Article
Chemistry, Multidisciplinary
Kazuhiro Kato, Hiroyuki Sugawara, Jun Taniguchi
Summary: There is a high demand for a highly mass-producible technology for manufacturing moth-eye-structured films with antireflection function. Conventional films are made using roll-to-roll ultraviolet nanoimprint lithography with aluminum, but the process is complicated and time-consuming. To solve this problem, a sputtering process for forming a thin film of glassy carbon on a roll substrate was proposed, which resulted in a moth-eye structure through oxygen plasma irradiation. The glassy carbon roll mold showed superior antireflection, water repellency, and productivity compared to the moth-eye-structured film made with porous alumina.
Article
Chemistry, Physical
Alejandra Jacobo-Martin, Jaime J. Hernandez, Eduardo Solano, Miguel A. Monclus, Juan Carlos Martinez, Daniel F. Fernandes, Patricia Pedraz, Jon M. Molina-Aldareguia, Tomas Kubart, Isabel Rodriguez
Summary: Moth-eye nanostructures have various functionalities, but their poor mechanical resilience and durability limit their practical applications. In this study, a thin oxide coating is used to protect the nanostructures and improve their thermal stability and self-cleaning functionality.
APPLIED SURFACE SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Yulei Huang, Hao Zhou, Fangjie Wang, Congliao Yan, Yao Ju, Qiongqiong Gu, Zixiao Miao, Rui Cai, Xiaolin Sui, Ziyan Wu, Hong Zhang, Guoliang Deng, Shouhuan Zhou
Summary: In this paper, a novel method using nanosphere lithography to fabricate biomimetic moth-eye nanostructures (MENS) on ZnSe surface was presented, which resulted in exceptional antireflection effect. The MENS showed broadband antireflection performance in the 2-5μm wavelength range with a maximum transmission of 82.6% and exhibited desirable hydrophobicity. This work has great potential in optoelectronic devices and high-power laser applications.
Article
Chemistry, Physical
Ting Hu, Zhi Xing, Lu Huang, Dengxue Li, Xiangchuan Meng, Xiaotian Hu, Yiwang Chen
Summary: To address the limitations of two-dimensional perovskites in photovoltaic applications, a strategy for developing high-quality patterned 2D perovskites was proposed. The patterned films showed improved light absorption and interfacial contact, leading to enhanced efficiencies and stability of the solar cells.
CHEMISTRY OF MATERIALS
(2022)
Article
Energy & Fuels
Yan Gu, Jichen Xu, Jieqiong Lin, Haihang Ma, Huibo Zhao, Yishuo Zhang, Baoyu Sun
Summary: This study proposes a vibration-assisted UV nanoimprint lithography technique to effectively improve the power conversion efficiency (PCE) of Si solar cells. By applying piezoelectric vibration, the contact area between the photoresist and the grating's side wall is increased, reducing surface tension and increasing the photoresist filling rate by 25%. The best grating parameters are determined using Finite Difference Time Domain (FDTD) and vibration-assisted UV nanoimprint is used to fabricate the periodic grating structures, resulting in a 25% increase in PCE compared to bare Si solar cells.
Article
Materials Science, Multidisciplinary
Yuanchi Cui, Xuewen Wang, Chengpeng Zhang, Jilai Wang, Zhenyu Shi
Summary: The study utilized a CFD simulation model to analyze resin filling behavior and investigated the effects of process parameters and boundary conditions. Results indicated that inlet velocity had a significant impact on filling height, and boundary slip influenced resin filling behavior significantly.
Article
Chemistry, Multidisciplinary
Kyeong-Ho Seo, Swarup Biswas, Junsu Eun, Hyeok Kim, Jin-Hyuk Bae
Summary: Lead-free Cs2AgBiBr6 double perovskite has potential as a new-generation photovoltaic material. However, the challenge of low power conversion efficiency due to high indirect bandgap is addressed in this study by using a light trapping strategy with a moth-eye antireflection layer.
Article
Nanoscience & Nanotechnology
Alejandra Jacobo-Martin, Jaime J. Hernandez, Patricia Pedraz, Eduardo Solano, Ivan Navarro-Baena, Isabel Rodriguez
Summary: The thermal stability of antireflective moth-eye topographical features fabricated by nanoimprint lithography on PMMA incorporating TiO2 nanoparticles is greatly improved, delaying pattern relaxation and enhancing pattern stability even at high temperatures. This enhancement in thermal behavior will significantly improve the functionality and performance of the antireflective films, especially in light-trapping applications where temperatures typically rise.
Article
Chemistry, Physical
Lea Marichez, Genevieve Chadeyron, Daniel Zambon, Francois Reveret, Audrey Potdevin, Damien Boyer, Valentin Gate, Isabelle Verrier, Damien Jamon, Emilie Gamet, Yves Jourlin
Summary: Sol-gel layers doped with Rhodamine B phosphors were microstructured using nanoimprint lithography to produce sub-lambda 2D gratings. Surface microstructuring improved fluorophore emission and resulted in 3-4 times higher emissions compared to flat surfaces. This approach holds great promise for low-cost, high-performance anti-counterfeiting marking processes and object traceability based on unique optical effects.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Engineering, Biomedical
Mahya Ganjian, Khashayar Modaresifar, Dionysios Rompolas, Lidy E. E. Fratila-Apachitei, Amir A. A. Zadpoor
Summary: Developing a high-throughput nanopatterning technique with precise control over feature dimensions is crucial for studying cell-nanopattern interactions. This study presents a process that fulfills these criteria by using electron-beam lithography to fabricate controlled arrays of submicron pillars and developing etching procedures to create the desired height. The study demonstrates the significance of the fabricated pillars in inducing osteogenic differentiation and utilizes replication techniques to pattern bio-instructive surfaces. Overall, the method enables the precise fabrication of submicron and nanopatterns for systematic cell studies.
ACTA BIOMATERIALIA
(2022)
Article
Materials Science, Multidisciplinary
Alejandra Jacobo-Martin, Jaime J. Hernandez, Patricia Pedraz, Ivan Navarro-Baena, Miguel A. Monclus, Jon M. Molina-Aldareguia, Isabel Rodriguez
Summary: This study presents a fabrication method for bioinspired moth-eye antireflective films using PVDF and TiO2 nanoparticles, which improves the mechanical and thermal stability of the films. Various tests were conducted to evaluate the optical performance and durability of the films, aiming to expand their potential for use in solar devices.
ADVANCED ENGINEERING MATERIALS
(2021)
Article
Energy & Fuels
Ramakrishnan Swathi, Jayaraj Shanthi, Subramaniam Aishwarya, Kiliyanamkandy Anoop
Summary: An antireflection coating with mechanical robustness has been developed using the spin coating technique. This coating demonstrates high transparency, scratch resistance, light-trapping ability, and self-cleaning ability, while maintaining stability under UV-B radiation. It offers a promising approach for improving the efficiency and reliability of solar and optical applications.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2022)
Article
Chemistry, Physical
Raghavendra Sagar, Asha Rao
Summary: This paper demonstrates that deposition of nanoscale TiO2 and Ta2O5 as antireflection coatings on commercial monocrystalline silicon solar cells can significantly enhance the photon to electron conversion efficiency, mainly attributed to the increase in fill factor.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Applied
Armen Tchobanian, Frederik Ceyssens, Mar Condor Salgado, Hans Van Oosterwyck, Pedro Fardim
Summary: The study synthesised dextran palmitates with a multipurpose functionality to modulate surface energy through surface chemistry and to be patterned, and produced films by spin coating and patterned by thermal nanoimprint lithography. These moderately hydrophobic films performed well in cell culture and guided multicellular arrangements on specific topographies after patterning.
CARBOHYDRATE POLYMERS
(2021)
Article
Optics
Sivan Tzadka Shalit, Natali Ostrovsky, Hadar Frankenstein Shefa, Evyatar Kassis, Shay Joseph, Mark Schvartzman
Summary: This article presents a new approach of direct imprint using solvent-based surface softening for patterning functional microstructures on the surface of As2Se3. The method allows for full pattern transfer while maintaining the shape of the imprinted substrate.
Article
Optics
Yicheng Wang, Pavel Loiko, Yongguang Zhao, Zhongben Pan, Weidong Chen, Mark Mero, Xiaodong Xu, Jun Xu, Xavier Mateos, Arkady Major, Mircea Guina, Valentin Petrov, Uwe Griebner
Summary: In this study, a Tm,Ho:CALGO laser passively mode-locked by a GaSb-based SESAM is reported. The laser generates pulses as short as 52 fs, with a central wavelength of 2015 nm and a broad spectral bandwidth of 82 nm. The laser performance is attributed to the combined gain profiles of the dopants and the polarized spectroscopic properties of Ho3+ ions.
Article
Energy & Fuels
Riku Isoaho, Timo Aho, Arto Aho, Antti Tukiainen, Jarno Reuna, Marianna Raappana, Mircea Guina
Summary: Low-bandgap GaInNAsSb single junction solar cells with a planar Au back surface reflector exhibit high short-circuit current density and external quantum efficiency, showing potential for future applications in multijunction solar cells.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2022)
Article
Optics
S. C. Burd, J. -P. Penttinen, P. -Y. Hou, H. M. Knaack, S. Ranta, M. Maki, E. Kantola, M. Guina, D. H. Slichter, D. Leibfried, A. C. Wilson
Summary: This article presents two systems based on vertical-external-cavity surface-emitting lasers (VECSELs) that can generate ultraviolet laser light at 235 and 313 nm wavelengths, suitable for quantum information processing with trapped beryllium ions. Each system includes a compact, single-frequency, continuous-wave VECSEL that produces high-power near-infrared light and can be tuned over tens of nanometers. One system produces 2.4 W of power at 940 nm, which is converted to 54 mW of 235 nm light for photoionization of neutral beryllium atoms. The other system uses a gain mirror based on GaInNAs/GaAs quantum wells, extending the wavelength above 1200 nm with manageable strain in the GaAs lattice, and generates 1.6 W at 1252 nm, which is converted to 41 mW of 313 nm light for laser cooling of trapped 9Be+ ions and quantum state preparation and detection. The 313 nm system is also suitable for implementing high-fidelity quantum gates.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Omer Donmez, Mustafa Aydin, Selman Mutlu, Janne Puustinen, Joonas Hilska, Mircea Guina, Ayse Erol
Summary: We present experimental and analytical results on hot electron transport in as-grown and annealed n-type modulation-doped Al0.15Ga0.85As/GaAs0.96Bi0.4 quantum well structures. The drift mobility and velocity of the annealed sample are lower due to the increased 2D electron density caused by annealing. Hot electron transport occurs in parallel mode, and inter-valley transfer dominates at higher electric fields.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Optics
Nouman Zia, Samu-pekka Ojanen, Jukka Viheriala, Eero Koivusalo, Joonas Hilska, Heidi Tuorila, Mircea Guina
Summary: This paper presents a hybrid laser that combines GaSb-based semiconductor gain chips with Si3N4 photonic integrated circuits. The low-loss features of Si3N4 waveguides are utilized to integrate a tunable Si3N4 Vernier mirror. The laser exhibits a maximum output power of 15 mW and a tuning range of about 90 nm at room temperature. The low-loss performance of various Si3N4 building blocks for photonic integrated circuits is also confirmed.
Article
Energy & Fuels
Andrea Scaccabarozzi, Stefano Vichi, Sergio Bietti, Federico Cesura, Timo Aho, Mircea Guina, Federica Cappelluti, Maurizio Acciarri, Stefano Sanguinetti
Summary: We investigate the impact of quantum dot aspect ratio on the sub-gap absorption properties of GaAs/AlGaAs quantum dot intermediate band solar cells. Using droplet epitaxy, we grow AlGaAs solar cells with GaAs quantum dots, which allows for strain-free nanostructures with lattice matched materials. By varying the dot aspect ratio, we can tune the energy levels of the intermediate band, thereby altering the sub-gap absorption spectrum and charge carrier extraction. The tradeoff between thermal and optical extraction is crucial for the proper functioning of the intermediate band solar cells, with the photonic extraction mechanism from the quantum dots becoming dominant at room temperature.
PROGRESS IN PHOTOVOLTAICS
(2023)
Article
Physics, Applied
Reuben Amedalor, Petri Karvinen, Henri Pesonen, Jari Turunen, Tapio Niemi, Subhajit Bej
Summary: This study demonstrates the coexistence of resonant modes with weak dispersion and a Q-factor of approximately 1000 in diffraction gratings, along with the modes with well-known linear dispersion. The dispersion characteristics of these modes can be adjusted by controlling the polarization of the incoming light, allowing for strong or almost flat dispersion. A semi-analytical model is introduced to explain the underlying physics of these observations, and theoretical conjecture is supported by full-wave numerical simulations and experiments. The findings presented in this study will benefit applications reliant on resonances in free-space-coupled geometries.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Philipp Tatar-Mathes, Hoy-My Phung, Aaron Rogers, Patrik Rajala, Sanna Rant, Mircea Guina, Hermann Kahle
Summary: This study presents the operation of a semiconductor membrane external-cavity surface-emitting laser (MECSEL) using a gain membrane with a non-resonant cavity design. The MECSEL delivers watt-level output power, comparable to state-of-the-art results. The research shows that the design criteria for the MECSEL gain region can be relaxed compared to designs using distributed Bragg reflectors, minimizing the impact of defective Fabry-Perot micro-cavity effects.
IEEE PHOTONICS TECHNOLOGY LETTERS
(2023)
Article
Optics
Samu-Pekka Ojanen, Jukka Viheriala, Nouman Zia, Eero Koivusalo, Joonas Hilska, Heidi Tuorila, Mircea Guina
Summary: Photonic integrated circuits fabricated using a Si3N4 waveguide platform exhibit low losses in a wide wavelength region. A high-performance integrated laser with broad wavelength tunability near a 2.6 μm wavelength region is demonstrated, based on a Si3N4 photonic integrated circuit incorporating a tunable reflector and a AlGaInAsSb/GaSb quantum-well gain element. The platform also supports low propagation loss up to 3.5 μm.
LASER & PHOTONICS REVIEWS
(2023)
Article
Optics
D. Mitten, M. Hart, S. H. Warner, J. -P. Penttinen, M. Guina, Y. Kaneda
Summary: A vertical external cavity surface emitting laser (VECSEL) has been developed for a sodium guide star application. Stable single frequency operation with 21 W of output power near 1178 nm with multiple gain elements while lasing in the TEM00 mode has been achieved. This is the first demonstration of a high power single frequency VECSEL using a twisted-mode configuration and multiple gain mirrors located at the cavity folds.
Article
Physics, Applied
Y. Q. Huang, V Polojarvi, A. Aho, R. Isoaho, T. Hakkarainen, M. Guina, I. A. Buyanova, W. M. Chen
Summary: This study demonstrates the existence of nonlinear spin response in nonmagnetic materials and showcases it in a (Ga, N)As-InAs quantum dot coupled all-semiconductor nanostructure. The observed spin nonlinearity can be conveniently tuned with an external magnetic field and potentially operates at a speed exceeding 1 GHz.
PHYSICAL REVIEW APPLIED
(2023)
Article
Optics
Samu-Pekka Ojanen, Jukka Viheriala, Nouman Zia, Eero Koivusalo, Joonas Hilska, Heidi Tuorila, Mircea Guina
Summary: A discrete, tunable photonic integrated laser is demonstrated for multiwavelength spectroscopy. The laser combines a reflective semiconductor optical amplifier with a photonic integrated circuit, allowing for switching between three distinct emission wavelengths. The design simplifies the tuning mechanism compared to other hybrid lasers.
LASER & PHOTONICS REVIEWS
(2023)
Article
Chemistry, Multidisciplinary
Tristan Smolka, Michal Rygala, Joonas Hilska, Janne Puustinen, Eero Koivusalo, Mircea Guina, Marcin Motyka
Summary: The optical properties of GaSbBi layers grown on GaSb (100) substrates with different bismuth contents were investigated. The band gaps of the materials were determined using Fourier-transform photoluminescence spectra, revealing the presence of localized states connected to bismuth clustering. Time-resolved photoluminescence measurements based on single-photon counting were used to determine the characteristic photoluminescence decay time constants, which showed an increase with increasing bismuth content and clustering effects.
Article
Energy & Fuels
Janne Puustinen, Joonas Hilska, Arto Aho, Esperanza Luna, Antti Fihlman, Mircea Guina
Summary: The development of low bandgap GaAsNBi solar cells grown using MBE is reported, and the As/Ga flux ratio is found to play an important role in controlling the solar cell performance.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2024)
Proceedings Paper
Nanoscience & Nanotechnology
Jukka Viheriala, Topi Uusitalo, Heikki Virtanen, Behzad Namvar, Patrik Rajala, Sanna Ranta, Teemu Hakkarainen, Antti Tukiainen, Guilhem Almuneau, Mircea Guina
Summary: This paper presents the development of vertical cavity surface emitting lasers (VCSELs) operating at 4.2K for energy efficient optical links between cryogenic systems and room-temperature data storage systems. The design considerations, material models, and validation of required electro-optical-thermal models are discussed. Successful operation at mA-level injection is demonstrated.
2023 IEEE PHOTONICS SOCIETY SUMMER TOPICALS MEETING SERIES, SUM
(2023)