Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study
We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of la...
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De Gruyter
2024-01-01
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| Series: | Nanophotonics |
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| Online Access: | https://doi.org/10.1515/nanoph-2023-0697 |
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| author | Talamas Simola Enrico Ortolani Michele Di Gaspare Luciana Capellini Giovanni De Seta Monica Virgilio Michele |
| author_facet | Talamas Simola Enrico Ortolani Michele Di Gaspare Luciana Capellini Giovanni De Seta Monica Virgilio Michele |
| author_sort | Talamas Simola Enrico |
| collection | DOAJ |
| description | We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of large off-diagonal elements in the χ
2 tensor, coupling optical modes with different polarization. To account for this effect, we generalize the coupled-mode theory, proposing a theoretical model suitable for concurrently resolving every second harmonic generation interaction among guide-sustained modes, regardless of which χ
2 tensor elements it originates from. Furthermore, we exploit the presence of off-diagonal χ
2 elements and the peculiarity of the SiGe material system to develop a simple and novel approach to achieve perfect phase matching without requiring any fabrication process. For a realistic design of the quantum heterostructure we estimate second order nonlinear susceptibility peak values of ∼7 and ∼1.4 × 105 pm/V for diagonal and off diagonal χ
2 elements, respectively. Embedding such heterostructure in Ge-rich SiGe waveguides of thicknesses of the order of 10–15 μm leads to second harmonic generation efficiencies comprised between 0.2 and 2 %, depending on the choice of device parameters. As a case study, we focus on the technologically relevant frequency of 7.1 THz, yet the results we report may be extended to the whole 5–20 THz range. |
| format | Article |
| id | doaj-art-9a99e09ac45e4afcb01f8675bf07f7b5 |
| institution | OA Journals |
| issn | 2192-8614 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | De Gruyter |
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| series | Nanophotonics |
| spelling | doaj-art-9a99e09ac45e4afcb01f8675bf07f7b52025-08-20T02:23:36ZengDe GruyterNanophotonics2192-86142024-01-0113101781179110.1515/nanoph-2023-0697Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical studyTalamas Simola Enrico0Ortolani Michele1Di Gaspare Luciana2Capellini Giovanni3De Seta Monica4Virgilio Michele5Dipartimento di Scienze, Università degli Studi Roma Tre, Viale G. Marconi 446, 00146, Roma, ItalyDepartment of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, I-00185Rome, ItalyDipartimento di Scienze, Università degli Studi Roma Tre, Viale G. Marconi 446, 00146, Roma, ItalyDipartimento di Scienze, Università degli Studi Roma Tre, Viale G. Marconi 446, 00146, Roma, ItalyDipartimento di Scienze, Università degli Studi Roma Tre, Viale G. Marconi 446, 00146, Roma, ItalyDipartimento di Fisica “E. Fermi”, Università di Pisa, Largo Pontecorvo 3, 56127, Pisa, ItalyWe present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of large off-diagonal elements in the χ 2 tensor, coupling optical modes with different polarization. To account for this effect, we generalize the coupled-mode theory, proposing a theoretical model suitable for concurrently resolving every second harmonic generation interaction among guide-sustained modes, regardless of which χ 2 tensor elements it originates from. Furthermore, we exploit the presence of off-diagonal χ 2 elements and the peculiarity of the SiGe material system to develop a simple and novel approach to achieve perfect phase matching without requiring any fabrication process. For a realistic design of the quantum heterostructure we estimate second order nonlinear susceptibility peak values of ∼7 and ∼1.4 × 105 pm/V for diagonal and off diagonal χ 2 elements, respectively. Embedding such heterostructure in Ge-rich SiGe waveguides of thicknesses of the order of 10–15 μm leads to second harmonic generation efficiencies comprised between 0.2 and 2 %, depending on the choice of device parameters. As a case study, we focus on the technologically relevant frequency of 7.1 THz, yet the results we report may be extended to the whole 5–20 THz range.https://doi.org/10.1515/nanoph-2023-0697second harmonic generationterahertzge/sige quantum wellsnon linear waveguidesilicon photonics |
| spellingShingle | Talamas Simola Enrico Ortolani Michele Di Gaspare Luciana Capellini Giovanni De Seta Monica Virgilio Michele Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study Nanophotonics second harmonic generation terahertz ge/sige quantum wells non linear waveguide silicon photonics |
| title | Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study |
| title_full | Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study |
| title_fullStr | Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study |
| title_full_unstemmed | Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study |
| title_short | Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study |
| title_sort | asymmetric coupled ge sige quantum wells for second harmonic generation at 7 1 thz in integrated waveguides a theoretical study |
| topic | second harmonic generation terahertz ge/sige quantum wells non linear waveguide silicon photonics |
| url | https://doi.org/10.1515/nanoph-2023-0697 |
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