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Design and Simulation of the Fourier Transform Beam Propagation Method in Different Optical Waveguides
摘要： Fundamentals of optical waveguides is a needed resource for any researcher, concerned in optics and communications engineering. Interested by designing or actively running with optical gadgets have to have a company hold close of the standards of light wave propagation. This paper presents an FFT Beam Propagation Method Models for optical waveguides. The technique is based on the use of the Propagation of a Gaussian pulse by a waveguide with a rectangular, triangular optical waveguides and free space the cases of straight and bent optical waveguides are successively considered.
关键词： Gaussian pulse,free space,triangular optical waveguides,optical waveguides,FFT Beam Propagation Method,rectangular
更新于2025-09-12 10:27:22
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Mass Producible Low-Loss Broadband Optical Waveguides in Eagle2000 by Femtosecond Laser Writing
摘要： Optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass, by femtosecond laser direct writing, with varying pulse energy and scan velocity. A spectral characterization, from 500 nm to 1700 nm, was made in order to determine their losses and understand its dependence on the processing parameters. Three major loss mechanisms were identified. At longer wavelengths, loss is mainly due to weak coupling. On the other hand, the behavior at shorter wavelengths is governed by propagation loss due to Rayleigh scattering, which was shown to be practically eliminated (<0.05 dB· cm?1· μm4) at higher scan velocities. Bulk absorption was also found to have an influence in the propagation losses at higher wavelengths. The combination of intermediate pulse energies (between 125-250 nJ) and high scan velocities (above 6 cm/s) allowed the fabrication of optical waveguides offering low losses across the entire range of wavelengths tested, facilitating applications that require larger wavelength working bands. Furthermore, since optimal fabrication conditions are achieved at higher scanning velocities, mass production with reduced fabrication times can be achieved.
关键词： femtosecond laser direct writing,Rayleigh scattering,propagation loss,Coupling loss,Mie scattering,integrated optics,low-loss broadband optical waveguides,mass production
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - On Chip Sub-Wavelength Grating Fabry-Perot Cavity, toward Integrated Cavity Optomechanics Applications
摘要： Sub-Wavelength Grating (SWG) periodic media are comprised of alternative dielectric layers with a pitch Λ small enough in comparison to the wavelength to supress any diffraction or interference effect. As a good first approximation, SWG media can be considered as uniform and lossless ones, with an averaging effect over the dielectric permittivity [1]. The use of SWG media as core and/or cladding materials of optical waveguides was first proposed and demonstrated in 2010 [2] as a way to realize easy engineering of the refractive guided index of light with simple lithographic patterning. Since then, SWG waveguides have found various applications such as waveguide crossing, multimode interferometers, optical filters, mid-infrared waveguides, or even optical biosensing [3]. We propose to include SWG waveguides within a suspended Fabry-Perot (FP) cavity (see Fig. 1a). The core of the cavity is formed by alternative Silicon and Air SWG layers, while the input and output mirrors are two Direct Bragg Reflectors (DBR). The whole structure is fully suspended through the use of two support arms. We present the theoretical modelization, technological realization and optical characterisations of such a cavity. The design was conducted through both an analytical model that treats SWG media with equivalent refractive indexes, and two dimensional effective index Finite-Difference Time-Domain (FDTD) simulations. Actual devices were realized on 200 mm silicon on insulator (SOI) wafers in our clean room facilities with e-beam patterning of the waveguide level, and characterized via full-scale wafer optical spectrum measurement between 1520 nm and 1580 nm. At time of writing, we measured optical quality factors of 10 000 over 2 μm long cavities. We believe this kind of suspended structure can be used in the field of Cavity Optomechanics, where an optical cavity is coupled to a mechanical resonator [4]. Indeed, because it is fully suspended, we await mechanical resonance to occur, the cavity behaving similarly to a doubly clamped holey cantilever (see Fig. 1c). Apart from the traditional optical phase shift occurring with propagation length variations of the cavity, there should also be a phase shift arising from the SWG nature of the waveguide, whose equivalent refractive index depends on the pitch Λ (and thus length) of the cavity. Due to this additional effect, we expect a strong optomechanical coupling rate.
关键词： Sub-Wavelength Grating,silicon on insulator,optical waveguides,Fabry-Perot cavity,cavity optomechanics
更新于2025-09-12 10:27:22
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Electrochromic Infrared Light Modulation in Optical Waveguides
摘要： Electrochromic materials and devices have attracted much attention with their ability to tune the transmissions of visible to infrared (IR) light, allowing the creation of smart windows. This study presents a novel electrochromic device (ECD)-based photonic device that can modulate IR light intensity in a planar optical waveguide ECD. To configure it, a multilayer ECD made of WO3 is integrated on a polymer optical waveguide platform. By using the waveguide to change the optical properties of the ECD electrically, IR light propagating along the optical waveguide core undergoes electroabsorption loss due to the change in charge carrier density in WO3 layer and its intensity is modulated with an extinction depth of 0.6 dB mm?1. Experimental results show that the device is capable of discrete intensity attenuation by applying a distinct level gate voltage. Periodic application of gate voltage leads the device to serve as an optical modulator on the order of subseconds. The results also confirm that a new approach to consider ECD-based optical modulators can pave the way for the development of planar photonic-integrated circuits and systems.
关键词： infrared light modulation,optical waveguides,electrochromic devices
更新于2025-09-12 10:27:22
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Orientation-Controlled 2D Anisotropic and Isotropic Photon Transport in Cocrystal Polymorph Microplates
摘要： Two-dimensional (2D) anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Herein, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transmissions in two self-assembled cocrystal polymorph microplates. The monoclinic microplate adopting a nearly horizontal molecular transition dipole orientation in the 2D plane, exhibits anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic microplate with a vertical transition dipole orientation, shows the 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on the anisotropic transport mechanism, a directional signal outcoupler (DSO) was further designed for the high-fidelity transmission of the real signals, which would enlighten the development of 2D anisotropic optical devices.
关键词： two-dimensional photonics,anisotropic optical waveguides,Cocrystal,polymorphs,transition dipole moment
更新于2025-09-12 10:27:22
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Demonstration of low loss <b> <i>β</i> </b> -Ga <sub/>2</sub> O <sub/>3</sub> optical waveguides in the UV–NIR spectra
摘要： In this paper, we report the fabrication of low loss beta-phase gallium oxide (b-Ga2O3) optical waveguides and the propagation loss analysis of the waveguides in the ultraviolet (UV) to near infrared (NIR) spectral region. The b-Ga2O3 thin films were grown on sapphire substrates using metal organic chemical vapor deposition and were fabricated into various waveguide structures using nanofabrication processes. A low propagation loss of 3.7 dB/cm was obtained on the b-Ga2O3 waveguide at the wavelength of 810 nm, which is comparable to the state of the art. Combined with theoretical simulations, various loss mechanisms from two-photon absorption, sidewall scattering, top surface scattering, and bulk scattering were discussed for b-Ga2O3 waveguides, and their contributions to the total optical loss were estimated. These results show that b-Ga2O3 is a promising optical material for the fabrication of various integrated photonic devices in the UV–NIR spectra region.
关键词： integrated photonic devices,b-Ga2O3,propagation loss,UV–NIR spectra,optical waveguides
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Adiabatic Transitions between Supersymmetric Structures as a Tool to Design Integrated Photonic Devices
摘要： Supersymmetry (SUSY), originally developed to unify the mathematical treatment of bosons and fermions, is a powerful mathematical tool with many applications in both non-relativistic quantum mechanics and Helmholtz optics [1]. The application of SUSY to optical systems has attracted a lot of attention, e.g. for mode filtering and multiplexing [2,3], exploiting the global phase-matching conditions among all the modes of two superpartner structures, except for the fundamental mode. So far, SUSY transformations have been proposed in a discrete way, i.e., evanescently coupling the superpartner structures. Here, instead, we introduce adiabatic transitions connecting superpartner profiles by smoothly modifying the transverse refractive index profile along the propagation direction, offering a new way to manipulate the modal content in systems of optical waveguides and to engineer efficient and robust photonic integrated devices [4]. The propagation of the transverse electric (TEm) component of the electric field along z-direction through a medium with arbitrary index of refraction n(x,z) can be described by the Helmholtz equation. At any fixed position, the problem is described by ?(cid:1857)(cid:3040)((cid:1876)) = (cid:2010)(cid:3040)(cid:2870) (cid:1857)(cid:3040)((cid:1876)), where (cid:1857)(cid:3040)((cid:1876)) is the transverse spatial distribution, and (cid:2010)(cid:3040) is the propagation constant of mode m. By factorizing the Hamiltonian using SUSY techniques, the superpartner index profiles can be derived [1]. To achieve a transition connecting two superpartner profiles (cid:1866)((cid:3044)(cid:2879)(cid:2869))((cid:1876)) and (cid:1866)((cid:3044))((cid:1876)), we introduce a continuous transformation function (cid:1859)(cid:3044)((cid:1878)) valued between 0 and 1: , where (cid:1849) ((cid:3044)(cid:2879)(cid:2869))((cid:1876)) = ?(cid:2034)(cid:3051)(cid:1864)(cid:1866)(cid:1857)(cid:2868)(cid:1856)(cid:1849) ((cid:3044)(cid:2879)(cid:2869))((cid:1876))(cid:1856)(cid:1876) is the superpotential and q identifies the number of discrete SUSY transformations applied (see Fig. 1(a)). In particular, we demonstrate that such transformations provide a systematic way to design efficient and robust tapered waveguides and mode filters by using single-waveguide structures (see Fig. 1(b)), and beam splitters (see Fig. 1(c)) and Mach-Zehnder Interferometers (MZI) by using two-waveguide structures. Numerically calculated fidelities above 0.999 and above 0.99 are achieved in a broad region of wavelengths for L > 1.8mm tapered waveguides and L>6mm symmetric beam splitters, respectively. Moreover, we design a single-waveguide mode filter with fidelities above 0.9 and a MZI with a visibility of 98.6%. Although we apply continuous SUSY transformations to single- and two-waveguide structures, more complex structures could be designed by increasing the number of waveguides, using waveguides with different widths, using optical fibers or combining continuous with discrete SUSY transformations. Such SUSY transformations could be incorporated in the design of novel quantum integrated photonic devices and even extended to other quantum platforms such as in atomtronics.
关键词： Supersymmetry,integrated photonic devices,adiabatic transitions,optical waveguides,mode filtering
更新于2025-09-12 10:27:22
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High coherence at f and 2f of mid-infrared supercontinuum generation in silicon germanium waveguides
摘要： Absorption-spectroscopy based on supercontinuum generation in the mid-infrared is a powerful technique to analyze the chemical composition of samples. Furthermore, phase-coherent fast data acquisition with coherent, stable pulses that allow single-shot measurements. We report here a numerical study of the coherence of an octave-spanning mid-infrared supercontinuum source that was experimentally obtained in an air clad SiGe/Si waveguide. We show that engineering two closely spaced zero-dispersion wavelengths that enclose an anomalous dispersion band centered around a fixed pump wavelength can produce supercontinuum pulses with high spectral density and full coherence at the extreme ends of the spectrum. This work is important for absorption spectroscopy, on-chip optical frequency metrology and ??-to-2?? interferometry applications.
关键词： Optical waveguides,Silicon photonics,Silicon germanium,Supercontinuum generation
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Diamond Functionalization by Ultrafast Laser Pulses
摘要： The extreme material properties of diamond make it an attractive candidate for many technological applications. However, these same material properties often prove disruptive to the machining of diamond into functional devices. Ultrashort laser pulses focused inside diamond offer a potential new route for the functionalisation of diamond, offering a range of fabrication modalities on a single platform. Focusing beneath the surface of diamond, there is sufficient intensity from ultrashort laser pulses for non-linear absorption of light, which can lead to modification of the diamond lattice. The non-linearity of the process confines the modification to the focal volume of the laser, without effecting the diamond surface or surrounding regions. At high pulse energies (above ~100nJ), the laser deposits sufficient energy to break down the diamond lattice and induce a graphitic phase. Tracing the diamond through the laser focus allows the creation of conductive graphitic wires embedded inside the diamond in 3D. The processing becomes deterministic and the wire conductivity increases when the fabrication is carried out at high numerical apertures (NA = 1.4) [1]. The large refractive index mismatch at the diamond surface generates a depth dependent spherical aberration which should be corrected using adaptive optics. The laser written electrical wires can be used to fabricate radiation sensors, as shown in Fig. 1(a), which benefit from the radiation hardness of diamond. The advances in laser fabrication allow the realisation of new detector geometries. The graphitic inclusions fabricated by ultrashort pulse lasers beneath the surface of diamond exert stress on the surrounding diamond, which in turn modifies the optical properties of the crystal. By designing stress fields, it is possible to fabricate optical waveguides [2] and waveguide Bragg gratings [3] inside the diamond. In a different fabrication regime, it is also possible functionalise the diamond using ultrashort pulses without causing breakdown of the diamond lattice. We have shown that with a single ultrashort pulse it is possible to generate an ensemble of vacancies at the laser focus inside the diamond. A thermal anneal process heals any damage to the lattice and is successful in forming highly coherent isolated single nitrogen vacancy (NV) colour centres [4, 5]. We have recently demonstrated improvements to the method using a laser based localised anneal with fluorescence feedback to write arrays of NV centres with near unity yield and in-plane positioning accuracy of 40nm [6].
关键词： functionalisation,diamond,graphitic wires,ultrafast laser pulses,NV centres,optical waveguides
更新于2025-09-11 14:15:04
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Vapour‐Phase Epitaxial Growth of Dual‐Colour‐Emitting DCM‐Perylene Micro‐Heterostructure Optical Waveguides
摘要： Organic micro-heterostructures (MHS) with dual optical emissions are essential to produce miniaturized optical waveguides for wavelength division multiplexing technologies. The bimolecular MHS produced by solution-based bottom-up self-assembly technique often leads to poor surface smoothness, edge imperfection, defects, and unwanted thin films deposits. Conversely, sequential sublimation technique at ambient pressure facilitates effective integration of a-perylene micro-square with dicyano-4H-pyran methylene-2-methyl-6-(p-dimethylaminostyryl) (DCM) microrods in an epitaxial manner to produce MHS. The obtained DCM/perylene MHS act as optical waveguides to produce red (lmax (cid:2) 670 nm) or/and yellow (lmax (cid:2) 607 nm) dual optical outputs via an energy transfer mechanism depending upon the heterostructures geometry and optical excitation positions. The presented dual-color emitting MHS optical waveguides are essential for the integrated nano-photonic and optoelectronic device structures.
关键词： Micro-heterostructures,DCM,Perylene,Optical waveguides,Vapour-Phase Epitaxy
更新于2025-09-11 14:15:04