Browsing by Author "Matikainen, Antti"

Now showing 1 - 12 of 12
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    Absorption modeling with FMM, FEM and FDTD
    (2019-07-01) Anttu, Nicklas; Mantynen, Henrik; Sadi, Toufik; Matikainen, Antti; Turunen, Jari; Lipsanen, Harri; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Department of Neuroscience and Biomedical Engineering; University of Eastern Finland; Hinzer, Karin; Piprek, Joachim
    Absorption modeling is at the core of the design process of nanostructured solar cells and photodetectors. We compare the performance of three of the most popular numerical modeling methods: the Fourier modal method (FMM), the finite element method (FEM) and the finite-difference time-domain (FDTD) method. We find that the numerically most efficient method depends on the geometry of the system, as well as on which physical quantities are needed for further analysis. From our study, we will highlight the optimum choice of method for various current nanostructures. With these guidelines, we enable design optimization that would otherwise be impossible with a suboptimal method choice.
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    Comparison of absorption simulation in semiconductor nanowire and nanocone arrays with the Fourier modal method, the finite element method, and the finite-difference time-domain method
    (IOP Publishing, 2020) Anttu, Nicklas; Mäntynen, Henrik; Sadi, Toufik; Matikainen, Antti; Turunen, Jari; Lipsanen, Harri; Harri Lipsanen Group; Department of Neuroscience and Biomedical Engineering; University of Eastern Finland; Department of Electronics and Nanoengineering
    For the design of nanostructured semiconductor solar cells and photodetectors, optics modelling can be a useful tool that reduces the need of time-consuming and costly prototyping. We compare the performance of three of the most popular numerical simulation methods for nanostructure arrays: the Fourier modal method (FMM), the finite element method (FEM) and the finite-difference time-domain (FDTD) method. The difference between the methods in computational time can be three orders of magnitude or more for a given system. The preferential method depends on the geometry of the nanostructures, the accuracy needed from the simulations, whether we are interested in the total, volume-integrated absorption or spatially resolved absorption, and whether we are interested in broadband or narrowband response. Based on our benchmarking results, we provide guidance on how to choose the method.
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    Comparison of FMM, FEM and FDTD for absorption modeling of nanostructured solar cells and photodetectors
    (2019-01-01) Anttu, Nicklas; Mantynen, Henrik; Sadi, Toufik; Matikainen, Antti; Turunen, Jari; Lipsanen, Harri; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Department of Neuroscience and Biomedical Engineering; University of Eastern Finland
    We compare FMM, FEM and FDTD for absorption modeling. We discuss optimum choice of modeling method for varying nanostructures, enabling solar cell and photodetector design optimization that would be impossible with a suboptimal method choice.
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    Computer Based Training in Change Process of Service Company
    (1999) Matikainen, Antti; Kasvi, Jyrki J. J.; Tietotekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Vartiainen, Matti
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    Erbium-doped hybrid waveguide amplifiers with net optical gain on a fully industrial 300 mm silicon nitride photonic platform
    (Optical Society of America, 2020-09-14) Ronn, John; Zhang, Jianhao; Zhang, Weiwei; Tu, Zhengrui; Matikainen, Antti; Leroux, Xavier; Duran-Valdeiglesias, Elena; Vulliet, Nathalie; Boeuf, Frederic; Alonso-Ramos, Carlos; Lipsanen, Harri; Vivien, Laurent; Sun, Zhipei; Cassan, Eric; Department of Neuroscience and Biomedical Engineering; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Université Paris-Sud; University of Southampton; STMicroelectronics SA
    Recently, erbium-doped integrated waveguide devices have been extensively studied as a CMOS-compatible and stable solution for optical amplification and lasing on the silicon photonic platform. However, erbium-doped waveguide technology still remains relatively immature when it comes to the production of competitive building blocks for the silicon photonics industry. Therefore, further progress is critical in this field to answer the industry's demand for infrared active materials that are not only CMOS-compatible and efficient, but also inexpensive and scalable in terms of large volume production. In this work, we present a novel and simple fabrication method to form cost-effective erbium-doped waveguide amplifiers on silicon. With a single and straightforward active layer deposition, we convert passive silicon nitride strip waveguide channels on a fully industrial 300 mm photonic platform into active waveguide amplifiers. We show net optical gain over sub-cm long waveguide channels that also include grating couplers and mode transition tapers, ultimately demonstrating tremendous progress in developing cost-effective active building blocks on the silicon photonic platform. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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    Fabrication-friendly polarization-sensitive plasmonic grating for optimal surface-enhanced Raman spectroscopy
    (SpringerOpen, 2020-12-01) Dutta, Arpan; Nuutinen, Tarmo; Alam, Khairul; Matikainen, Antti; Li, Peng; Hulkko, Eero; Toppari, J. Jussi; Lipsanen, Harri; Kang, Guoguo; University of Jyväskylä; University of Eastern Finland; Harri Lipsanen Group; Beijing Institute of Technology; Department of Electronics and Nanoengineering
    Plasmonic nanostructures are widely utilized in surface-enhanced Raman spectroscopy (SERS) from ultraviolet to near-infrared applications. Periodic nanoplasmonic systems such as plasmonic gratings are of great interest as SERS-active substrates due to their strong polarization dependence and ease of fabrication. In this work, we modelled a silver grating that manifests a subradiant plasmonic resonance as a dip in its reflectivity with significant near-field enhancement only for transverse-magnetic (TM) polarization of light. We investigated the role of its fill factor, commonly defined as a ratio between the width of the grating groove and the grating period, on the SERS enhancement. We designed multiple gratings having different fill factors using finite-difference time-domain (FDTD) simulations to incorporate different degrees of spectral detunings in their reflection dips from our Raman excitation (488 nm). Our numerical studies suggested that by tuning the spectral position of the optical resonance of thegrating, via modifying their fill factor, we could optimize the achievable SERS enhancement. Moreover, by changing the polarization of the excitation light from transverse-magnetic to transverse-electric, we can disable the optical resonance of the gratings resulting in negligible SERS performance. To verify this, we fabricated and optically characterized the modelled gratings and ensured the presence of the desired detunings in their optical responses. Our Raman analysis on riboflavin confirmed that the higher overlap between the grating resonance and the intended Raman excitation yields stronger Raman enhancement only for TM polarized light. Our findings provide insight on the development of fabrication-friendly plasmonic gratings for optimal intensification of the Raman signal with an extra degree of control through the polarization of the excitation light. This feature enables studying Raman signal of exactly the same molecules with and without electromagnetic SERS enhancements, just by changing the polarization of the excitation, and thereby permits detailed studies on the selection rules and the chemical enhancements possibly involved in SERS.
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    Implementation of the OPC UA Skills concept on a laboratory model of the assembly process
    (2023-05-15) Matikainen, Antti; Udayanto, Atmojo Dwi; Sähkötekniikan korkeakoulu; Vyatkin, Valeriy
    The OPC UA Skills concept proposes a generic model for communicating the capabilities of a system as well as a novel solution for control through the use of a simple interface. This proposed solution is explored within the thesis through hypothetical examples as well as through the development of a practical example using a laboratory model of the assembly process. Further, the aim of this thesis is to iterate upon previous work done on the topic by a project group within Aalto University. In addition, the thesis seeks to examine the effects of architectural design decisions on the program developed during the course of the project based on observations from the course of development.
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    Measurement of Nanowire Optical Modes Using Cross-Polarization Microscopy
    (2017-12-19) Kakko, Joona-Pekko; Matikainen, Antti; Anttu, Nicklas; Kujala, Sami; Mäntynen, Henrik; Khayrudinov, Vladislav; Autere, Anton; Sun, Zhipei; Lipsanen, Harri; Department of Electronics and Nanoengineering
    A method to detect optical modes from vertical InGaAs nanowires (NWs) using cross-polarization microscopy is presented. Light scattered from the optical modes in the NWs is detected by filtering out the polarized direct reflection with a crossed polarizer. A spectral peak and a valley were seen to red-shift with increasing NW diameter in the measured spectra. The peak was assigned to scattering from the TE01 optical mode and the valley was an indication of the HE11 mode, based on finite-element and scattering matrix method simulations. The cross-polarization method can be used to experimentally determine the spectral positions of the TE01 and HE11 optical modes. The modes are significantly more visible in comparison to conventional reflectance measurements. The method can be beneficial in the characterization of NW solar cells, light-emitting diodes and lasers where precise mode control is required.
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    Scalable fabrication of the graphitic substrates for graphene-enhanced Raman spectroscopy
    (2017-12-01) Kaplas, Tommi; Matikainen, Antti; Nuutinen, Tarmo; Suvanto, Sari; Vahimaa, Pasi; Svirko, Yuri; University of Eastern Finland; Department of Electronics and Nanoengineering
    We propose direct synthesis of ultra-thin graphitic films on a dielectric substrate using sacrificial Ni catalyst layer, which significantly increases the crystallinity of the photoresist pyrolyzed at the temperature of 800 °C and above. A considerable amount of multilayer graphene in the photoresist film pyrolyzed in the presence of the Ni catalyst gives rise to an enhancement of the Raman signal of dye Sudan III molecules deposited on the substrate. We demonstrate comparable enhancement of the Raman signal from Sudan III molecules deposited on the fabricated graphitic substrate and those deposited on graphene, which was conventionally transferred to the silica substrate.
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    SERS Activity of Photoreduced Silver Chloride Crystals
    (2020) Dutta, Arpan; Matikainen, Antti; Andoh, Sampson; Nuutinen, Tarmo; University of Jyväskylä; Harri Lipsanen Group; University of Eastern Finland; Department of Electronics and Nanoengineering; Shekhawat, MS; Bhardwaj, S; Suthar, B
    Metal nanoparticles are widely acclaimed as plasmonic substrates for surface -enhanced Raman spectroscopy (SERS) due to their unique particle plasmon resonances at visible and near infrared regions. Silver nanoparticles are typically employed in SERS when the targeted Raman signature zone of analytes lies at ultra-violet and/or blue to green spectral regimes. Even though silver has strong plasmonic properties, silver-based substrates are often affected by the atmospheric oxidation and show degradation in their SERS performance. One way to overcome this limitation is to use silver chloride crystals as oxidation resistant intermediate and photoreduce them to 'fresh' silver just before SERS analysis. In this work, we study the SERS activity of the photoreduced silver chloride crystals. We perform Raman analysis of three Raman active analytes, adenine, rhodamine 6G and riboflavin at both visible (514 nm) and near-infrared (785 nm) excitations. Our experimental outcomes show that such photoreduced silver chloride crystals can be exploited as SERS active substrates for both visible and near-infrared applications. Our numerical simulations reveal that these photoreduced silver chloride crystals are strong scatterers at multiple wavelengths and hence, could be very useful for plasmon-enhanced spectroscopic applications where multiple wavelengths are involved.
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    Tapahtumapohjainen päättely
    (2017-05-05) Matikainen, Antti; Aarnio, Pekka; Sähkötekniikan korkeakoulu; Forsman, Pekka
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    Transfer and patterning of chemical vapor deposited graphene by a multifunctional polymer film
    (2018-02-12) Kaplas, Tommi; Bera, Arijit; Matikainen, Antti; Pääkkönen, Pertti; Lipsanen, Harri; University of Eastern Finland; Department of Electronics and Nanoengineering
    Graphene is seeking pathways towards applications, but there are still plenty of unresolved problems on the way. Many of those obstacles are related to synthesis and processing of graphene. Chemical vapor deposition (CVD) of graphene is currently one of the most promising techniques that enable scalable synthesis of high quality graphene on a copper substrate. From the transient metal substrate, the CVD graphene film is transferred to the desired dielectric substrate. Most often, the transfer process is done by using a supporting poly(methyl methacrylate) (PMMA) film, which is also a widely used electron beam resist. Conventionally, after graphene is transferred to the substrate, the supporting PMMA film is removed by organic solvents. Hence, the potential of using the same PMMA layer as a resist mask remains unexplored. Since PMMA is an electron beam resist, the same polymer film can be useful both for transferring and for patterning of graphene. In this work, we demonstrate simultaneous transfer and patterning of graphene by using the same PMMA film. With our demonstrated method, we are able to receive sub-micron resolution very easily. The graphene transfer and its subsequent patterning with the same resist layer may help developing device applications based on graphene and other 2D materials in the near future.