Patentes:

1. Apparatus for signaling and communicating, called PHOTOPHONE US235199 (1880): https://patents.google.com/patent/US235199A/en?oq=us+235199

2. Photophone transmitter US235496A (1880): https://patents.google.com/patent/US235496A/en

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Artigos sobre o assunto:

1. Thompson, S. The PhotoPhone. Nature 22, 481 (1880). https://doi.org/10.1038/022481a0

2. "The Photophone" in SA Supplements 10, 246supp, 176 (September 1880): doi:10.1038/scientificamerican09181880-3921esupp https://www.scientificamerican.com/article/the-photophone/

3. Bell, Alexander Graham. The Photophone. Science. 130-134. 11 Sep 1880. doi:10.1126/science.os-1.11.130. https://www.science.org/doi/abs/10.1126/science.os-1.11.130

4. W. S. Huxford and John R. Platt, "Survey of Near Infra-Red Communication Systems," J. Opt. Soc. Am. 38, 253-268 (1948) https://opg.optica.org/josa/abstract.cfm?uri=josa-38-3-253

5. The Photophone. La Science populaire (2 junho 1881): https://gallica.bnf.fr/ark:/12148/bpt6k5419232p

6. The Photophone. La Science populaire (14 outubro 1880): https://gallica.bnf.fr/ark:/12148/bpt6k5803023v

7. DL HUTT, KJ SNELL, e PA BÉLANGER, "PHOTOPHONE de Alexander Graham Bell" Optics & Photonics News 4 (6), 20-25 (1993) https://doi.org/10.1364/OPN.4.6.000020

8. Effect of Light on Selenium During the Passage of An Electric Current . Nature 7, 303 (1873). https://doi.org/10.1038/007303e0

9. DRAPER, H. Effect of Light on the Electric Conductivity of Selenium. Nature 7, 340 (1873). https://doi.org/10.1038/007340e0

10. SABINE, R. Action of Light on a Selenium (Galvanic) Element. Nature 17, 512–513 (1878). https://doi.org/10.1038/017512a0

11. Technical World. Wireless Telephony. March 1905: https://babel.hathitrust.org/cgi/pt?id=mdp.39015057148481&view=1up&seq=23&skin=2021

12. Plyler EK. The Scientific Contributions of William Weber Coblentz. Applied Spectroscopy. 1962;16(3):73-77. doi:10.1366/000370262774415903 https://doi.org/10.1366/000370262774415903

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Manuscritos e relatórios:

1. Drawing by Alexander Graham Bell and Charles Sumner Tainter, April 1880: https://www.loc.gov/resource/magbell.25200104/

2. Relatório Americano sobre o Fotofone Alemão de 80 mm capturado pelas forças aliadas no norte da África: https://pt.scribd.com/document/161571591/German-80mm-Photophone

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Sites:

1. Scientific American. The Photophone. https://www.scientificamerican.com/article/the-photophone/

2. O fotofone (telefone óptico): https://paleo-energetique.org/en/paleoinventions/the-photophone-optical-phone/

3. ThoughtCo. Bellis, Mary. "Alexander Graham Bell's Photophone Was An Invention Ahead of Its Time." https://www.thoughtco.com/alexander-graham-bells-photophone-1992318

4. Photophone de Graham Bell: http://www.fotonicaseculo21.com.br/2012/11/photophone-de-graham-bell.html

5. MOLIBDÊNIO E MOLIBDENITA: https://sistemas.anm.gov.br/publicacao/mostra_imagem.asp?IDBancoArquivoArquivo=8995

6. German 80mm Photophone - Carl Zeiss Lichtsprechgerät: http://chris-intel-corner.blogspot.com/2013/08/german-80mm-photophone-carl-zeiss.html

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Consultas realizadas na wikipedia, com muito bom senso é claro:

1. Photophone: https://en.wikipedia.org/wiki/Photophone

2. Willoughby Smith: https://en.wikipedia.org/wiki/Willoughby_Smith

3. William Weber Coblentz: https://pt.wikipedia.org/wiki/William_Coblentz

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A maioria das imagens e vídeos estão em domínio público, são autorais de Invenções na História ou são cortesia de:

Imagens (Ampliadas e restauradas utilizando Inteligência Artificial):

1. [Wikimedia Commons]. https://commons.wikimedia.org/wiki/File:Photophone_transmitter_4074931746_9f996df841_b.jpg

2. [T. Gilbert via Wikimedia Commons]. https://commons.wikimedia.org/wiki/File:Photophone_receiver_4074172975_288f2808f0_o.jpg

3. [Library of Congress] Graham Bell Family: http://loc.gov/pictures/resource/ppmsc.00856/

4. [Wikimedia Commons]. Photophony1: https://commons.wikimedia.org/wiki/File:Photophony1.jpg

5. [Wikimedia Commons]. Photophone2: https://commons.wikimedia.org/wiki/File:Photophone2.jpg

6. [Wikimedia Commons]. Alexander Graham Bell and Mabel Hubbard Gardiner Bell kissing: https://commons.wikimedia.org/wiki/File:Alexander_Graham_Bell_and_Mabel_Hubbard_Gardiner_Bell_kissing.gif

7. [Library of Congress]. Alexander Graham Bell in his later years: http://loc.gov/pictures/resource/ggbain.00882/

8. [Wikimedia Commons]. Willoughby Smith: https://commons.wikimedia.org/wiki/File:Willoughby_Smith.jpg

9. [Indianapolis Museum of Art at Newfields] Washington Street, Indianapolis at Dusk: https://artsandculture.google.com/asset/washington-street-indianapolis-at-dusk/hAF4O-eVDq2kNg

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Vídeos (Ampliados e restaurados utilizando Inteligência Artificial):

1. Video by Ron Lach from Pexels

2. Video by Ron Lach from Pexels

3. Video by Kelly L from Pexels

4. [Department of Defense via PublicResourceOrg]. MSTS ARCTIC OPERATIONS - 1950-1957: https://www.youtube.com/watch?v=H3fO3bBqf_Q

5. [Harvard Natural Sciences Lecture Demonstrations]. Infrared Camera: https://www.youtube.com/watch?v=baJtBDJDQDQ

6. Video by Adam Fackelman from Pexels

Entre tantas outras pesquisas que não lembrei de anotar aqui. Acredito que com estas referências, já consigo dar uma direcionada em quem tiver interesse de pesquisar sobre o tema.