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In this paper, a 256-channel, 10-GHz arrayed waveguide gratings demultiplexer for ultra-dense wavelength division multiplexing was designed using an in-house developed tool called AWG-Parameters. The AWG demultiplexer was designed for a central wavelength of 1550 nm and the structure was simulated in PHASAR tool from Optiwave. Two different AWG designs were developed and the influence of the design parameters on the AWG performance was studied.
The paper shows concepts of optical splitting based on three dimensional (3D) optical splitters based on multimode interference principle. This paper is focused on the design, fabrication and characterization of 3D MMI splitter with formed output waveguides based on IP-Dip polymer for direct application on optical fiber. The MMI optical splitter was simulated and fabricated using direct laser writing process. Output characteristics were characterized by highly resolved near-field scanning optical microscope (NSOM) and compared with 3D MMI splitter without output waveguides.
In this paper, we document optical splitters based on Y-branch and also on MMI splitting principle. The 1×4 Y-branch splitter was prepared in 3D geometry fully from polymer approaching the single mode transmission at 1550 nm. We also prepared new concept of 1×4 MMI optical splitter. Their optical properties and character of output optical field were measured by near-field scanning optical microscope. Splitting properties and optical outputs of both splitters are very promising and increase an attractiveness of presented 3D technology and polymers.
We present a new concept of 3D polymer-based 1 × 4 beam splitter for wavelength splitting around 1550 nm. The beam splitter consists of IP-Dip polymer as a core and polydimethylsiloxane (PDMS) Sylgard 184 as a cladding. The splitter was designed and simulated with two different photonics tools and the results show high splitting ratio for single-mode and multi-mode operation with low losses. Based on the simulations, a 3D beam splitter was designed and realized using direct laser writing (DLW) process with adaptation to coupling to standard single-mode fiber. With respect to the technological limits, the multi-mode splitter having core of (4 × 4) μm 2 was designed and fabricated together with supporting stable mechanical construction. Splitting properties were investigated by intensity monitoring of splitter outputs using optical microscopy and near-field scanning optical microscopy. In the development phase, the optical performance of fabricated beam splitter was examined by splitting of short visible wavelengths using red light emitting diode. Finally, the splitting of 1550 nm laser light was studied in detail by near-field measurements and compared with the simulated results. The nearly single-mode operation was observed and the shape of propagating mode and mode field diameter was well recognized.
Synthetic polymers, such as polyamide (PA), inherently possess a moderate number of surface functionalities compared to natural polymers, which negatively impacts the uniformity of metallic coatings obtained through wet-chemical methods like electroless plating. The paper presents the use of a siloxane interlayer formed from the condensation of the hydrolyzed 3-triethoxysilylpropyl succinic anhydride (TESPSA) precursor as a strategy to modify the surface properties of polyamide 6.6 (PA66) fabrics and improve the uniformity of the copper surface coating. The application of the siloxane intermediate coating demonstrates a significant improvement in electrical conductivity, up to 20 times higher than fabrics without the interlayer. The morphology of the coatings was investigated using scanning electron (SEM) and laser confocal scanning microscopy (LSM). In addition, dye adsorption, flexural rigidity, air permeability and contact angle measurements were conducted to monitor the change in the PA66 properties after the siloxane functionalization.
A quantum-light source that delivers photons with a high brightness and a high degree of entanglement is fundamental for the development of efficient entanglement-based quantum-key distribution systems. Among all possible candidates, epitaxial quantum dots are currently emerging as one of the brightest sources of highly entangled photons. However, the optimization of both brightness and entanglement currently requires different technologies that are difficult to combine in a scalable manner. In this work, we overcome this challenge by developing a novel device consisting of a quantum dot embedded in a circular Bragg resonator, in turn, integrated onto a micromachined piezoelectric actuator. The resonator engineers the light-matter interaction to empower extraction efficiencies up to 0.69(4). Simultaneously, the actuator manipulates strain fields that tune the quantum dot for the generation of entangled photons with fidelities up to 0.96(1). This hybrid technology has the potential to overcome the limitations of the key rates that plague current approaches to entanglement-based quantum key distribution and entanglement-based quantum networks. Introduction
An electrochemical study with three redox substances on a carbon based nanogap electrode array
(2020)
Application of various tools to design, simulate and evaluate optical demultiplexers based on AWG
(2015)
Arrayed Waveguide Gratings
(2016)
Arrayed Waveguide Grating (AWG) is a passive optical component, which have found applications in a wide range of photonic applications including telecommunications and medicine. Silica-on-Silicon (SoS) based AWGs use a low refractive-index contrast between the core (waveguide) and the cladding which leads to some significant advantages such as low propagation losses and low fiber coupling losses between the AWG waveguides and the fibres. Therefore, they are an attractive DWDM solution offering higher channel count technology and good performance characteristics compared to other methods. However, the very low refractive-index contrast means the bending radius of the waveguides needs to be very large (on the order of several millimeters) and may not fall below a particular critical value to suppress bending losses. As a result, silica-based waveguide devices usually have a very large size that limits the integration density of SiO2-based photonic integrated devices. High-index contrast AWGs (such as silicon, silicon nitride or polymer-based waveguide devices) feature much smaller waveguide size compared to low index contrast AWGs. Such compact devices can easily be implemented on a chip and have already found applications in emerging applications such as optical sensors, devices for DNA diagnostics and optical spectrometers for infrared spectroscopy.In this work, we present the design, simulation, technological verification and applications of both, the low-index contrast and high-index contrast AWGs. For telecommunication applications AWG-MUX/Demux with up to 128-channels will be presented. For medical applications the AWG-spectrometer with up to 512-channels will be presented.This work was carried out in the framework of the projects: ADOPT No. SK-AT-20-0012, NOVASiN No. SK-AT-20-0017 and AUTOPIC No. APVV-17-0662 from Slovak research and development agency of Ministry of Education, Science, Research and Sport of the Slovak Republic and No. SK 07/2021 and SK 08/2021 from Austrian Agency for International Cooperation in Education and Research (OeAD-GmbH); and project PASTEL, no. 2020-10-15-001, funded by SAIA.
The photonic integrated circuits are required in the next generations of coherent terabit optical communications. The software tools for automated adjustment and coupling of optical fiber arrays to photonic integrated circuits has been developed. The obtained results are needed in final production phase in the technology process of photonic integrated circuits packaging.
A new software tool, called AWG-Channel-Spacing, is developed to calculate accurate channel spacing of an arrayed waveguide gratings (AWG) optical multiplexer/demultiplexer. This tool has been developed with the application framework QT in the programming language C++. The tool was evaluated with a design of 20-channel 200 GHz AWG. The achieved simulated transmission characteristics prove the correct functionality of the tool.
By a simple femtosecond laser process, we fabricated metal-oxide/gold composite films for electrical and optical gas sensors. We designed a dripple wavelength AWG-spectrometer, matched to the plasma absorption wavelength region of the composite films. H2/CO absorptions fit well with the AWG design for multi gas detection sensor arrays
A new software tool, called AWG-Wuckler, is developed to calculate geometric parameters of arrayed waveguide grating structures for telecommunication and medical applications. These parameters are crucial for a AWG layout which will be created and simulated using commercial photonic design tools. The design process of AWG is very complex because its geometric dimensions depend on a large number of input design parameters and other input design parameters. Often geometric constraints require an adjustment of the input design parameters and vice versa. Calculation and adjustment of the geometric parameters is a time-consuming process that is currently not fully supported by any commercial photonic tool. AWG-Wuckler tool overcomes this issue and offers a fast and easy to use solution. The tool was already applied in various AWG designs and is technologically well proven.
Beyond the Four-Level Model: Dark and Hot States in Quantum Dots Degrade Photonic Entanglement
(2023)
Entangled photon pairs are essential for a multitude of quantum photonic applications. To date, the best performing solid-state quantum emitters of entangled photons are semiconductor quantum dots operated around liquid-helium temperatures. To favor the widespread deployment of these sources, it is important to explore and understand their behavior at temperatures accessible with compact Stirling coolers. Here we study the polarization entanglement among photon pairs from the biexciton–exciton cascade in GaAs quantum dots at temperatures up to ∼65 K. We observe entanglement degradation accompanied by changes in decay dynamics, which we ascribe to thermal population and depopulation of hot and dark states in addition to the four levels relevant for photon pair generation. Detailed calculations considering the presence and characteristics of the additional states and phonon-assisted transitions support the interpretation. We expect these results to guide the optimization of quantum dots as sources of highly entangled photons at elevated temperatures.
Black titanium dioxide in situ generated on femtosecond laser induced periodic surface structures
(2018)
Calculation of accurate channel spacing of an AWG optical demultiplexer applying proportional method
(2015)
We report resent results on the fabrication and characterization of carbon nanogap interdigitated electrode arrays (IDAs) for biosensor applications based on redox cycling. The electrochemical results of the carbon electrodes are compared to our fabricated gold electrodes with similar nanogap distances. The amplification factor and the collection efficiency were recorded by chronoamperometry. Cyclic voltammetry (CV) was utilized to determine the oxidation and reduction potentials as well as for monitoring the electron transfer process. The different deposited carbon materials were characterized by Raman spectroscopy.At present, we successfully fabricated carbon nanogaps down to 80 nm and we are convinced to reach the present fabrication limit of about 30 nm (for gold and platinum electrodes) with carbon as electrode material as well. To the best of our knowledge, this is the first IDA nanogap sensor, which features a gap distance under 100 nm with amorphous carbon as electrode material. Moreover, we present a signal amplification of 32 for carbon electrodes by redox cycling, which is the highest reported amplification so far.
Whether at the intramolecular or cellular scale in organisms, cell-cell adhesion adapt to external mechanical cues arising from the static environment of cells and from dynamic interactions between neighboring cells. Cell-cell adhesions need to resist detachment forces to secure the integrity and internal organization of organisms. In the past, various techniques have been developed to characterize adhesion properties of molecules and cells in vitro, and to understand how cells sense and probe their environment. Atomic force microscopy and dual-pipette aspiration, where cells are mainly present in suspension, are common methods for studying detachment forces of cell-cell adhesions. How cell-cell adhesion forces are developed for adherent and environment-adapted cells, however, is less clear. Here, we designed the Cell-Cell Separation Device (CC-SD), a microstructured substrate that measures both intercellular forces and external stresses of cells towards the matrix. The design is based on micropillar arrays originally designed for cell traction-force measurements. We designed PDMS micropillar-blocks, to which cells could adhere and be able to connect to each other across the gap. Controlled stretching of the whole substrate changed the distance between blocks and increased gap size. That allowed us to apply strains to cell-cell contacts, eventually leading to cell-cell adhesion detachment, which was measured by pillar deflections. The CC-SD provided an increase of the gap between the blocks of up to 2.4-fold, which was sufficient to separate substrate-attached cells with fully developed F-actin network. Simultaneously measured pillar deflections allowed us to address cellular response to the intercellular strain applied. The CC-SD thus opens up possibilities for the analysis of intercellular force detachments and sheds light on the robustness of cell-cell adhesions in dynamic processes in tissue development.
In this study, we carried out the structural and thermal characterization of a medical-grade poly (lactide) (PLA) by SEC, TGA, DSC, NMR, ICP-MS and Py-GC/MS. Moreover, we investigated the laser-induced degradation occurring when ultrashort laser pulses (ULP) were employed to cut extremely thin polymer films prepared by solvent-casting. ULP polymer cutting technology is an interesting manufacturing process for its advantages in potential medical applications. In fact, heat transmission to the region surrounding the cuts is limited, so that the incisions are precise and the effects on the regions around them are small. In this way, the need for post-processing is reduced and ULP cutting becomes interesting for industrial applications. However, degradation induced by ULP may occur and compromise the properties of the polymer samples. To investigate this possibility, portions of PLA films, ultrashort laser cut (ULC) and uncut, were analysed by SEC, DSC, NMR and FTIR. Furthermore, PLA oligomers were studied by ESI-MS. Both SEC and NMR showed a decrease in the molecular weight. FTIR, ESI-MS and NMR spectra revealed the presence of olefin end groups originated from a \beta-H transfer mechanism, induced by heat and/or light (Norrish II mechanism). Additionally, the inspection of the ESI mass spectra highlighted the cleavage of ester bonds related to the Norrish I type mechanism, undetected by the other techniques.
Combining parallel pattern generation of electrohydrodynamic lithography with serial addressing
(2018)
Compact and high-resolution 256-channel silicon nitride based AWG-spectrometer for OCT on a chip
(2019)
We present design, simulation and technological verification of a compact 256-channel, 42-GHz silicon nitride based AWG-spectrometer. The spectrometer was designed for TM-polarized light with a central wavelength of 850 nm, applying “AWG-Parameters” tool. This design is based on a previous study of various AWG designs (8-channel, 100-GHz; 20-channel, 50-GHz; 40-channel, 50-GHz, 80-channel, 50-GHz and 160-channel, 50-GHz AWGs), which were all technologically verified. The spectrometer features small size and high resolution. It is integrated on OCT chip using standard CMOS processes. The SD-OCT system is developed to operate in a wavelength range from 800 nm to 900 nm, having 0.1 nm resolution.
In this paper, the design of three-dimensional configuration of Y-branch splitter is compared with Multimode Interference splitter. Both splitters use the IP-Dip polymer as a standard material for 3D laser lithography. The optical properties of the splitters for both approaches are discussed and compared.
This paper describes two different designs of 1×8 passive optical splitters. The first splitter consists of cascade arranged directional waveguide branches (Y-branch splitter) with (0.8×0.16) µm2 waveguide cross-section. The second splitter is based on multimode interference occurring in a large MMI coupler, which uses a self-imaging effect for beam propagation, exhibiting the same waveguide core size as a Y-branch splitter. The waveguide channel profile, used in both approaches, is based on a silicon nitride material platform, with a refractive index of core being nc = 1.925 and a refractive index of cladding ncl = 1.4575. The splitters are designed as a planar structure for a medical operating wavelength 850 nm. Design, simulation, and optimization of passive optical components are performed by a commercial photonic software tool BeamPROP simulation engine by RSoft Photonics Suite tool, employing beam propagation method. This work aims to find the minimum physical dimensions of the designed splitters with the satisfactory optical performance. According to the minimum insertion loss and minimum non-uniformity, the optimum length of the splitters is determined. Finally, the optical properties of splitters for both approaches are discussed and compared with each other.
Comparison of silicon nitride based 1x8 Y-branch splitters applying different waveguide structures
(2019)
This paper presents design, simulation and optimization of 1x8 Y-branch power splitters based on Si/SiO2/SiN/SiOx material platform. For the designs, two different waveguide structures were used, i.e. ridge and rib waveguides. The splitters were designed for 850 nm spectral optical window and the simulations were performed applying FEM and BPM methods in RSoft photonic tool. The aim of this work was to find minimum physical dimensions of the designed splitters occupying minimal space on PIC chip. The optimization was done with regards to high symmetrical splitting ratio and low insertion loss. Finally, the optical properties of both splitters were studied and compared with each other.
Comparison of silicon nitride based 8-channel 100-GHz AWGs applying different waveguide structures
(2019)
This paper presents design and simulation of 8-channel, 100-GHz AWGs based on Si/SiO2/SiN/SiOx material platform. For the designs, two different waveguide structures were used, i.e. ridge and rib waveguides. AWGs were designed for central wavelength of 850 nm applying AWG-Parameters tool. The simulations were performed applying FEM and BPM methods in RSoft and PHASAR photonic tools. The simulation results show considerably lower losses but slightly higher channel crosstalk when applying rib waveguides.
Compression of ultrashort laser pulses via gated multiphoton intrapulse interference phase scans
(2014)
Progress in integrated photonics enables development of integrated photonics circuits with new unique properties, circuits of the future, and overcomes current limits in information and communication technologies. The packaging of photonic integrated circuits is necessary for taking them out of research laboratories into real implementation in the information and communication technology applications.
Telecom optical fibers are still being the best transmission medium of digital data and analogue signals for long distance applications. The effective coupling of optical radiation between telecom optical fiber with ten microns core dimension and photonic integrated circuits optical waveguides with submicron dimensions are necessary. To address these challenges, we present our concept of photonics integrated circuit packaging with radio frequency, direct current and fiber array ports with automated active alignment system.