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- Thermal and optical properties of the femtosecond-laser-structured and stress-induced birefringent regions in sapphire
- Morikawa, Junko; Orie, Akihiro; Hashimoto, Toshimasa; Juodkazis, Saulius
- Temperature diffusivity of laser micro-structured regions in sapphire is determined by a temperature wave method with a lateral resolution reduced to ∼10 μm using a directly sputtered micro-sensor and heater. A record high reduction of the temperature diffusivity of sapphire by 12% from its (1.26±0.02) × 10-5m2/s in-bulk value inside the femtosecond laser-structured volumes is determined; in a BK7 glass (∼4.8×10-7 m2/s), a 2% decrease of the thermal diffusivity has been observed. Origin of the reduction is consistent with disorder and scattering of phonons around the laser photo-modified micro-volumes. The stress-induced birefringence is directly measured by polariscopy together with its radial distribution, and azimuthal orientation of the polarization ellipsis near the laser structured regions in sapphire. The maximum birefringence of Δn ≃ 1×10-3 is achieved without crack formation and corresponds to a local stress of ∼1.3 GPa. The stress (and birefringence) decay radially with a single-exponential constant of τR = 24 μm while the azimuthal orientation of the polarization ellipsis is spiraling around the laser structured volume. Such structures are promising in waveguiding and lasing applications of optical vortices where spatial control of birefringence and optical activity are required.
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Engineering and Industrial Sciences. Centre for Micro-Photonics
- Optics Express, Vol. 18, no. 8 (Apr 2010), pp. 8300-8310
- Publication year
- Optical Society of America
- Publisher URL
- Copyright © 2010 Optical Society of America. Published version of the paper reproduced here in accordance with the copyright policy of the publisher. This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.18.008300. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.