Discriminating the role of sample length in thermal lensing of solids

Thermal lens (TL) is a key effect in laser engineering and photothermal spectroscopy. The amplitude of the TL signal or its dioptric power is proportional to the optical path difference (OPD) between the center and border of the beam, which is proportional to the heat power (Ph). Due to thermally in...

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Bibliographic Details
Published in:Optics letters 2014-07, Vol.39 (13), p.4013-4016
Main Authors: Rodrigues, T P, Zanuto, V S, Cruz, R A, Catunda, T, Baesso, M L, Astrath, N G C, Malacarne, L C
Format: Article
Language:English
Subjects:
Amplitudes
Beams (radiation)
Borders
Bulging
Lasers
Optical paths
Spectroscopy
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Summary:Thermal lens (TL) is a key effect in laser engineering and photothermal spectroscopy. The amplitude of the TL signal or its dioptric power is proportional to the optical path difference (OPD) between the center and border of the beam, which is proportional to the heat power (Ph). Due to thermally induced mechanical stress and bulging of end faces of the sample, OPD depends critically on the geometry of the sample. In this investigation, TL measurements were performed as a function of the sample length keeping the same Ph. It is experimentally demonstrated that for materials with positive ∂n/∂T OPD increases typically 30 to 50% with the decrease of sample length (from long rod to thin-disk geometry). For materials with negative ∂n/∂T, this variation is much larger due to the cancelation of the different contributions to OPD with opposite signs. Furthermore, the experimental investigation presented here validates a recently proposed unified theoretical description of the TL effect.
ISSN:0146-9592
1539-4794
DOI:10.1364/OL.39.004013