{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T19:55:23Z","timestamp":1777406123462,"version":"3.51.4"},"reference-count":66,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2023,6,29]],"date-time":"2023-06-29T00:00:00Z","timestamp":1687996800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"FCT-Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UIDB\/50014\/2020"],"award-info":[{"award-number":["UIDB\/50014\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper presents a thorough analysis on the temperature dependence of the thermo-optic coefficient, dn\/dT, of four bulk annealed pure-silica glass samples (type I\u2014natural quartz: Infrasil 301; type II\u2014quartz crystal powder: Heraeus Homosil; type III\u2014synthetic vitreous silica: Corning 7980 and Suprasil 3001) from room temperature down to 0 K. The three\/four term temperature dependent Sellmeier equations and respective coefficients were considered, which results from fitting to the raw data obtained by Leviton et al. The thermo-optic coefficient was extrapolated down to zero Kelvin. We have obtained dn\/dT values ranging from 8.16 \u00d7 10\u22126 up to 8.53 \u00d7 10\u22126 for the four samples at 293 K and for a wavelength of 1.55 \u03bcm. For the Corning 7980 SiO2 glass, the thermo-optic coefficient decreases monotonically, from 8.74 \u00d7 10\u22126 down to 8.16 \u00d7 10\u22126, from the visible range up to the third telecommunication window, being almost constant above 1.3 \u03bcm. The Ghosh\u2019s model was revisited, and it was concluded that the thermal expansion coefficient only accounts for about 2% of the thermo-optic coefficient, and we have obtained an expression for the temperature behavior of the silica excitonic bandgap. Wemple\u2019s model was also analyzed where we have also considered the material dispersion in order to determine the coefficients and respective temperature dependences. The limitations of this model were also discussed.<\/jats:p>","DOI":"10.3390\/s23136023","type":"journal-article","created":{"date-parts":[[2023,6,30]],"date-time":"2023-06-30T01:14:12Z","timestamp":1688087652000},"page":"6023","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":65,"title":["Temperature Dependence of the Thermo-Optic Coefficient of SiO2 Glass"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8807-4108","authenticated-orcid":false,"given":"Gaspar","family":"Rego","sequence":"first","affiliation":[{"name":"ADiT-LAB, Instituto Polit\u00e9cnico de Viana do Castelo, Rua Escola Industrial e Comercial Nun\u2019\u00c1lvares, 4900-347 Viana do Castelo, Portugal"},{"name":"Center for Applied Photonics, INESC TEC, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Ivanov, O.V., Caldas, P., and Rego, G. 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