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 - 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 - JOUR
AB - We demonstrate the integration of amorphous tungsten silicide superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides. We show proof-of-principle detection of evanescently coupled photons of 1550 nm wavelength using bidirectional waveguide coupling for two orthogonal polarization directions. We investigate the internal detection efficiency as well as detector absorption using coupling-independent characterization measurements. Furthermore, we describe strategies to improve the yield and efficiency of these devices.
AU - Höpker, Jan Philipp
AU - Verma, Varun B
AU - Protte, Maximilian
AU - Ricken, Raimund
AU - Quiring, Viktor
AU - Eigner, Christof
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Förstner, Jens
AU - Silberhorn, Christine
AU - Mirin, Richard P
AU - Woo Nam, Sae
AU - Bartley, Tim
ID - 23728
JF - Journal of Physics: Photonics
SN - 2515-7647
TI - Integrated superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides
VL - 3
ER -
TY - JOUR
AB - Gaussian-beam-like bundles of semi-guided waves propagating in a dielectric slab can excite modes with high-order optical angular momentum supported by a circular fiber. We consider a multimode step-index fiber with a high-index coating, where the waves in the slab are evanescently coupled to the modes of the fiber. Conditions for effective resonant interaction are identified. Based on a hybrid analytical–numerical coupled mode model, our simulations predict that substantial fractions of the input power can be focused into waves with specific orbital angular momentum, of excellent purity, with a clear distinction between degenerate modes with opposite vorticity.
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ID - 21932
IS - 5
JF - Journal of the Optical Society of America B
KW - tet_topic_waveguides
SN - 0740-3224
TI - Resonant evanescent excitation of guided waves with high-order optical angular momentum
VL - 38
ER -
TY - JOUR
AB - A dielectric step-index optical fiber with tube-like profile is considered, being positioned with a small gap on top of a dielectric slab waveguide. We propose a 2.5-D hybrid analytical/numerical coupled mode model for the evanescent excitation of the tube through semi-guided waves propagating in the slab at oblique angles. The model combines the directional polarized modes supported by the slab with analytic solutions for the TE-, TM-, and orbital-angular-momentum (OAM) modes of the tube-shaped fiber. Implementational details of the scheme are discussed, complemented by finite-element simulations for verification purposes. Our results include configurations with resonant in-fiber excitation of OAM modes with large orbital angular momentum and strong field enhancement.
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ID - 20189
JF - Optical and Quantum Electronics
KW - tet_topic_waveguides
SN - 0306-8919
TI - Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles
VL - 52
ER -
TY - JOUR
AB - A stepwise angular spectrum method (SASM) for curved interfaces is presented to calculate the wave propagation in planar lens-like integrated optical structures based on photonic slab waveguides. The method is derived and illustrated for an effective 2D setup first and then for 3D slab waveguide lenses. We employ slab waveguides of different thicknesses connected by curved surfaces to realize a lens-like structure. To simulate the wave propagation in 3D including reflection and scattering losses, the stepwise angular spectrum method is combined with full vectorial finite element computations for subproblems with lower complexity. Our SASM results show excellent agreement with rigorous numerical simulations of the full structures with a substantially lower computational effort and can be utilized for the simulation-based design and optimization of complex and large scale setups.
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Förstner, Jens
ID - 20372
IS - 24
JF - Optics Express
KW - tet_topic_waveguides
SN - 1094-4087
TI - Light diffraction in slab waveguide lenses simulated with the stepwise angular spectrum method
VL - 28
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 - A rectangular dielectric strip at some distance above an optical slab waveguide is
being considered, for evanescent excitation of the strip through the semi-guided waves supported
by the slab, at specific oblique angles. The 2.5-D configuration shows resonant transmission
properties with respect to variations of the angle of incidence, or of the excitation frequency,
respectively. The strength of the interaction can be controlled by the gap between strip and slab.
For increasing distance, our simulations predict resonant states with unit extremal reflectance
of an angular or spectral width that tends to zero, i.e. resonances with a Q-factor that tends
to infinity, while the resonance position approaches the level of the guided mode of the strip.
This exceptionally simple system realizes what might be termed a “bound state coupled to the
continuum”.
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ID - 8634
IS - 7
JF - Optics Express
KW - tet_topic_waveguides
TI - Oblique evanescent excitation of a dielectric strip: A model resonator with an open optical cavity of unlimited Q
VL - 27
ER -
TY - JOUR
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Förstner, Jens
ID - 12908
JF - Journal of the Optical Society of America B
KW - tet_topic_waveguides
SN - 0740-3224
TI - Oblique quasi-lossless excitation of a thin silicon slab waveguide: a guided-wave variant of an anti-reflection coating
VL - 36
ER -
TY - JOUR
AB - We investigate optical microresonators consisting of either one or two coupled rectangular strips between upper and lower slab waveguides. The cavities are evanescently excited under oblique angles by thin-film guided, in-plane unguided waves supported by one of the slab waveguides. Beyond a specific incidence angle, losses are fully suppressed. The interaction between the guided mode of the cavity-strip and the incoming slab modes leads to resonant behavior for specific incidence angles and gaps. For a single cavity, at resonance, the input power is equally split among each of the four output ports, while for two cavities an add-drop filter can be realized that, at resonance, routes the incoming power completely to the forward drop waveguide via the cavity. For both applications, the strength of the interaction is controlled by the gaps between cavities and waveguides.
AU - Ebers, Lena
AU - Hammer, Manfred
AU - Berkemeier, Manuel B.
AU - Menzel, Alexander
AU - Förstner, Jens
ID - 14990
JF - OSA Continuum
KW - tet_topic_waveguides
SN - 2578-7519
TI - Coupled microstrip-cavities under oblique incidence of semi-guided waves: a lossless integrated optical add-drop filter
VL - 2
ER -
TY - GEN
AB - Die Erfindung betrifft einen optischen Übergang zwischen zwei optischen Schichtwellenleitern. Dazu ist eine Anordnung vorgesehen aus einem ersten optischen Schichtwellenleiter (2) und einem zweiten optischen Schichtwellenleiter (3), wobei der erste optische Schichtwellenleiter (2) und der zweite optische Schichtwellenleiter (3) voneinander verschiedene über ihre jeweilige Länge konstante Dicken (d, r) aufweisen, der erste optische Schichtwellenleiter (2) mit dem zweiten optischen Schichtwellenleiter (3) mittels einer optischen Schichtwellenleiterstruktur (4) verbunden ist, die über ihre gesamte Länge (w) eine Dicke (h) aufweist, die zwischen der Dicke (d) des ersten optischen Schichtwellenleiters (2) und der Dicke (r) des zweiten optischen Schichtwellenleiters (3) liegt. Erfindungsgemäß ist die Dicke (h) der optischen Schichtwellenleiterstruktur (4) über die gesamte Länge (w) der optischen Schichtwellenleiterstruktur (4) konstant. Damit wird eine Möglichkeit für einen effizienten und mit geringen Verlusten behafteten Übergang zwischen zwei optischen Schichtwellenleitern mit unterschiedlicher Dicke bereitgestellt.
AU - Hammer, Manfred
AU - Förstner, Jens
AU - Ebers, Lena
ID - 7720
KW - tet_topic_waveguides
TI - Optical transition between two optical waveguides layer and method for transmitting light
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 - CONF
AB - Semi-guided waves confined in dielectric slab waveguides are being considered for oblique angles of propagation. If the waves encounter a linear discontinuity of (mostly) arbitrary shape and extension, a variant of Snell's law applies, separately for each pair of incoming and outgoing modes. Depending on the effective indices involved, and on the angle of incidence, power transfer to specific outgoing waves can be allowed or forbidden. In particular, critical angles of incidence can be identified, beyond which any power transfer to non-guided waves is forbidden, i.e. all radiative losses are suppressed. In that case the input power is carried away from the discontinuity exclusively by reflected semi-guided waves in the input slab, or by semi-guided waves that are transmitted into other outgoing slab waveguides. Vectorial equations on a 2-D cross sectional domain apply. These are formally identical to the equations that govern the eigenmodes of 3-D channel waveguides. Here, however, these need to be solved not as an eigenvalue problem, but as an inhomogeneous problem with a right-hand-side that is given by the incoming semi-guided wave, and subject to transparent boundary conditions. The equations resemble a standard 2-D Helmholtz problem, with an effective permittivity in place of the actual relative permittivity. Depending on the properties of the incoming wave, including the angle of incidence, this effective permittivity can become locally negative, causing the suppression of propagating outgoing waves. A series of high-contrast example configurations are discussed, where these effects lead to - in some respects - quite surprising transmission characteristics.
AU - Hammer, Manfred
AU - Ebers, Lena
AU - Hildebrandt, Andre
AU - Alhaddad, Samer
AU - Förstner, Jens
ID - 4579
KW - tet_topic_waveguides
SN - 9781538654385
T2 - 2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET)
TI - Oblique Semi-Guided Waves: 2-D Integrated Photonics with Negative Effective Permittivity
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 -