration of nanoparticles using optical methods is an extremely important topic in this area. However, existing research has not recognized that the light absorption of blood can lead to significant errors in related optical measurements. This paper, considering the absorption properties of the background medium, meticulously discusses the variations in the single-scattering characteristics of nanoparticles in plasma and whole blood, and analyzes the influence of parameters such as incident wavelength, particle size, refractive index, and background medium refractive index. The results indicate that neglecting the light absorption of the background medium may lead to differences of up to approximately 50% in the results, but this is also influenced by parameters such as incident wavelength, particle size, and refractive index. Furthermore, there are still significant differences in the variations of the single-scattering properties of nanoparticles with identical characteristics in plasma and whole blood. These results indicate the importance of in-depth research into calibration techniques for optical instruments in monitoring nanoparticles in the blood, and further enhance the development of nanoparticle monitoring technology in nanomedicine. (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： Electromagnetic scattering finite-difference time-domain method Mie scattering Multiple scattering Optical properties Scattering theory

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Sliding-tunable terahertz beam meta-deflector based on a 3D-printed bilayer

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OPTICS LETTERS 2024年第24期49卷 6912-6915页

作者： Wu, Xudong Xiong, Chenjie Huang, Jianzhou Liu, Weiguang Zhang, Jia Hu, Bin Beijing Inst Technol Beijing Engn Res Ctr Mixed Real & Adv Display Sch Opt & Photon Beijing 100081 Peoples R China China Acad Aerosp Sci & Innovat Beijing 100000 Peoples R China

To cope with the rapid preparation and tunable function of terahertz (THz) devices, a kind of THz beam meta-deflector (BMD) based on a bilayer metasurface doublet is proposed to implement tunable beam deflection with additional functions. By superimposing functional phases on one of the layers and sliding the other layer, the BMDs can achieve continuously beam deflection with beam splitting or beam focusing. It is possible to quickly switch between different functions by replacing the functional phase. As a demonstration, two devices are designed and fabricated by 3D printing, including a splitting BMD (s-BMD) and a focusing BMD (f-BMD). The experimental results show that the designed metasurfaces can achieve a deflection of +/- 26.96 degrees while achieving a splitting angle of 38.94 degrees-44.11 degrees for the s-BMD and a focus deflection of +/- 30.76 degrees for the f-BMD. The BMD is expected to be applied as a multifunctional and tunable device in THz communication and imaging. (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： 3D printing finite-difference time-domain method Phase modulation Refractive index Scanning electron microscopy Terahertz imaging

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Dual-mode 2 x 2 electro-optic switch on a SOI platform

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OPTICS LETTERS 2024年第21期49卷 6125-6128页

作者： Ding, Yingzhi Zhang, Daming Zhang, Peng Tang, Bo Wang, Fei Wang, Xibin Yokoyama, Shiyoshi Yin, Yuexin Jilin Univ Coll Elect Sci & Engn State Key Lab Integrated Optoelect 2699 Qianjin St Changchun 130012 Peoples R China Chinese Acad Sci Inst Microelect Beijing 100029 Peoples R China Kyushu Univ Inst Mat Chem & Engn 6-1 Kasuga Koen Kasuga Fukuoka 8168580 Japan Kyushu Univ Dept Mol & Mat Sci 6-1 Kasuga Koen Kasuga Fukuoka 8168580 Japan

Mode-division multiplexing (MDM) technology is promising for enhancing the capacity of communication networks. In this Letter, we demonstrate a dual-mode 2 x 2 electro-optical switch on a silicon-on-insulator platform. The dual-mode Mach-Zehnder interferometer switch comprises of four p-i-n phase shifters and two mode-insensitive multimode interferences that can be used for TE0 and TE1, simultaneously. With pi/2 phase shifters introduced, push-pull like operation enables the power consumption lower than 2.15 mW. The average insertion loss of the switch in "cross" and "bar" states are 1.31 dB +/- 0.19 dB for the TE0 mode and 3.39 dB +/- 0.16 dB for the TE1 mode, respectively. The cross talk is less than -16.47 dB in the C band. The compact dual- mode switch is promising to conduct a large-scale, flexible MDM system on chip. (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： Complementary metal oxide semiconductors finite-difference time-domain method Mode conversion Mode division multiplexing Multimode interference Phase modulation

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Broadband spontaneous parametric downconversion in reconfigurable poled linearly uncoupled resonators

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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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Compact inverse-designed tilted waveguide crossing

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OPTICS LETTERS 2025年第6期50卷 1889-1892页

作者： Zhang, Xiaoyan Xie, Wu Leong, Chewping Gao, Feng ASTAR ISCE2 Singapore 627833 Singapore Adv Micro Foundry Pte Ltd Singapore 117685 Singapore Pengcheng Lab Shenzhen 518063 Guangdong Peoples R China

Waveguide crossings are key components for increasing integration density and routing flexibility. We propose a novel, to the best of our knowledge, compact, tilted silicon waveguide crossing designed using inverse design methods, specifically optimized to minimize both insertion loss and crosstalk. Through adjoint optimization algorithms and finite-difference time-domain simulations, we achieve a significant reduction in crosstalk from -46 dB at 90 degrees to -54 dB at 86 degrees, with a remarkably low insertion loss of -0.14 dB at 1310 nm. The footprint is further minimized to only 8 x 8 mu m2, setting what we believe to be a new benchmark in terms of both size and performance compared to existing silicon waveguide crossings. The impact of the tilt angle on performance is thoroughly analyzed through both simulations and experimental validation. This device highlights the potential of inverse design to deliver optimized overall performance while maintaining an ultra-compact footprint. Fabricated on a commercial foundry, with its low loss, low crosstalk, and small size, our waveguide crossing is ideally suited for high-density photonic integrated circuits, offering promising applications in data centers and quantum photonics. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Bend loss Coupling efficiency finite-difference time-domain method Inverse design Optical computing Photonics

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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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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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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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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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