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arXiv 1005.4490physics.optics
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利用光热自相位调制测量小折射率

Measuring small absorptions exploiting photo-thermal self-phase modulation

Nico Lastzka, Jessica Steinlechner, Sebastian Steinlechner, Roman Schnabel

摘要:

本文提出了一种测量微小光吸收系数的方法。该方法利用了腔艾里峰的变形,如果腔包含具有非零热折射系数dn/dT或非零膨胀系数ath的吸收材料,则会发生这种变形。光吸收导致局部温度变化和强度相关的相移,即光热自相位调制。的吸收系数来自时间分辨的测量与数值时域模拟应用马尔可夫链蒙特卡罗(MCMC)算法的比较。我们将我们的方法应用于掺杂7mol%氧化镁(MgO)的锂离子电池(LN)的吸收系数,并得出α LN =(5.9 +/- 0.9)*10^-4/cm。我们的方法也适用于具有低得多的吸收系数的材料。根据我们的模型,我们估计在腔精细度值为10 ^4量级时,可以测量到低至10^-8 /cm的吸收系数。

英文摘要:

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 non-zero thermo-refractive coefficient dn/dT or a non-zero expansion coefficient ath . Light absorption leads to a local temperature change and to an intensity-dependent phase shift, i.e. to a photo-thermal 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 (MCMC) algorithm. We apply our method to the absorption coefficient of lithium niobate (LN) doped with 7mol% magnesium oxide (MgO) and derive a value of alphaLN = (5.9 +/- 0.9) *10^-4/cm . Our method should also apply to materials with much lower absorption coefficients. Based on our modelling we estimate that with cavity finesse values of the order 10^4, absorption coefficients of as low as 10^-8 /cm can be measured.

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