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3 pages, 171 KiB

Open AccessEditorial

Special Issue on Recent Advances and Future Trends in Nanophotonics

by Maria Antonietta Ferrara and Principia Dardano

Appl. Sci. 2022, 12(2), 663; https://doi.org/10.3390/app12020663 - 11 Jan 2022

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Abstract

Nanophotonics is an emerging multidisciplinary frontier of science and engineering [...] Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

Research

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18 pages, 6830 KiB

Open AccessArticle

Development and Testing of a Dual-Wavelength Sensitive Photopolymer Layer for Applications in Stacking of HOE Lenses

by Sanjay Keshri, Brian Rogers, Kevin Murphy, Kevin Reynolds, Izabela Naydenova and Suzanne Martin

Appl. Sci. 2021, 11(12), 5564; https://doi.org/10.3390/app11125564 - 16 Jun 2021

Cited by 4 | Viewed by 1837

Abstract

Diffractive optical elements (DOEs) have been in development for many years and are an exciting technology with the capability to re-direct light, using diffraction rather than refraction. Holographic Optical Elements (HOEs) are a subset of diffractive optical elements for which the photonic structure [...] Read more.

Diffractive optical elements (DOEs) have been in development for many years and are an exciting technology with the capability to re-direct light, using diffraction rather than refraction. Holographic Optical Elements (HOEs) are a subset of diffractive optical elements for which the photonic structure is created holographically, i.e., by recording a specific interference pattern in a suitable, photosensitive optical material. Volume HOEs are of particular interest for some applications because of their very high diffraction efficiency and single diffracted order; however, high dispersion and angular wavelength selectivity still present significant challenges. This paper explores a method for producing a compound DOE useful for situations where elements designed for two separate target wavelengths can be advantageously combined to achieve a highly efficient HOE with reduced dispersion. A photopolymer material consisting of two independently sensitized laminated layers is prepared and used in sequential holographic recording at two different wavelengths. The photonic structures recorded are investigated through examination of their diffraction peaks and comparison with the structure predicted by modeling. Finally, the device is illuminated with an expanded diverging beam at both target wavelengths and with white light, and a strong diffracted beam is observed. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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10 pages, 2113 KiB

Open AccessFeature PaperArticle

Analysis of Pulses Bandwidth and Spectral Resolution in Femtosecond Stimulated Raman Scattering Microscopy

by Luigi Sirleto, Rajeev Ranjan and Maria Antonietta Ferrara

Appl. Sci. 2021, 11(9), 3903; https://doi.org/10.3390/app11093903 - 26 Apr 2021

Cited by 7 | Viewed by 2513

Abstract

In the last decade, stimulated Raman scattering (SRS) imaging has been demonstrated to be a powerful method for label-free, non-invasive mapping of individual species distributions in a multicomponent system. This is due to the chemical selectivity of SRS techniques and the linear dependence [...] Read more.

In the last decade, stimulated Raman scattering (SRS) imaging has been demonstrated to be a powerful method for label-free, non-invasive mapping of individual species distributions in a multicomponent system. This is due to the chemical selectivity of SRS techniques and the linear dependence of SRS signals on the individual species concentrations. However, even if significant efforts have been made to improve spectroscopic coherent Raman imaging technology, what is the best way to resolve overlapped Raman bands in biological samples is still an open question. In this framework, spectral resolution, i.e., the ability to distinguish closely lying resonances, is the crucial point. Therefore, in this paper, the interplay among pump and Stokes bandwidths, the degree of chirp-matching and the spectral resolution of femtosecond stimulated Raman scattering microscopy are experimentally investigated and the separation of protein and lipid bands in the C-H region, which are of great interest in biochemical studies, is, in principle, demonstrated. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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11 pages, 792 KiB

Open AccessArticle

Theoretical Investigation of Responsivity/NEP Trade-off in NIR Graphene/Semiconductor Schottky Photodetectors Operating at Room Temperature

by Teresa Crisci, Luigi Moretti and Maurizio Casalino

Appl. Sci. 2021, 11(8), 3398; https://doi.org/10.3390/app11083398 - 10 Apr 2021

Cited by 5 | Viewed by 1929

Abstract

In this work we theoretically investigate the responsivity/noise equivalent power (NEP) trade-off in graphene/semiconductor Schottky photodetectors (PDs) operating in the near-infrared regime and working at room temperature. Our analysis shows that the responsivity/NEP ratio is strongly dependent on the Schottky barrier height (SBH) [...] Read more.

In this work we theoretically investigate the responsivity/noise equivalent power (NEP) trade-off in graphene/semiconductor Schottky photodetectors (PDs) operating in the near-infrared regime and working at room temperature. Our analysis shows that the responsivity/NEP ratio is strongly dependent on the Schottky barrier height (SBH) of the junction, and we derive a closed analytical formula for maximizing it. In addition, we theoretically discuss how the SBH is related to the reverse voltage applied to the junction in order to show how these devices could be optimized in practice for different semiconductors. We found that graphene/n-silicon (Si) Schottky PDs could be optimized at 1550 nm, showing a responsivity and NEP of 133 mA/W and 500 fW/

\sqrt{Hz}

, respectively, with a low reverse bias of only 0.66 V. Moreover, we show that graphene/n-germanium (Ge) Schottky PDs optimized in terms of responsivity/NEP ratio could be employed at 2000 nm with a responsivity and NEP of 233 mA/W and 31 pW/

\sqrt{Hz}

, respectively. We believe that our insights are of great importance in the field of silicon photonics for the realization of Si-based PDs to be employed in power monitoring, lab-on-chip and environment monitoring applications. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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9 pages, 1130 KiB

Open AccessArticle

Design and Modelling of a Novel Integrated Photonic Device for Nano-Scale Magnetic Memory Reading

by Figen Ece Demirer, Chris van den Bomen, Reinoud Lavrijsen, Jos J. G. M. van der Tol and Bert Koopmans

Appl. Sci. 2020, 10(22), 8267; https://doi.org/10.3390/app10228267 - 21 Nov 2020

Cited by 2 | Viewed by 1754

Abstract

Design and simulations of an integrated photonic device that can optically detect the magnetization direction of its ultra-thin (∼12 nm) metal cladding, thus ‘reading’ the stored magnetic memory, are presented. The device is an unbalanced Mach Zehnder Interferometer (MZI) based on InP Membrane [...] Read more.

Design and simulations of an integrated photonic device that can optically detect the magnetization direction of its ultra-thin (∼12 nm) metal cladding, thus ‘reading’ the stored magnetic memory, are presented. The device is an unbalanced Mach Zehnder Interferometer (MZI) based on InP Membrane on Silicon (IMOS) platform. The MZI consists of a ferromagnetic thin-film cladding and a delay line in one branch, and a polarization converter in the other. It quantitatively measures the non-reciprocal phase shift caused by the Magneto-Optic Kerr Effect in the guided mode which depends on the memory bit’s magnetization direction. The current design is an analytical tool for research exploration of all-optical magnetic memory reading. It has been shown that the device is able to read a nanoscale memory bit (400 × 50 × 12 nm) by using a Kerr rotation as small as

{0.2}^{\circ}

, in the presence of a noise ∼10 dB in terms of signal-to-noise ratio. The device is shown to tolerate performance reductions that can arise during the fabrication. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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12 pages, 3861 KiB

Open AccessArticle

Characterization and Optimal Design of Silicon-Rich Nitride Nonlinear Waveguides for 2 μm Wavelength Band

by Zhihua Tu, Daru Chen, Hao Hu, Shiming Gao and Xiaowei Guan

Appl. Sci. 2020, 10(22), 8087; https://doi.org/10.3390/app10228087 - 15 Nov 2020

Cited by 2 | Viewed by 1925

Abstract

Optical communication using the 2 μm wavelength band is attracting growing attention for the sake of mitigating the information ‘capacity crunch’ on the way, where on-chip nonlinear waveguides can play vital roles. Here, silicon-rich nitride (SRN) ridge waveguides with different widths and rib [...] Read more.

Optical communication using the 2 μm wavelength band is attracting growing attention for the sake of mitigating the information ‘capacity crunch’ on the way, where on-chip nonlinear waveguides can play vital roles. Here, silicon-rich nitride (SRN) ridge waveguides with different widths and rib heights are fabricated and measured. Linear characterizations show a loss of ~2 dB/cm of the SRN ridge waveguides and four-wave mixing (FWM) experiments with a continuous wave (CW) pump reveal a nonlinear refractive index of ~1.13 × 10⁻¹⁸ m²/W of the SRN material around the wavelength 1950 nm. With the extracted parameters, dimensions of the SRN ridge waveguides are optimally designed for improved nonlinear performances for the 2 μm band, i.e., a maximal nonlinear figure of merit (i.e., the ratio of nonlinearity to loss) of 0.0804 W⁻¹ or a super-broad FWM bandwidth of 518 nm. Our results and design method open up new possibilities for achieving high-performance on-chip nonlinear waveguides for long-wavelength optical communications. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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10 pages, 2658 KiB

Open AccessArticle

Double Spectral Electromagnetically Induced Transparency Based on Double-Bar Dielectric Grating and Its Sensor Application

by Guofeng Li, Junbo Yang, Zhaojian Zhang, Kui Wen, Yuyu Tao, Yunxin Han and Zhenrong Zhang

Appl. Sci. 2020, 10(9), 3033; https://doi.org/10.3390/app10093033 - 27 Apr 2020

Cited by 13 | Viewed by 2169

Abstract

The realization of the electromagnetically induced transparency (EIT) effect based on guided-mode resonance (GMR) has attracted a lot of attention. However, achieving the multispectral EIT effect in this way has not been studied. Here, we numerically realize a double EIT-ike effect with extremely [...] Read more.

The realization of the electromagnetically induced transparency (EIT) effect based on guided-mode resonance (GMR) has attracted a lot of attention. However, achieving the multispectral EIT effect in this way has not been studied. Here, we numerically realize a double EIT-ike effect with extremely high Q factors based on a GMR system with the double-bar dielectric grating structure, and the Q factors can reach 35,104 and 24,423, respectively. Moreover, the resonance wavelengths of the two EIT peaks can be flexibly controlled by changing the corresponding structural parameters. The figure of merit (FOM) of the dual-mode refractive index sensor based on this system can reach 571.88 and 587.42, respectively. Our work provides a novel method to achieve double EIT-like effects, which can be applied to the dual mode sensor, dual channel slow light and so on. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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Review

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22 pages, 5932 KiB

Open AccessReview

Optical Realization of Wave-Based Analog Computing with Metamaterials

by Kaiyang Cheng, Yuancheng Fan, Weixuan Zhang, Yubin Gong, Shen Fei and Hongqiang Li

Appl. Sci. 2021, 11(1), 141; https://doi.org/10.3390/app11010141 - 25 Dec 2020

Cited by 17 | Viewed by 4458

Abstract

Recently, the study of analog optical computing raised renewed interest due to its natural advantages of parallel, high speed and low energy consumption over conventional digital counterpart, particularly in applications of big data and high-throughput image processing. The emergence of metamaterials or metasurfaces [...] Read more.

Recently, the study of analog optical computing raised renewed interest due to its natural advantages of parallel, high speed and low energy consumption over conventional digital counterpart, particularly in applications of big data and high-throughput image processing. The emergence of metamaterials or metasurfaces in the last decades offered unprecedented opportunities to arbitrarily manipulate the light waves within subwavelength scale. Metamaterials and metasurfaces with freely controlled optical properties have accelerated the progress of wave-based analog computing and are emerging as a practical, easy-integration platform for optical analog computing. In this review, the recent progress of metamaterial-based spatial analog optical computing is briefly reviewed. We first survey the implementation of classical mathematical operations followed by two fundamental approaches (metasurface approach and Green’s function approach). Then, we discuss recent developments based on different physical mechanisms and the classical optical simulating of quantum algorithms are investigated, which may lead to a new way for high-efficiency signal processing by exploiting quantum behaviors. The challenges and future opportunities in the booming research field are discussed. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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25 pages, 6591 KiB

Open AccessReview

Recent Developments in Instrumentation of Functional Near-Infrared Spectroscopy Systems

by Murad Althobaiti and Ibraheem Al-Naib

Appl. Sci. 2020, 10(18), 6522; https://doi.org/10.3390/app10186522 - 18 Sep 2020

Cited by 22 | Viewed by 8010

Abstract

In the last three decades, the development and steady improvement of various optical technologies at the near-infrared region of the electromagnetic spectrum has inspired a large number of scientists around the world to design and develop functional near-infrared spectroscopy (fNIRS) systems for various [...] Read more.

In the last three decades, the development and steady improvement of various optical technologies at the near-infrared region of the electromagnetic spectrum has inspired a large number of scientists around the world to design and develop functional near-infrared spectroscopy (fNIRS) systems for various medical applications. This has been driven further by the availability of new sources and detectors that support very compact and wearable system designs. In this article, we review fNIRS systems from the instrumentation point of view, discussing the associated challenges and state-of-the-art approaches. In the beginning, the fundamentals of fNIRS systems as well as light-tissue interaction at NIR are briefly introduced. After that, we present the basics of NIR systems instrumentation. Next, the recent development of continuous-wave, frequency-domain, and time-domain fNIRS systems are discussed. Finally, we provide a summary of these three modalities and an outlook into the future of fNIRS technology. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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22 pages, 8022 KiB

Open AccessReview

Polarization-Sensitive Digital Holographic Imaging for Characterization of Microscopic Samples: Recent Advances and Perspectives

by Giuseppe Coppola and Maria Antonietta Ferrara

Appl. Sci. 2020, 10(13), 4520; https://doi.org/10.3390/app10134520 - 29 Jun 2020

Cited by 19 | Viewed by 4861

Abstract

Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very [...] Read more.

Polarization-sensitive digital holographic imaging (PS-DHI) is a recent imaging technique based on interference among several polarized optical beams. PS-DHI allows simultaneous quantitative three-dimensional reconstruction and quantitative evaluation of polarization properties of a given sample with micrometer scale resolution. Since this technique is very fast and does not require labels/markers, it finds application in several fields, from biology to microelectronics and micro-photonics. In this paper, a comprehensive review of the state-of-the-art of PS-DHI techniques, the theoretical principles, and important applications are reported. Full article

(This article belongs to the Special Issue Recent Advances and Future Trends in Nanophotonics)

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