The paper presents concept, summary of numerical modeling and technology chain proposition for fabrication of measurement heads of integrated grating interferometer and interferometric tomograph. In both cases, the measurement head is a monolithic PMMA cuboidal block with diffraction grating integrated. The structures replace a set of bulk optical elements used in classical interferometric setups. Fabrication of the measurement heads by replication is the crucial aspect of significant reduction of proposed system manufacturing. Numerical treatment performed in geometrical and scalar-wave regime, covers investigation of external as well as internal properties of the measurement heads. Modeling was also the basis for determination of acceptable measurement head replicas quality providing beam propagation proper for both considered interferometric techniques. The technology chain proposed in the paper covers master fabrication and its replication steps leading to fabrication of truly low-cost measurement devices.
The technology path to produce low cost microinterferometric heads in plastic and the optical methods for quality
investigations of these elements are presented. Specifically the interferometric and photoelastic tomography methods,
applied for the 3D studies of refractive index (n) and birefringence (B) in photonics components replicated by means of
hot embossing (HE) technology, are investigated. The enhanced automated measurement and data analysis procedures
are described and the experimental results obtained for micro-objects working in transmission are given. Also the
methodology to combine the tomographic data for full characterization of internal structure of 3D photonics elements is
provided. The samples under test are massive waveguide microinterferometerers in the form of cuboids produced by hot
embossing process characterized by a variety of parameters. The systematic tomographic studies of 3D distribution of n
and B provided important information for extending knowledge about the process and optimization hot embossing
technology. The tomographic measurements are supported by measurements of top and side walls profile and roughness.
Microstructured metallic moulding tools or mould inserts are needed for mass production of micro-optical components.
These tools are used for hot embossing or injection moulding of micro components in plastic. Because of the extremely
tight specifications like small sidewall roughness and high aspect ratios these tools are usually fabricated by lithographic
procedures followed by electroforming. In this case the structural geometry is limited to Manhattan-like structures and
only a limited number of technologies can be used to fabricate the master structures. Applicable techniques are e.g. X-ray
lithography (LIGA technology) or Deep Proton Writing (DPW). However these processes are not suitable for low-cost
mass production. They are limited by the exposure area and the design of the microstructures. To overcome these
limitations a new process has been developed which allows the transfer of micro-optical structures fabricated by other
technologies as well as assembled structures or structures with varying geometries into a moulding tool. The master
structures, either plastic, glass, metal or a combination of these materials, serve as sacrificial parts. With electroforming
technology, a negative copy of the microstructured master is built up in the metal subsequently used as a moulding tool.
Low-cost mass production is possible with these moulding tools.
We present the process chain in this paper and demonstrate its feasibility by producing reliable moulding tools from
three challenging and different components. The possibility of mass fabrication of the components by replication was
demonstrated.
Over the last decades the significant grow of interest of photonics devices is observed in various fields of applications.
Due to the market demands, the current research studies are focused on the technologies providing miniaturized, reliable
low-cost micro-optical systems, particularly the ones featuring the fabrication of high aspect ratio structures. A high
potential of these technologies comes from the fact that fabrication process is not limited to single optical components,
but entire systems integrating sets of elements could be fabricated. This could in turn result in a significant saving on the
assembly and packaging costs.
We present a brief overview of the most common high aspect ratio fabrication technologies for micro-optical
components followed by some characterization studies of these techniques. The sidewall quality and internal
homogeneity will be considered as the most crucial parameters, having an impact on the wavefront propagation in the
fabricated components. We show the characterization procedure and measurement results for components prototyped
with Deep Proton Writing and glass micromachining technology replicated with Hot Embossing and Elastomeric Mould
Vacuum Casting technology. We discuss the pros and cons for using these technologies for the production of
miniaturized interferometers blocks.
In this paper we present the status of our research on the new technology chain and we show the concept of
microinterferometers to be fabricated within presented technology chain.
In this paper we present the novel concept of tomography system for characterization of small phase microelements such as telecom fiber splices. We demonstrate the measurement method, existing setup and its modification towards creation of miniaturized waveguide based Mach-Zehnder interferometer for telecom fiber assessment. Additionally we present and analyze Deep Proton Writing as a promising technology for rapid prototyping of monolithic microinterferometer in PMMA.
Nowadays development of optical networks causes significant grow of interest in reliable fiber connections. Although fiber splicing techniques are well known, the assessment of a joint quality still bases on the simple image processing estimation. In advanced applications such solution is not sufficient and more trustworthy method is needed. One of the promising techniques of reliable measurements is microinterferometric tomography which allows determination of three-dimensional refractive index distributions in phase isotropic microelements. Measurement bases on interferometric scan of the tested element. Contrary to the classical testing methods based on attenuation tests microinterferometric tomography analyses an inspected fiber with the beam passing perpendicularly to the fiber axis. Tomographic scans taken for numerous, well defined angular positions and further calculations result 3D map of the area with clearly seen splice zone.
In this paper we propose the novel design of the integrated low-cost microinterferometric tomography setup (fig.1). The system is built as the waveguide Mach-Zehnder interferometer with reduced vibration sensitivity due to using the grating beamsplitter and recombiner. Additionally we present the details of design of microinterferometric tomography setup and the initial remarks on the possibility to fabricate it with Deep Lithography with Protons (DLP) - unique master prototyping technology of fabrication both micromechanical and microoptical elements in polymer material.
We aim to take an advantage of compactness and reduced dimensions of the interferometer to implement it as the possible accessory of the commercial optical fiber splicer.
Microinterferometric tomography allows for determination of three-dimensional refractive index distributions in phase isotropic microelements. In this paper we present the measurement of the refractive index profile of the optical fibers exposed to the gamma radiation. Nuclear radiation is known to affect the guiding properties of optical fibers and it is therefore essential to characterize these effects to assess the applicability of fiber-optic technology for communication and sensing in nuclear industry. It is already well known that radiation affects the absorption of the fiber. Here, we investigated whether we could quantify the effect of radiation on the refractive index of core and cladding of an optical fiber.
We present Deep Lithography with Protons (DLP) for the fabrication
of ultra-dense fiber coupling elements which consist of circular,
conical-shaped alignment features, ordered in a 2D array with
high-precision pitches. This technology relies on the irradiation
of PMMA-resist layers with a swift proton beam featuring a
well-defined circular shape, followed by a selective development
of these exposed zones. To increase the coupling efficiency, the
DLP-technology allows to integrate uniform spherical micro-lenses,
which are created by a controlled swelling of the proton-bombarded
domains in a monomer vapor, in front of the micro-alignment holes.
We will first discuss our work on the improvement of the DLP
irradiation and development process step to enhance the coupling
efficiency and the field-installability of the connector
components. Furthermore, we will illustrate the optical design of
micro-lens arrays and their integration in fiber connectors with
improved tolerances.
In this paper we present Deep Lithography with Protons (DLP) as a promising technology for the fabrication of mechanical fiber alignment structures accurately ordered in massive 2D arrays. The fabrication process consists of irradiating PMMA-resist layers with high-energetic proton beams through a lithographic mask with a well-defined circular shape, followed by a selective development of these irradiated zones. To increase the coupling efficiency, we can additionally integrate uniform spherical micro-lenses created by swelling the proton-bombarded zones in a monomer vapor. We highlight the influence of the etching time, the proton beam intensity and the absorbed doses in the PMMA layers on the diameters of the finally developed alignment holes. While selecting the correct process parameters, we prove DLP to be a suitable technology for the fabrication of circular micro-holes with diameters of 125&mum and 155&mum at the front and the back side of a 500&mum thick PMMA plate respectively. We finally illustrate the potentialities of these type of fiber holding plates to realize a user-friendly and accurate 2D fibre positioning component.
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