All-Optical Beam Deflection Method For Simultaneous Thermal Conductivity And Thermo-Optic Coefficient (Dn/Dt) Measurements

Abstract

This work describes an all-optical beam deflection method to simultaneously measure the thermal conductivity (Λ) and thermo-optic coefficient (d n / d T) of materials that are absorbing at λ = 10.6 μm and are transparent to semi-transparent at λ = 632.8 nm. The technique is based on the principle of measuring the beam deflection of a probe beam (632.8 nm) in the frequency-domain due to a spatially and temporally varying index gradient that is thermally induced by 50:50 split pump beam from a CO2 laser (10.6 μm). The technique and analysis methods are validated with measurements of 10 different optical materials having Λ and dn/dT properties ranging between 0.7 W/m K ≲ Λ ≲ 33.5 W/m K and -12 × 10-6 K-1 ≲ dn/dT ≲ 14 × 10-6 K-1, respectively. The described beam deflection technique is highly related to other well-established, all-optical materials characterization methods, namely, thermal lensing and photothermal deflection spectroscopy. Likewise, due to its all-optical, pump-probe nature, it is applicable to materials characterization in extreme environments with minimal errors due to black-body radiation. In addition, the measurement principle can be extended over a broad range of electromagnetic wavelengths (e.g., ultraviolet to THz) provided the required sources, detectors, and focusing elements are available.

Publication Date

5-7-2016

Publication Title

Journal of Applied Physics

Volume

119

Issue

17

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1063/1.4948429

Socpus ID

84973546889 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84973546889

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