TY - JOUR
AB - Lithium niobate on insulator (LNOI) has a great potential for photonic integrated circuits, providing substantial versatility in design of various integrated components. To properly use these components in the implementation of different quantum protocols, photons with different properties are required. In this paper, we theoretically demonstrate a flexible source of correlated photons built on the LNOI waveguide of a special geometry. This source is based on the parametric down-conversion (PDC) process, in which the signal and idler photons are generated at the telecom wavelength and have different spatial profiles and polarizations, but the same group velocities. Distinguishability in polarizations and spatial profiles facilitates the routing and manipulating individual photons, while the equality of their group velocities leads to the absence of temporal walk-off between photons. We show how the spectral properties of the generated photons and the number of their frequency modes can be controlled depending on the pump characteristics and the waveguide length. Finally, we discuss special regimes, in which narrowband light with strong frequency correlations and polarization-entangled Bell states are generated at the telecom wavelength.
AU - Ebers, Lena
AU - Ferreri, Alessandro
AU - Hammer, Manfred
AU - Albert, Maximilian
AU - Meier, Cedrik
AU - Förstner, Jens
AU - Sharapova, Polina R.
ID - 30210
JF - Journal of Physics: Photonics
KW - tet_topic_waveguide
SN - 2515-7647
TI - Flexible source of correlated photons based on LNOI rib waveguides
ER -
TY - CONF
AB - Resonant evanescent coupling can be utilized to selectively excite orbital angular momentum (OAM) modes of high angular order supported by a thin circular dielectric rod. Our 2.5-D hybrid-analytical coupled mode model combines the vectorial fields associated with the fundamental TE- and TM-modes of a standard silicon photonics slab waveguide, propagating at oblique angles with respect to the rod axis, and the hybrid modes supported by the rod. One observes an efficient resonant interaction in cases where the common axial wavenumber of the waves in the slab matches the propagation constant of one or more modes of the rod. For certain modes of high angular order, the incident wave is able to transfer its directionality to the field in the fiber, exciting effectively only one of a pair of degenerate OAM modes
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ED - Andrews, David L.
ED - Galvez, Enrique J.
ED - Rubinsztein-Dunlop, Halina
ID - 30387
KW - tet_topic_waveguide
T2 - Complex Light and Optical Forces XVI
TI - Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber
ER -
TY - CONF
AB - Online solvers for a series of standard 1-D or 2-D problems in integrated optics will be discussed. Implemented on the basis of HTML/JavaScript/SVG with core routines compiled from well tested C++-sources, the quasi-analytical algorithms require a computational load that can be handled easily even by current mobile devices. So far the series covers the 1-D guided modes of dielectric multilayer slab waveguides and the oblique plane wave reflection from these, the modes of rectangular channel waveguides (in an approximation of effective indices), bend modes of curved multilayer slabs, whispering-gallery resonances (“Quasi-Normal-Modes”) supported by circular dielectric cavities, the hybrid modes of circular multi-step-index optical fibers, bound and leaky modes of 1-D complex multilayers, including plasmonic surface modes, and, with restrictions, quite general rectangular scattering problems in 2-D.
AU - Hammer, Manfred
ED - García-Blanco, Sonia M.
ED - Cheben, Pavel
ID - 30389
KW - tet_topic_waveguide
T2 - Integrated Optics: Devices, Materials, and Technologies XXVI
TI - Small-scale online simulations in guided-wave photonics
ER -
TY - THES
AB - In dieser Arbeit wird die elektromagnetische Wellenausbreitung in integrierten optischen Wellenleitern mit Hilfe von halb analytischen und numerischen Simulationsmethoden untersucht. Im ersten Teil werden 2-D Si/SiO2-Wellenleiterkonfigurationen mit hohem Brechungsindexkontrast betrachtet. Die Strukturen werden mit halb geführten Wellen unter schrägen Ausbreitungswinkeln angeregt. Dadurch kann die Leistungsübertragung zu bestimmten ausgehenden Moden unterdrückt werden, wodurch vollständig verlustfreie Systeme entstehen. Zusätzlich dient die Anregung mit einem seitlich begrenzten, einfallenden Wellenbündel aus halb geführten Wellen dazu, praktisch relevantere 3-D Konfigurationen zu realisieren. Darüber hinaus wird eine schrittweise Winkelspektrum-Methode vorgestellt, die es ermöglicht, in Kombination mit voll vektoriellen 2-D Finite-Elemente-Lösungen für Teilprobleme mit geringerer Komplexität, die Wellenausbreitung in planaren, linsenförmigen Wellenleitern numerisch in drei Raumrichtungen zu berechnen. Im zweiten Teil dieser Arbeit wird die Ausbreitung in Wellenleiterstrukturen aus Lithiumniobat untersucht, welche für quantenoptische Effekte genutzt werden. Zur Detektion einzelner Photonen werden supraleitende Nanodrähte auf eindiffundierten Lithiumniobat Wellenleitern mit zusätzlicher Taperschicht aus Silizium betrachtet. Um die Wellenausbreitung in diesen 3-D Wellenleitern zu beschreiben, wird eine einseitig gerichtete Finite-Elemente „Modal Matching“ Methode eingeführt. Abschließend werden Rippenwellenleiter aus Lithiumniobat analysiert, die auf Siliziumdioxid Plattformen aufgebracht sind. Der Schwerpunkt liegt hier auf dem nichtlinearen „Parametric Down-Conversion“ Prozess, der für die Erzeugung verschränkter Photonen verwendet wird.
AU - Ebers, Lena
ID - 30722
KW - tet_topic_waveguide
TI - Semi-guided waves in integrated optical waveguide structures
ER -
TY - JOUR
AB - We show that narrow trenches in a high-contrast silicon-photonics slab can act as lossless power dividers for semi-guided waves. Reflectance and transmittance can be easily configured by selecting the trench width. At sufficiently high angles of incidence, the devices are lossless, apart from material attenuation and scattering due to surface roughness. We numerically simulate a series of devices within the full 0-to-1-range of splitting ratios, for semi-guided plane wave incidence as well as for excitation by focused Gaussian wave bundles. Straightforward cascading of the trenches leads to concepts for 1×M-power dividers and a polarization beam splitter.
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ID - 28196
IS - 12
JF - OSA Continuum
KW - tet_topic_waveguide
SN - 2578-7519
TI - Configurable lossless broadband beam splitters for semi-guided waves in integrated silicon photonics
VL - 4
ER -
TY - CONF
AB - We fabricate silicon tapers to increase the mode overlap of superconducting detectors on Ti:LiNbO3 waveguides. Mode images show a reduction in mode size from 6 µm to 2 µm FWHM, agreeing with beam propagation simulations.
AU - Protte, Maximilian
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Höpker, Jan Philipp
AU - Albert, Maximilian
AU - Quiring, Viktor
AU - Meier, Cedrik
AU - Förstner, Jens
AU - Silberhorn, Christine
AU - Bartley, Tim
ID - 21719
KW - tet_topic_waveguide
SN - 9781943580811
T2 - OSA Quantum 2.0 Conference
TI - Towards Semiconductor-Superconductor-Crystal Hybrid Integration for Quantum Photonics
ER -
TY - JOUR
AB - Oblique propagation of semi-guided waves across slab waveguide structures with bent corners is investigated. A critical angle can be defined beyond which all radiation losses are suppressed. Additionally an increase of the curvature radius of the bends also leads to low-loss configurations for incidence angles below that critical angle. A combination of two bent corner systems represents a step-like structure, behaving like a Fabry-Perot interferometer, with two partial reflectors separated by the vertical height between the horizontal slabs. We numerically analyse typical high-index-contrast Si/SiO2 structures for their reflectance and transmittance properties. When increasing the curvature radius the resonant effect becomes less relevant such that full transmittance is reached with less critical conditions on the vertical distance or the incidence angle. For practical interest 3-D problems are considered, where the structures are excited by the fundamental mode of a wide, shallow rib waveguide. High transmittance levels can be observed also for these 3-D configurations depending on the width of the rib.
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Förstner, Jens
ID - 3740
IS - 14
JF - Optics Express
KW - tet_topic_waveguide
TI - Oblique incidence of semi-guided planar waves on slab waveguide steps: effects of rounded edges
VL - 26
ER -
TY - CHAP
AB - Frequently, optical integrated circuits combine elements (waveguide channels, cavities), the simulation of which is well established through mature numerical eigenproblem solvers. It remains to predict the interaction of these modes. We address this task by a general, “Hybrid” variant (HCMT) of Coupled Mode Theory. Using methods from finite-element numerics, the properties of a circuit are approximated by superpositions of eigen-solutions for its constituents, leading to quantitative, computationally cheap, and easily interpretable models.
AU - Hammer, Manfred
ED - Agrawal, Arti
ID - 3743
KW - tet_topic_waveguide
KW - tet_topic_numerics
SN - 978-3-319-55438-9
T2 - Recent Trends in Computational Photonics
TI - Guided Wave Interaction in Photonic Integrated Circuits — A Hybrid Analytical/Numerical Approach to Coupled Mode Theory
VL - 204
ER -
TY - JOUR
AB - The 3D implementation of a hybrid analytical/numerical variant of the coupled-mode theory is discussed.
Eigenmodes of the constituting dielectric channels are computed numerically. The frequency-domain
coupled-mode models then combine these into fully vectorial approximations for the optical electromagnetic
fields of the composite structure. Following a discretization of amplitude functions by 1D finite elements, pro-
cedures from the realm of finite-element numerics are applied to establish systems of linear equations for the then-
discrete modal amplitudes. Examples substantiate the functioning of the technique and allow for some numerical
assessment. The full 3D simulations are highly efficient in memory consumption, moderately demanding in com-
putational time, and, in regimes of low radiative losses, sufficiently accurate for practical design. Our results
include the perturbation of guided modes by changes of the refractive indices, the interaction of waves in parallel,
horizontally or vertically coupled straight waveguides, and a series of crossings of potentially overlapping channels
with fairly arbitrary relative positions and orientations.
AU - Hammer, Manfred
AU - Alhaddad, Samer
AU - Förstner, Jens
ID - 3828
IS - 3
JF - Journal of the Optical Society of America B
KW - tet_topic_waveguide
KW - tet_topic_numerics
SN - 0740-3224
TI - Hybrid coupled-mode modeling in 3D: perturbed and coupled channels, and waveguide crossings
VL - 34
ER -
TY - JOUR
AB - The modal properties of curved dielectric slab waveguides are investigated. We
consider quasi-confined, attenuated modes that propagate at oblique angles with respect to
the axis through the center of curvature. Our analytical model describes the transition from
scalar 2-D TE/TM bend modes to lossless spiral waves at near-axis propagation angles,
with a continuum of vectorial attenuated spiral modes in between. Modal solutions are
characterized in terms of directional wavenumbers and attenuation constants. Examples for
vectorial mode profiles illustrate the effects of oblique wave propagation along the curved
slab segments. For the regime of lossless spiral waves, the relation with the guided modes
of corresponding dielectric tubes is demonstrated.
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Förstner, Jens
ID - 3830
IS - 4
JF - Optical and Quantum Electronics
KW - tet_topic_waveguide
SN - 0306-8919
TI - Spiral modes supported by circular dielectric tubes and tube segments
VL - 49
ER -
TY - CONF
AU - Hildebrandt, Andre
AU - Alhaddad, Samer
AU - Hammer, Manfred
AU - Förstner, Jens
ED - Broquin, Jean-Emmanuel
ED - Nunzi Conti, Gualtiero
ID - 3543
KW - tet_topic_waveguide
T2 - Integrated Optics: Devices, Materials, and Technologies XX
TI - Oblique incidence of semi-guided waves on step-like folds in planar dielectric slabs: Lossless vertical interconnects in 3D integrated photonic circuits
ER -
TY - CONF
AB - Typical optical integrated circuits combine elements, like straight and curved waveguides, or cavities, the simulation and design of which is well established through numerical eigenproblem-solvers. It remains to predict the interaction of these modes. We address this task by a ”Hybrid” variant (HCMT) of Coupled Mode Theory. Using methods from finite-element numerics, the optical properties of a circuit are approximated by superpositions of eigen-solutions for its constituents, leading to quantitative, low-dimensional, and interpretable models in the frequency domain. Spectral scans are complemented by the direct computation of supermode properties (spectral positions and linewidths, coupling-induced phase shifts). This contribution outlines the theoretical background, and discusses briefly limitations and implementational details, with the help of an example of a 2-D coupled-resonator-optical-waveguide configuration.
AU - Hammer, Manfred
ED - Broquin, Jean-Emmanuel
ED - Nunzi Conti, Gualtiero
ID - 3934
IS - 9750
KW - tet_topic_waveguide
KW - tet_topic_numerics
T2 - Integrated Optics: Devices, Materials, and Technologies XX
TI - Wave interaction in photonic integrated circuits: Hybrid analytical / numerical coupled mode modeling
ER -
TY - JOUR
AB - The device principle of a prism-based on-chip spectrometer for TE polarization is introduced. The spectrometer exploits the modal dispersion in planar waveguides in a layout with slab regions having two different thicknesses of the guiding layer. The set-up uses parabolic mirrors, for the collimation of light of the input waveguide and focusing of the light to the receiver waveguides, which relies on total internal reflection at the interface between two such regions. These regions are connected adiabatically to prevent unwanted mode conversion and loss at the edges of the prism. The structure can be fabricated with two wet etching steps. The paper presents basic theory and a general approach for device optimization. The latter is illustrated with a numerical example assuming SiON technology.
AU - Civitci, F.
AU - Hammer, Manfred
AU - Hoekstra, H.J.W.M.
ID - 3845
JF - Optics Communications
KW - tet_topic_waveguide
SN - 0030-4018
TI - Planar prism spectrometer based on adiabatically connected waveguiding slabs
VL - 365
ER -
TY - JOUR
AB - Sheets of slab waveguides with sharp corners are investigated. By means of rigorous
numerical experiments, we look at oblique incidence of semi-guided plane waves. Radiation losses
vanish beyond a certain critical angle of incidence. One can thus realize lossless propagation through
90-degree corner configurations, where the remaining guided waves are still subject to pronounced
reflection and polarization conversion. A system of two corners can be viewed as a structure akin to
a Fabry-Perot-interferometer. By adjusting the distance between the two partial reflectors, here the
90-degree corners, one identifies step-like configurations that transmit the semi-guided plane waves
without radiation losses, and virtually without reflections. Simulations of semi-guided beams with
in-plane wide Gaussian profiles show that the effect survives in a true 3-D framework.
AU - Hammer, Manfred
AU - Hildebrandt, Andre
AU - Förstner, Jens
ID - 3847
IS - 3
JF - Journal of Lightwave Technology
KW - tet_topic_waveguide
SN - 0733-8724
TI - Full Resonant Transmission of Semiguided Planar Waves Through Slab Waveguide Steps at Oblique Incidence
VL - 34
ER -
TY - JOUR
AB - We show how to optically connect guiding layers at different elevations in a 3-D integrated photonic circuit. Transfer of
optical power carried by planar, semi-guided waves is possible without reflections or radiation losses, and over large
vertical distances. This functionality is realized through simple step-like folds of high-contrast dielectric slab waveguides, in combination with oblique wave incidence, and fulfilling a resonance condition. Radiation losses vanish, and polarization conversion is suppressed for TE wave incidence beyond certain critical angles. This can be understood by fundamental arguments resting on a version of Snell’s law. The two 90° corners of a step act as identical partial reflectors in a Fabry–Perot-like resonator setup. By selecting the step height, i.e., the distance between the reflectors, one realizes resonant states with full transmission. Rigorous quasi-analytical simulations
for typical silicon/silica parameters demonstrate the functioning. Combinations of several step junctions can lead
to other types of optical on-chip connects, e.g., U-turn- or bridge-like configurations.
AU - Hammer, Manfred
AU - Hildebrandt, Andre
AU - Förstner, Jens
ID - 3894
IS - 16
JF - Optics Letters
KW - tet_topic_waveguide
SN - 0146-9592
TI - How planar optical waves can be made to climb dielectric steps
VL - 40
ER -
TY - JOUR
AB - The incidenceofthin-film-guided, in-planeunguidedwavesatobliqueanglesonstraightdiscontinuities of dielectricslabwaveguides,anearlyproblemofintegratedoptics,isbeingre-considered.The3-D frequencydomainMaxwellequationsreducetoaparametrizedinhomogeneousvectorialproblemona
2-D computationaldomain,withtransparent-influx boundaryconditions.Weproposearigorousvec-
torial solverbasedonsimultaneousexpansionsintopolarizedlocalslabeigenmodesalongthetwo
orthogonal crosssectioncoordinates(quadridirectionaleigenmodepropagationQUEP).Thequasi-ana-
lytical schemeisapplicabletoconfigurations with — in principle — arbitrary crosssectiongeometries.
Examples forahigh-contrastfacetofanasymmetricslabwaveguide,forthelateralexcitationofa
channel waveguide,andforastepdiscontinuitybetweenslabwaveguidesofdifferentthicknessesare
discussed.
AU - Hammer, Manfred
ID - 3890
JF - Optics Communications
KW - tet_topic_waveguide
KW - tet_topic_numerics
SN - 0030-4018
TI - Oblique incidence of semi-guided waves on rectangular slab waveguide discontinuities: A vectorial QUEP solver
VL - 338
ER -
TY - JOUR
AB - The relevance of our definition for sensitivity in refractometric sensing, being the relative change in the transmittance
of a certain output channel of an optical device over the change in the refractive index of the probed
material, is discussed. It is compared to one based on spectral shift per refractive index unit change. Further, there
is discussion on how group delay and sensitivity are interrelated and can be converted into each other and which
physical quantities are relevant for high sensitivity. As a by-product of the theory presented, a general expression
relating group delay and the ratio of the time-averaged optical energy and the input power is presented.
AU - Hoekstra, Hugo J. W. M.
AU - Hammer, Manfred
ID - 3937
IS - 7
JF - Journal of the Optical Society of America B
KW - tet_topic_waveguide
SN - 0740-3224
TI - General relation for group delay and the relevance of group delay for refractometric sensing
VL - 31
ER -