Browsing by Author "Semmlinger, Michael"

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    Harmonic light-generating metasurface
    (2022-11-15) Semmlinger, Michael; Tseng, Ming-lun; Yang, Jian; Zhang, Ming; Tsai, Din Ping; Dong, Liangliang; Ahmadivand, Arash; Nordlander, Peter; Halas, Naomi Jean; Rice University; William Marsh Rice University; Academia Sinica; United States Patent and Trademark Office
    A harmonic light-generating metasurface includes a base substrate and a plurality of structures, that include nonlinear material, that are disposed in a pattern on a surface of the base substrate. Each structure of the plurality of structures individually supports a magnetic dipole mode. An electromagnetic field enhancement of the magnetic dipole mode induces generation of a harmonic signal by the plurality of structures. Alternatively, a harmonic light-generating metasurface, includes a base substrate, a supporting substrate that includes a nonlinear material, and a plurality of paired structures disposed in a pattern on a surface of the supporting substrate. Each paired structure, of the plurality of paired structures, collectively supports a toroidal dipole mode. An electromagnetic field enhancement of the toroidal dipole mode penetrates the supporting substrate to induce generation of a harmonic signal by the supporting substrate.
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    Metamaterials for Deep and Vacuum Ultraviolet Light Generation and Manipulation
    (2020-12-04) Semmlinger, Michael; Halas, Naomi J
    Deep (DUV, 200 – 280 nm) and vacuum ultraviolet (VUV, 100 – 200 nm) light has many important applications ranging from photodissociation to lithography. However, the generation and manipulation of electromagnetic radiation in this wavelength regime remains challenging. Popular sources like excimer lasers are bulky and many traditional optical materials suffer from strong absorption in this short wavelength regime. In this thesis, I experimentally demonstrate how nonlinear metasurfaces provide an alternative approach to simultaneously generate and control such radiation. Metasurfaces are composed of highly engineered subwavelength nanostructures, called meta-atoms, that give them the exceptional ability to manipulate the amplitude, phase, and polarization of the light they are interacting with. The ability of meta-atoms to strongly confine the local electric field, enables enhancement of nonlinear processes like second (SHG) and third harmonic generation (THG). This allows the conversion of longer wavelength radiation to the DUV and VUV regime via a compact device. In addition, unlike nonlinear crystals, nonlinear metasurfaces do not require phase matching due to their subwavelength interaction length. Local phase control via meta-atoms makes it possible to manipulate the output wavefront of a metasurface. In this way, nonlinear metasurfaces can be used not just for the generation but also the manipulation of DUV and VUV light. This thesis consists of three main parts. The first part presents a plasmonic metasurface consisting of gold nanostructures on top of an indium tin oxide (ITO) thin film that were designed to exhibit a toroidal resonance at the pump wavelength of 785 nm. The nanostructures can generate an electric field enhancement pattern that reaches into the underlying ITO layer, where it enhances THG to generate DUV light at 262 nm. The nonlinear signal from the toroidal metasurface is about five times larger than that of a dimer metasurface fabricated for comparison with the same amount of gold per unit area and underlying ITO layer. The second part presents an all-dielectric metasurface consisting of titanium dioxide (TiO2) nanostructures designed to facilitate an anapole resonance around the pump wavelength of 555 nm. An anapole resonance is caused by an interference between an electric and a toroidal dipole mode giving rise to exceptional electric field enhancement. Here, this is utilized to enhance THG and produce VUV light at 185 nm. Notably, the observed nonlinear signal from the nonlinear metasurface is around 180 times stronger compared to an unpatterned TiO2 substrate of the same thickness. In the third part, multifunctional nonlinear metasurfaces for VUV generation and manipulation are demonstrated. They consist of zinc oxide (ZnO) nanotriangles that show a magnetic dipole resonance around the pump wavelength of 394 nm that was designed to boost SHG. Geometric rotation of individual nanotriangles allows for local phase manipulation via the geometric phase, when excited with circularly polarized light. In this way, nonlinear metasurfaces for both focusing and beam steering of VUV light are demonstrated.
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    Photonic Metamaterials for Color Devices and Deep UV Second Harmonic Generation
    (2018-03-15) Semmlinger, Michael; Halas, Naomi J
    Photonic Metamaterials are novel materials that consist of subwavelength optical resonators called meta-atmos. They have attracted much attention, due to their ability to control and confine light. In particular, they have promising applications in color generation and nonlinear optics. Here, I give one example for each of these two applications. Chapter one presents an actively tunable full-spectrum device. An array of plasmonic aluminum particles is integrated into a stretchable polymer substrate. Stretching the substrate in either of its two dimensions causes a change in the array period, and therefore changes the associated scattering color. Using a two-dimensional stretching approach, I demonstrate full-spectrum tuning, as well as image switching. In chapter two I present an all-dielectric metamaterial consisting of an array of zinc oxide (ZnO) nanodisks. The material shows a magnetic dipole resonance around 400nm. When pumped at resonance, the associated field enhancement can be used to generate the second harmonic frequency. This serves as a first demonstration for a simple device to generate deep UV light.
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    Toroidal Dipole-Enhanced Third Harmonic Generation of Deep Ultraviolet Light Using Plasmonic Meta-atoms
    (American Chemical Society, 2019) Ahmadivand, Arash; Semmlinger, Michael; Dong, Liangliang; Gerislioglu, Burak; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics
    The harmonic generation of light with plasmonic and all-dielectric nanostructures has gained much recent interest. This approach is especially promising for short wavelength (i.e., ultraviolet (UV)) generation, where conventional nonlinear crystals reach their limits both in transparency and in their ability to achieve phase-matching between the input and output fields. Here, we demonstrate that the third harmonic generation of deep UV light in an indium tin oxide (ITO) film can be substantially enhanced by a metasurface consisting of metallic toroidal meta-atoms covered with an alumina layer for protection against laser-induced damage. This approach combines the benefits of the large nonlinear susceptibility of ITO with the unique field enhancement properties of a toroidal metasurface. This ITO–meta-atom combination produces a third harmonic signal at a wavelength of 262 nm that is nominally five times larger than that of an ITO film patterned with a conventional hotspot-enhanced plasmonic dimer array. This result demonstrates the potential for toroidal meta-atoms as the active engineered element in a new generation of enhanced nonlinear optical materials and devices.