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The paper deals with designing and numerical modelling a 2 x 2 optical switch for photonic integrated circuits based on 2 x 2 MMI elements and phase modulators. The 2 x 2 optical switch was modelled in the RsoftCAD with the simulation tool BeamPROP. The 2 x 2 optical switch is a common element for creating more complex 1 x N or N x N optical switches in all-optical signal processing.
The paper deals with the optimization of 2x2 optical switch for photonic integrated circuits based on two 2x2 MMI splitters and two phase-modulators. The optical switch was modelled in the RSoftCAD with the simulation tool BeamPROP. The optimization was done to minimise the insertion losses and broaden the spectral band at 1550 nm by using linear tapers in a 2x2 MMI splitter topology. The 2x2 optical switch is a common element for creating more complex 1xN or NxN optical switches in all-optical signal processing.
The production of liquid-gas dispersions places high demands on the process technology, which requires knowledge of the bubble formation mechanisms, as well as the phase parameters of the media combinations used. To obtain the bubble sizes introduced to a flow not knowing the phase parameters, different process parameters are investigated. Their quality and applicability are evaluated. The results obtained make it possible to simplify long design processes of dispersion processes in manufacturing plants and to ensure the product quality of the products manufactured, by reducing waste.
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.
Deep etched structures in GaAs with high aspect ratio have promising applications in optoelectronics and MEMS devices. The key factors in their fabrication process are the choosing of proper mask material and etching conditions which results in high selectivity and an anisotropic etch profile with smooth sidewalls. In this work, we studied several types of mask materials (Al, Ni, Cr, SiO2) for deep reactive ion etching of GaAs using inductively coupled plasma system. Thus, several sets of experiments were performed with varying gas mixture, pressure and ICP/RF power. As a result, we find optimized conditions and minimal thickness of mask material for achieving deep etched (>140 m) GaAs structures.
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.
In previous studies of linear rotary systems with active magnetic bearings, parametric excitation was introduced as an open-loop control strategy. The parametric excitation was realized by a periodic, in-phase variation of the bearing stiffness. At the difference between two of the eigenfrequencies of the system, a stabilizing effect, called anti-resonance, was found numerically and validated in experiments. In this work, preliminary results of further exploration of the parametric excitation are shared. A Jeffcott rotor with two active magnetic bearings and a disk is investigated. Using Floquet theory, a deeper insight into the dynamic behavior of the system is obtained. Aiming at a further increase of stability, a phase difference between excitation terms is introduced.
Various carbon (nano-) forms, so-called allotropes, have become one of the most supporting activities in fundamental and applied research trends. Therefore, a universal deposition process capable of “adjusting” system parameters in one “deposition chamber” is highly demanding. Here, we present a low-pressure large area deposition system combining radiofrequency (RF) and microwave (MW) plasma in one chamber in different configurations, which offers a wide deposition window for the growth of sp2 carbon (carbon nanotubes, amorphous carbon), a mixture of sp2 and sp3 (diamond-like films) and pure sp3 carbon represented by diamond films. We will show that not only the type of plasma source (RF vs. MW) but also the gas mixture and plasma chemistry are crucial parameters for the controllable and reproducible growth of these allotropes at temperatures from 250 to 800 °C.
Experimental multi-state quantum discrimination in the frequency domain with quantum dot light
(2022)
The quest for the realization of effective quantum state discrimination strategies is of great interest for quantum information technology, as well as for fundamental studies. Therefore, it is crucial to develop new and more efficient methods to implement discrimination protocols for quantum states. Among the others, single photon implementations are more advisable, because of their inherent security advantage in quantum communication scenarios. In this work, we present the experimental realization of a protocol employing a time-multiplexing strategy to optimally discriminate among eight non-orthogonal states, encoded in the four-dimensional Hilbert space spanning both the polarization degree of freedom and photon energy. The experiment, built on a custom-designed bulk optics analyser setup and single photons generated by a nearly deterministic solid-state source, represents a benchmarking example of minimum error discrimination with actual quantum states, requiring only linear optics and two photodetectors to be realized. Our work paves the way for more complex applications and delivers a novel approach towards high-dimensional quantum encoding and decoding operations.
Due to the increasing trend of photonic element miniaturisation and the need for optical splitting, we propose and simulate a new type of three-dimensional (3D) optical splitter based on multimode interference (MMI) for the wavelength of 1550 nm. We present various designs and simulations of various parameters for the optimized MMI splitter. We focus on the possibility of its integration on an optical fiber. The design is focused on a possible production process using 3D laser lithography for the prepared experiments. The MMI splitter was prepared by laser lithography using direct writing process and finally investigated by output characterisation by the near-field measurement.