Talbot self-imaging with whispering gallery modes of multimode fibers
Eriksson, Matias (2023)
2023
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-08-03
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202307047048
https://urn.fi/URN:NBN:fi:tuni-202307047048
Tiivistelmä
Talbot self-imaging in cylindrical systems can be used to realize compact higher-order beamsplitters, which are interesting for applications in fundamental research, optical telecommunications and quantum information science. In contrast to conventional beamsplitter implementations, the cylindrical Talbot effect beamsplitter has the advantage of becoming more compact for higher-order realizations while always requiring only a single optical component, making the effect highly scalable. Until now, all realizations of the cylindrical Talbot effect have relied on the intermodal interference in ring-core fibers, which are specialized optical fibers with limited availability.
In this thesis, a novel realization of the cylindrical Talbot effect using whispering gallery modes of standard step-index profile multimode fibers is demonstrated. Whispering gallery modes, named after the famous acoustic whispering galleries, are high orbital angular momentum (OAM) eigenmodes of waves bound to concave cavities, whose intensity distributions are closely confined to the vicinity of the concave interface. The intermodal interference of these modes, much like the eigenmodes of a ring-core fiber, gives rise to the distinct Talbot interference pattern known as the Talbot carpet. This realization of the cylindrical Talbot effect has the advantage of relying only on a single, short piece of standard step-index multimode fiber, which is already mass-produced and easily available, unlike the ring-core fiber.
The thesis begins with the necessary theoretical background to understand the whispering gallery Talbot effect and a brief overview of the proposed applications. In continuation, by simulating the propagation of light in multimode fibers the emergence of full and fractional self-images of the input field are observed, and the efficiency of interfacing the effect with single-mode fibers as input and output channels is estimated. Finally, the first experimental realizations of the whispering gallery Talbot effect, used to split a single beam into 9 and 30 output beams, are shown. The qualities of the realized whispering gallery Talbot beamsplitters with single-mode fibers as input and output channels are analyzed, and total power efficiencies are measured at 34.18 ± 0.29 % and 44.04 ± 0.15 % for the 1-to-9 and 1-to-30 whispering gallery Talbot beamsplitters, respectively.
In this thesis, a novel realization of the cylindrical Talbot effect using whispering gallery modes of standard step-index profile multimode fibers is demonstrated. Whispering gallery modes, named after the famous acoustic whispering galleries, are high orbital angular momentum (OAM) eigenmodes of waves bound to concave cavities, whose intensity distributions are closely confined to the vicinity of the concave interface. The intermodal interference of these modes, much like the eigenmodes of a ring-core fiber, gives rise to the distinct Talbot interference pattern known as the Talbot carpet. This realization of the cylindrical Talbot effect has the advantage of relying only on a single, short piece of standard step-index multimode fiber, which is already mass-produced and easily available, unlike the ring-core fiber.
The thesis begins with the necessary theoretical background to understand the whispering gallery Talbot effect and a brief overview of the proposed applications. In continuation, by simulating the propagation of light in multimode fibers the emergence of full and fractional self-images of the input field are observed, and the efficiency of interfacing the effect with single-mode fibers as input and output channels is estimated. Finally, the first experimental realizations of the whispering gallery Talbot effect, used to split a single beam into 9 and 30 output beams, are shown. The qualities of the realized whispering gallery Talbot beamsplitters with single-mode fibers as input and output channels are analyzed, and total power efficiencies are measured at 34.18 ± 0.29 % and 44.04 ± 0.15 % for the 1-to-9 and 1-to-30 whispering gallery Talbot beamsplitters, respectively.