Effect of spin–phonon interactions on Urbach tails in flexible [M2(bdc)2(dabco)]

2020 ◽  
Vol 22 (27) ◽  
pp. 15242-15247 ◽  
Author(s):  
Svetlana G. Kozlova ◽  
Maxim R. Ryzhikov ◽  
Vladimir R. Shayapov ◽  
Denis G. Samsonenko

The optical properties of MOFs [M2(bdc)2(dabco)] (M = Co, Ni, Cu, Zn) in the wavelength region of 300–1000 nm were studied, the electronic band-to-band transitions were determined and characterized by the Kubelka–Munk approach and DFT calculations.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinho Lee ◽  
Young In Jhon ◽  
Kyungtaek Lee ◽  
Young Min Jhon ◽  
Ju Han Lee

Abstract We report the first investigation results of the nonlinear optical properties of As2Te3. More specifically, the nonlinear optical absorption properties of the prepared α-As2Te3 were investigated at wavelengths of 1.56 and 1.9 μm using the open-aperture (OA) Z-scan technique. Using the OA Z-scan technique, the nonlinear absorption coefficients (β) of α-As2Te3 were estimated in a range from (− 54.8 ± 3.4) × 104 cm/GW to (− 4.9 ± 0.4) × 104 cm/GW depending on the irradiance of the input beam at 1.56 μm, whereas the values did from (− 19.8 ± 0.8) × 104 cm/GW to (− 3.2 ± 0.1) × 104 cm/GW at 1.9 μm. In particular, the β value at 1.56 μm is an order of magnitude larger than the previously reported values of other group-15 sesquichalcogenides such as Bi2Se3, Bi2Te3, and Bi2TeSe2. Furthermore, this is the first time report on β value of a group-15 sesquichalcogenide at a 1.9-μm wavelength. The density functional theory (DFT) calculations of the electronic band structures of α-As2Te3 were also conducted to obtain a better understanding of their energy band structure. The DFT calculations indicated that α-As2Te3 possess sufficient optical absorption in a wide wavelength region, including 1.5 μm, 1.9 μm, and beyond (up to 3.7 μm). Using both the measured nonlinear absorption coefficients and the theoretically obtained refractive indices from the DFT calculations, the imaginary parts of the third-order optical susceptibilities (Im χ(3)) of As2Te3 were estimated and they were found to vary from (− 39 ± 2.4) × 10–19 m2/V2 to (− 3.5 ± 0.3) × 10–19 m2/V2 at 1.56 μm and (− 16.5 ± 0.7) × 10–19 m2/V2 to (− 2.7 ± 0.1) × 10–19 m2/V2 at 1.9 μm, respectively, depending on the irradiance of the input beam. Finally, the feasibility of using α-As2Te3 for SAs was investigated, and the prepared SAs were thus tested by incorporating them into an erbium (Er)-doped fiber cavity and a thulium–holmium (Tm–Ho) co-doped fiber cavity for both 1.5 and 1.9 μm operation.



2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.



2021 ◽  
Vol 67 (1 Jan-Feb) ◽  
pp. 7
Author(s):  
B. Bachir Bouiadjra ◽  
N. Mehnane ◽  
N. Oukli

Based on the full potential linear muffin-tin orbitals (FPLMTO) calculation within density functional theory, we systematically investigate the electronic and optical properties of (100) and (110)-oriented (InN)/(GaN)n zinc-blende superlattice with one InN monolayer and with different numbers of GaN monolayers. Specifically, the electronic band structure calculations and their related features, like the absorption coefficient and refractive index of these systems are computed over a wide photon energy scale up to 20 eV. The effect of periodicity layer numbers n on the band gaps and the optical activity of (InN)/(GaN)n SLs in the both  growth axis (001) and (110) are examined and compared. Because of prospective optical aspects of (InN)/(GaN)n such as light-emitting applications, this theoretical study can help the experimental measurements.



2021 ◽  
Vol 23 (6) ◽  
pp. 3963-3973
Author(s):  
Jianxun Song ◽  
Hua Zheng ◽  
Minxia Liu ◽  
Geng Zhang ◽  
Dongxiong Ling ◽  
...  

The structural, electronic and optical properties of a new vdW heterostructure, C2N/g-ZnO, with an intrinsic type-II band alignment and a direct bandgap of 0.89 eV at the Γ point are extensively studied by DFT calculations.



RSC Advances ◽  
2021 ◽  
Vol 11 (14) ◽  
pp. 7779-7789 ◽  
Author(s):  
Asmat Ullah Khan ◽  
Rasheed Ahmad Khera ◽  
Naveed Anjum ◽  
Rao Aqil Shehzad ◽  
Saleem Iqbal ◽  
...  

DFT calculations are carried out to investigate nonlinear optical (NLO) properties of superhalogen (BCl4) and superalkali (NLi4) doped graphitic carbon nitride (GCN).





2017 ◽  
Vol 4 (6) ◽  
pp. 1024-1028 ◽  
Author(s):  
Rafael Sandoval-Torrientes ◽  
Joaquín Calbo ◽  
David García-Fresnadillo ◽  
José Santos ◽  
Enrique Ortí ◽  
...  

A series of new broad-absorbing rhodanine-fluorene dyes conjugated with triarylamines are presented. Spectroscopic and electrochemical characterizations, along with theoretical DFT calculations, unveil the electronic and optical properties of the dyes.





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