Measuring small absorptions by exploiting photothermal self-phase modulation

Lastzka, N., Steinlechner, J., Steinlechner, S. and Schnabel, R. (2010) Measuring small absorptions by exploiting photothermal self-phase modulation. Applied Optics, 49(28), pp. 5391-5398. (doi: 10.1364/AO.49.005391)

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We present a method for the measurement of small optical absorption coefficients. The method exploits the deformation of cavity Airy peaks that occur if the cavity contains an absorbing material with a nonzero thermorefractive coefficient dn=dT or a nonzero expansion coefficient ath. Light absorption leads to a local temperature change and to an intensity-dependent phase shift, i.e., to a photothermal self-phase modulation. The absorption coefficient is derived from a comparison of time-resolved measurements with a numerical time-domain simulation applying a Markov-chain Monte Carlo algorithm. We apply our method to the absorption coefficient of lithium niobate doped with 7 mol: % magnesium oxide and derive a value of α = (5.9 +/- 0.9) x 10^(-4)/cm. Our method should also apply to materials with much lower absorption coefficients. Based on our modeling, we estimate that, with cavity finesse values of the order of 10^4, absorption coefficients of as low as 10^(−8)/cm can be measured.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Steinlechner, Dr Jessica and Steinlechner, Dr Sebastian
Authors: Lastzka, N., Steinlechner, J., Steinlechner, S., and Schnabel, R.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Applied Optics
Publisher:Optical Society of America
ISSN (Online):2155-3165

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