Photonics and Nanostructures-Fundamentals and Applications最新文献

{"title":"Numerical analysis of a MIM waveguide sensor for refractive index and potential concentration sensing","authors":"Jigang Li ,&nbsp;L.U. Meiqu ,&nbsp;Jun Zhu","doi":"10.1016/j.photonics.2026.101572","DOIUrl":"10.1016/j.photonics.2026.101572","url":null,"abstract":"<div><div>This study introduces a MIM waveguide–coupled ring resonator configuration developed for optical index detection purposes. We explored how variations in the cavity–waveguide geometry affect Fano resonance characteristics, including resonance profile, field localization, transmission spectra, and sensing capability. After structural optimization, the device exhibits a resonance peak at 1119 nm with 0.64 transmission efficiency. At this wavelength, the electric field energy is approximately 3.14 × 10⁻¹ ⁴ J, whereas the magnetic field stores around 1.50 × 10⁻¹ ⁴ J, with the resulting Fano resonance transmission peak characterized by a linewidth (FWHM) of 29 nm. The sensor operates through resonance wavelength shifts, reaching a sensitivity of 1395 nm/RIU. Numerical analysis suggests that this platform holds significant potential for high-resolution biosensing and integrated optical spectral analysis.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101572"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147991181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-FOM and high-sensitivity mid-IR graphene metasurface absorber biosensor based on two concentric gold–silver ring resonators for tuberculosis detection","authors":"Anas A.M. Alqanoo ,&nbsp;K.H. Ibnaouf ,&nbsp;Mahmoud M.M. Abu Hasanein ,&nbsp;Samer M. Srour","doi":"10.1016/j.photonics.2026.101578","DOIUrl":"10.1016/j.photonics.2026.101578","url":null,"abstract":"<div><div>Tuberculosis (TB) remains a major global health challenge, highlighting the need for rapid and reliable detection techniques. In this work, a graphene-assisted plasmonic metasurface absorber is proposed and numerically investigated as a refractive-index biosensing platform in the mid-infrared region. The unit-cell design combines a circular ring with four quarter-ring resonators based on silver and gold nanostructures to achieve strong electromagnetic field confinement and tunable absorption characteristics. A systematic parametric study is performed to optimize the sensor performance by varying the spacer thickness <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span>, quarter-ring radius <span><math><msub><mrow><mi>R</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>, resonator thickness <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span>, and graphene Fermi energy <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span>. The optimized configuration achieves maximum sensitivities of 4666.66, 4750, 4666.66, and 4500 nm/RIU for TB1–TB4, respectively, with corresponding maximum figure of merit (FOM) values of 388.88, 279.41, 245.61, and 204.54 RIU⁻¹. Electric-field distributions further confirm the resonance mechanism and the wavelength-dependent interaction within the metasurface structure. The obtained results demonstrate the potential of the proposed design for high-performance mid-IR refractometric biosensing and motivate future experimental validation toward practical TB-related sensing applications.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101578"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148230734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PT-symmetry modulated TiO2 all-dielectric metasurface for refractive index sensing based on multimodal fano resonances","authors":"Ying Chen,&nbsp;Xin Luo,&nbsp;Haoliang Zhou,&nbsp;Zhongyao Wang,&nbsp;Zhe Han","doi":"10.1016/j.photonics.2026.101573","DOIUrl":"10.1016/j.photonics.2026.101573","url":null,"abstract":"<div><div>All-dielectric metasurfaces have attracted considerable attention in refractive index sensing owing to their low optical loss, strong field confinement, and flexible modal regulation capability. In this work, a PT-symmetry modulated TiO₂ all-dielectric metasurface is numerically investigated for refractive index sensing based on multimodal Fano resonances. The proposed unit cell contains a cylindrical cavity filled with balanced gain and loss regions, and subwavelength geometric perturbation is introduced to regulate the coupling between radiative and confined modes. Full wave simulations are performed to analyze the transmission spectra, near field distributions, multipolar scattering contributions, and parameter dependent resonance evolution. To verify the Fano nature of the resonance, the transmission dip near 522 THz is fitted using the standard Fano line shape model. The extracted asymmetry factor is <span><math><mrow><mi>q</mi><mo>=</mo><mo>−</mo><mn>0.23</mn></mrow></math></span>, with a fitting goodness of <span><math><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>0.9995</mn></mrow></math></span>, confirming that the resonance originates from asymmetric modal interference rather than a conventional Lorentzian response. In addition, the analytical phase estimated from the fitted complex Fano amplitude is <span><math><mrow><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>F</mi></mrow></msub><mo>(</mo><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>)</mo><mo>=</mo><mn>1.571</mn><mi>rad</mi></mrow></math></span>at the fitted resonance center. Multipole decomposition and field distribution analysis further reveal that the sharp Fano resonance is mainly associated with the interference between a broadband dipolar radiation channel and a higher order electric multipole mode. The refractive index sensing results show a frequency sensitivity of 17.87 THz/RIU, corresponding to an equivalent wavelength sensitivity of 32.36 nm/RIU, with a figure of merit of 65.48 and an estimated detection limit of <span><math><mrow><mn>1.68</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span>RIU. The feasibility and limitations of implementing balanced gain and loss in the visible to near infrared range are also discussed. These results suggest that PT-symmetric gain-loss modulation provides an additional non-Hermitian degree of freedom for engineering Fano resonances in all-dielectric metasurfaces.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101573"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148230735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Artificial intelligence-based optimization for high-performance optoelectronic nanowires solar cells","authors":"Karim Ahmed ,&nbsp;Eman Teleb ,&nbsp;Mohamed G. Mahmoud ,&nbsp;Mohamed Farhat O. Hameed ,&nbsp;Hamdy Abdelhamid ,&nbsp;S.S.A. Obayya ,&nbsp;Ramy El-Bashar","doi":"10.1016/j.photonics.2026.101560","DOIUrl":"10.1016/j.photonics.2026.101560","url":null,"abstract":"<div><div>We present an advanced reinforcement learning (RL)-driven optimization approach employing neural networks to boost the optical and electrical performance of nanowire (NW) silicon solar cells (SCs). The proposed assembly consists of 2 × 2 periodic cylindrical (C) NWs with different diameters which disrupt structure mirror’s symmetry. Our results show that the RL methodology successfully improves the optoelectronic performance of the suggested design. In this study, the RL-optimized asymmetric array design increased average absorption to 0.65-an improvement of 12% over the symmetric C-NWs configuration. The photo-generated current density (J_ph) is elevated by 7%, reaching 13.6 mA/cm², while reducing the filling area by nearly 50%. Incorporation of a bottom Si substrate and back metal further boosted the J_ph and ultimate optical efficiency to 19.3 mA/cm² and 21.9%, respectively. After taking into consideration recombination effects, an extensive electrical simulation revealed an optical-to-electrical conversion efficiency (PCE) of 6%, which is 13.2% higher than that of a traditional C-NWs array. This work highlights the potential of RL-based design methodologies in improving NW architectures in addition to providing a path towards affordable and highly efficient silicon NW SC technologies.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101560"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148167531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polarization switchable broadband-to-narrowband metamaterial perfect absorber integrating trapezoidal Ti/TiN and Ag grating arrays","authors":"Weiwei Tan ,&nbsp;Jinyong Hu","doi":"10.1016/j.photonics.2026.101574","DOIUrl":"10.1016/j.photonics.2026.101574","url":null,"abstract":"<div><div>Metamaterial perfect absorbers have attracted considerable attention because of their strong capabilities for light manipulation and energy conversion. However, switching between broadband and narrowband absorption within a single device remains challenging for multifunctional photonic applications. Here, we propose and numerically investigate a polarization-switchable metamaterial perfect absorber that switches between broadband and narrowband absorption modes. The structure integrates two resonant modules within a compact unit cell: an upper trapezoidal titanium/titanium nitride (Ti/TiN) grating and a lower symmetric pair of silver (Ag) gratings embedded within a silicon dioxide (SiO₂) isolator. Under TE polarization, the device operates as an ultra-broadband absorber with an average absorptance of 97.15% across 500–3423 nm. Under TM polarization, it switches to a narrowband absorption peak at 964.29 nm with an absorptance of 99.85%, a refractive index sensitivity of 330.58 nm·RIU⁻¹, and a figure of merit of 13.6 RIU⁻¹. Electromagnetic field analysis shows that the broadband mode arises from cavity resonance, gap surface plasmon modes, localized surface plasmon resonance, and adiabatic nanofocusing, whereas the narrowband mode is mainly governed by LSPR-Fabry-Perot cavity coupling. Parametric studies clarify the trade-off between the two polarization-dependent modes. The TE-polarized broadband mode shows strong polarization-selective photothermal absorption under AM 1.5 illumination, while the TM-polarized narrowband mode enables refractive index sensing. These results suggest potential applications in polarization-selective photothermal absorption, photodetection, polarization-sensitive imaging, and refractive index sensing.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101574"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148167532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Au nanoantennas embedded into silicon for surface enhanced infrared absorption spectroscopy","authors":"I.A. Milekhin ,&nbsp;D.A. Sherbakov ,&nbsp;V.S. Tumashev ,&nbsp;S.A. Kuznetsov ,&nbsp;E.E. Rodyakina ,&nbsp;T.A. Duda ,&nbsp;A.G. Milekhin ,&nbsp;A.V. Latyshev","doi":"10.1016/j.photonics.2026.101569","DOIUrl":"10.1016/j.photonics.2026.101569","url":null,"abstract":"<div><div>Surface-enhanced infrared absorption (SEIRA) spectroscopy based on plasmonic nanoantennas is a powerful tool for ultrasensitive molecular detection; however, further enhancement of its performance remains a key challenge. In this work, we demonstrate arrays of gold nanoantennas embedded into a silicon substrate using metal-assisted chemical etching (MACE). This approach enables precise control of the nanoantenna embedment depth and formation of nanoscale capillary gaps. We show that both the embedment depth and the capillary gap critically influence the localized surface plasmon resonance (LSPR) energy and near-field distribution. Full-wave electromagnetic simulations reveal that the capillary gap acts as a key parameter governing field confinement. By comparing experimental and simulated IR transmission spectra, the gap size is determined to be 6 ± 1 nm. The embedded geometry enhances the effective interaction volume between the analyte and the plasmonic field, resulting in improved SEIRA sensitivity by factor 3. This approach provides a robust platform for designing highly sensitive mid-IR plasmonic sensors.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101569"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148167533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Second and third harmonic generation in “6–n” GaAs/AlGaAs quantum wells: Influence of asymmetry and external fields","authors":"Ozan Öztürk","doi":"10.1016/j.photonics.2026.101550","DOIUrl":"10.1016/j.photonics.2026.101550","url":null,"abstract":"<div><div>In this study, we examine the nonlinear optical response of GaAs/AlGaAs quantum wells (QWs) by employing a tunable \"6-n\" confinement potential. Given that the second harmonic generation (SHG) coefficient inherently vanishes in centrosymmetric systems, we engineering structural asymmetry into the structure by setting the structural asymmetry parameter (n) to 1, 3, and 5. Electronic states were computed under external electric, magnetic, and intense laser fields using the finite element method (FEM); subsequently, we used these states to systematically calculate the SHG and third harmonic generation (THG) coefficients. Our findings demonstrate that the n parameter acts as a pivotal structural mechanism for tuning quantum confinement and electron localization. Specifically, modulating the degree of asymmetry significantly enhances the sensitivity of the QW to external fields. This amplified sensitivity enables versatile and precise control over both the magnitudes and the red/blueshifts of the harmonic peaks. Collectively, this study highlights the substantial potential of asymmetric \"6-n\" QWs as highly efficient, tunable components for next-generation nonlinear optoelectronic devices and nanophotonic frequency converters.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101550"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147703462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconfigurable high-Q terahertz chiral sensing enabled by quasi-bound states in the continuum in a Ge2Sb2Te5 metasurface","authors":"Shuyu Li,&nbsp;Zhe Chen,&nbsp;Wenzhuo Li,&nbsp;Jianfeng Shi,&nbsp;Qihao Zhang,&nbsp;Shuang Li,&nbsp;Zhongming Kang","doi":"10.1016/j.photonics.2026.101558","DOIUrl":"10.1016/j.photonics.2026.101558","url":null,"abstract":"<div><div>Achieving high-Q resonances in active metasurfaces is fundamentally limited by the intrinsic optical loss of phase-change materials (PCMs). In order to address this limitation, we propose a reconfigurable terahertz chiral metasurface based on Ge₂Sb₂Te₅ (GST225) that excites intrinsically chiral quasi-bound states in the continuum (quasi-BICs) through controlled in-plane symmetry breaking of an I-shaped unit cell. When GST225 is in the amorphous state, the metasurface supports a narrow, high-Q chiral resonance with a circular dichroism (CD) of 0.98 and a Q factor of 1150, effectively suppressing the total damping of the system. This quasi-BIC further enables ultrasensitive refractive-index sensing, achieving a sensitivity of 0.61 THz/RIU and a figure of merit (FOM) of 305. In contrast, the crystalline phase produces a broadband, spectrally flat chiral response (CD &gt; 0.98), allowing reversible switching between broadband and high-Q narrowband chiral modes using only the GST225 phase transition. This work demonstrates the realization of intrinsically chiral quasi-BIC-driven broadband-to-narrowband switching with simultaneously high CD, high Q, and high FOM in the terahertz regime. These results offer a promising approach for developing multifunctional terahertz devices capable of both high-performance chiral sensing and dynamic spectral reconfiguration.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101558"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147991177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of symmetry, isosbestic points and degeneracy in plasmonic scattering spectra","authors":"Qianjiao He,&nbsp;Haodong Ding,&nbsp;Qinglin Liu,&nbsp;Yuhang Liu,&nbsp;Quanshui Li","doi":"10.1016/j.photonics.2026.101555","DOIUrl":"10.1016/j.photonics.2026.101555","url":null,"abstract":"<div><div>We present an approach to explain the relationships between the symmetries, the isosbestic points, and the degeneracy of the far field scattering spectra of the plasmonic nanoparticles or arrays in the quasistatic approximation. The theoretical framework involves the polarization responses in nanostructures, scattering spectra arising from the radiation of dipole moments, and orthogonal decomposition of the spectra. For a plasmonic structure with mirror symmetry irradiated by linearly polarized light, the special directions termed as eigenpolarization directions are found. One eigenpolarization is perpendicular to the symmetry plane, while the other is parallel to it. If the polarization of incident light is aligned with one eigenpolarization, the total field (the superposition of the external field and the depolarization field) has no component along the other orthogonal eigenpolarization. The orthogonal eigenpolarization directions form the basis of the far-field spectrum, and the far-field scattering spectrum can be only orthogonally decomposed along this set of eigenpolarization directions. If the scattering cross-sections at these directions are ideal, the isosbestic points will emerge in the spectra. Then we illustrate those conclusions by a silver ellipsoidal nanostructure with the theoretical derivation and simulations, and we obtain a formula for the positions of the isosbestic points in the scattering spectra. Then by this approach, we also verified that for nanostructures with <em>n</em>-fold rotational symmetry (C<em>n</em>, <em>n</em> ≥ 3), the scattering spectra of linearly polarized light with different polarization directions incident along the rotation axis are degenerate.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101555"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147850718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Statistical analysis of phase depth in periodically poled lithium niobate gratings","authors":"Abhinav Kumar ,&nbsp;Ugrasen Singh ,&nbsp;Prashant Povel Dwivedi ,&nbsp;Ajay Mishra ,&nbsp;Nimish Dixit","doi":"10.1016/j.photonics.2026.101553","DOIUrl":"10.1016/j.photonics.2026.101553","url":null,"abstract":"<div><div>Phase depth variation is inherent in the fabrication of periodically poled lithium niobate (PPLN), primarily due to imperfections during the etching process. These variations in phase depth can significantly influence phase grating of quasi-phase matching (QPM) device. In this paper, we evaluate the phase depth of the PPLN grating after etching. The etched QPM device was statistically analysed to quantify the phase depth variations along a 10 mm- long PPLN grating. The mean phase depth was found to be 30.8 nm with a standard deviation (STD) of 1.8 nm. Histograms of the measured data reveal that the phase depth follows a Gaussian distribution, as deviations from Gaussianity can introduce phase noise, thereby degrading grating performance. This statistical characterization provides a reliable approach for assessing the fabrication quality of the phase grating.</div></div>","PeriodicalId":49699,"journal":{"name":"Photonics and Nanostructures-Fundamentals and Applications","volume":"71 ","pages":"Article 101553"},"PeriodicalIF":2.9,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147798503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}