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Photo: Paderborn University

Dr. Christof Eigner

Contact
Biography
Publications
Dr. Christof Eigner

Institute for photonic quantum systems (PhoQS)

Academic Councillor - manager infrastructure

Integrated Quantum Optics

Academic Councillor - Group leader "Technology"

Phone:
+49 5251 60-5896
Office:
ST0.335
Visitor:
Warburger Str. 100
33098 Paderborn
Dr. Christof Eigner
04/2021 - today

Member of the Transregional Collaborative Research Center TRR 142- Tailored Nonlinear Photonics: From Fundamental Concepts to Functional Structures

The central goal of the TRR 142 is the establishment of a new kind of tailored nonlinear photonics, which is driven by concepts from quantum optics, coherent optics, ultrafast optoelectronics, and solid state physics.

04/2019 - today

Group leader "Technology" in IQO group

The "Technology" group is part of the Integrated Quantum Optics group led by Christine Silberhorn. We focus on the fabrication of quantum optical components based on ferroelectric materials such as lithium niobate, thin-film lithium niobate or potassium titanyl phosphate. A wide variety of (electro-) optical components are combined on one system and form the basis for our quantum optical experiments.

11/2013 - 03/2019

Doctoral thesis

Periodically Poled Waveguides in Potassium Titanyl Phosphate: From Technology Development to Applications

10/2014 - 03/2017

Member of the Research Training Group "Micro and Nanostructures in Optoelectronics and Photonics"

In the “Center of Optoelectronics and Photonics Paderborn” (CeOPP), physicists, chemists, and electrical engineers work together to study both fundamental and application-oriented topics. For this work, they have access to excellent laboratories and clean rooms. The research work in the field of optical technologies was supported by the DFG from 2008 to 2017 through the Research Training Group GRK 1464 “Micro and Nanostructures in Optoelectronics and Photonics”.

10/2011 - 10/2013

M.Sc. in Physics

Periodically Poled Waveguides in Potassium Titanyl Phosphate for Applications in Quantum Optics

10/2008 - 09/2011

B.Sc. in Physics

Untersuchung der Polungseigenschaften von oberflächennah Ti-diffusionsdotiertem, kongruentem Lithiumniobat


Open list in Research Information System

2022

Broadband optical Ta2O5 antennas for directional emission of light

H. Farheen, L. Yan, V. Quiring, C. Eigner, T. Zentgraf, S. Linden, J. Förstner, V. Myroshnychenko, Optics Express (2022), 30(11), pp. 19288

Highly directive antennas with the ability of shaping radiation patterns in desired directions are essential for efficient on-chip optical communication with reduced cross talk. In this paper, we design and optimize three distinct broadband traveling-wave tantalum pentoxide antennas exhibiting highly directional characteristics. Our antennas contain a director and reflector deposited on a glass substrate, which are excited by a dipole emitter placed in the feed gap between the two elements. Full-wave simulations in conjunction with global optimization provide structures with an enhanced linear directivity as high as 119 radiating in the substrate. The high directivity is a result of the interplay between two dominant TE modes and the leaky modes present in the antenna director. Furthermore, these low-loss dielectric antennas exhibit a near-unity radiation efficiency at the operational wavelength of 780 nm and maintain a broad bandwidth. Our numerical results are in good agreement with experimental measurements from the optimized antennas fabricated using a two-step electron-beam lithography, revealing the highly directive nature of our structures. We envision that our antenna designs can be conveniently adapted to other dielectric materials and prove instrumental for inter-chip optical communications and other on-chip applications.


DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking

L. Padberg, V. Quiring, A. Bocchini, M. Santandrea, U. Gerstmann, W.G. Schmidt, C. Silberhorn, C. Eigner, Crystals (2022), 12(10)

We study the DC conductivity in potassium titanyl phosphate (KTiOPO4, KTP) and its isomorphs KTiOAsO4 (KTA) and Rb1%K99%TiOPO4 (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications.


Cryogenic integrated spontaneous parametric down-conversion

N.A. Lange, J.P. Höpker, R. Ricken, V. Quiring, C. Eigner, C. Silberhorn, T. Bartley, Optica (2022), 9(1), 108

DOI


Cryogenic electro-optic modulation in titanium in-diffused lithium niobate waveguides

F. Thiele, F. vom Bruch, J. Brockmeier, M. Protte, T. Hummel, R. Ricken, V. Quiring, S. Lengeling, H. Herrmann, C. Eigner, C. Silberhorn, T. Bartley, Journal of Physics: Photonics (2022), 4(3), 034004

<jats:title>Abstract</jats:title> <jats:p>Lithium niobate is a promising platform for integrated quantum optics. In this platform, we aim to efficiently manipulate and detect quantum states by combining superconducting single photon detectors and modulators. The cryogenic operation of a superconducting single photon detector dictates the optimisation of the electro-optic modulators under the same operating conditions. To that end, we characterise a phase modulator, directional coupler, and polarisation converter at both ambient and cryogenic temperatures. The operation voltage <jats:inline-formula> <jats:tex-math><?CDATA $V_{\pi/2}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>V</mml:mi> <mml:mrow> <mml:mi>π</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of these modulators increases, due to the decrease in the electro-optic effect, by 74% for the phase modulator, 84% for the directional coupler and 35% for the polarisation converter below 8.5<jats:inline-formula> <jats:tex-math><?CDATA $\,\mathrm{K}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The phase modulator preserves its broadband nature and modulates light in the characterised wavelength range. The unbiased bar state of the directional coupler changed by a wavelength shift of 85<jats:inline-formula> <jats:tex-math><?CDATA $\,\mathrm{nm}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> while cooling the device down to 5<jats:inline-formula> <jats:tex-math><?CDATA $\,\mathrm{K}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>. The polarisation converter uses periodic poling to phasematch the two orthogonal polarisations. The phasematched wavelength of the utilised poling changes by 112<jats:inline-formula> <jats:tex-math><?CDATA $\,\mathrm{nm}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> when cooling to 5<jats:inline-formula> <jats:tex-math><?CDATA $\,\mathrm{K}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="jpphotonac6c63ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>.</jats:p>


2021

Cryogenic Second-Harmonic Generation in Periodically Poled Lithium Niobate Waveguides

M. Bartnick, M. Santandrea, J.P. Höpker, F. Thiele, R. Ricken, V. Quiring, C. Eigner, H. Herrmann, C. Silberhorn, T.J. Bartley, Physical Review Applied (2021)

DOI


Non-Invasive Visualization of Ferroelectric Domain Structures on the Non-Polar y-Surface of KTiOPO4 via Raman Imaging

J. Brockmeier, P.W.M. Mackwitz, M. Rüsing, C. Eigner, L. Padberg, M. Santandrea, C. Silberhorn, A. Zrenner, G. Berth, Crystals (2021), 1086

<jats:p>Potassium titanyl phosphate (KTP) is a nonlinear optical material with applications in high-power frequency conversion or quasi-phase matching in submicron period domain grids. A prerequisite for these applications is a precise control and understanding of the poling mechanisms to enable the fabrication of high-grade domain grids. In contrast to the widely used material lithium niobate, the domain growth in KTP is less studied, because many standard methods, such as selective etching or polarization microscopy, provides less insight or are not applicable on non-polar surfaces, respectively. In this work, we present results of confocal Raman-spectroscopy of the ferroelectric domain structure in KTP. This analytical method allows for the visualization of domain grids of the non-polar KTP y-face and therefore more insight into the domain-growth and -structure in KTP, which can be used for improved domain fabrication.</jats:p>


Improved non-linear devices for quantum applications

J. Gil López, M. Santandrea, G. Roland, B. Brecht, C. Eigner, R. Ricken, V. Quiring, C. Silberhorn, New Journal of Physics (2021), 063082

DOI


Integrated superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides

J.P. Höpker, V.B. Verma, M. Protte, R. Ricken, V. Quiring, C. Eigner, L. Ebers, M. Hammer, J. Förstner, C. Silberhorn, R.P. Mirin, S. Woo Nam, T. Bartley, Journal of Physics: Photonics (2021), 3, pp. 034022

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.


2020

Characterisation of width-dependent diffusion dynamics in rubidium-exchanged KTP waveguides

L. Padberg, M. Santandrea, M. Rüsing, J. Brockmeier, P. Mackwitz, G. Berth, A. Zrenner, C. Eigner, C. Silberhorn, Optics Express (2020), 24353

DOI


Pulse shaping using dispersion-engineered difference frequency generation

M. Allgaier, V. Ansari, J.M. Donohue, C. Eigner, V. Quiring, R. Ricken, B. Brecht, C. Silberhorn, Physical Review A (2020), 101, 043819

DOI


Spatially single mode photon pair source at 800 nm in periodically poled Rubidium exchanged KTP waveguides

C. Eigner, L. Padberg, M. Santandrea, H. Herrmann, B. Brecht, C. Silberhorn, Optics Express (2020), 28(22), 32925-32935

DOI


Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations

F. Schmidt, A.L. Kozub, T. Biktagirov, C. Eigner, C. Silberhorn, A. Schindlmayr, W.G. Schmidt, U. Gerstmann, Physical Review Research (2020), 2(4), 043002

Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb_Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb_Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.


Understanding gray track formation in KTP: $\mathrmTi^3+$ centers studied from first principles

A. Bocchini, C. Eigner, C. Silberhorn, W.G. Schmidt, U. Gerstmann, Phys. Rev. Materials (2020), 4, pp. 124402

DOI


Waveguide resonator with an integrated phase modulator for second harmonic generation

M. Stefszky, M. Santandrea, F. vom Bruch, S. Krapick, C. Eigner, R. Ricken, V. Quiring, H. Herrmann, C. Silberhorn, Optics Express (2020), 1991

DOI


Characterisation of width-dependent diffusion dynamics in rubidium-exchanged KTP waveguides

L. Padberg, M. Santandrea, M. Rüsing, J. Brockmeier, P. Mackwitz, G. Berth, A. Zrenner, C. Eigner, C. Silberhorn, Optics Express (2020), 24353

DOI


Cryogenic electro-optic polarisation conversion in titanium in-diffused lithium niobate waveguides

F. Thiele, F. vom Bruch, V. Quiring, R. Ricken, H. Herrmann, C. Eigner, C. Silberhorn, T. Bartley, Optics Express (2020), 28961

DOI


2019

Counter-propagating photon pair generation in a nonlinear waveguide

K. Luo, V. Ansari, M. Massaro, M. Santandrea, C. Eigner, R. Ricken, H. Herrmann, C. Silberhorn, Optics Express (2019), 3215

DOI


Nonlinear integrated quantum electro-optic circuits

K. Luo, S. Brauner, C. Eigner, P.R. Sharapova, R. Ricken, T. Meier, H. Herrmann, C. Silberhorn, Science Advances (2019), eaat1451

<jats:p>Future quantum computation and networks require scalable monolithic circuits, which incorporate various advanced functionalities on a single physical substrate. Although substantial progress for various applications has already been demonstrated on different platforms, the range of diversified manipulation of photonic states on demand on a single chip has remained limited, especially dynamic time management. Here, we demonstrate an electro-optic device, including photon pair generation, propagation, electro-optical path routing, as well as a voltage-controllable time delay of up to ~12 ps on a single Ti:LiNbO<jats:sub>3</jats:sub> waveguide chip. As an example, we demonstrate Hong-Ou-Mandel interference with a visibility of more than 93 ± 1.8%. Our chip not only enables the deliberate manipulation of photonic states by rotating the polarization but also provides precise time control. Our experiment reveals that we have full flexible control over single-qubit operations by harnessing the complete potential of fast on-chip electro-optic modulation.</jats:p>


Engineering integrated photon pair sources and multiplexed detectors (Conference Presentation)

E. Meyer-Scott, N. Prasannan, N. Montaut, J. Tiedau, C. Eigner, G. Harder, L. Sansoni, T. Nitsche, H. Herrmann, R. Ricken, V. Quiring, T. Bartley, S. Barkhofen, C. Silberhorn, in: Advances in Photonics of Quantum Computing, Memory, and Communication XII, 2019

DOI


2018

High-power waveguide resonator second harmonic device with external conversion efficiency up to 75%

M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, C. Silberhorn, Journal of Optics (2018), 065501

DOI


High-performance source of spectrally pure, polarization entangled photon pairs based on hybrid integrated-bulk optics

E. Meyer-Scott, N. Prasannan, C. Eigner, V. Quiring, J.M. Donohue, S. Barkhofen, C. Silberhorn, Optics Express (2018), 32475

DOI


Streak camera imaging of single photons at telecom wavelength

M. Allgaier, V. Ansari, C. Eigner, V. Quiring, R. Ricken, J.M. Donohue, T. Czerniuk, M. Aßmann, M. Bayer, B. Brecht, C. Silberhorn, Applied Physics Letters (2018), 112, 031110

DOI


Periodically poled ridge waveguides in KTP for second harmonic generation in the UV regime

C. Eigner, M. Santandrea, L. Padberg, M.F. Volk, C.E. Rüter, H. Herrmann, D. Kip, C. Silberhorn, Optics Express (2018), 28827

DOI


Heralded generation of high-purity ultrashort single photons in programmable temporal shapes

V. Ansari, E. Roccia, M. Santandrea, M. Doostdar, C. Eigner, L. Padberg, I. Gianani, M. Sbroscia, J.M. Donohue, L. Mancino, M. Barbieri, C. Silberhorn, Optics Express (2018), 2764

DOI


High-performance source of spectrally pure, polarization entangled photon pairs based on hybrid integrated-bulk optics

E. Meyer-Scott, N. Prasannan, C. Eigner, V. Quiring, J.M. Donohue, S. Barkhofen, C. Silberhorn, Optics Express (2018), 32475

DOI


Engineering integrated sources of entangled photon pairs

E. Meyer-Scott, N. Prasannan, N. Montaut, J. Tiedau, G. Harder, L. Sansoni, H. Herrmann, C. Eigner, R. Ricken, V. Quiring, T. Bartley, S. Barkhofen, C. Silberhorn, in: Frontiers in Optics / Laser Science, 2018

DOI


Engineering integrated sources of entangled photon pairs

E. Meyer-Scott, N. Prasannan, N. Montaut, J. Tiedau, G. Harder, L. Sansoni, H. Herrmann, C. Eigner, R. Ricken, V. Quiring, T.J. Bartley, S. Barkhofen, C. Silberhorn, in: Frontiers in Optics / Laser Science, 2018

DOI


High-power waveguide resonator second harmonic device with external conversion efficiency up to 75%

M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, C. Silberhorn, Journal of Optics (2018), 065501

DOI


Streak camera imaging of single photons at telecom wavelength

M. Allgaier, V. Ansari, C. Eigner, V. Quiring, R. Ricken, J.M. Donohue, T. Czerniuk, M. Aßmann, M. Bayer, B. Brecht, C. Silberhorn, Applied Physics Letters (2018), 031110

DOI


2017

Waveguide Cavity Resonator as a Source of Optical Squeezing

M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, C. Silberhorn, Physical Review Applied (2017)

DOI


Fast time-domain measurements on telecom single photons

M. Allgaier, G. Vigh, V. Ansari, C. Eigner, V. Quiring, R. Ricken, B. Brecht, C. Silberhorn, Quantum Science and Technology (2017), 2, 034012

DOI


Highly efficient frequency conversion with bandwidth compression of quantum light

M. Allgaier, V. Ansari, L. Sansoni, C. Eigner, V. Quiring, R. Ricken, G. Harder, B. Brecht, C. Silberhorn, Nature Communications (2017), 8, 14288

DOI


Highly efficient frequency conversion with bandwidth compression of quantum light

M. Allgaier, V. Ansari, L. Sansoni, C. Eigner, V. Quiring, R. Ricken, G. Harder, B. Brecht, C. Silberhorn, Nature Communications (2017), 14288

DOI


Waveguide Cavity Resonator as a Source of Optical Squeezing

M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, C. Silberhorn, Physical Review Applied (2017)

DOI


Fabrication of low-loss Rb-exchanged ridge waveguides in z-cut KTiOPO_4

M.F. Volk, C.E. Rüter, M. Santandrea, C. Eigner, L. Padberg, H. Herrmann, C. Silberhorn, D. Kip, Optical Materials Express (2017), 82

DOI


A monolithic, doubly-resonant parametric down-conversion source for Caesium Raman memories

B. Brecht, O. Lazo-Arjona, K.T. Kaczmarek, T. Parker, R. Ricken, V. Quiring, C. Eigner, K.H. Luo, H. Herrmann, C. Silberhorn, I.A. Walmsley, in: Frontiers in Optics 2017, 2017

DOI


Fast time-domain measurements on telecom single photons

M. Allgaier, G. Vigh, V. Ansari, C. Eigner, V. Quiring, R. Ricken, B. Brecht, C. Silberhorn, Quantum Science and Technology (2017), 034012

DOI


Waveguide Cavity Resonator as a Source of Optical Squeezing

M. Stefszky, R. Ricken, C. Eigner, V. Quiring, H. Herrmann, C. Silberhorn, Physical Review Applied (2017)

DOI


A two-channel, spectrally degenerate polarization entangled source on chip

L. Sansoni, K.H. Luo, C. Eigner, R. Ricken, V. Quiring, H. Herrmann, C. Silberhorn, npj Quantum Information (2017)

DOI


2016

Identification of ferroelectric domain structure sensitive phonon modes in potassium titanyl phosphate: A fundamental study

M. Rüsing, C. Eigner, P. Mackwitz, G. Berth, C. Silberhorn, A. Zrenner, Journal of Applied Physics (2016), 044103

DOI


Open list in Research Information System

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