Special Issue "Nonlinear Photonics Devices"

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A:Physics".

Deadline for manuscript submissions: closed (15 December 2019).

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A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Luigi Sirleto
E-Mail Website
Guest Editor
Institute of Applied Sciences and Intelligent Systems (ISASI), National Research Council, Italy
Interests: nonlinear optics; ultrafast optics; photonic devices
Special Issues and Collections in MDPI journals
Dr. Giancarlo C. Righini
E-Mail Website
Guest Editor
“Nello Carrara" Institute of Applied Physics (IFAC), National Research Council, Italy
Interests: glassy and nanostructured materials, integrated optics, optical microresonators, photonic devices
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

The first nonlinear optical effect was observed in the 19th century by John Kerr. Nonlinear optics, however, started to grow up only after the invention of laser, when intense light sources became easily available. The seminal studies by Peter Franken and Nicolaas Bloembergen, in the 1960s, paved the way for the development of today’s nonlinear photonics, the field of research that encompasses all the studies, designs, and implementations of nonlinear optical devices that can be used for the generation, communication, and processing of information.

This field has attracted significant attention, partly due to the great potential of exploiting the optical nonlinearities of new or advanced materials to induce new phenomena and achieve new functions. According to Clarivate Web of Science, almost 200,000 papers were published that refer to the topic “nonlinear optic*”. Over 36,000 papers were published in the last four years (2015–2018) with the same keyword, and over 17,000 used the keyword “nonlinear photonic*”.

The present Special Issue of Micromachines aims at reviewing the current state of the art and presenting perspectives of further development. Fundamental and applicative aspects will be considered, with special attention paid to hot topics that may lead to technological and scientific breakthroughs.

Papers in all areas of nonlinear optics and photonics will be considered, including but not limited to the following:

Fundamental nonlinear processes in optical devices and systems:

  • Active and dissipative effects;
  • Attosecond physics;
  • Computational analysis;
  • Frequency combs;
  • Harmonics generation and mixing;
  • Instabilities and chaos;
  • Nonlinear interactions and non-classical light;
  • Nonlinear optics at surface;
  • Nonlinear optics in the mid-IR;
  • Nonlinear optics with singular beams;
  • Optical soliton physics;
  • Parametric processes;
  • Quantum nonlinear optics;
  • Supercontinuum physics;
  • Temporal and spatiotemporal effects;
  • Ultrafast nonlinear optics;
  • Wavelength conversion.

Nonlinear materials and structures related to optical devices and systems:

  • Characterization of nonlinear materials;
  • Hybrid nonlinear materials;
  • Nonlinear effects in glasses, glass-ceramics, and crystals;
  • Nonlinear effects in microstructures and microcavities;
  • Nonlinear pulse propagation in optical fibers;
  • Optical nonlinearities in nanostructures (0D, 1D, and 2D);
  • Optical nonlinearities in organic materials;
  • Optical nonlinearities in poled materials;
  • Optical nonlinearities in semiconductors.

Nonlinear optical devices, systems, and applications:

  • All-optical photonic devices;
  • Chip-scale nonlinear photonic devices;
  • Guided-wave nonlinear devices;
  • Integrated nonlinear optical sources;
  • Nonlinear detectors;
  • Nonlinear dynamics of semiconductor devices;
  • Nonlinear microscopy and imaging;
  • Nonlinear optical spectroscopy;
  • Nonlinear photonic crystals and metamaterials;
  • Nonlinear plasmonics and nanoplasmonic devices;
  • Parametric oscillators and amplifiers;
  • Parametric sources of quantum light.

Both research articles dealing with the latest work in the field and reviews on all aspects of nonlinear photonic theory, materials, and devices will be considered.

Dr. Luigi Sirleto
Dr. Giancarlo C. Righini
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nonlinear optics
  • nonlinear photonics
  • nonlinear optical materials
  • optical harmonics generation
  • stimulated scattering
  • optical solitons
  • controlling light with light, nonlinear guided-wave photonics
  • nonlinear spectroscopy and microscopy

Published Papers (13 papers)

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Editorial

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Editorial
Editorial for the Special Issue on Nonlinear Photonics Devices
Micromachines 2020, 11(8), 760; https://doi.org/10.3390/mi11080760 - 07 Aug 2020
Viewed by 600
Abstract
There is some incertitude on the creation of the term “photonics” and some ambiguity about its frontiers (and differences with respect to optoelectronics and electro-optics) [...] Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)

Research

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Article
Route to Intelligent Imaging Reconstruction via Terahertz Nonlinear Ghost Imaging
Micromachines 2020, 11(5), 521; https://doi.org/10.3390/mi11050521 - 20 May 2020
Cited by 4 | Viewed by 1084
Abstract
Terahertz (THz) imaging is a rapidly emerging field, thanks to many potential applications in diagnostics, manufacturing, medicine and material characterisation. However, the relatively coarse resolution stemming from the large wavelength limits the deployment of THz imaging in micro- and nano-technologies, keeping its potential [...] Read more.
Terahertz (THz) imaging is a rapidly emerging field, thanks to many potential applications in diagnostics, manufacturing, medicine and material characterisation. However, the relatively coarse resolution stemming from the large wavelength limits the deployment of THz imaging in micro- and nano-technologies, keeping its potential benefits out-of-reach in many practical scenarios and devices. In this context, single-pixel techniques are a promising alternative to imaging arrays, in particular when targeting subwavelength resolutions. In this work, we discuss the key advantages and practical challenges in the implementation of time-resolved nonlinear ghost imaging (TIMING), an imaging technique combining nonlinear THz generation with time-resolved time-domain spectroscopy detection. We numerically demonstrate the high-resolution reconstruction of semi-transparent samples, and we show how the Walsh–Hadamard reconstruction scheme can be optimised to significantly reduce the reconstruction time. We also discuss how, in sharp contrast with traditional intensity-based ghost imaging, the field detection at the heart of TIMING enables high-fidelity image reconstruction via low numerical-aperture detection. Even more striking—and to the best of our knowledge, an issue never tackled before—the general concept of “resolution” of the imaging system as the “smallest feature discernible” appears to be not well suited to describing the fidelity limits of nonlinear ghost-imaging systems. Our results suggest that the drop in reconstruction accuracy stemming from non-ideal detection conditions is complex and not driven by the attenuation of high-frequency spatial components (i.e., blurring) as in standard imaging. On the technological side, we further show how achieving efficient optical-to-terahertz conversion in extremely short propagation lengths is crucial regarding imaging performance, and we propose low-bandgap semiconductors as a practical framework to obtain THz emission from quasi-2D structures, i.e., structure in which the interaction occurs on a deeply subwavelength scale. Our results establish a comprehensive theoretical and experimental framework for the development of a new generation of terahertz hyperspectral imaging devices. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Article
Second-Harmonic Generation in Suspended AlGaAs Waveguides: A Comparative Study
Micromachines 2020, 11(2), 229; https://doi.org/10.3390/mi11020229 - 23 Feb 2020
Cited by 3 | Viewed by 836
Abstract
Due to adjustable modal birefringence, suspended AlGaAs optical waveguides with submicron transverse sections can support phase-matched frequency mixing in the whole material transparency range, even close to the material bandgap, by tuning the width-to-height ratio. Furthermore, their single-pass conversion efficiency is potentially huge, [...] Read more.
Due to adjustable modal birefringence, suspended AlGaAs optical waveguides with submicron transverse sections can support phase-matched frequency mixing in the whole material transparency range, even close to the material bandgap, by tuning the width-to-height ratio. Furthermore, their single-pass conversion efficiency is potentially huge, thanks to the extreme confinement of the interacting modes in the highly nonlinear and high-refractive-index core, with scattering losses lower than in selectively oxidized or quasi-phase-matched AlGaAs waveguides. Here we compare the performances of two types of suspended waveguides made of this material, designed for second-harmonic generation (SHG) in the telecom range: (a) a nanowire suspended in air by lateral tethers and (b) an ultrathin nanorib, made of a strip lying on a suspended membrane of the same material. Both devices have been fabricated from a 123 nm thick AlGaAs epitaxial layer and tested in terms of SHG efficiency, injection and propagation losses. Our results point out that the nanorib waveguide, which benefits from a far better mechanical robustness, performs comparably to the fully suspended nanowire and is well-suited for liquid sensing applications. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Article
Circular Dichroism in the Second Harmonic Field Evidenced by Asymmetric Au Coated GaAs Nanowires
Micromachines 2020, 11(2), 225; https://doi.org/10.3390/mi11020225 - 23 Feb 2020
Cited by 4 | Viewed by 912
Abstract
Optical circular dichroism (CD) is an important phenomenon in nanophotonics, that addresses top level applications such as circular polarized photon generation in optics, enantiomeric recognition in biophotonics and so on. Chiral nanostructures can lead to high CD, but the fabrication process usually requires [...] Read more.
Optical circular dichroism (CD) is an important phenomenon in nanophotonics, that addresses top level applications such as circular polarized photon generation in optics, enantiomeric recognition in biophotonics and so on. Chiral nanostructures can lead to high CD, but the fabrication process usually requires a large effort, and extrinsic chiral samples can be produced by simpler techniques. Glancing angle deposition of gold on GaAs nanowires can (NWs) induces a symmetry breaking that leads to an optical CD response that mimics chiral behavior. The GaAs NWs have been fabricated by a self-catalyzed, bottom-up approach, leading to large surfaces and high-quality samples at a relatively low cost. Here, we investigate the second harmonic generation circular dichroism (SHG-CD) signal on GaAs nanowires partially covered with Au. SHG is a nonlinear process of even order, and thus extremely sensitive to symmetry breaking. Therefore, the visibility of the signal is very high when the fabricated samples present resonances at first and second harmonic frequencies (i.e., 800 and 400 nm, in our case). Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Article
Dynamical Control of Broadband Coherent Absorption in ENZ Films
Micromachines 2020, 11(1), 110; https://doi.org/10.3390/mi11010110 - 20 Jan 2020
Cited by 3 | Viewed by 1556
Abstract
Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of [...] Read more.
Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of the scattering matrix and often requires engineered optical properties. For instance, thin film CPA benefits from complex nanostructures with suitable resonance, albeit at a loss of operational bandwidth. In this work, we theoretically and experimentally demonstrate a broadband CPA based on light-with-light modulation in epsilon-near-zero (ENZ) subwavelength films. We show that unpatterned ENZ films with different thicknesses exhibit broadband CPA with a near-unity maximum value located at the ENZ wavelength. By using Kerr optical nonlinearities, we dynamically tune the visibility and peak wavelength of the total energy modulation. Our results based on homogeneous thick ENZ media open a route towards on-chip devices that require efficient light absorption and dynamical tunability. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Article
Generation of Pure State Photon Triplets in the C-Band
Micromachines 2019, 10(11), 775; https://doi.org/10.3390/mi10110775 - 13 Nov 2019
Cited by 1 | Viewed by 796
Abstract
In this work, the cascaded second-order spontaneous parametric down-conversion (SPDC) is considered to produce pure state photon triplets in periodically poled lithium niobite (PPLN) doped with 5% MgO. A set of parameters are optimized through calculating the Schmidt number of two-photon states generated [...] Read more.
In this work, the cascaded second-order spontaneous parametric down-conversion (SPDC) is considered to produce pure state photon triplets in periodically poled lithium niobite (PPLN) doped with 5% MgO. A set of parameters are optimized through calculating the Schmidt number of two-photon states generated by each down-conversion process with different pump durations and crystal lengths. We use a Gaussian filter in part and obtain three photons with 100% purity in spectrum. We provide a feasible and unprecedented scheme to manipulate the spectrum purity of photon triplets in the communication band (C-band). Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Article
Intersubband Optical Nonlinearity of GeSn Quantum Dots under Vertical Electric Field
Micromachines 2019, 10(4), 243; https://doi.org/10.3390/mi10040243 - 12 Apr 2019
Cited by 4 | Viewed by 957
Abstract
The impact of vertical electrical field on the electron related linear and 3rd order nonlinear optical properties are evaluated numerically for pyramidal GeSn quantum dots with different sizes. The electric field induced electron confining potential profile’s modification is found to alter the transition [...] Read more.
The impact of vertical electrical field on the electron related linear and 3rd order nonlinear optical properties are evaluated numerically for pyramidal GeSn quantum dots with different sizes. The electric field induced electron confining potential profile’s modification is found to alter the transition energies and the transition dipole moment, particularly for larger dot sizes. These variations strongly influence the intersubband photoabsorption coefficients and changes in the refractive index with an increasing tendency of the 3rd order nonlinear component with increasing both quantum dot (QD) size and applied electric field. The results show that intersubband optical properties of GeSn quantum dots can be successively tuned by external polarization. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review

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Review
Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces
Micromachines 2020, 11(4), 449; https://doi.org/10.3390/mi11040449 - 24 Apr 2020
Cited by 3 | Viewed by 1088
Abstract
Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in [...] Read more.
Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review
Integrated Raman Laser: A Review of the Last Two Decades
Micromachines 2020, 11(3), 330; https://doi.org/10.3390/mi11030330 - 23 Mar 2020
Cited by 6 | Viewed by 1180
Abstract
Important accomplishments concerning an integrated laser source based on stimulated Raman scattering (SRS) have been achieved in the last two decades in the fields of photonics, microphotonics and nanophotonics. In 2005, the first integrated silicon laser based upon SRS was realized in the [...] Read more.
Important accomplishments concerning an integrated laser source based on stimulated Raman scattering (SRS) have been achieved in the last two decades in the fields of photonics, microphotonics and nanophotonics. In 2005, the first integrated silicon laser based upon SRS was realized in the nonlinear waveguide. This breakthrough promoted an intense research activity addressed to the realization of integrated Raman sources in photonics microstructures, like microcavities and photonics crystals. In 2012, a giant Raman gain in silicon nanocrystals was measured for the first time. Starting from this impressive result, some promising devices have recently been realized combining nanocrystals and microphotonics structures. Of course, the development of integrated Raman sources has been influenced by the trend of photonics towards the nano-world, which started from the nonlinear waveguide, going through microphotonics structures, and finally coming to nanophotonics. Therefore, in this review, the challenges, achievements and perspectives of an integrated laser source based on SRS in the last two decades are reviewed, side by side with the trend towards nanophotonics. The reported results point out promising perspectives for integrated micro- and/or nano-Raman lasers. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review
Nonlinear Optics in Microspherical Resonators
Micromachines 2020, 11(3), 303; https://doi.org/10.3390/mi11030303 - 13 Mar 2020
Cited by 4 | Viewed by 1175
Abstract
Nonlinear frequency generation requires high intensity density which is usually achieved with pulsed laser sources, anomalous dispersion, high nonlinear coefficients or long interaction lengths. Whispering gallery mode microresonators (WGMRs) are photonic devices that enhance nonlinear interactions and can be exploited for continuous wave [...] Read more.
Nonlinear frequency generation requires high intensity density which is usually achieved with pulsed laser sources, anomalous dispersion, high nonlinear coefficients or long interaction lengths. Whispering gallery mode microresonators (WGMRs) are photonic devices that enhance nonlinear interactions and can be exploited for continuous wave (CW) nonlinear frequency conversion, due to their capability of confine light for long time periods in a very small volume, even though in the normal dispersion regime. All signals must be resonant with the cavity. Here, we present a review of nonlinear optical processes in glass microspherical cavities, hollow and solid. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review
Fiber Amplifiers and Fiber Lasers Based on Stimulated Raman Scattering: A Review
Micromachines 2020, 11(3), 247; https://doi.org/10.3390/mi11030247 - 26 Feb 2020
Cited by 8 | Viewed by 1324
Abstract
Nowadays, in fiber optic communications the growing demand in terms of transmission capacity has been fulfilling the entire spectral band of the erbium-doped fiber amplifiers (EDFAs). This dramatic increase in bandwidth rules out the use of EDFAs, leaving fiber Raman amplifiers (FRAs) as [...] Read more.
Nowadays, in fiber optic communications the growing demand in terms of transmission capacity has been fulfilling the entire spectral band of the erbium-doped fiber amplifiers (EDFAs). This dramatic increase in bandwidth rules out the use of EDFAs, leaving fiber Raman amplifiers (FRAs) as the key devices for future amplification requirements. On the other hand, in the field of high-power fiber lasers, a very attractive option is provided by fiber Raman lasers (FRLs), due to their high output power, high efficiency and broad gain bandwidth, covering almost the entire near-infrared region. This paper reviews the challenges, achievements and perspectives of both fiber Raman amplifier and fiber Raman laser. They are enabling technologies for implementation of high-capacity optical communication systems and for the realization of high power fiber lasers, respectively. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review
Optical Frequency Combs in Quadratically Nonlinear Resonators
Micromachines 2020, 11(2), 230; https://doi.org/10.3390/mi11020230 - 24 Feb 2020
Cited by 12 | Viewed by 1330
Abstract
Optical frequency combs are one of the most remarkable inventions in recent decades. Originally conceived as the spectral counterpart of the train of short pulses emitted by mode-locked lasers, frequency combs have also been subsequently generated in continuously pumped microresonators, through third-order parametric [...] Read more.
Optical frequency combs are one of the most remarkable inventions in recent decades. Originally conceived as the spectral counterpart of the train of short pulses emitted by mode-locked lasers, frequency combs have also been subsequently generated in continuously pumped microresonators, through third-order parametric processes. Quite recently, direct generation of optical frequency combs has been demonstrated in continuous-wave laser-pumped optical resonators with a second-order nonlinear medium inside. Here, we present a concise introduction to such quadratic combs and the physical mechanism that underlies their formation. We mainly review our recent experimental and theoretical work on formation and dynamics of quadratic frequency combs. We experimentally demonstrated comb generation in two configurations: a cavity for second harmonic generation, where combs are generated both around the pump frequency and its second harmonic and a degenerate optical parametric oscillator, where combs are generated around the pump frequency and its subharmonic. The experiments have been supported by a thorough theoretical analysis, aimed at modelling the dynamics of quadratic combs, both in frequency and time domains, providing useful insights into the physics of this new class of optical frequency comb synthesizers. Quadratic combs establish a new class of efficient frequency comb synthesizers, with unique features, which could enable straightforward access to new spectral regions and stimulate novel applications. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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Review
Thermal Poling of Optical Fibers: A Numerical History
Micromachines 2020, 11(2), 139; https://doi.org/10.3390/mi11020139 - 27 Jan 2020
Cited by 1 | Viewed by 608
Abstract
This review gives a perspective of the thermal poling technique throughout its chronological evolution, starting in the early 1990s when the first observation of the permanent creation of a second order non-linearity inside a bulk piece of glass was reported. We then discuss [...] Read more.
This review gives a perspective of the thermal poling technique throughout its chronological evolution, starting in the early 1990s when the first observation of the permanent creation of a second order non-linearity inside a bulk piece of glass was reported. We then discuss a number of significant developments in this field, focusing particular attention on working principles, numerical analysis and theoretical advances in thermal poling of optical fibers, and conclude with the most recent studies and publications by the authors. Our latest works show how in principle, optical fibers of any geometry (conventional step-index, solid core microstructured, etc) and of any length can be poled, thus creating an advanced technological platform for the realization of all-fiber quadratic non-linear photonics. Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
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