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S-Bend and Y Waveguide Architectures in Germanate Glasses Irradiated by Femtosecond Laser

MICROMACHINES 2025年第2期16卷 171-171页

作者： Fernandes, Thiago Vecchi Bordon, Camila Dias da Silva Wetter, Niklaus Ursus de Rossi, Wagner Kassab, Luciana Reyes Pires Univ Sao Paulo Dept Engn Sistemas Eletron Escola Politecn Ave Prof Luciano Gualberto 158Travessa 3 BR-05508010 Sao Paulo SP Brazil IPEN CNEN Inst Pesquisas Energet & Nucl 2242 Ave Prof Lineu Prestes BR-05508000 Sao Paulo SP Brazil CEETEPS Fac Tecnol Sao Paulo Praca Fernando Prestes 30 BR-01124060 Sao Paulo SP Brazil

This study is focused on the fabrication and characterization of various dual waveguides through femtosecond (fs) laser irradiation of GeO2-based glass samples. The objective of the present work is to develop diverse waveguide configurations, namely straight, S-bend and Y-shaped waveguides within GeO2-PbO glasses embedded with silver nanoparticles, utilizing a double-guide platform, for photonic applications such as resonant rings and beam splitters. Enhanced guidance was observed with a larger radius of curvature (80 mm) among the two distinct S-bend waveguides produced. The maximum relative propagation loss was recorded for the S-bend waveguide with a 40 mm radius, while the minimum loss was noted for the Y-shaped waveguide. In the latter configuration, with an opening angle of 5 degrees and a separation of 300 mu m between the two arms, an output power ratio of 50.5/49.5 between the left and right arms indicated promising potential for beam splitter applications. During the study, the quality factor (M-2) of the proposed architectures was measured and the 80 mm S-bend configuration presented the best symmetry between the x and y axes;in the case of the Y configuration the similarity between the M-2 values in both axes, for the first and second arms, indicates comparable light guidance.

关键词： waveguides GeO2-PbO glasses S-bend Y-shaped waveguides

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Wideband OMT for the 210-373 GHz Band With Built-In 90° Waveguide Twist

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IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 2025年第2期15卷 151-157页

作者： Lapkin, Igor Lopez, Cristian Daniel Meledin, Denis Helldner, Leif Fredrixon, Mathias Pavolotsky, Alexey B. Ferm, Sven-Erik Desmaris, Vincent Belitsky, Victor Chalmers Univ Technol Dept Space Earth & Environm Sci Grp Adv Receiver Dev Onsala Space Observ SE-41296 Gothenburg Sweden

In this article, we present the design of a wideband orthomode transducer (OMT) that aims for the frequency band 210-373 GHz. The OMT employs a modified B empty set ifot layout and is optimized to fit into the tight spatial constraints, e.g., of the ALMA cartridge. The OMT layout harmonizes the receiver cartridge components for both polarizations by allowing the use of the same configuration and components in both polarization chains because of the OMT outputs' colinear positioning. The OMT features a built-in novel broadband 90 degrees waveguide twist, which minimizes the insertion RF loss by removing the H-split waveguide while eases receiver component integration with the 2SB mixers in the ALMA cartridge. The manufactured OMT was characterized by direct measurements with a VNA employing frequency extension modules. The waveguide adapters were used accommodating the OMT waveguide ports having dimensions 760 x 760 mu m for the input port and 380 x 760 mu m for the output ports to the VNA extension modules. The OMT demonstrated the cross pol better than -25 dB across 95% of the frequency band, the output reflections better than 15 dB, and the RF insertion loss better than 0.8 dB.

关键词： Radio frequency Receivers Transducers Insertion loss Layout Loss measurement Waveguide junctions Optical waveguides Wideband Three-dimensional displays ALMA receiver cartridge dual-polarization receivers orthomode transducer (OMT) waveguides

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Design and development of resonant ring test setup at 325 MHz for high power testing of RF couplers used in accelerator

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2025年 1070卷

作者： Sharma, Sonal Jose, Mentes Singh, Gireesh Kumar, Rajesh Bhabha Atom Res Ctr Ion Accelerator Dev Div Mumbai 400085 India

A travelling wave resonant ring has been developed at Bhabha Atomic Research Centre (BARC) to test 325 MHz radio frequency (RF) power couplers for accelerator cavities. It mainly consists of half height rectangular waveguide components. The ring has been tested for output power of 30 kW with gain of 14.4 dB. Presently, RF characterization and high power testing has been completed without RF couplers. The design, RF simulations and characterization of the entire ring, along with the high power test results, are presented in this paper.

关键词： RF couplers Resonant ring High power Travelling wave RF simulation Directional coupler waveguides

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Ultra-flat electro-optic frequency comb based on a chirp-modulated lithium niobate resonator

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OPTICS EXPRESS 2025年第2期33卷 3123-3133页

作者： Zhang, Yujie Jia, Tao Rong, Jiamin Xing, Enbo Li, Jianglong Yang, Xinrong Yue, Hongbo Zhou, Yanru Liu, Wenyao Tang, Jun Liu, Jun North Univ China Sch Semicond & Phys State Key Lab Widegap Semicond Optoelect Mat & Tec Taiyuan 030051 Shanxi Peoples R China North Univ China Sch Instrument & Elect State Key Lab Dynam Measurement Technol Taiyuan 030051 Peoples R China North Univ China Shanxi Prov Key Lab Quantum Sensing & Precis Measu Taiyuan 030051 Shanxi Peoples R China

Chirp modulation can generate a relatively flat electro-optic frequency comb (EO comb) and offers the advantage of frequency reconfigurability, demonstrating significant potential in high-precision sensing and absorption spectroscopy measurements. However, nonresonant devices such as waveguides are susceptible to limitations in modulation efficiency and bandwidth during electro-optic modulation. In this paper, by utilizing chirp modulation resonance mode, we have realized an EO comb based on a lithium niobate resonator with small tooth spacing and high flatness. Theoretically, the chirp modulation of phase is achieved by modulating the dispersion coupling term in the resonant mode transmission equation. Compared with conventional waveguide-based EO combs, the resonant mode chirp modulation is capable of generating a multistage flat comb, and thus the bandwidth of the comb is significantly expanded. In the experiment, with a repetition rate as low as 20 kHz and a bias voltage of 1 V, the comb bandwidth extended to over 150 MHz, where the number of 3 dB flat comb teeth for a single stage exceeds 2,000. Finally, we evaluated the measurement capability of the frequency comb at different temperatures by utilizing the transmission spectrum of the germanium-doped silica waveguide cavity as the absorption spectrum, measuring a temperature sensitivity of 1505.00 MHz/K and a temperature instability of 1.13 mK/Hz1/2.

关键词： Absolute distance measurement Frequency combs Lithium niobate Lithium niobate waveguides Phase modulation waveguides

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3D-Printed Terahertz Subwavelength Dual-Core Fibers With Dense Channel-Integration

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2025年第5期43卷 2329-2339页

作者： Ge, Haiyuan Li, Haisu Jie, Lu Wang, Jianshuai Cao, Yang Atakaramians, Shaghik Gong, Yandong Ren, Guobin Pei, Li Beijing Jiaotong Univ Inst Lightwave Technol Minist Educ Key Lab All Opt Network & Adv Telecommun Network Beijing 100044 Peoples R China Hebei Univ Technol Ctr Adv Laser Technol Tianjin 300401 Peoples R China Univ New South Wales Sch Elect Engn & Telecommun Terahertz Innovat Grp Sydney NSW 2052 Australia Beijing Informat Sci & Technol Univ Sch Instrument Sci & Optoelect Engn Beijing 100192 Peoples R China

Terahertz (THz) fiber that provides high-speed connections is one of the most essential components in THz communication systems. The emerging space-division-multiplexing technology is expected to increase the transmission capacity of THz communications. A promising candidate to achieve that is integrating multiple channels in a compact THz multi-core fiber system. Here, we propose and experimentally demonstrate a THz subwavelength rectangular dielectric dual-core fiber structure, where two identical cores can be densely integrated, thanks to the polarization-maintaining feature of the rectangular fiber. Different configurations of the fiber structure, including the placements, core-spacings, and polarization states of two fiber cores, are comprehensively investigated to improve the channel isolation. Numerical simulations show that the fractional power in core of fiber mode has a dominant effect on inter-core coupling performance. Moreover, we design the core size (1 mm x 0.5 mm) slightly less than the WR5.1 waveguide (1.295 mm x 0.6475 mm) so that the fiber can be conveniently connected with the WR5.1 flange port with mode excitation efficiencies up to 62.8%. A cost-efficient dielectric 3D printing technique is employed for rapid fabrications of dual-core fibers as well as corresponding polymer flange structures that offer solid integration between the fiber samples and the WR5.1 port. Experimental measurements of dual-core fibers demonstrate that a 4-mm core-spacing (less than three times of the operation wavelengths over a frequency range of 0.17-0.21 THz) is sufficient to support robust dual-channel propagation with channel isolation values more than 15 dB, which are consistent with the theoretical and numerical results. This work provides a densely integrated dual-core fiber system with low fabrication cost and practical connection to WR5.1 flange, holding exciting potentials for high-capacity THz space-division-multiplexing communication systems.

关键词： Optical fiber polarization Terahertz communications Optical fiber couplers Couplings Optical fiber sensors Optical waveguides Dielectrics Terahertz radiation Planar waveguides Optical fiber theory Birefringence coupling dual-core fibers terahertz waveguides

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Fiber Tip Empowered by Axial-Asymmetric Four-Sector Nanostructure for Broad-Angle Light Coupling

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LASER & PHOTONICS REVIEWS 2025年第5期19卷

作者： Wang, Jianwei Yermakov, Oleh Gu, Yitong Zeisberger, Matthias Fischer, Bennet Yu, Fei Yu, Chunlei Hu, Lili Schmidt, Markus A. Wang, Ning Univ Chinese Acad Sci Hangzhou Inst Adv Study Hangzhou 310024 Peoples R China Chinese Acad Sci Shanghai Inst Opt & Fine Mech Shanghai 201800 Peoples R China Leibniz Inst Photon Technol Albert Einstein Str 9 D-07745 Jena Germany Kharkov Natl Univ Svobody Sq 4 UA-61022 Kharkiv Ukraine Otto Schott Inst Mat Res Fraunhoferstr 6 D-07743 Jena Germany

Efficient light coupling into the fiber waveguides is important in numerous applications, while the low in-coupling coefficients of commercially available step-index fibers significantly narrow their application domains. It is recently introduced that well-defined periodic nanostructures, such as annulus gratings, allow to substantially boost in-coupling coefficients. In this study, the genetic algorithm is applied for the optimization of trapezoidal polymer gratings. The experimental data showcase multiply enhanced light coupling at preselected incident angles with respect to a bare fiber. As a breakthrough result, the development of an axial-asymmetric four-sector grating, reaching the percentage level of light coupling efficiency in a broad angular range from 0 degrees$<^>{\circ }$ to 70 degrees$<^>{\circ }$ that outperforms axial-symmetric gratings by about order of magnitude. Further, the high average light coupling efficiency is verified in the finite angular intervals at multiple wavelengths of 650, 1000, and 1550 nm. This solution highlights the enhancement of algorithm-designed structures axially-asymmetric systems for fiber-based highly efficient light collections, that will further benefit extensive applications such as wide-field endoscopies.

关键词： energy collection gratings light coupling waveguides

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On-Chip Cascaded Metasurfaces for Visible Wavelength Division Multiplexing and Color-Routing Meta-Display

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NANO LETTERS 2025年第6期25卷 2452-2458页

作者： Rao, Runlong Shi, Yangyang Wang, Zejing Wan, Shuai Li, Zhongyang Wuhan Univ Elect Informat Sch Wuhan 430072 Peoples R China Wuhan Univ Sch Microelect Wuhan 430072 Peoples R China Wuhan Inst Quantum Technol Wuhan 430206 Peoples R China

Integrating metasurfaces on-chip offers a promising strategy for modulating and extracting guided waves, suggesting tremendous applications in compact wearable devices. However, despite the full acquisition of on-chip manipulation of optical parameters, including phase, amplitude, and polarization, the functionality of on-chip metasurfaces remains limited by the lack of wavelength selectivity. Here, an on-chip approach to differentiate wavelength components is proposed in the visible regime for wavelength division multiplexing (WDM). Through horizontally cascading on-chip meta-atoms with structural dimension variation and optimization, different wavelength components propagating along the waveguide would be selectively extracted, realizing meta-demultiplexing functionality. More intriguingly, color nanoprinting images or holographic displays can be correspondingly enabled. This approach surpasses conventional free-space meta-devices in terms of exhibiting improved wavelength-selective allocation and eliminating the energy waste caused by spatial multiplexing. We envision that such an on-chip cascading strategy paves the way for next-generation WDM devices in photonic integrated circuits and wearable miniature meta-displays.

关键词： On-chip metasurfaces Wavelength divisionmultiplexing Wavelength selectivity Color-routingdisplay waveguides

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Giant Helical Dichroism in Twisted Hollow-Core Photonic Crystal Fibers

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ACS PHOTONICS 2025年第2期12卷 564-569页

作者： Helfrich, Christof Frosz, Michael H. Tani, Francesco Univ Erlangen Nurnberg D-91058 Erlangen Germany Max Planck Inst Sci Light D-91058 Erlangen Germany Univ Lille CNRS UMR 8523 PhLAM Phys Lasers Atomes & Mol F-59000 Lille France

We show that twisted single-ring hollow-core fibers can exhibit strong helical dichroism, i.e., a different transmission depending on the orbital angular momentum of the launched light. Experimentally, we observe loss differences of at least 40 dB/m over a broad spectral range (>60 THz). We investigate the effect via analytical and numerical studies and show that considerably higher differential loss can be achieved over a broader spectral range (>180 THz). Our observation provides new routes for controlling the polarization state, extends previous studies of circularly dichroic waveguides, and has many potential applications, such as the realization of new polarizing elements in previously inaccessible spectral regions, chiral sensing, broadband generation of vortex beams, and optical communication.

关键词： waveguides photonic crystal fiber chiral orbital angular momentum

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Splitter engineering through optimizing topological adiababtic passage

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Frontiers of physics 2025年第1期20卷 145-163页

作者： Jia-Ning Zhang Jin-Lei Wu Cheng Lv Jiabao Yao Jie Song Yong-Yuan Jiang School of Physics Harbin Institute of TechnologyHarbin 150001China School of Physics Zhengzhou UniversityZhengzhou 450001China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China Key Laboratory of Micro-Nano Optoelectronic Information System Ministry of Industry and Information TechnologyHarbin 150001China Key Laboratory of Micro-Optics and Photonic Technology of Heilongjiang Province Harbin Institute of TechnologyHarbin 150001China

Topologically protected states are important in realizing robust optical behaviors that are quite insensitive to local defects or perturbations,which provide a promising solution for robust photonic ***,we propose to implement fast topological beam splitters and routers via the adiabatic passage of edge and interface states in the cross-linking configuration of Su-Schrieffer-Heeger(SSH)chains with interface *** channel state does not immerse into the band continuum during the adiabatic cycle,making the adiabatic restriction less stringent and the transport process more *** on the accelerated topological pumping,the beam splitters and routers exhibit improved robustness against losses of the system yet degraded resilience to fluctuation of coupling strengths and on-site energies compared with the conventional topological splitting and routing *** addition,we confirm that the model demonstrates good scalability when the system size is *** simulation results of topological beam splitting in coupled waveguide arrays are in good consistency with theoretical *** topological design provides a robust way to control photons,which may suggest further application of topological devices with unique properties and functionalities for integrated photonics.

关键词： topological effects in photonic systems Su-Schrieffer-Heeger topological photonics waveguides

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Mechanical Design of the VSR Cavity: An Elliptical 4-Cell 1.5 GHz SRF Cavity With Strong Waveguide HOM Damping for High-Current Accelerators

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IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 2025年第4期35卷

作者： Wunderer, N. Fendinger, S. Glock, H. -w. Gloeckner, F. Knobloch, J. Sharples-Milne, E. Scherer, S. Tsakanian, A. Velez, A. Helmholtz Zentrum Berlin Mat & Energy Inst Appl Mat D-14109 Berlin Germany RI Res Instruments GmbH D-51429 Bergisch Gladbach Germany Univ Siegen D-57068 Siegen Germany Tech Univ Dortmund D-44227 Dortmund Germany

The mechanical design of an elliptical 1.5 GHz superconducting RF 4-cell cavity with strong waveguide higher order mode (HOM) damping is presented. It was developed in the variable storage ring project framework to serve as part of an upgrade for the synchrotron light source BESSY II operating at beam currents of up to 300 mA. This poses a great design challenge, demanding both: a system capable of extracting very high HOM powers (above 2 kW per cavity), the stresses arising during operation, and an overall cavity length of less than 1 m to fit into a given magnet lattice. As a result, a compact HOM waveguide-loaded cavity has been developed, fulfilling all the required criteria. The most remarkable feature of the cavity are the five waveguide extensions. The article describes the mechanical solutions adopted in the layout of the cavity with its subgroups. Special attention is given to numerical studies aiming for high pressure resistance whilst allowing for required tuning. A standardized pressure vessel code was not followed. Instead, a dedicated quality control procedure for manufacturing including ancillary material testing and welding qualification, was developed to allow for peak pressures of 3.5 bar(a) of the cooling medium. This article shows the successful mechanical design solutions developed to allow for the operation of such cavities in demanding operational regimes featuring both high gradients and strong beam currents. At time of writing, the first prototype is mechanically completed, and the first RF tests have been performed. Relevant manufacturing experiences which led to late-stage design modifications are included in this article.

关键词： Radio frequency Flanges Helium Cooling Titanium Synchrotrons Storage rings Damping Welding Manufacturing Cryogenic vessel design engineering manufacturing material properties mechanical engineering mechanical simulation niobium safety analysis superconducting radiofrequency cavity synchrotron ultrahigh vacuum flanges waveguides

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