Surface Lattice Resonances for Multiresonant Second-Harmonic Generation
Vesala, Anna Sofia Amanda (2023)
Vesala, Anna Sofia Amanda
2023
Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2023-12-20
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202311089473
https://urn.fi/URN:NBN:fi:tuni-202311089473
Tiivistelmä
Nonlinear optics plays a critical role in various fields ranging from laser manufacturing to biomedical imaging. However, due to the inherently weak nonlinear response of materials, achieving substantial nonlinear responses often requires long interaction lengths and phase-matching techniques. This presents a significant challenge when attempting to implement nonlinear optics in small volumes. As a result, it is necessary to develop creative and specialized approaches to overcome the constraints imposed by weak nonlinear effects.
One way to address the low nonlinear conversion efficiency in small dimensions is through the use of artificial structures called metamaterials. Plasmonic metamaterials are of particular interest in nanoscale nonlinear optics because they can exhibit collective responses called surface lattice resonances (SLRs), which produce strong local fields that can enhance nonlinear effects. Unfortunately, the conversion efficiencies of plasmonic metamaterials are not yet as high as those of conventional nonlinear materials. To improve the performance of nonlinear optics at the nanoscale, researchers need to explore new metamaterial designs and techniques.
Research on nonlinear plasmonic metamaterials in recent years has mainly centered on materials showcasing a single SLR at either the pump or signal wavelength of a nonlinear process. Our work delves into enhancing the conversion efficiency of second harmonic generation (SHG) through the use of multiresonant metamaterials that are resonant at both the signal and pump wavelengths.
In this Thesis, a thorough investigation is conducted on two metasurfaces that demonstrate multiresonant behavior. These metasurfaces consist of a rectangular arrangement of aluminum nanoparticles on a glass substrate. We first measured angle-resolved optical transmission spectra to show the position and dispersion of the SLRs in our samples. This way, we are able to extract information about the pump wavelengths and incident angles that allow for multiresonant behavior. Next, we measured the variation in second-harmonic emission of the metasurfaces with respect to both pump wavelength and incident angle. By comparing the results obtained under multiresonant and non-multiresonant conditions, we can then understand how multiresonant metasurfaces affect the emission of SHG.
The results presented in this work provide strong evidence for the effectiveness of multiresonant metamaterials in nonlinear optics. Our preliminary linear experiments demonstrated that the SLRs in our samples had an angle-dependent behavior that was in excellent agreement with different modeling methods. Furthermore, the nonlinear experiments illustrated SHG that reached its maximum value when the sample exhibited multiresonant behavior. By tilting the samples, we were able to obtain a roughly 10-fold enhancement of SHG at multiple wavelength-angle combinations. This approach has provided a new way to tailor the properties of metamaterials and could lead to the development of flat, tunable nonlinear devices.
One way to address the low nonlinear conversion efficiency in small dimensions is through the use of artificial structures called metamaterials. Plasmonic metamaterials are of particular interest in nanoscale nonlinear optics because they can exhibit collective responses called surface lattice resonances (SLRs), which produce strong local fields that can enhance nonlinear effects. Unfortunately, the conversion efficiencies of plasmonic metamaterials are not yet as high as those of conventional nonlinear materials. To improve the performance of nonlinear optics at the nanoscale, researchers need to explore new metamaterial designs and techniques.
Research on nonlinear plasmonic metamaterials in recent years has mainly centered on materials showcasing a single SLR at either the pump or signal wavelength of a nonlinear process. Our work delves into enhancing the conversion efficiency of second harmonic generation (SHG) through the use of multiresonant metamaterials that are resonant at both the signal and pump wavelengths.
In this Thesis, a thorough investigation is conducted on two metasurfaces that demonstrate multiresonant behavior. These metasurfaces consist of a rectangular arrangement of aluminum nanoparticles on a glass substrate. We first measured angle-resolved optical transmission spectra to show the position and dispersion of the SLRs in our samples. This way, we are able to extract information about the pump wavelengths and incident angles that allow for multiresonant behavior. Next, we measured the variation in second-harmonic emission of the metasurfaces with respect to both pump wavelength and incident angle. By comparing the results obtained under multiresonant and non-multiresonant conditions, we can then understand how multiresonant metasurfaces affect the emission of SHG.
The results presented in this work provide strong evidence for the effectiveness of multiresonant metamaterials in nonlinear optics. Our preliminary linear experiments demonstrated that the SLRs in our samples had an angle-dependent behavior that was in excellent agreement with different modeling methods. Furthermore, the nonlinear experiments illustrated SHG that reached its maximum value when the sample exhibited multiresonant behavior. By tilting the samples, we were able to obtain a roughly 10-fold enhancement of SHG at multiple wavelength-angle combinations. This approach has provided a new way to tailor the properties of metamaterials and could lead to the development of flat, tunable nonlinear devices.