--- _id: '43246' abstract: - lang: eng text: The biexciton-exciton emission cascade commonly used in quantum-dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work we focus on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishibility. We achieve this goal by selectively reducing the biexciton lifetime with an optical resonator. We demonstrate that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and two-fold degenerate optical modes. Our in-depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum-dot cavity excitation dynamics with full access to photon properties. We report non-trivial dependencies on system parameters and use the predictive power of our combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values in the telecom C-band at $1550\,\mathrm{nm}$. author: - first_name: David full_name: Bauch, David last_name: Bauch - first_name: Dustin full_name: Siebert, Dustin last_name: Siebert - first_name: Klaus full_name: Jöns, Klaus id: '85353' last_name: Jöns - first_name: Jens full_name: Förstner, Jens id: '158' last_name: Förstner orcid: 0000-0001-7059-9862 - first_name: Stefan full_name: Schumacher, Stefan id: '27271' last_name: Schumacher orcid: 0000-0003-4042-4951 citation: ama: Bauch D, Siebert D, Jöns K, Förstner J, Schumacher S. On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs. Published online 2023. apa: Bauch, D., Siebert, D., Jöns, K., Förstner, J., & Schumacher, S. (2023). On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs. bibtex: '@article{Bauch_Siebert_Jöns_Förstner_Schumacher_2023, title={On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs}, author={Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}, year={2023} }' chicago: Bauch, David, Dustin Siebert, Klaus Jöns, Jens Förstner, and Stefan Schumacher. “On-Demand Indistinguishable and Entangled Photons at Telecom Frequencies Using Tailored Cavity Designs,” 2023. ieee: D. Bauch, D. Siebert, K. Jöns, J. Förstner, and S. Schumacher, “On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs.” 2023. mla: Bauch, David, et al. On-Demand Indistinguishable and Entangled Photons at Telecom Frequencies Using Tailored Cavity Designs. 2023. short: D. Bauch, D. Siebert, K. Jöns, J. Förstner, S. Schumacher, (2023). date_created: 2023-03-31T13:22:05Z date_updated: 2023-12-21T10:41:17Z department: - _id: '61' - _id: '230' - _id: '429' - _id: '623' - _id: '15' - _id: '35' - _id: '170' - _id: '297' keyword: - tet_topic_phc - tet_topic_qd language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/pdf/2303.13871.pdf oa: '1' project: - _id: '52' name: 'PC2: Computing Resources Provided by the Paderborn Center for Parallel Computing' - _id: '173' grant_number: '231447078' name: 'TRR 142 - C09: TRR 142 - Subproject C09' - _id: '167' grant_number: '231447078' name: 'TRR 142 - B06: TRR 142 - Subproject B06' - _id: '53' grant_number: '231447078' name: 'TRR 142: TRR 142' - _id: '55' name: 'TRR 142 - B: TRR 142 - Project Area B' - _id: '56' name: 'TRR 142 - C: TRR 142 - Project Area C' related_material: record: - id: '48599' relation: later_version status: public status: public title: On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs type: preprint user_id: '16199' year: '2023' ... --- _id: '28413' abstract: - lang: eng text: Optical traveling wave antennas offer unique opportunities to control and selectively guide light into a specific direction, which renders them excellent candidates for optical communication and sensing. These applications require state-of-the-art engineering to reach optimized functionalities such as high directivity and radiation efficiency, low sidelobe levels, broadband and tunable capabilities, and compact design. In this work, we report on the numerical optimization of the directivity of optical traveling wave antennas made from low-loss dielectric materials using full-wave numerical simulations in conjunction with the particle swarm optimization algorithm. The antennas are composed of a reflector and a director deposited on a glass substrate, and an emitter placed in the feed gap between them serves as an internal source of excitation. In particular, we analyze antennas with rectangular- and horn-shaped directors made of either hafnium dioxide or silicon. The optimized antennas produce highly directional emissions due to the presence of two dominant guided TE modes in the director in addition to leaky modes. These guided modes dominate the far-field emission pattern and govern the direction of the main lobe emission, which predominately originates from the end facet of the director. Our work also provides a comprehensive analysis of the modes, radiation patterns, parametric influences, and bandwidths of the antennas, which highlights their robust nature. author: - first_name: Henna full_name: Farheen, Henna last_name: Farheen - first_name: Till full_name: Leuteritz, Till last_name: Leuteritz - first_name: Stefan full_name: Linden, Stefan last_name: Linden - first_name: Viktor full_name: Myroshnychenko, Viktor id: '46371' last_name: Myroshnychenko - first_name: Jens full_name: Förstner, Jens id: '158' last_name: Förstner orcid: 0000-0001-7059-9862 citation: ama: Farheen H, Leuteritz T, Linden S, Myroshnychenko V, Förstner J. Optimization of optical waveguide antennas for directive emission of light. Journal of the Optical Society of America B. 2022;39(1):83. doi:10.1364/josab.438514 apa: Farheen, H., Leuteritz, T., Linden, S., Myroshnychenko, V., & Förstner, J. (2022). Optimization of optical waveguide antennas for directive emission of light. Journal of the Optical Society of America B, 39(1), 83. https://doi.org/10.1364/josab.438514 bibtex: '@article{Farheen_Leuteritz_Linden_Myroshnychenko_Förstner_2022, title={Optimization of optical waveguide antennas for directive emission of light}, volume={39}, DOI={10.1364/josab.438514}, number={1}, journal={Journal of the Optical Society of America B}, author={Farheen, Henna and Leuteritz, Till and Linden, Stefan and Myroshnychenko, Viktor and Förstner, Jens}, year={2022}, pages={83} }' chicago: 'Farheen, Henna, Till Leuteritz, Stefan Linden, Viktor Myroshnychenko, and Jens Förstner. “Optimization of Optical Waveguide Antennas for Directive Emission of Light.” Journal of the Optical Society of America B 39, no. 1 (2022): 83. https://doi.org/10.1364/josab.438514.' ieee: 'H. Farheen, T. Leuteritz, S. Linden, V. Myroshnychenko, and J. Förstner, “Optimization of optical waveguide antennas for directive emission of light,” Journal of the Optical Society of America B, vol. 39, no. 1, p. 83, 2022, doi: 10.1364/josab.438514.' mla: Farheen, Henna, et al. “Optimization of Optical Waveguide Antennas for Directive Emission of Light.” Journal of the Optical Society of America B, vol. 39, no. 1, 2022, p. 83, doi:10.1364/josab.438514. short: H. Farheen, T. Leuteritz, S. Linden, V. Myroshnychenko, J. Förstner, Journal of the Optical Society of America B 39 (2022) 83. date_created: 2021-12-08T07:14:39Z date_updated: 2022-01-06T06:58:04Z ddc: - '530' department: - _id: '61' - _id: '230' - _id: '429' doi: 10.1364/josab.438514 file: - access_level: local content_type: application/pdf creator: fossie date_created: 2021-12-08T08:26:57Z date_updated: 2021-12-08T08:26:57Z embargo: 2022-12-08 embargo_to: open_access file_id: '28417' file_name: 2021-12 Farheen - JOSA B - Optimization of optical nanoantennas.pdf file_size: 14029741 relation: main_file - access_level: open_access content_type: application/pdf creator: fossie date_created: 2021-12-08T08:29:49Z date_updated: 2021-12-08T08:29:49Z file_id: '28418' file_name: 2021-12 Farheen - JOSA B - Optimization of optical nanoantennas SUPPLEMENTARY MATERIAL.pdf file_size: 655495 relation: supplementary_material file_date_updated: 2021-12-08T08:29:49Z has_accepted_license: '1' intvolume: ' 39' issue: '1' keyword: - tet_topic_opticalantenna language: - iso: eng oa: '1' page: '83' project: - _id: '53' name: TRR 142 - _id: '56' name: TRR 142 - Project Area C - _id: '75' name: TRR 142 - Subproject C5 - _id: '52' name: Computing Resources Provided by the Paderborn Center for Parallel Computing publication: Journal of the Optical Society of America B publication_identifier: issn: - 0740-3224 - 1520-8540 publication_status: published status: public title: Optimization of optical waveguide antennas for directive emission of light type: journal_article user_id: '158' volume: 39 year: '2022' ... --- _id: '29075' abstract: - lang: eng text: We study a double-scattering coherent mechanism of negative polarization (NP) near opposition that is observed for powder-like surfaces. The problem is solved numerically for absorbing structures with irregular constituents, cubes, spheres, and ellipsoids larger than the wavelength of incident light. Our simulations show that double scattering between two random irregular particles shows weak NP. Adding one more particle significantly increases the relative contribution of double scattering which enhances NP. Simulations with regular shapes and controlled geometric parameters show that the interference mechanism is sensitive to the geometry of the scattering system and can also result in no polarization or even strong enhancement of positive polarization at backscattering. author: - first_name: Samer full_name: Alhaddad, Samer id: '42456' last_name: Alhaddad - first_name: Yevgen full_name: Grynko, Yevgen id: '26059' last_name: Grynko - first_name: Henna full_name: Farheen, Henna last_name: Farheen - first_name: Jens full_name: Förstner, Jens id: '158' last_name: Förstner orcid: 0000-0001-7059-9862 citation: ama: Alhaddad S, Grynko Y, Farheen H, Förstner J. Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles. Optics Letters. 2022;47(1):58. doi:10.1364/ol.444953 apa: Alhaddad, S., Grynko, Y., Farheen, H., & Förstner, J. (2022). Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles. Optics Letters, 47(1), 58. https://doi.org/10.1364/ol.444953 bibtex: '@article{Alhaddad_Grynko_Farheen_Förstner_2022, title={Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles}, volume={47}, DOI={10.1364/ol.444953}, number={1}, journal={Optics Letters}, author={Alhaddad, Samer and Grynko, Yevgen and Farheen, Henna and Förstner, Jens}, year={2022}, pages={58} }' chicago: 'Alhaddad, Samer, Yevgen Grynko, Henna Farheen, and Jens Förstner. “Numerical Analysis of the Coherent Mechanism Producing Negative Polarization at Backscattering from Systems of Absorbing Particles.” Optics Letters 47, no. 1 (2022): 58. https://doi.org/10.1364/ol.444953.' ieee: 'S. Alhaddad, Y. Grynko, H. Farheen, and J. Förstner, “Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles,” Optics Letters, vol. 47, no. 1, p. 58, 2022, doi: 10.1364/ol.444953.' mla: Alhaddad, Samer, et al. “Numerical Analysis of the Coherent Mechanism Producing Negative Polarization at Backscattering from Systems of Absorbing Particles.” Optics Letters, vol. 47, no. 1, 2022, p. 58, doi:10.1364/ol.444953. short: S. Alhaddad, Y. Grynko, H. Farheen, J. Förstner, Optics Letters 47 (2022) 58. date_created: 2021-12-21T13:49:29Z date_updated: 2022-01-06T06:58:46Z ddc: - '530' department: - _id: '61' - _id: '230' - _id: '429' doi: 10.1364/ol.444953 file: - access_level: local content_type: application/pdf creator: fossie date_created: 2021-12-21T13:53:47Z date_updated: 2021-12-21T13:53:47Z embargo: 2022-12-21 embargo_to: open_access file_id: '29076' file_name: 2022-01 Alhaddad - Optics Letter - Double Scattering.pdf file_size: 3197213 relation: main_file file_date_updated: 2021-12-21T13:53:47Z has_accepted_license: '1' intvolume: ' 47' issue: '1' keyword: - tet_topic_scattering language: - iso: eng page: '58' project: - _id: '52' name: Computing Resources Provided by the Paderborn Center for Parallel Computing publication: Optics Letters publication_identifier: issn: - 0146-9592 - 1539-4794 publication_status: published status: public title: Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles type: journal_article user_id: '158' volume: 47 year: '2022' ... --- _id: '30387' abstract: - lang: eng text: 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 author: - first_name: Manfred full_name: Hammer, Manfred id: '48077' last_name: Hammer orcid: 0000-0002-6331-9348 - first_name: Lena full_name: Ebers, Lena id: '40428' last_name: Ebers - first_name: Jens full_name: Förstner, Jens id: '158' last_name: Förstner orcid: 0000-0001-7059-9862 citation: ama: 'Hammer M, Ebers L, Förstner J. Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber. In: Andrews DL, Galvez EJ, Rubinsztein-Dunlop H, eds. Complex Light and Optical Forces XVI. SPIE; 2022:120170F. doi:10.1117/12.2612179' apa: Hammer, M., Ebers, L., & Förstner, J. (2022). Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber. In D. L. Andrews, E. J. Galvez, & H. Rubinsztein-Dunlop (Eds.), Complex Light and Optical Forces XVI (p. 120170F). SPIE. https://doi.org/10.1117/12.2612179 bibtex: '@inproceedings{Hammer_Ebers_Förstner_2022, title={Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber}, DOI={10.1117/12.2612179}, booktitle={Complex Light and Optical Forces XVI}, publisher={SPIE}, author={Hammer, Manfred and Ebers, Lena and Förstner, Jens}, editor={Andrews, David L. and Galvez, Enrique J. and Rubinsztein-Dunlop, Halina}, year={2022}, pages={120170F} }' chicago: Hammer, Manfred, Lena Ebers, and Jens Förstner. “Resonant Evanescent Excitation of OAM Modes in a High-Contrast Circular Step-Index Fiber.” In Complex Light and Optical Forces XVI, edited by David L. Andrews, Enrique J. Galvez, and Halina Rubinsztein-Dunlop, 120170F. SPIE, 2022. https://doi.org/10.1117/12.2612179. ieee: 'M. Hammer, L. Ebers, and J. Förstner, “Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber,” in Complex Light and Optical Forces XVI, 2022, p. 120170F, doi: 10.1117/12.2612179.' mla: Hammer, Manfred, et al. “Resonant Evanescent Excitation of OAM Modes in a High-Contrast Circular Step-Index Fiber.” Complex Light and Optical Forces XVI, edited by David L. Andrews et al., SPIE, 2022, p. 120170F, doi:10.1117/12.2612179. short: 'M. Hammer, L. Ebers, J. Förstner, in: D.L. Andrews, E.J. Galvez, H. Rubinsztein-Dunlop (Eds.), Complex Light and Optical Forces XVI, SPIE, 2022, p. 120170F.' date_created: 2022-03-21T10:12:58Z date_updated: 2022-03-22T18:04:20Z ddc: - '530' department: - _id: '61' - _id: '230' - _id: '429' doi: 10.1117/12.2612179 editor: - first_name: David L. full_name: Andrews, David L. last_name: Andrews - first_name: Enrique J. full_name: Galvez, Enrique J. last_name: Galvez - first_name: Halina full_name: Rubinsztein-Dunlop, Halina last_name: Rubinsztein-Dunlop file: - access_level: open_access content_type: application/pdf creator: fossie date_created: 2022-03-22T18:03:50Z date_updated: 2022-03-22T18:03:50Z file_id: '30444' file_name: 2022-03 Hammer - SPIE Photonics West 2022 - Resonant evanescent excitation of OAM modes in a high-contrast circular (official version).pdf file_size: 2015899 relation: main_file file_date_updated: 2022-03-22T18:03:50Z has_accepted_license: '1' keyword: - tet_topic_waveguide language: - iso: eng oa: '1' page: 120170F project: - _id: '56' name: 'TRR 142 - C: TRR 142 - Project Area C' - _id: '53' name: 'TRR 142: TRR 142' - _id: '75' name: 'TRR 142 - C5: TRR 142 - Subproject C5' publication: Complex Light and Optical Forces XVI publication_status: published publisher: SPIE status: public title: Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber type: conference user_id: '158' year: '2022' ... --- _id: '30722' abstract: - lang: eng text: 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. - lang: eng text: In this work, the electromagnetic wave propagation in integrated optical waveguides is studied by using semi-analytical and numerical simulation methods. In the first part, 2-D high-index contrast Si/SiO2 dielectric slab waveguide configurations are investigated. The structures are excited with semi-guided waves at oblique angles of propagation. Due to this, power transfer to specific outgoing modes can be suppressed, resulting in completely lossless configurations. The excitation is further examined for incoming, laterally confined wave bundles of semi-guided waves to realize practically more relevant 3-D configurations. Additionally, a stepwise angular spectrum method in combination with full vectorial 2-D finite element solutions for subproblems of lower complexity to numerically simulate the wave propagation in full 3-D planar lens-like waveguides is presented. In the second part, the wave propagation in lithium niobate waveguide structures is examined, which are used for quantum optical effects. On the one hand, superconducting nanowires on titanium in-diffused lithium niobate waveguides with an additional tapered silicon layer are used for single photon detection. The wave propagation in these 3-D multiscale tapers is studied by introducing a unidirectional finite element modal matching method. On the other hand, lithium niobate rib waveguides on silicon dioxide platforms are analyzed, focusing on the nonlinear parametric down-conversion process used for the generation of entangled photons. author: - first_name: Lena full_name: Ebers, Lena id: '40428' last_name: Ebers citation: ama: Ebers L. Semi-Guided Waves in Integrated Optical Waveguide Structures.; 2022. doi:10.17619/UNIPB/1-1288 apa: Ebers, L. (2022). Semi-guided waves in integrated optical waveguide structures. https://doi.org/10.17619/UNIPB/1-1288 bibtex: '@book{Ebers_2022, title={Semi-guided waves in integrated optical waveguide structures}, DOI={10.17619/UNIPB/1-1288}, author={Ebers, Lena}, year={2022} }' chicago: Ebers, Lena. Semi-Guided Waves in Integrated Optical Waveguide Structures, 2022. https://doi.org/10.17619/UNIPB/1-1288. ieee: L. Ebers, Semi-guided waves in integrated optical waveguide structures. 2022. mla: Ebers, Lena. Semi-Guided Waves in Integrated Optical Waveguide Structures. 2022, doi:10.17619/UNIPB/1-1288. short: L. Ebers, Semi-Guided Waves in Integrated Optical Waveguide Structures, 2022. date_created: 2022-03-29T18:42:08Z date_updated: 2022-03-29T18:44:30Z department: - _id: '61' - _id: '230' doi: 10.17619/UNIPB/1-1288 keyword: - tet_topic_waveguide language: - iso: eng status: public supervisor: - first_name: Jens full_name: Förstner, Jens id: '158' last_name: Förstner orcid: 0000-0001-7059-9862 title: Semi-guided waves in integrated optical waveguide structures type: dissertation user_id: '158' year: '2022' ...