Simultaneous measurements of the thermal optical and linear thermal expansion coefficients of a thin film etalon from the reflection spectra of a super-luminescent diode

Incı, Mehmet Nacı

doi:10.1088/0022-3727/37/22/015

Cited by 6 publications

(4 citation statements)

References 9 publications

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“…In some cases, there has even been some controversy regarding some measurements. In the case of the CTE, measurements have ranged from −4.4 × 10 −5 K −1 for ion-assisted e-beam sputtered tantala [8], to 2.4×10 −6 K −1 for IBS tantala [9]. Measurements made by Braginsky and Samoilenko [10] suggested that the CTE of tantala was roughly (5 ± 1) × 10 −6 K −1 .…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Young’s modulus and thermal expansion of amorphous titania-doped tantala films

et al. 2014

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The current generation of advanced gravitational wave detectors utilize titania-doped tantala/silica multilayer stacks for their mirror coatings. The properties of the low-refractive-index silica are well known; however, in the absence of detailed direct measurements, the material parameters of Young's modulus and coefficient of thermal expansion (CTE) of the high refractive index material, titania-doped tantala, have been assumed to be equal to values measured for pure tantala coatings. In order to ascertain the true values necessary for thermal noise calculations, we have undertaken measurements of Young's modulus and CTE through the use of nanoindentation and thermal-bending measurements. The measurements were designed to assess the effects of titania-doping concentration and postdeposition heat-treatment on the measured values in order to evaluate the possibility of optimizing material parameters to further improve thermal noise in the detector. Young's modulus measurements on pure tantala and 25% and 55% titania-doped tantala show a wide range of values, from 132 to 177 GPa, which are dependent on both titania concentration and heat-treatment. Measurements of CTE give values of 3.9 0.1 × 10 −6 K −1 and 4.9 0.3 × 10 −6 K −1 for 25% and 55% titania-doped tantala, respectively, without dependence on post-deposition heat-treatment.

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Section: Introductionmentioning

confidence: 99%

Investigation of the Young’s modulus and thermal expansion of amorphous titania-doped tantala films

et al. 2014

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“…Previous measurements of the thermorefractive properties of Ta 2 O 5 have produced results for β that vary by about two orders of magnitude. The published values of β include 2.3 × 10 -6 [30], 4.76 × 10 -5 [31], and 1.21 × 10 -4 [32]. Differences in deposition methods or annealing conditions may result in differing values for β but some of this variation may be due to temperatureinduced coating stress.…”

Section: Contribution To β From Temperature-induced Coating Stressmentioning

confidence: 99%

Three methods for characterizing thermo-optic noise in optical cavities

Gretarsson

2018

Phys. Rev. D

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Thermo-optic noise is likely to be the dominant noise source in next generation ultra-low noise optical cavities. We developed three measurement and analysis methods allowing us to estimate the level of coating thermo-optic noise in optical cavities, including interferometric gravitational wave detectors. We measured the shift in the broadband transmission spectra as a function of temperature for single-layer, high index coatings in order to find the thermo-optic coefficient, βH , of a coating while assuming the thermal expansion coefficient, αH . Our value for βH could then be used to calculate the thermo-optic noise in any high-finesse optical cavity using coatings with the same high index layer material. We also measured the spectra as a function of temperature of a multi-layer, high-reflective coating where the material composition of the layers was similar to the coatings installed in Advanced LIGO. This method has the advantage of allowing us to calculate thermo-optic noise directly; αH and βH don't need to be known separately although we do need to know the value of the overall coating thermal expansion coefficient. Finally, we used lasers of different wavelengths to measure transmission changes on the band edges of a multi-layer high reflective coating. This gave measurements with high statistical precision but potentially lower systematic accuracy. To address systematic accuracy concerns, we used a constrained Monte-Carlo application of the theory of multilayer coating transmission. d dλ 1 L dL dT= -1.5 × 10 −8 nm −1 K −1 intersecting λ = 500 nm at 1.34×10 −5 K −1 . Extrapolating the trend gives α + β/n = 5 × 10 −6 at λ = 1064 nm.

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“…Values of refractive index and extinction coefficient may vary depending on the fabrication technique used. Optical characterization (Inci, 2004) of the reflection response of a Ta 2 O 5 film deposited by electron beam evaporation on the cleaved end-face of a single-mode optical fiber made it possible to measure a TOC of about 1.21 × 10 24 K 21 around 1550 nm.…”

Section: Tantalum Pentoxide (Ta 2 O 5 )mentioning

confidence: 99%