Browsing by Author "Dogan, Anil"

Now showing 1 - 3 of 3

Citation - WoS: 11
Citation - Scopus: 12
Excitation Wavelength Dependent Nonlinear Absorption Mechanisms and Optical Limiting Properties of Bi12sio20 Single Crystal
(Elsevier, 2023) Dogan, Anil; Karatay, Ahmet; Isik, Mehmet; Pepe, Yasemin; Gasanly, Nizami; Elmali, Ayhan; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
Nonlinear absorption mechanisms (NA), excitation wavelength dependence, and defect states of Bi12SiO20 (BSO) single crystal were investigated. The band gap and Urbach energies were found to be 2.51 and 0.4 eV from the absorption spectra. To evaluate the effect of excitation energy on the NA mechanism of the BSO single crystal, open aperture Z-scan experiment with 4 ns laser pulse at 532 and 1064 nm wavelengths with different intensities was performed. Obtained data were analyzed with a theoretical model considering the contributions of one photon absorption (OPA), two photon absorption (TPA) and free carrier absorption (FCA) to NA. The results indicated that the NA behavior decreased with increasing of the pump intensity as the defect states at around 2.32 eV by OPA at 532 nm, and TPA at 1064 nm excitations. The dominant NA mechanisms are OPA and sequential TPA at 532 nm as compared to the 1064 nm. A higher NA coefficient was obtained at 532 nm as compared to 1064 nm excitation. This observation was attributed to higher contribution of OPA at 532 nm even at lower input intensities compared to TPA contribution at 1064 nm. Onset optical limiting thresholds were found as 0.34 and 0.68 mJ/cm2 for 532 and 1064 nm input beams, respectively. In the light of the results, the BSO single crystal may be used as a saturable absorber or an optical limiter at convenient input intensity by effectively adjusting defect states and excitation wavelength.
Citation - WoS: 6
Citation - Scopus: 6
Revealing Photoluminescence and Nonlinear Optical Absorption Characteristics of Pbmo_0.75w_{0.25< Single Crystal for Optical Limiting Applications}
(Iop Publishing Ltd, 2024) Dogan, Anil; Karatay, Ahmet; Isik, Mehmet; Yildiz, Elif Akhuseyin; Gasanly, Nizami; Elmali, Ayhan; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
Nonlinear absorption properties of PbMo0.75W0.25O4 single crystal fabricated by the Czochralski method were studied. The band gap energy of the crystal was determined as 3.12 eV. Urbach energy which represents the defect states inside the band gap was found to be 0.106 eV. PbMo0.75W0.25O4 single crystal has a broad photoluminescence emission band between 376 and 700 nm, with the highest emission intensity occurring at 486 nm and the lowest intensity peak at 547 nm, depending on the defect states. Femtosecond transient absorption measurements reveal that the lifetime of localized defect states is found to be higher than the 4 ns pulse duration. Open aperture (OA) Z-scan results demonstrate that the PbMo0.75W0.25O4 single crystal exhibits nonlinear absorption (NA) that includes two-photon absorption (TPA) as the dominant mechanism at the 532 nm excitations corresponding to 2.32 eV energy. NA coefficient (beta(eff)) increased from 7.24 x 10(-10) m W-1 to 8.81 x 10(-10) m W-1 with increasing pump intensity. At higher intensities beta(eff) tends to decrease with intensity increase. This decrease is an indication that saturable absorption (SA) occurred along with the TPA, called saturation of TPA. The lifetime of the defect states was measured by femtosecond transient absorption spectroscopy. Saturable absorption behavior was observed due to the long lifetime of the localized defect states. Closed aperture (CA) Z-scan trace shows the sign of a nonlinear refractive index. The optical limiting threshold of PbMo0.75W0.25O4 single crystal at the lowest intensity was determined as 3.45 mJ/cm(2). Results show that the PbMo0.75W0.25O4 single crystal can be a suitable semiconductor material for optical limiting applications in the visible region.
Citation - WoS: 20
Citation - Scopus: 19
Revealing the Effects of Defect States on the Nonlinear Absorption Properties of the Tlinsse and Tl₂in_{2< Crystals in Near-Infrared Optical Limiting Applications}
(Amer Chemical Soc, 2024) Dogan, Anil; Karatay, Ahmet; Isik, Mehmet; Yildiz, Elif Akhuseyin; Gasanly, Nizami Mamed; Elmali, Ayhan; Department of Electrical & Electronics Engineering; 15. Graduate School of Natural and Applied Sciences; 01. Atılım University
The present study represents the effect of defect states on the nonlinear absorption and optical limiting performances of TlInSSe and Tl2In2S3Se single crystals with near-infrared excitations. The band gap energies were 2.2 and 2.22 eV, and the Urbach energies were 0.049 and 0.034 eV for TlInSSe and Tl2In2S3Se, respectively. The trapping time of localized defect states was found to be 8 ns by femtosecond transient absorption measurements. The analysis of open-aperture Z-scan data depends on two different fitting models to determine the effect of defect states on the nonlinear absorption (NA) properties of the studied crystals. Model 1 only considers two-photon absorption (TPA), while model 2 includes one-photon absorption (OPA), TPA, and free carrier absorption (FCA). The NA coefficients (ss(eff)) obtained from model 2 are higher than the values (ss) obtained from model 1 at the same intensities, revealing that defect states contribute to NA through OPA. The optical limiting properties of the TlInSSe and Tl2In2S3Se crystals were examined under 1064 nm wavelength excitation. The limiting thresholds were found to be 1.16 and 0.27 mJ/cm(2) at 29.8 GW/m(2) and 99.5 GW/m(2) input intensities, respectively. The results show that TlInSSe and Tl2In2S3Se crystals have promising potential for near-infrared optical limiting applications.