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Photothermal Lensing in Mid-Infrared Materials

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Date Issued:
2017
Abstract/Description:
A thorough understanding of laser-materials interactions is crucial when designing and building optical systems. An ideal test method would probe both the thermal and optical properties simultaneously for materials under large optical loads where detrimental thermal effects emerge. An interesting class of materials are those used for infrared wavelengths due to their wide spectral transmission windows and large optical nonlinearities. Since coherent sources spanning the mid-wave and long-wave infrared wavelength regions have only become widely available in the past decade, data regarding their thermal and optical responses is lacking in literature.Photothermal Lensing (PTL) technique is an attractive method for characterizing the optical and thermal properties of mid-infrared materials as it is nondestructive and can be implemented using both continuous wave and pulsed irradiation. Analogous to the well-known Z-scan, the PTL technique involves creating a thermal lens within a material and subsequently measuring this distortion with a probe beam. By translating the sample through the focus of the pump laser, information can be obtained regarding the nonlinear absorption, thermal diffusivity and thermo-optic coefficient. This thesis evaluates the effectiveness and scope of the PTL method using numerical simulations of low loss infrared materials. Specifically, the response of silicon, germanium, and As2Se3 glass is explored. The 2 ?m pump and 4.55 ?m probe beam geometries are optimized in order to minimize experimental error. Methodologies for estimating the thermal diffusivity, nonlinear absorption coefficient and thermo-optic coefficient directly from the experimentally measured PTL signal are presented. Finally, the ability to measure the nonlinear absorption coefficient without the need for high-energy or ultrashort optical pulses is demonstrated.
Title: Photothermal Lensing in Mid-Infrared Materials.
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Name(s): Cook, Justin, Author
Richardson, Martin, Committee Chair
Shah, Lawrence, Committee Member
Gaume, Romain, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2017
Publisher: University of Central Florida
Language(s): English
Abstract/Description: A thorough understanding of laser-materials interactions is crucial when designing and building optical systems. An ideal test method would probe both the thermal and optical properties simultaneously for materials under large optical loads where detrimental thermal effects emerge. An interesting class of materials are those used for infrared wavelengths due to their wide spectral transmission windows and large optical nonlinearities. Since coherent sources spanning the mid-wave and long-wave infrared wavelength regions have only become widely available in the past decade, data regarding their thermal and optical responses is lacking in literature.Photothermal Lensing (PTL) technique is an attractive method for characterizing the optical and thermal properties of mid-infrared materials as it is nondestructive and can be implemented using both continuous wave and pulsed irradiation. Analogous to the well-known Z-scan, the PTL technique involves creating a thermal lens within a material and subsequently measuring this distortion with a probe beam. By translating the sample through the focus of the pump laser, information can be obtained regarding the nonlinear absorption, thermal diffusivity and thermo-optic coefficient. This thesis evaluates the effectiveness and scope of the PTL method using numerical simulations of low loss infrared materials. Specifically, the response of silicon, germanium, and As2Se3 glass is explored. The 2 ?m pump and 4.55 ?m probe beam geometries are optimized in order to minimize experimental error. Methodologies for estimating the thermal diffusivity, nonlinear absorption coefficient and thermo-optic coefficient directly from the experimentally measured PTL signal are presented. Finally, the ability to measure the nonlinear absorption coefficient without the need for high-energy or ultrashort optical pulses is demonstrated.
Identifier: CFE0006730 (IID), ucf:51885 (fedora)
Note(s): 2017-08-01
M.S.
Optics and Photonics, Optics and Photonics
Masters
This record was generated from author submitted information.
Subject(s): Mid-infrared -- photothermal lensing -- thermal -- optical -- laser
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0006730
Restrictions on Access: campus 2022-08-15
Host Institution: UCF

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