Effect of the band gap and the defect states present within band gap on the non-linear optical absorption behaviour of yttrium aluminium iron garnets

Kumar, A and Kumar, R and Verma, N and Anupama, AV and Choudhary, HK and Philip, R and Sahoo, B (2020) Effect of the band gap and the defect states present within band gap on the non-linear optical absorption behaviour of yttrium aluminium iron garnets. In: Optical Materials, 108 .

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Abstract

The effect of variation of band gap and electronic defect energy levels within the band gap on non-linear optical absorption of 532 nm (green) laser light by coral-like yttrium aluminium-iron garnet (YAIG, Y3Al5-xFexO12) ceramics prepared by solution combustion route is investigated using Z-scan technique. Our yttrium aluminium garnet (YAG) sample with band gap of � ~ 6.5 eV, is transparent to visible light. The band gap of YAG was tuned by substituting Fe at the aluminium site and consequently, the surface defects in YAG were also modified. The defects in the YAIG samples introduce electronic defect states within the band gap. We observed that the intensity of the non-linear absorption (NLA) signal increases with increase in the amount of iron content. We assigned this enhancement of NLA signal to: (1) the decrease in the band gap from � ~ 6.5 eV for YAG to ~ 2.6 eV for yttrium iron garnet (YIG) facilitating two photon absorption (2 PA) process rather than three photon absorption (3 PA), and (2) the increase in excited state absorption (ESA) due to the spread of the defect energy states into the band gap region. As the band gap gets closer to the photon energy of the laser, the non-linear optical absorption is enhanced due to ESA, in combination with the occurrence of the relatively stronger 2 PA process rather than the very weak 3 PA process. Our results demonstrate a method to tune the NLA performance of YAG through iron substitution at the Al sites and provide a better understanding of the non-linear absorption behaviour of YAIG ceramics for their application in optical limiting devices such as laser shields. © 2020 Elsevier B.V.

Item Type:	Journal Article
Publication:	Optical Materials
Publisher:	Elsevier B.V.
Additional Information:	Copy right for this article belongs to Elsevier B.V.
Keywords:	Aluminum compounds; Excited states; Iron; Iron compounds; Laser pulses; Light absorption; Photons; Surface defects; Two photon processes; Yttrium aluminum garnet; Yttrium iron garnet, Excited state absorption; Non-linear optical; Nonlinear absorptions; Optical limiting devices; Solution combustion; Three photon absorption; Two photon absorption; Yttrium aluminium garnet, Energy gap
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	11 Nov 2020 06:58
Last Modified:	11 Nov 2020 06:58
URI:	http://eprints.iisc.ac.in/id/eprint/66139

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