Nanomaterials

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4 pages, 182 KiB

Open AccessEditorial

Editorial of the Special Issue ‘Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends’

by Hai-Zhi Song

Nanomaterials 2024, 14(2), 169; https://doi.org/10.3390/nano14020169 - 12 Jan 2024

Viewed by 1459

Abstract

Through nano-optics and nano-optoelectronics, we can investigate the characteristics of light at the nanometer scale and the interaction of nanometer-scale objects with light [...] Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

Research

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9 pages, 1826 KiB

Open AccessArticle

Design and Fabrication of High Performance InGaAs near Infrared Photodetector

by Hezhuang Liu, Jingyi Wang, Daqian Guo, Kai Shen, Baile Chen and Jiang Wu

Nanomaterials 2023, 13(21), 2895; https://doi.org/10.3390/nano13212895 - 1 Nov 2023

Cited by 11 | Viewed by 4867

Abstract

InGaAs photodiodes have a wide range of important applications; for example, NIR imaging, fiber optical communication, and spectroscopy. In this paper, we studied InGaAs photodiodes with different doping concentration absorber layers. The simulated results suggested that, by reducing the absorber doping concentration from [...] Read more.

InGaAs photodiodes have a wide range of important applications; for example, NIR imaging, fiber optical communication, and spectroscopy. In this paper, we studied InGaAs photodiodes with different doping concentration absorber layers. The simulated results suggested that, by reducing the absorber doping concentration from 1 × 10¹⁶ to 1 × 10¹⁵ cm⁻³, the maximum quantum efficiency of the devices can rise by 1.2%, to 58%. The simulation also showed that, by increasing the doping concentration of the absorber layer within a certain range, the dark current of the device can be slightly reduced. A PIN structure was grown and fabricated, and CV measurements suggested a low doping concentration of about 1.2 × 10¹⁵ cm⁻³. Although the thermal activation energy of the dark current suggested a distinct component of shunt dark current at a high temperature range, a dark current of ~6 × 10⁻⁴ A/cm² (−0.5 V) was measured at room temperature. The peak quantum efficiency of the InGaAs device was characterized as 54.7% without antireflection coating and 80.2% with antireflection coating. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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13 pages, 5605 KiB

Open AccessArticle

The Tunable Electronic and Optical Properties of Two-Dimensional Bismuth Oxyhalides

by Yong Zhou, Beitong Cheng, Shuai Huang, Xingyong Huang, Ruomei Jiang, Xule Wang, Wei Zhang, Baonan Jia, Pengfei Lu and Hai-Zhi Song

Nanomaterials 2023, 13(20), 2798; https://doi.org/10.3390/nano13202798 - 20 Oct 2023

Cited by 5 | Viewed by 1667

Abstract

Two-dimensional (2D) bismuth oxyhalides (BiOX) have attracted much attention as potential optoelectronic materials. To explore their application diversity, we herewith systematically investigate the tunable properties of 2D BiOX using first-principles calculations. Their electronic and optical properties can be modulated by changing the number [...] Read more.

Two-dimensional (2D) bismuth oxyhalides (BiOX) have attracted much attention as potential optoelectronic materials. To explore their application diversity, we herewith systematically investigate the tunable properties of 2D BiOX using first-principles calculations. Their electronic and optical properties can be modulated by changing the number of monolayers, applying strain, and/or varying the halogen composition. The band gap shrinks monotonically and approaches the bulk value, the optical absorption coefficient increases, and the absorption spectrum redshifts as the layer number of 2D BiOX increases. The carrier transport property can be improved by applying tensile strain, and the ability of photocatalytic hydrogen evolution can be obtained by applying compressive strain. General strain engineering will be effective in linearly tuning the band gap of BiOX in a wide strain range. Strain, together with halogen composition variation, can tune the optical absorption spectrum to be on demand in the range from visible to ultraviolet. This suggests that 2D BiOX materials can potentially serve as tunable novel photodetectors, can be used to improve clean energy techniques, and have potential in the field of flexible optoelectronics. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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15 pages, 6425 KiB

Open AccessArticle

Broadband Achromatic Metalens for Tunable Focused Vortex Beam Generation in the Near-Infrared Range

by Lvrong Zhao, Xiaoqiang Jiang, Zhihai Wang, Yuwei Chen, Lu Chen, Bo Gao and Weixing Yu

Nanomaterials 2023, 13(20), 2765; https://doi.org/10.3390/nano13202765 - 15 Oct 2023

Cited by 5 | Viewed by 1957

Abstract

Vortex beams accompanied with orbital angular momentum have attracted significant attention in research fields due to their formidable capabilities in various crucial applications. However, conventional devices for generating vortex beams still suffer from bulky sizes, high cost, and confined performances. Metalens, as an [...] Read more.

Vortex beams accompanied with orbital angular momentum have attracted significant attention in research fields due to their formidable capabilities in various crucial applications. However, conventional devices for generating vortex beams still suffer from bulky sizes, high cost, and confined performances. Metalens, as an advanced platform to arbitrarily control the optical waves, has promising prospects to address the predicament for conventional devices. Although great progress has been demonstrated in the applications of vortex beams, they are still confronted with fixed functionality after fabrication that severely hinders their application range. In this work, the phase-change material of Ge₂Sb₂Te₅ (GST) is employed to design the meta-atoms to realize tunable optical responses. Moreover, the focused vortex beam can be accomplished by superimposing a helical phase and hyperbolic phase, and the chromatic aberrations in near-infrared (NIR) range can be corrected by introducing an additional phase compensation. And the design strategy is validated by two different metalenses (BAMTF-1 and BAMTF-2). The numerical results indicate that the chromatic aberrations for two metalens can be corrected in 1.33–1.60 μm covering the telecom range. Moreover, the average focusing efficiency of BAMTF-1 is 51.4%, and that of BAMTF-2 is 39.9%, indicating the favorable performances of designed BAMTF. More importantly, their average focal lengths have a relative tuning range of 38.82% and 33.17% by altering the crystallization ratio of GST, respectively. This work may provide a significant scheme for on-chip and tunable devices for NIR imaging and communication systems. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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12 pages, 3120 KiB

Open AccessArticle

Investigation of Vacancy-Ordered Double Perovskite Halides A₂Sn_1−xTi_xY₆ (A = K, Rb, Cs; Y = Cl, Br, I): Promising Materials for Photovoltaic Applications

by Wen Chen, Gang Liu, Chao Dong, Xiaoning Guan, Shuli Gao, Jinbo Hao, Changcheng Chen and Pengfei Lu

Nanomaterials 2023, 13(20), 2744; https://doi.org/10.3390/nano13202744 - 11 Oct 2023

Cited by 7 | Viewed by 1821

Abstract

In the present study, the structural, mechanical, electronic and optical properties of all-inorganic vacancy-ordered double perovskites A₂Sn_1−xTixY₆ (A = K, Rb, Cs; Y = Cl, Br, I) are explored by density functional theory. The structural and thermodynamic stabilities [...] Read more.

In the present study, the structural, mechanical, electronic and optical properties of all-inorganic vacancy-ordered double perovskites A₂Sn_1−xTixY₆ (A = K, Rb, Cs; Y = Cl, Br, I) are explored by density functional theory. The structural and thermodynamic stabilities are confirmed by the tolerance factor and negative formation energy. Moreover, by doping Ti ions into vacancy-ordered double perovskite A₂SnY₆, the effect of Ti doping on the electronic and optical properties was investigated in detail. Then, according to the requirement of practical applications in photovoltaics, the optimal concentration of Ti ions and the most suitable halide element are determined to screen the right compositions. In addition, the mechanical, electronic and optical properties of the selected compositions are discussed, exhibiting the maximum optical absorption both in the visible and ultraviolet energy ranges; thus, the selected compositions can be considered as promising materials for application in solar photovoltaics. The results suggest a great potential of A₂Sn_1−xTi_xY₆ (A = K, Rb, Cs; Y = Cl, Br, I) for further theoretical research as well as experimental research on the photovoltaic performance of stable and toxic-free perovskite solar cells. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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15 pages, 6121 KiB

Open AccessArticle

A Novel Strategy for the Synthesis of High Stability of Luminescent Zero Dimensional–Two Dimensional CsPbBr₃ Quantum Dot/1,4-bis(4-methylstyryl)benzene Nanoplate Heterostructures at an Atmospheric Condition

by Yanran Wang, Ming-yu Li, Shijie Liu, Yuan Ma, Bo Sun, Liangyu Wang, Haifei Lu, Xiaoyan Wen, Sisi Liu and Xumin Ding

Nanomaterials 2023, 13(19), 2723; https://doi.org/10.3390/nano13192723 - 7 Oct 2023

Cited by 3 | Viewed by 1966

Abstract

Perovskite quantum dots (QDs), emerging with excellent bright-green photoluminescence (PL) and a large absorption coefficient, are of great potential for the fabrication of light sources in underwater optical wireless communication systems. However, the instability caused by low formation energy and abundant surface traps [...] Read more.

Perovskite quantum dots (QDs), emerging with excellent bright-green photoluminescence (PL) and a large absorption coefficient, are of great potential for the fabrication of light sources in underwater optical wireless communication systems. However, the instability caused by low formation energy and abundant surface traps is still a major concern for perovskite-based light sources in underwater conditions. Herein, we propose ultra-stable zero dimensional–two dimensional (0D–2D) CsPbBr₃ QD/1,4-bis(4-methylstyryl)benzene (p-MSB) nanoplate (NP) heterostructures synthesized via a facile approach at room temperature in air. CsPbBr₃ QDs can naturally nucleate on the p-MSB NP toluene solution, and the radiative combination is drastically intensified owing to the electron transfer within the typical type-II heterostructures, leading to a sharply increased PLQY of the heterostructure thin films up to 200% compared with the pristine sample. The passivation of defects within CsPbBr₃ QDs can be effectively realized with the existence of p-MSB NPs, and thus the obviously improved PL is steadily witnessed in an ambient atmosphere and thermal environment. Meanwhile, the enhanced humidity stability and a peak EQE of 9.67% suggests a synergetic strategy for concurrently addressing the knotty problems on unsatisfied luminous efficiency and stability of perovskites for high-performance green-emitting optoelectronic devices in underwater applications. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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13 pages, 11442 KiB

Open AccessArticle

Anti-Reflective Coatings Produced via Atomic Layer Deposition for Hybrid Polymer 3D Micro-Optics

by Darija Astrauskytė, Karolis Galvanauskas, Darius Gailevičius, Mantas Drazdys, Mangirdas Malinauskas and Lina Grineviciute

Nanomaterials 2023, 13(16), 2281; https://doi.org/10.3390/nano13162281 - 8 Aug 2023

Cited by 10 | Viewed by 3645

Abstract

The increasing demand for optics quality requires the lowest optical power loss, which can occur from unwanted reflections. Laser direct writing (LDW) allows for the fabrication of complex structures, which is particularly advantageous in micro-optic applications. This research demonstrates the possibility of forming [...] Read more.

The increasing demand for optics quality requires the lowest optical power loss, which can occur from unwanted reflections. Laser direct writing (LDW) allows for the fabrication of complex structures, which is particularly advantageous in micro-optic applications. This research demonstrates the possibility of forming an anti-reflective coating on hybrid polymer micro-lenses fabricated by employing LDW without changing their geometry. Such coating deposited via atomic layer deposition (ALD) decreased the reflection from 3.3% to 0.1% at a wavelength of 633 nm for one surface of hybrid organic–inorganic SZ2080™ material. This research validates the compatibility of ALD with LDW 3D multiphoton lithography synergistically, expanding its applications on optical grade sub-100 μm scale micro-optics. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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11 pages, 2155 KiB

Open AccessArticle

A Multi-Channel Frequency Router Based on an Optimization Algorithm and Dispersion Engineering

by Hongyi Yuan, Nianen Zhang, Hongyu Zhang and Cuicui Lu

Nanomaterials 2023, 13(14), 2133; https://doi.org/10.3390/nano13142133 - 23 Jul 2023

Cited by 6 | Viewed by 1566

Abstract

Integrated frequency routers, which can guide light with different frequencies to different output ports, are an important kind of nanophotonic device. However, frequency routers with both a compact size and multiple channels are difficult to realize, which limits the application of these frequency [...] Read more.

Integrated frequency routers, which can guide light with different frequencies to different output ports, are an important kind of nanophotonic device. However, frequency routers with both a compact size and multiple channels are difficult to realize, which limits the application of these frequency routers in nanophotonics. Here, a kind of bandgap optimization algorithm, which consists of the finite element method and topology optimization, is proposed to design a multi-channel frequency router. Channels supporting photonic edge states with different frequencies are built through the synthetic dimension of translational deformation. Due to the help of the developed optimization algorithms, the number of channels and output ports can be increased up to nine while maintaining ultracompact device size. The device operates within a working band of 0.585–0.665 c/a, corresponding to 1.504–1.709 μm when the lattice constant is set as 1 μm, covering the telecom wavelength of 1.55 μm. The average crosstalk is about −11.49 dB. The average extinction ratio is around 16.18 dB. Because the bus of the device can be regarded as a part of a topological rainbow, the results show that the structure is robust to fabrication errors. This method is general, which can be used for different materials and different frequency ranges. The all-dielectric planar configuration of our router is compact, robust, and easy to integrate, providing a new method for on-chip multi-channel broadband information processing. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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12 pages, 3615 KiB

Open AccessArticle

Angular-Dependent THz Modulator with Hybrid Metal-Graphene Metastructures

by Huan Wang, Jiajun Linghu, Xuezhi Wang, Qiyi Zhao and Hao Shen

Nanomaterials 2023, 13(13), 1914; https://doi.org/10.3390/nano13131914 - 23 Jun 2023

Cited by 2 | Viewed by 1528

Abstract

The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal–graphene metastructures. The metastructures composed of the period gold split-rod arrays on top [...] Read more.

The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal–graphene metastructures. The metastructures composed of the period gold split-rod arrays on top of a monolayer graphene, which show redshift modulation in the THz region with an increasing incident angle due to the strong out-of-plane magnetic flux introduced by the clockwise circular current at the oblique incidence. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the hybrid metal–graphene metastructure modulator can reach ~37.6% at 0.62 THz with a gate voltage of −3 V. The theoretical modeling of transmitted dependency on frequency and incident angle is demonstrated at different Fermi energies, which fits well with the experimental results. This hybrid device can offer a useful method for THz applications (such as angle sensors or angular-resolved spectroscopy), where angle-dependent modulation is needed. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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16 pages, 4920 KiB

Open AccessArticle

An Innovative Polarisation-Insensitive Perfect Metamaterial Absorber with an Octagonal-Shaped Resonator for Energy Harvesting at Visible Spectra

by Mohammad Jakir Hossain, Md. Habibur Rahman and Mohammad Rashed Iqbal Faruque

Nanomaterials 2023, 13(12), 1882; https://doi.org/10.3390/nano13121882 - 19 Jun 2023

Cited by 17 | Viewed by 3074

Abstract

Perfect metamaterial absorber (PMA) is an attractive optical wavelength absorber with potential solar energy and photovoltaic applications. Perfect metamaterials used as solar cells can improve efficiency by amplifying incident solar waves on the PMA. This study aims to assess a wide-band octagonal PMA [...] Read more.

Perfect metamaterial absorber (PMA) is an attractive optical wavelength absorber with potential solar energy and photovoltaic applications. Perfect metamaterials used as solar cells can improve efficiency by amplifying incident solar waves on the PMA. This study aims to assess a wide-band octagonal PMA for a visible wavelength spectrum. The proposed PMA consists of three layers: nickel, silicon dioxide, and nickel. Based on the simulations, polarisation-insensitive absorption transverse electric (TE) and transverse magnetic (TM) modes were achieved due to symmetry. The proposed PMA structure was subjected to computational simulation using a FIT-based CST simulator. The design structure was again confirmed using FEM-based HFSS to maintain pattern integrity and absorption analysis. The absorption rates of the absorber were estimated at 99.987% and 99.997% for 549.20 THz and 653.2 THz, respectively. The results indicated that the PMA could achieve high absorption peaks in TE and TM modes despite being insensitive to polarisation and the incident angle. Electric field and magnetic field analyses were performed to understand the absorption of the PMA for solar energy harvesting. In conclusion, the PMA possesses outstanding visible frequency absorption, making it a promising option. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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14 pages, 4225 KiB

Open AccessArticle

Post-Processing Trimming of Silicon Photonic Devices Using Femtosecond Laser

by Yating Wu, Hongpeng Shang, Xiaorui Zheng and Tao Chu

Nanomaterials 2023, 13(6), 1031; https://doi.org/10.3390/nano13061031 - 13 Mar 2023

Cited by 5 | Viewed by 3270

Abstract

Fabrication errors inevitably occur in device manufacturing owing to the limited processing accuracy of commercial silicon photonic processes. For silicon photonic devices, which are mostly processing-sensitive, their performances usually deteriorate significantly. This remains an unsolved issue for mass production, particularly for passive devices, [...] Read more.

Fabrication errors inevitably occur in device manufacturing owing to the limited processing accuracy of commercial silicon photonic processes. For silicon photonic devices, which are mostly processing-sensitive, their performances usually deteriorate significantly. This remains an unsolved issue for mass production, particularly for passive devices, because they cannot be adjusted once fixed in processes. This study presents a post-processing trimming method to compensate for fabrication errors by changing the cladding equivalent refractive indices of devices with femtosecond lasers. The experimental results show that the resonant wavelengths of micro-ring resonators can be regularly shifted within their free spectral range via tuning the illuminating area, focusing position, emitting power, and scanning speed of the trimming femtosecond laser with an acceptable loss increase. These experiments, as well as the trimming experiments in improving the phase balance of Mach-Zehnder interferometer switches, indicate that the femtosecond laser trimming method is an effective and fast method for silicon photonic devices. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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8 pages, 1790 KiB

Open AccessCommunication

Optically Controlling Broadband Terahertz Modulator Based on Layer-Dependent PtSe₂ Nanofilms

by Hong Su, Zesong Zheng, Zhisheng Yu, Shiping Feng, Huiting Lan, Shixing Wang, Min Zhang, Ling Li and Huawei Liang

Nanomaterials 2023, 13(5), 795; https://doi.org/10.3390/nano13050795 - 21 Feb 2023

Cited by 4 | Viewed by 1981

Abstract

In this paper, we propose an optically controlling broadband terahertz modulator of a layer-dependent PtSe₂ nanofilm based on a high-resistance silicon substrate. Through optical pump and terahertz probe system, the results show that compared with 6-, 10-, and 20-layer films, a 3-layer [...] Read more.

In this paper, we propose an optically controlling broadband terahertz modulator of a layer-dependent PtSe₂ nanofilm based on a high-resistance silicon substrate. Through optical pump and terahertz probe system, the results show that compared with 6-, 10-, and 20-layer films, a 3-layer PtSe₂ nanofilm has better surface photoconductivity in the terahertz band and has a higher plasma frequency ω_p of 0.23 THz and a lower scattering time τ_s of 70 fs by Drude–Smith fitting. By the terahertz time-domain spectroscopy system, the broadband amplitude modulation of a 3-layer PtSe₂ film in the range of 0.1–1.6 THz was obtained, and the modulation depth reached 50.9% at a pump density of 2.5 W/cm². This work proves that PtSe₂ nanofilm devices are suitable for terahertz modulators. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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11 pages, 2547 KiB

Open AccessEditor’s ChoiceArticle

Silver Nanoparticle Chains for Ultra-Long-Range Plasmonic Waveguides for Nd³⁺ Fluorescence

by Javier Fernández-Martínez, Sol Carretero-Palacios, Pablo Molina, Jorge Bravo-Abad, Mariola O. Ramírez and Luisa E. Bausá

Nanomaterials 2022, 12(23), 4296; https://doi.org/10.3390/nano12234296 - 3 Dec 2022

Cited by 2 | Viewed by 1957

Abstract

Plasmonic waveguides have been shown to be a promising approach to confine and transport electromagnetic energy beyond the diffraction limit. However, ohmic losses generally prevent their integration at micrometric or millimetric scales. Here, we present a gain-compensated plasmonic waveguide based on the integration [...] Read more.

Plasmonic waveguides have been shown to be a promising approach to confine and transport electromagnetic energy beyond the diffraction limit. However, ohmic losses generally prevent their integration at micrometric or millimetric scales. Here, we present a gain-compensated plasmonic waveguide based on the integration of linear chains of Ag nanoparticles on an optically active Nd³⁺-doped solid-state gain medium. By means of dual confocal fluorescence microscopy, we demonstrate long-range optical energy propagation due to the near-field coupling between the plasmonic nanostructures and the Nd³⁺ ions. The subwavelength fluorescence guiding is monitored at distances of around 100 µm from the excitation source for two different emission ranges centered at around 900 nm and 1080 nm. In both cases, the guided fluorescence exhibits a strong polarization dependence, consistent with the polarization behavior of the plasmon resonance supported by the chain. The experimental results are interpreted through numerical simulations in quasi-infinite long chains, which corroborate the propagation features of the Ag nanoparticle chains at both excitation (λ_exc = 590 nm) and emission wavelengths. The obtained results exceed by an order of magnitude that of previous reports on electromagnetic energy transport using linear plasmonic chains. The work points out the potential of combining Ag nanoparticle chains with a small interparticle distance (~2 nm) with rare-earth-based optical gain media as ultra-long-range waveguides with extreme light confinement. The results offer new perspectives for the design of integrated hybrid plasmonic–photonic circuits based on rare-earth-activated solid-state platforms. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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10 pages, 3793 KiB

Open AccessArticle

Generation of Subdiffraction Optical Needles by Simultaneously Generating and Focusing Azimuthally Polarized Vortex Beams through Pancharatnam–Berry Metalenses

by Zhe Shen and Shijie Huang

Nanomaterials 2022, 12(22), 4074; https://doi.org/10.3390/nano12224074 - 19 Nov 2022

Cited by 13 | Viewed by 2027

Abstract

Needle beams have received widespread attention due to their unique characteristics of high intensity, small focal size, and extended depth of focus (DOF). Here, a single–layer all–dielectric metalens based on Pancharatnam–Berry (PB) was used to efficiently generate and focus an azimuthally polarized vortex [...] Read more.

Needle beams have received widespread attention due to their unique characteristics of high intensity, small focal size, and extended depth of focus (DOF). Here, a single–layer all–dielectric metalens based on Pancharatnam–Berry (PB) was used to efficiently generate and focus an azimuthally polarized vortex beam at the same time. Then, additional phase or amplitude modulation was respectively adopted to work with the metalens to produce optical needles. By decorating the PB metalens with the binary optical element (BOE), an optical needle with full–width–at–half–maximum (FWHM) of 0.47 λ and DOF of 3.42 λ could be obtained. By decorating the PB metalens with an annular aperture, an optical needle with long DOF (16.4 λ) and subdiffraction size (0.46 λ) could be obtained. It is expected that our work has potential applications in super–resolution imaging, photolithography, and particle trapping. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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13 pages, 4264 KiB

Open AccessArticle

Electro-Optical Modulation in High Q Metasurface Enhanced with Liquid Crystal Integration

by Ruoying Kanyang, Cizhe Fang, Qiyu Yang, Yao Shao, Genquan Han, Yan Liu and Yue Hao

Nanomaterials 2022, 12(18), 3179; https://doi.org/10.3390/nano12183179 - 13 Sep 2022

Cited by 11 | Viewed by 2725

Abstract

Electro-optical tuning metasurfaces are particularly attractive since they open up routes for dynamic reconfiguration. The electro-optic (EO) modulation strength essentially depends on the sensitivity to the EO-induced refractive index changes. In this paper, lithium niobate (LiNbO₃) metasurfaces integrated with liquid crystals [...] Read more.

Electro-optical tuning metasurfaces are particularly attractive since they open up routes for dynamic reconfiguration. The electro-optic (EO) modulation strength essentially depends on the sensitivity to the EO-induced refractive index changes. In this paper, lithium niobate (LiNbO₃) metasurfaces integrated with liquid crystals (LCs) are theoretically investigated. Cylinder arrays are proposed to support quasi-bound states in the continuum (quasi-BICs). The quasi-BIC resonances can significantly enhance the lifetime of photons and the local field, contributing to the EO-refractive index changes. By integrating metasurfaces with LCs, the combined influence of the LC reorientation and the Pockels electro-optic effect of LiNbO₃ is leveraged to tune the transmitted wavelength and phase spectrum around the quasi-BIC wavelength, resulting in an outstanding tuning sensitivity up to Δλ/ΔV ≈ 0.6 nm/V and relieving the need of high voltage. Furthermore, the proposed structure can alleviate the negative influence of sidewall tilt on device performance. The results presented in this work can foster wide application and prospects for the implementation of tunable displays, light detection and ranging (LiDAR), and spatial light modulators (SLMs). Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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Review

Jump to: Editorial, Research

38 pages, 7393 KiB

Open AccessReview

Research Progress in Surface-Enhanced Infrared Absorption Spectroscopy: From Performance Optimization, Sensing Applications, to System Integration

by Dongxiao Li, Cheng Xu, Junsheng Xie and Chengkuo Lee

Nanomaterials 2023, 13(16), 2377; https://doi.org/10.3390/nano13162377 - 19 Aug 2023

Cited by 19 | Viewed by 6249

Abstract

Infrared absorption spectroscopy is an effective tool for the detection and identification of molecules. However, its application is limited by the low infrared absorption cross-section of the molecule, resulting in low sensitivity and a poor signal-to-noise ratio. Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy is [...] Read more.

Infrared absorption spectroscopy is an effective tool for the detection and identification of molecules. However, its application is limited by the low infrared absorption cross-section of the molecule, resulting in low sensitivity and a poor signal-to-noise ratio. Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy is a breakthrough technique that exploits the field-enhancing properties of periodic nanostructures to amplify the vibrational signals of trace molecules. The fascinating properties of SEIRA technology have aroused great interest, driving diverse sensing applications. In this review, we first discuss three ways for SEIRA performance optimization, including material selection, sensitivity enhancement, and bandwidth improvement. Subsequently, we discuss the potential applications of SEIRA technology in fields such as biomedicine and environmental monitoring. In recent years, we have ushered in a new era characterized by the Internet of Things, sensor networks, and wearable devices. These new demands spurred the pursuit of miniaturized and consolidated infrared spectroscopy systems and chips. In addition, the rise of machine learning has injected new vitality into SEIRA, bringing smart device design and data analysis to the foreground. The final section of this review explores the anticipated trajectory that SEIRA technology might take, highlighting future trends and possibilities. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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14 pages, 2570 KiB

Open AccessReview

Neuromorphic Photonics Based on Phase Change Materials

by Tiantian Li, Yijie Li, Yuteng Wang, Yuxin Liu, Yumeng Liu, Zhan Wang, Ruixia Miao, Dongdong Han, Zhanqiang Hui and Wei Li

Nanomaterials 2023, 13(11), 1756; https://doi.org/10.3390/nano13111756 - 29 May 2023

Cited by 13 | Viewed by 4403

Abstract

Neuromorphic photonics devices based on phase change materials (PCMs) and silicon photonics technology have emerged as promising solutions for addressing the limitations of traditional spiking neural networks in terms of scalability, response delay, and energy consumption. In this review, we provide a comprehensive [...] Read more.

Neuromorphic photonics devices based on phase change materials (PCMs) and silicon photonics technology have emerged as promising solutions for addressing the limitations of traditional spiking neural networks in terms of scalability, response delay, and energy consumption. In this review, we provide a comprehensive analysis of various PCMs used in neuromorphic devices, comparing their optical properties and discussing their applications. We explore materials such as GST (Ge₂Sb₂Te₅), GeTe-Sb₂Te₃, GSST (Ge₂Sb₂Se₄Te₁), Sb₂S₃/Sb₂Se₃, Sc_0.2Sb₂Te₃ (SST), and In₂Se₃, highlighting their advantages and challenges in terms of erasure power consumption, response rate, material lifetime, and on-chip insertion loss. By investigating the integration of different PCMs with silicon-based optoelectronics, this review aims to identify potential breakthroughs in computational performance and scalability of photonic spiking neural networks. Further research and development are essential to optimize these materials and overcome their limitations, paving the way for more efficient and high-performance photonic neuromorphic devices in artificial intelligence and high-performance computing applications. Full article

(This article belongs to the Special Issue Nano-Optics and Nano-Optoelectronics: Challenges and Future Trends)

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