Spontaneous and induced absorption in amorphous Ta2O5 dielectric thin films

A. S. Markosyan; R. Route; M. M. Fejer; D. Patel; C. S. Menoni

doi:10.1117/12.899217

6 December 2011 Spontaneous and induced absorption in amorphous Ta₂O₅ dielectric thin films

A. S. Markosyan, R. Route, M. M. Fejer, D. Patel, C. S. Menoni

Proceedings Volume 8190, Laser-Induced Damage in Optical Materials: 2011; 81900F (2011) https://doi.org/10.1117/12.899217
Event: SPIE Laser Damage, 2011, Boulder, Colorado, United States

Abstract

Tantalum pentoxide (Ta₂O₅) is the high index material most commonly used in optical coatings for high average-power lasers since high density sputtered oxide films with absorption losses at mid-infrared wavelengths of less than 1 ppm can be obtained. We have chosen this 'model' oxide to investigate the spontaneous and optically induced absorption at λ = 1064 nm by photothermal common-path interferometric (PCI) technique. This technique is capable of detecting sub-ppm levels of optical absorption and its changes at a given wavelength when a second beam is also incident on the thin film oxide sample. In this work dual beam experiments are implemented to assess changes in the optical absorption at λ = 1064 nm Ta2O5 thin films deposited on fused silica with accompanying electromagnetic radiation with wavelengths ranging from 266 nm to 780 nm. The accompanying radiation was found to have a substantial impact on the optical absorption at 1064 nm. The effect is associated with various electron traps existing in the forbidden gap and depends essentially on the film's preparation conditions. The substantially greater effect observed in the case of 266 nm is suggested to be the result of additional excitations from the valence band involved in the process since the photon energy of 266 nm radiation is higher than the forbidden gap.

Citation Download Citation

A. S. Markosyan, R. Route, M. M. Fejer, D. Patel, and C. S. Menoni "Spontaneous and induced absorption in amorphous Ta₂O₅ dielectric thin films", Proc. SPIE 8190, Laser-Induced Damage in Optical Materials: 2011, 81900F (6 December 2011); https://doi.org/10.1117/12.899217

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