Fabrication of mid-index contrast ring resonators with a well-defined gap is very challenging, while gapless rings suffer from substantial coupling losses. To avoid these issues, we propose a gapless design based on a step-like structuring of the bus/ring waveguides. As we show with numerical simulations, our design allows to spatially confine the modes to the steps formed on the bus/ring waveguides thus mitigating the coupling losses. Additionally, the step on the ring waveguide reduces the bending losses. Finally, we show how varying the heights and widths of the steps allows to tailor the transmittance and quality factor of the ring.
For many years ionic liquids (ILs) have attracted the interest of the scientific community, finding new applications in green chemistry, chemical engineering, environmental science, and others. All applications have emerged due to ILs unique physiochemical properties like negligible volatility, high thermal stability, low toxicity, and very wide range of structural diversity. In our research we develop and exploit all of the advantages associated with the ILs molecules for lithographic patterning, expanding their applications to lithography resists. In this work we present the results of patterning achieved for different types of ionic liquids with vinylbenzyl and trimethoxysilyl groups.
Due to unique properties such as low vapor pressure and high ionic conductivity, room-temperature ionic liquids (RTILs) are very attractive not only for the chemical industry, but also for nano- and microstructures fabrication. The fabrication process conventionally involves usage of radiation sensitive polymer-based solutions (resists). We propose to replace those resists with eco-friendly solvent-free RTILs, which are polymerized by electron beam or UV light. Ionic liquids are also promising material for passive and active photonics components fabrication since their properties can be tuned in many ways by introducing special functionalities to the chemical structure of ions. In the present study, it is shown that different ionic liquids (with allyl or vinylbenzyl substituent) can be solidified on solid substrates (e.g. silicon or glass) by standard patterning lithography methods such as electron beam lithography in vacuum chamber and optical lithography with UV lamp. The thickness of the layer can be modified with ionic liquids mixture or by modified spin coating technique. By using patterning techniques, microstructures of different geometrical shapes are obtained from polymerizable RTILs containing fluorescein dianions. The shapes of obtained polymerized microstructures are also related to properties of the material including viscosities of selected ionic liquids. Various properties of polymerizable ionic liquids, such as thermal stability, viscosity, refractive index and light absorption can be adapted depending on the final application. Due to good optical properties, the fabricated microstructures can be used as photonic components, such as optical microresonators and waveguides.
The concept of fluorescent sensing in a microchannel equipped with focusing light Fresnel lenses has been demonstrated. The concept employs a line or array of Fresnel lenses generating a line or array of focused light spots within a microfluidic channel, to increase the sensitivity of fluorescent signal detection in the system. We have presented efficient methods of master mold fabrication based on the lithography method and focused ion beam milling. The flexible microchannel was fabricated by an imprint process with new thiolene-epoxy resin with a good ability to replicate even submicron-size features. For final imprinted lenses, the measured background to peak signal level shows more than nine times the increase in brightness at the center of the focal spot for the green part of the spectrum (532 nm). The effectiveness of the microlenses in fluorescent-marked Escherichia coli bacteria was confirmed in a basic fluoroscope experiment, showing the increase of the sensitivity of the detection by the order of magnitude.
Photolithographic processes of multilevel features in microfluidics can be complex and expensive. This paper demonstrates a quick method for manufacturing multilevel patterns, which is based on liquid crystal display masking during a standard lithography process for master mold fabrication for the polydimethysiloxane replica process. An active mask, based on a liquid crystal display, can simplify the process due to the ability to quickly modify designs and reduce the overhead for alignment between mask levels. The possibility of multilevel patterning, with the help of active masking, creates new opportunities for optical lithography processes. We have developed the process for a standard, mercury lamp exposure mask aligner system. The patterning characteristics were evaluated with a step pattern fabricated as an example of three-dimensional patterning for multilevel structuring. The application of a liquid crystal mask for resist contrast measurements was demonstrated.
In this paper we present preliminary studies on liquid crystal materials suitable for near-infrared applications. This
includes initial analysis of the liquid crystal properties when doped with CuInS2 quantum dots. We also discuss potential applications of LCs. Passively mode-locked fiber laser is presented in which simple LC-cells are used for intracavity
polarization control, which greatly simplifies the configuration of the laser.
In recent years silicon photonics has become a mature technology enabling the integration of a variety of optical and optoelectronic functions by means of advanced CMOS technology. While most efforts in this field have gone to telecom and datacom/interconnect applications, there is a rapidly growing interest in using the same technology for sensing applications, ranging from refractive index sensing to spectroscopic sensing. In this paper the prospect of silicon photonics for absorption, fluorescence and Raman spectroscopy on-a-chip will be discussed. To allow spectroscopy in the visible and near infrared the silicon photonics platform is extended with silicon nitride waveguides.
Enzyme-linked immunosorbent assays (ELISA) are the most popular immunoassay techniques performed every day in
hospitals and laboratories and they are used as a diagnostic tool in medicine and plant pathology, as well as a qualitycontrol check in various industries. However, complex labeling techniques are required to be able to perform the assay and non-specific binding and endpoint timing are difficult to optimize. These issues could be solved by label-free techniques such as silicon nanophotonic microring resonator sensors, but this platform requires complex microfluidics, which is very much removed from the daily practice in e.g. hospital labs, which still relies to a large degree on platforms like 96-well microtiter plates or reaction tubes. To address these issues, here, we propose the combination of a simple and compatible reaction tube platform with label free silicon-on-insulator (SOI) photonic biosensors, where the flow is through the sensor chip as opposed to over the chip as in more conventional approaches. This device allows real time detection and analysis. Its great flexibility and small footprint make it ideal for an easy handling in any laboratory.
We present an integrated silicon Michelson interferometer for OCT fabricated with wafer scale deep UV lithography. Silicon waveguides of the interferometer are designed with GVD less than 50 ps/nm.km. The footprint of the device is 0.5 mm x 3 mm. The effect of sidewall roughness of silicon waveguides has been observed, possible solutions are discussed.
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