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)

Abstract

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
• Status: Published
• Refereed: Yes
• 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: 0003-6935
• ISSN (Online): 2155-3165