Photonics / Fotonik

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

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Citation - WoS: 4
Citation - Scopus: 4
Electromagnetically Induced Transparency and Absorption Cross-Over With a Four-Level Rydberg System
(IOP Publishing, 2022-07) Oyun, Yağız; Çakır, Özgür; Sevinçli, Sevilay; 04.04. Department of Photonics; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
Electromagnetically induced transparency (EIT) and absorption (EIA) are quantum coherence phenomena which result from the interference of excitation pathways. Combining these with Rydberg atoms have opened up many possibilities for various applications. We introduce a theoretical model to study Rydberg-EIT and Rydberg-EIA effects in cold Cs and Rb atomic ensembles in a four-level ladder type scheme taking into account van der Waals type interactions between the atoms. The proposed many-body method for analysis of such systems involves a self-consistent mean field approach and it produces results which display a very good agreement with recent experiments. Our calculations also successfully demonstrate experimentally observed EIT-EIA cross-over in the Rb case. Being able to simulate the interaction effects in such systems has significant importance, especially for controlling the optical response of these.
Citation - WoS: 9
Citation - Scopus: 11
White Led Light Production Using Dibromoperylene Derivatives in Down Conversion of Energy
(Canadian Science Publishing, 2018) Aksoy, Erkan; Demir, Nuriye; Varlıklı, Canan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
Perylene derivatives of N,N′-bis(2,6-diisopropylphenyl)-1,6(7)-dibromoperylene-3,4,9,10-tetracarboxylic diimide (DBrPDI) and 1,7-dibromo perylene-3,4,9,10-tetracarboxylic acid butyl ester (DBrPTE) were synthesized, and their structural and optical characterizations were explored. Both DBrPDI and DBrPTE, which were utilized as wavelength converters on a GaN/InGaN based blue LED, were singlet sensitizers and had molar absorptivity constants around 104 Lmol-1cm-1. The blue LED that was used had Commission internationale de l'eclairage (CIE) coordinates of x, y = 0.13, 0.06; power and luminous efficiencies of 2.7 lm/W and 6.6 cd/A @5 mA, respectively. Because the fluorescence quantum yield of DBrPDI was much higher than that of DBrPTE, a meaningful white light efficiency was obtained with the diimide derivative. The use of DBrPDI resulted in white light with CIE coordinates of x, y = 0.34, 0.29 and luminous efficiency of 6.35 cd/A @5 mA, respectively. Using DBrPDI in a resin matrix resulted in more than three orders of magnitude increase in the luminous efficiency value (23.0 cd/A @5 mA) while the CIE coordinates remained the same. Whenever the applied current reached 20 mA, a CRI value of Ra = 90 was obtained.

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