Photonics / Fotonik

Permanent URI for this collectionhttps://hdl.handle.net/11147/2590

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Author: search.filters.author.Peeters, François M.Publisher: search.filters.publisher.Royal Society of Chemistry

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Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 6
    Citation - Scopus: 7
    Interface-Dependent Phononic and Optical Properties of Geo/Moso Heterostructures
    (Royal Society of Chemistry, 2022) Yağmurcukardeş, Mehmet; Sözen, Yiğit; Sözen, Yiğit; Peeters, François M.; Şahin, Hasan; Şahin, Hasan; Yağmurcukardeş, Mehmet; 04.04. Department of Photonics; 01. Izmir Institute of Technology; 04. Faculty of Science
    The interface-dependent electronic, vibrational, piezoelectric, and optical properties of van der Waals heterobilayers, formed by buckled GeO (b-GeO) and Janus MoSO structures, are investigated by means of first-principles calculations. The electronic band dispersions show that O/Ge and S/O interface formations result in a type-II band alignment with direct and indirect band gaps, respectively. In contrast, O/O and S/Ge interfaces give rise to the formation of a type-I band alignment with an indirect band gap. By considering the Bethe-Salpeter equation (BSE) on top of G0W0 approximation, it is shown that different interfaces can be distinguished from each other by means of the optical absorption spectra as a consequence of the band alignments. Additionally, the low-and high-frequency regimes of the Raman spectra are also different for each interface type. The alignment of the individual dipoles, which is interface-dependent, either weakens or strengthens the net dipole of the heterobilayers and results in tunable piezoelectric coefficients. The results indicate that the possible heterobilayers of b-GeO/MoSO asymmetric structures possess various electronic, optical, and piezoelectric properties arising from the different interface formations and can be distinguished by means of various spectroscopic techniques.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Ultra-Thin Structures of Manganese Fluorides: Conversion From Manganese Dichalcogenides by Fluorination
    (Royal Society of Chemistry, 2021) Şahin, Hasan; Nair, Rahul R.; Peeters, François M.; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, it is predicted by density functional theory calculations that graphene-like novel ultra-thin phases of manganese fluoride crystals, that have nonlayered structures in their bulk form, can be stabilized by fluorination of manganese dichalcogenide crystals. First, it is shown that substitution of fluorine atoms with chalcogens in the manganese dichalcogenide host lattice is favorable. Among possible crystal formations, three stable ultra-thin structures of manganese fluoride, 1H-MnF2, 1T-MnF2 and MnF3, are found to be stable by total energy optimization calculations. In addition, phonon calculations and Raman activity analysis reveal that predicted novel single-layers are dynamically stable crystal structures displaying distinctive characteristic peaks in their vibrational spectrum enabling experimental determination of the corresponding phases. Differing from 1H-MnF2 antiferromagnetic (AFM) large gap semiconductor, 1T-MnF2 and MnF3 single-layers are semiconductors with ferromagnetic (FM) ground state.
  • Article
    Citation - WoS: 68
    Citation - Scopus: 71
    Strong Dichroic Emission in the Pseudo One Dimensional Material Zrs3
    (Royal Society of Chemistry, 2016) Pant, Anupum; Şahin, Hasan; Chen, Bin; Bhat, Soumya; Fan, Xi; Wu, Kedi; Wright, David P.; Peeters, François M.; Soignard, Emmanuel; Şahin, Hasan; Tongay, Sefaattin; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Zirconium trisulphide (ZrS3), a member of the layered transition metal trichalcogenides (TMTCs) family, has been studied by angle-resolved photoluminescence spectroscopy (ARPLS). The synthesized ZrS3 layers possess a pseudo one-dimensional nature where each layer consists of ZrS3 chains extending along the b-lattice direction. Our results show that the optical properties of few-layered ZrS3 are highly anisotropic as evidenced by large PL intensity variation with the polarization direction. Light is efficiently absorbed when the E-field is polarized along the chain (b-axis), but the field is greatly attenuated and absorption is reduced when it is polarized vertical to the 1D-like chains as the wavelength of the exciting light is much longer than the width of each 1D chain. The observed PL variation with polarization is similar to that of conventional 1D materials, i.e., nanowires, and nanotubes, except for the fact that here the 1D chains interact with each other giving rise to a unique linear dichroism response that falls between the 2D (planar) and 1D (chain) limit. These results not only mark the very first demonstration of PL polarization anisotropy in 2D systems, but also provide novel insight into how the interaction between adjacent 1D-like chains and the 2D nature of each layer influences the overall optical anisotropy of pseudo-1D materials. Results are anticipated to have an impact on optical technologies such as polarized detectors, near-field imaging, communication systems, and bio-applications relying on the generation and detection of polarized light.