This PDF file contains the front matter associated with SPIE Proceedings Volume 13508, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The temperature dependence of the laser output properties of the Fe:ZnSe single crystal was investigated under ~4.04 μm laser radiation excitation in the quasi-collinear configuration. A non-selective laser cavity consisted of a flat highly reflective mirror in a range of ~3.9-5 μm and a concave (r = 200 mm) output coupler with a reflectivity of 88% in a range of ~4-5.3 μm. The pumping energy of ~9.3 mJ at ~4.04 μm in ~125 ns long pulses was applied. The angle between pumping and generated laser beam was ~20°. The maximum laser output energy of ~0.32 mJ with corresponding slope efficiency of ~7.5% was obtained at 230 K at a wavelength centred at ~4.5 μm.

We present a self-starting all-polarization maintaining Tm-doped fiber laser oscillator mode-locked by a Nonlinear Optical Loop Mirror (NOLM). According to our knowledge this is the first dispersion-managed Tm-doped fiber laser with NOLM constructed entirely of polarization maintaining fibers. The cavity provides a stable generation of linearly polarized, linearly chirped picosecond pulses at 1998 nm, which can be compressed by a piece of an anomalous dispersion fiber down to 688 fs. The average output power in a single pulse train regime is 200 μW at a repetition rate of 9.39 MHz.

We compared the acoustic responses of three hollow-core fibres to the response of a standard single mode fibre. Our efforts focused on decoupling the interaction of the fibre with supports and the acoustic box walls. Contrary to published results we found that the normalized responsivity of fibres grows with frequency over the relevant acoustic range. It was shown that the normalized responsivity can be controlled over the range of at least 40 dB by appropriate design of the hollow-core fibre.

The dissemination of phase-coherent signals through optical fibre links is typically influenced by induced phase noise. This is due to the Doppler effect and fibre length changes due to disturbing environmental influences (temperature changes, mechanical vibration, etc.). In the case of long-range fibre links, compensation methods based on fibre interferometers and appropriate action elements (acousto-optical modulator/frequency shifter, fibre stretcher) are usually involved in suppressing these unwanted signal distortions. In the case of short-range links, like interconnections between neighbouring laboratories or fibres between two different optical tables in the same room, these traditional methods are too sophisticated and complex. In this work, we describe the pilot experiment and the resulting performance of the optical frequency transfer through hollow-core photonic crystal fibre link, where the optical signal of 729 nm is disseminated by an air-filled hollow-core. We mainly focused on the link sensitivity to induced phase noise and its comparison to standard solid-core fibre link performance.

With a continuous growth of the data-hungry applications, conventional electrical connections are unable to fulfill ever rising requirements on the bandwidth, speed, power consumption, and data capacity. Optical communications has gradually replaced electronic wires in short-reach, metropolitan, and long-distance transmission links, allowing to form 100 Gbps to 400 Gbps links per single wavelength and simple On-Off Keying (OOK) modulation. However, optical fibers still suffer from many degradation effects, and Polarization Mode Dispersion (PMD) remains the most critical one due to its stochastic nature and complex mitigation schemes. The effect of PMD is dominant for data rates above 10 Gbps, which is however, common in recent wavelength division multiplexing networks. In this work, we present an innovative model to reduce the impact of PMD effect via effective spectral management using inter-channel switching. The model is based on the experimentally measured PMD data and leverages transmission quality monitoring using eye diagram inspection. For this, we study various system configurations, including single optical fiber with densely spaced wavelength channels and different of optical fibers with various direct transmission and back-up reservoir channels, respectively. We expect that PMD-based optical signal degradation is a manageable system task and proposed numerical model is promising for inexpensive high-speed link control and system monitoring.

The research addressed in this paper concerns unconventional optical architecture and software modifications to the Variable Wavelength Interferometry (VAWI). The structure of two birefringent prisms constitutes the instrument’s key constructional element, which coexist with a classical microscope with the Kӧhler illumination system. In the conventional form the optical design utilizes a continuously tuned light source and the measurement algorithms analyze a relatively large number of images consecutively recorded at slightly different wavelengths. The traditional and new fringe processing algorithms are presented. The micro-interferometer can be used in both transmitted and reflected-light configurations. It allows for measuring optical and geometrical parameters of transparent or reflective objects. The current presentation concerns the reflected-light mode set-up and measuring the collection of the stem height standards. The optical path difference is measured with low uncertainty thanks to multispectral nature of the device, and analysis of which creates the concluding part of the paper.

A novel tomographic microscope setup utilizing the principle of Holographic Incoherent-light-source Quantitative Phase Imaging is introduced. This setup combines the advantages of achromatic off-axis holography with the ultrafast operation of a digital micromirror device-based tomographic illuminator. The imaging theory is explained, and the optical design of the microscope is described. The functionality of the microscope modules is demonstrated experimentally using a light source of limited spatial coherence.

In this work, we numerically compare accuracy and robustness of five popular phase retrieval approaches for lensless digital holographic microscopy. In our analysis we consider three single-frame approaches: (1) seminal Gabor method, (2) optimization-based method exploiting data fidelity and object priors, and (3) UTIRnet as a representative of deep learning methods. We also analyze two multi-frame approaches: (4) conventional Gerchberg-Saxton (GS) algorithm and (5) recently proposed optimization-based algorithm called defocus-interdependence conjugate gradient method (DI-CG). In our numerical study we focus on robustness of the phase retrieval algorithms to disturbances in the captured data with a distinction between the influence of high and low-frequency intensity errors. Our study shows that although single-frame algorithms fail to recover slowly varying phase features, they offer excellent resistance to external disturbances. Contrary, more refined multiple-frame approaches are generally more accurate but suffer from increased sensitivity to data errors, which, to some extent, can be mitigated with a regularization technique.

This paper describes a portable, experimental all-fiber interferometer designed for acoustic vibration sensing using telecommunication optical fibers. The optical and electronic components of the setup are detailed. The interferometer operates on the principle of heterodyne beatnote detection, with electronic processing to produce a quadrature complementary signal that conveys information about the interference phase. System parameters and measurement examples are presented.

In the paper, we describe the construction of a sensor for measuring the arterial pulse waveform using the method of applanation tonometry and demonstrate its practical use. The sensor works on the principle of detecting an optical signal that arises due to the two-beam interference of beams reflected within the Fabry-Perot cavity, which is created at the end of the optical fiber. One of the two reflecting surfaces of the Fabry-Perot cavity is formed by an elastic membrane. An innovative solution to the construction of the sensor is created using two coaxial tubes, the inner one of which contains an optical fiber, and the outer one carries an elastic membrane. The tubes can be moved in the direction of their axes to set the sensor's optimal sensitivity. The sensor's size enables locating the cardiovascular system's arterial pulse points, even by pushing into the tissues at the level of a few millimeters. We demonstrate the way of using the described sensor by measuring the interference optical signal on the carotid and radial arteries.

Monitoring of moving rolling stock from the phase change of light caused by elongation of the sensing optical fiber is presented. An optical sensor consisting of sensing optical fiber and supported construction is placed on the bottom of the rail. Due to rail bending caused by the wheel applied on the rail, the length of the sensing optical fiber is changed. Since the sensing optical fiber serves as the cavity of the Fabry-Perot interferometer, there will be a phase change of light. The value of phase change depends on the rail profile, the distance between railway sleepers, the place of sensor attachment, and the length of an active part of the sensing optical fiber. The only parameter that we can influence on the existing railway infrastructure is the sensitivity of the sensor by changing the length of the sensing fiber. So, two optical sensors with different sensitivities were prepared and placed on the foot of the rail at a distance of 50 cm apart to compare the obtained results of such sensors.

With the increasing demand for ultra-precise time synchronization and frequency dissemination across various scientific, industrial, and communication fields, the Czech Republic has developed an innovative, non-commercial fiber-based infrastructure. This infrastructure serves as a shared platform, utilizing optical fibers to enable high-precision timing, coherent frequency transfer, and a newly implemented vibrational sensing capability. The project also addresses challenges posed by classical communication noise—particularly from Raman scattering—on quantum channels, especially for Quantum Key Distribution (QKD). By strategically separating classical and quantum channels into distinct wavelength bands, such as the C-band and O-band, the infrastructure achieves minimal interference while enabling multiple concurrent applications over shared fiber lines.

This study deals with a cost-effective modification of a general purpose Integrating Sphere (IS). The aim is to create an extended uniform light source for calibration purposes focusing on matrix camera of fluorescence telescopes. Therefore, a low intensity near-UV primary light source is being used to approach the detection parameters of fluorescence telescopes. First, the radiance uniformity, which is the most important parameter, of the IS was measured in detail using an experimental setup developed in our laboratory. However, the resulting radiance uniformity of general purpose IS did not exhibit the required level, which is in general 98 %. Thus, the second step was to optimize the IS on the base of a validated optical ray-tracing model in terms of virtual prototyping. Eventually, suggested changes were implemented, the modified IS was assembled in our workshop, and finally its radiance uniformity was re-measured on the same experimental setup. The resulting radiance uniformity of the modified IS exceeds the desired 98 % and confirmed that the optimization was beneficial. This study presents methodology and results of experimental radiance uniformity measurements and introduces the modified IS for calibration purposes of fluorescence telescopes and detectors of astroparticle experiments in general.

The contribution reviews actual trends in the design of molecular iodine reference cells intended for laser standards operated in space-related applications and which were recently developed at ISI CAS. The need for the optical setup compactness and robustness introduced multipass arrangements, leading to reduced system weight and volume while maintaining long laser beam–absorber interaction lengths. The resilience to harsh environmental conditions, especially during the mission launch, and system reliability for the whole mission lifetime led to the investigation of novel approaches in reference cells development and performance evaluation.

Spintronic Terahertz Emitters (STEs) are novel sources capable of emitting radiation in a wide THz frequency band. They, however, suffer from low efficiency and emitted power. To increase their power, we have proposed in this work the possibility of integrating a focusing metasurface (metalens) directly on top of the STE substrate backside. The feasibility of this metasurface is achieved with the generalized Snell’s law and the non-resonant propagation phase mechanism. The proposed basic unit cell of the metasurface is a high aspect ratio cylinder made of poly(methyl methacrylate) (PMMA) resist, which is producible simply by the initial steps of the LiGA (lithography, electroplating, molding) process. These structures are designed and optimized using simulations in the commercial software CST Microwave Studio with the frequency and time domain solvers. Simulation results are compared to those obtained with analytical relations from diffraction theory, which allows easier calculation for large-scale problems.

This work revolves around preparation of microfluidic chip that can generate surface acoustic wave and standing surface acoustic wave with its own designed frequency. This wave is generated on lithium niobate by interdigital transducers placed directly on the substrate. Chip prepared this way was ready for its primary usage in particles flow manipulation and separation particles in flow by their size. Our pilot measurements included separation, sorting and trapping of polystyrene particles with diameter of 5 and 15 μm. Platform based on surface acoustic wave techniques could be used for biological fluid samples. This platform enables manipulation and study of cells, while preserving their structure, function and biological integrity. Thus, we also studied Trachydiscus minutus as a testing biological cell for trapping. Apart from separation, sorting and trapping, we have observed polystyrene particle accumulation in the field between uniform pair of IDTs.

In this paper, we present a mechanical microgripper structure at the end of an optical fiber, whose movement is controlled by a magnetic field. The mechanical structure is created using modern 3D laser lithography from the IP-Dip polymer. This technique allows the creation of arbitrary structures, and the flexibility of the polymer enables the formation of various movable and mechanical parts of the structure. Our proposed structure has two jaws, one of which is movable and contains a ferromagnetic microparticle that interacts with the magnetic field to open the microgripper's jaw. Once the magnetic field is removed, the jaws return to their original position. The structure is attached to the end face of the optical fiber with epoxy, allowing it to move in a liquid. This way, we aim to capture microparticles present in the liquid. Since IP-Dip also has excellent optical properties, the proposed structure has the potential to create a multidisciplinary sensor in the future and become part of optomechanical components.

One-dimensional photonic crystals (1DPhCs) have a wide range of potential sensing applications. By using two 1DPhCs-mirrors, a resonator can be created that supports cavity mode resonances. This concept is crucial to proposing highly sensitive optical sensors that employ spectral interrogation. In this paper, several 1DPhC-based resonators were theoretically analyzed for different analytes with varying cavity lengths. It is revealed that cavity mode resonances shift with changes in the Refractive Index (RI) of the cavity media. Moreover, the sensitivity to RI, along with a Figure of Merit (FOM), is evaluated. Additionally, it was demonstrated that these quantities depend on both 1DPhC composition and mirror distance. Theoretical analysis is accompanied by experiments for normal incidence in Relative Humidity (RH) sensing. Furthermore, the sensitivity to RH, together with FOM, are evaluated.

In this paper, we focused on a specific concept of the mirror grating with the table-like arrangement. We designed the mirror grating structure in two configurations and prepared in IP-Dip material using three-dimensional (3D) laser lithography according to the proposed theoretical design. The morphology of the prepared structures was analyzed using a confocal microscope. Finally, we experimentally demonstrated near-field measurement over the table-like grating mirror structure.

In this contribution, we focused on the design and preparation of new concept of two-beam fiber optical interference lithography device for fabrication of one-dimensional gratings with automatically adjusted period. The developed concept allows fabrication of broad range of gratings from 600 to 5200 nm on a very compact device. Prepared gratings were analyzed by confocal laser microscope where we confirmed high quality gratings with depth of app. 200 nm.

We present results obtained by laser interference lithography (LIL) as a useful tool for fabrication of high-symmetry gratings. Specifically, we focus on thin resist layer patterning by Moiré lattices and 2D quasicrystals. We use two-beam LIL in Mach-Zehnder configuration which creates one-dimensional interference field. By multiple exposure process with in-plane rotation we achieved different Moiré patterns. Additional pattern modulations were realized by changing the period of interference optical field. LIL setup allows automated exposure process with period tuning from 250 nm to 2500 nm on the area of 5x5 cm². For design of the lattices, we developed simulation software in LabView environment. Experimentally prepared 2D quasicrystals and Moiré lattices were analyzed by confocal laser microscope and their quality was investigated by diffraction images.

Integrated photonics is envisioned as a key enabler for numerous emerging applications, including high-speed communications, ultra-fast optical computing, and quantum information processing. These applications call upon efficient connection between the sub-micrometric planar photonic waveguides and standard optical fibers (SMF-28). Fiber-to-chip optical interfacing has always been recognized as an issue of fundamental importance in the field of integrated photonics, particularly by imposing a critical constraint on the power budget for the chip-scale photonic systems. Hence the direct fiber-chip connection is vastly inefficient with position-restricted accessibility, the key challenge for light coupling involves several factors. This includes geometrical and material discrepancies, different mode field diameters of SMF-28 fibers and photonic waveguides, on-chip design flexibility, and fast optical testing, preferably utilizing available die-level or wafer-scale accessories. In this work, we report on our recent progress in the development of efficient fiber-to-chip optical interfaces based on compact surface grating couplers. We present and discuss prospective design approaches and experimental results for grating-coupled devices implemented on surging silicon (Si) and silicon nitride (SiN) waveguide platforms, supporting advanced photonic integration with coupling efficiencies approaching -1 dB level.

Silicon nitride waveguides play a leading role in photonic system integration. Silicon nitride leverages unique low-loss passive functions, mature deposition techniques of low-pressure chemical vapor deposition and plasma-enhanced chemical vapor deposition, and compatibility with complementary metal–oxide–semiconductor fabrication. So far, a wide variety of photonic devices have been demonstrated in Silicon nitride platforms, including ultra-low-loss waveguides, filters, multiplexers, and grating or edge couplers, to name a few. Among these elements, beam splitters based on multimode interference couplers are key building blocks for complex chip-scale photonic systems, including coherent communications or advanced optical networks. This work is focused on O-band (spectral range between 1260 nm and 1360 nm) multimode interference beam splitters on silicon nitride platform for power and polarization on-chip management. It is used three-dimensional eigenmode expansion and finite difference time domain solvers, respectively. We proposed a 1x2 power and polarization splitters with a compact footprint of 2.6 μm and 5.55 μm and insertion loss as low as 0.3 dB across 400 nm wavelength range. Also, we designed multimode interference power splitters 1:4 and 1:8 with insertion loss as low as 0.5 dB with bandwidth 240 nm and 60 nm, respectively. These results are promising for the development of scalable and high-performance chip-integrated components in power-hungry and polarization-sensitive applications. For effective designing of polarization splitter based on multimode interference it is necessary using apodization techniques to avoid large footprint and very low bandwidth.

The rapid advancement of optical communication technologies has necessitated the development of highly efficient and stable photonic integrated circuits that enable coherent signal processing in the optical domain. Among them, Arrayed Waveguide Gratings (AWG) has emerged as a crucial component in Dense Wavelength Division Multiplexing (DWDM) systems. However, the performance of conventional AWGs is strongly affected by temperature fluctuations, resulting in central wavelength shifts and increased insertion losses. The aim of this study is to achieve a significant reduction of this dependency by using silicon oxynitride and polymethyl methacrylate on a silicon substrate with a thermal silicon dioxide buffer layer, thereby improving the overall performance and reliability of AWG-based DWDM systems. To achieve this, we have designed an athermal waveguide structure that can operate efficiently over a wide temperature range of -40°C to 80°C without the need for active temperature control mechanisms. Such a waveguide creates the basis for the AWGs in photonics integrated circuits.

The Multimode Interference (MMI) splitter employs interference principle to split optical signals in photonic integrated circuits in small volume. In MMI splitters, optical signals are split using the self-imaging effect - a property of output modes, reproducing the input field profile at regular intervals along the propagation direction in the multi-mode waveguide. The applications of the MMI splitters cover a wide range, starting with basic power splitting, switching, polarization dividing, and so on. Standard MMI splitters use the on-chip planar splitting in multimode waveguide. However, the latest research has confirmed the high-quality processing of MMI splitters in three dimensions (3D) as well. The 3D MMI power optical splitter with branched output waveguides based on multimode interference for the wavelength of 1550 nm is here designed, simulated, fabricated and optimized. The design is focused on using a 3D laser lithography based on direct laser writing process Based on a new concept of 1x6 splitting. The output characteristics of 1x6 MMI splitter were investigated by a near-field measurements where we confirmed well 1x6 splitting and branching into six output waveguides arranged in 2x3 array.

In the field of optical diffraction elements, laser lithography has an important role in the preparation of 2- and 2.5 dimensional microstructures in polymer materials. Rapid prototyping in the process of manufacturing such fine structures is key to boosting research of photonic components and devices. Standard Direct Laser Writing (DLW) lithography process allows to create only on very small scales, limited by the construction of used setup. Using extremely fine and precise manipulation, we are creating these structures on relatively large surfaces in tens of millimeters squared. The latest results show that we can create structures with complex topography by manipulating height gradient of structures with exposure dose modulation, also known as grayscale lithography. This device can speed up of the preparation and expand the area of structure in single-step process.

Atomic Force Microscopy (AFM) enables high-resolution imaging of a sample surface based on atomic interactions between the surface and a scanning probe. Geometry, and material composition of fiber tips and cantilever strongly influence the capability of any measurement and can be tailored to the desired application. Especially, the modern three-dimensional (3D) technologies open new platform of tips with complicated 3D architecture. Such tips could bring novel mechanical properties tailored to the desired application. We focused on design and fabrication of novel probes based on polymers with different cantilevers. We investigate different shapes and geometries including the very attractive Controlled Microstructurally Architecture (CMA) tips. The prepared probes were examined by scanning electron microscopy and their quality was analyzed by scanning the AFM images.

Presence of microplastics is responsible for a large part of today’s environmental pollution. At the same time, identification of the MPs in the real environmental conditions (such as presence of organic material, namely algae, in water) is still highly challenging. In this contribution, we demonstrate the application of ToF SIMS and XPS spectroscopy methods for evaluation of the presence of polystyrene microplastics in the absence and in the presence of algae Chlorella sp.

A prominent procedure emerging in a medical practice called surface-enhanced Raman spectroscopy-guided photothermal therapy is a step toward achieving patient-specific, less damaging treatment for cancer. This procedure requires that an agent used for determining the placement of the unhealthy tissue also contributes to the treatment itself. As an agent, we created six different polymer-based structures using Nanoscribe Photonic Professional GT nanolithography 3D printer. Afterwards, these structures were Au-coated with two different thicknesses: 5 nm and 10 nm. To ascertain their ability to enhance the Raman signal within the procedure's diagnostic part, we investigated the presence of localized plasmon resonance by measuring the transmittance in the visible and the near-infrared spectrum. Consequently, the structures were used as a substrate for Raman spectroscopy with rhodamine 6G as an analyte molecule. In the final step, we determined the structure's ability to convert electromagnetic energy into thermal energy by measuring the difference in temperature between the structures and their surroundings, which is an integral part of the treatment enabling it to cause hyperthermia in the affected tissue.

We present gold-coated 3D structures patterned in the surface of IP-Dip polymer by direct laser polymerization. The structures consist of parallel rods with V-profile arranged in 1D and 2D grid. The period of the structure is 3 µm. After patterning, an Au layer with two different thicknesses (5 nm and 10 nm) was evaporated. For characterization of prepared structures, the transmission spectra were measured. Examination of absorption peaks and their shift with Au thickness leads to definition of resonant wavelengths of localized surface plasmon polariton that can be present at the rod edges in metal-dielectric interface. The radiation characteristics were examined by near-field scanning optical microscope measurements as well. The radiation pattern varies with the illumination wavelength, and it is strongly modified when using the wavelength close to the plasmonic resonant one.

PDMS samples enclosed in glass cuvettes are individually exposed to two different liquids, toluene and limonene. Due to the absorption of the used liquid, the PDMS sample tends to increase its volume, but due to spatial confinement, the cuvette walls exert stress on the sample. As a result of the uneven directional distribution of this stress, the initially optically isotropic PDMS becomes optically anisotropic. We monitor the temporal development of the optical anisotropy using a linear polariscope in which the sample is placed. The optical anisotropy of PDMS manifests itself by optical birefringence. Using a white light source and monitoring the spectral distribution of the light intensity at the output of the polariscope as a function of time, we can obtain from the measured data information about the temporal evolution of the optical birefringence in the spectral region corresponding to visible light. This information can be used to determine the spectral dependence of the value of the relative stress-optic coefficient C₀ and to monitor the dynamics of the liquid absorption process into PDMS. Also, the observed phenomenon is potentially usable in optical sensors detecting the presence of certain liquids and gases.

This work is dealing with actual topic in the field of internet service providers that are solving the question of metallic and optical networks convergence. The aim was to construct an experimental network topology in the form of WAN or LAN topology consisting of GPON network with VDSL2 technology, which led to the creation of a hybrid access network, on which the parameters of multimedia services were then measured. In particular, focusing on the distribution of video streams through SDTV & HDTV (MPEG-2) + HDTV (MPEG-4). As part of the network integrity measurements, tests are performed according to the recommendations of RFC 6349 and ITU-T Y.1564 standard.

Nowadays, there is strong demand for high-bitrate systems that can provide and distribute large bandwidth while assuring minimal error rate and high-quality communication with regards to the implementation of cloud centres, new 6G networks and smart applications. This all leads to continuous dynamic development in the field of xPON networks bringing new solutions for future optical networks. The presented work focuses on NG-PON2 networks, which are represented by Time and Wavelength Division Multiplexing Passive Optical Network (TWDM-PON) (G.989.1) or Super-PON (IEEE P802.3cs). The basis of the introduced topology is in combination of wave and time access through the TWDM-PON network. In our simulation, we were focusing on the utilization of eight wavelengths operating in the C and L band with amplifiers implementation, namely Erbium Doped Fiber Amplifier (EDFA) or Semiconductor Optical Amplifier (SOA). Regarding to used amplifier the ODN (Optical Distribution Network) reach of TWDM-PON were studied as well as the bitrate of 10 Gbps per wavelength in both upstream and downstream directions with the help of parameters such as bit error rate (BER), Q-factor. From the simulation results, it is shown that by implementing an EDFA amplifier, a longer range of up to 60 km and a lower BER than that of SOA can be achieved. The proposed TWDM-PON system provides a communication network for urban as well as rural areas with guaranteed high bit rates and range.

With the increasing number of end users that are using multimedia services, demand for access network high bitrate systems with sufficient quality of services also increases. However, this might not always be ensured by the telecom operators, as they must perform network optimization concerning Quality of Service (QoS) and multimedia data transmission. In this work, we focused on Gigabit Passive Optical Network (GPON) performance testing with the help of various tools (iPerf, RFC 6349 or ITU-T Y.1564). The Grafana software tool is used to monitor data streams. Measurements were made to limit the downstream bitrate of up to 20 end users at 100 Mbit/s. Based on the repeated measurements, an aggregation curve is modelled indicating the available bitrate with respect to the network load.

This work deals with the study of implementation possibilities of broadband optical multiplexer/demultiplexer in the form of AWG (Arrayed Waveguide Gratings) in TWDM-PON topology (Time and Wavelength Division Multiplexing Passive Optical Network) by norm G.989.1 as a key component of the hybrid network. The functionality possibilities of the TWDM-PON system are observed where the goal of AWG design is to support also wavelengths different from standard wavelengths used for TWDM-PON in C-band (Conventional) ranges from 1530 nm to 1565nm and L-band (Long-wavelength, 1565–1625nm) bands. This should allow for older communication systems (for example EPON (Ethernet Passive Optical Network) given by norm IEEE 802.3ah and GPON (Gigabit-capable Passive Optical Network) by norm ITU-T G.984) to be operating concurrently over ODN (optical distribution network) without mutual disturbance with newer xPON communication systems. The network topology operating in this manner makes efficient use of passive infrastructure, including reducing the cost of construction (CAPEx) or operation (OPEx) while creating hybrid types of optical networks.

Quantum Key Distribution (QKD) protocols offer top-tier secure communication but face challenges with noise, particularly when quantum and classical channels coexist. In fiber-optic systems, strong classical signals for data and synchronization create noise through scattering, with inelastic scattering being the main contributor. This broad-spectrum noise can overlap with quantum communication wavelengths, leading to errors and deterioration of the quantum signal. Our study examines the theoretical coexistence limit for a 1500 nm classical synchronization signal from a White Rabbit switch and a 1320 nm quantum signal from an S-Fifteen Instruments source, identifying the maximum fiber length where the quantum signal remains clear of noise. We chose the BB84 protocol for our QKD implementation, which we plan to first test in a laboratory setting without an intermediate node. In the future, adding a node (often referred to as Charlie) would improve scalability and help manage synchronization delays.

Experimental realization of photon addition and subtraction in a twin beam is performed in one experimental setup. This allows us to directly compare the properties of photon added and subtracted twin beams whose similarity is manifested when switching the signal and idler beams: Photon addition (subtraction) in the signal beam modifies the signal (idler) beam. We illustrate this similarity using the corresponding photon-number distributions obtained by photon number resolving detection performed with an intensified CCD camera. Strong photon-number correlations in the two beams and sub-Poissonian marginal photon-number distributions are the most important feature of both fields.

Commercial sources of polarization entanglement at telecommunication wavelengths are already available on the market, but they lack proper certification or third-party testing. We aim to provide a comprehensive testing framework for photon counting and correlation measurements to characterize the parameters of these sources in a scalable and repeatable manner. The detection setup is included in our considerations, as the non-idealities of the components negatively affect the relevance of the measurement results. We discuss bounds for both true and false coincidences with rigorous probabilistic approach, as their ratio directly impacts the resolution of coincidence measurements and is reflected in Quantum Bit Error Rate (QBER) in the quantum telecommunication system. Quantum State Tomography (QST), polarization visibility measurements, temporal correlations measurements, and computations of other statistics are to be performed and compared at the state-of-the-art level for a three commercially available sources. Given that QST is demanding in terms of number of measurements and post-processing analysis, we discuss the relevance of determining the degree of polarization entanglement considering solely other statistics of direct measurement approach.

Quantum experiments are an essential part of research into innovative quantum technologies that protect us, determine time, or help us navigate every day. Such platforms include quantum computers, quantum cryptography, and optical clock. A key part of this research is the observation of ongoing quantum processes, ideally with the ability to respond to these processes in real-time. We have developed hardware and software solution for a system of trapped and cooled calcium ions in a Paul trap, which allows for spatially resolved ions with live detection of their quantum states. This system is used for the development of multi-ion clocks and other previously unrealizable quantum experiments.

A clock is a device that uses a stable oscillation pattern as a reference (i.e. pendulum, quartz). An atomic clock is a laser whose frequency is stabilized relative to a narrow optical atomic transition. Thus, the oscillator, in this case, is a trapped and isolated atom with a natural, very high oscillation rate. Thanks to this revolutionary idea and the evolution of atomic frequency and time standards have taken a giant leap forward. For nearly 100 years, the atomic frequency standard played a critical role in basic science and precision measurement. During this period, the increasing need for more precise timing and synchronization for various applications, including navigation or tests of fundamental physics, has demanded oscillators with higher frequencies and higher performance. This paper introduces the design and instrumentation needed to build an optical reference based on an ultra-cold calcium ion that we built at our Institute of Scientific Instruments in Brno. The isolated, trapped, and laser-cooled ion has a stable oscillation rate in hundreds of terahertz. In the most recent results, we demonstrate that our frequency reference reaches the stability or instability of 5,9 parts in a quadrillion (one followed by 16 zeros) in just a few thousand seconds. The measured full width at half maximum of the frequency stabilized clock laser is 20 Hz.

The optical fibres utilized for scintillator signal transport offer the potential for the long-term and high-energy measurement of ionizing radiation. The optical link based on the optical fibres prolongs the life of photosensitive electronics by placing them outside the radiation field. The issue arising from the optical fibre placement between the scintillator and photosensitive electronics consists of gamma spectra recognition loss. Moreover, the absence of spectra recognition leads to an inability to recognize the ionizing radiation source in an unknown environment. This is caused mainly by the diameter and numerical aperture of the fibre. The fibre shades much of the light emitted by the irradiated scintillator and resolves it into a weaker signal at the end. To simulate the behavior of this system, the optical fibre is replaced by the iris. By adjusting the diameter of the aperture, we investigate changes in the transmitted signal and its impact on the spectra. These changes were then evaluated for the optimal diameter of the optical link.

We present our latest educational initiatives with the learning kit Photonics Explorer. This kit serves as a “lab-in-a-box” enabling 2nd and 3rd grade students to independently conduct photonics experiments in school, utilizing lasers, LEDs, lenses, optical fibers and other high-tech components. As part of the Austrian project MINKT@FHV, we organized two photonics workshops focused on the topic of “Light signals”. During these workshops, we hosted three classes from Gymnasium Dornbirn at our university, where students learned how modern optical communication networks operate.

The flotation froth content assessment can be carried out in various ways. One of them is the Machine Learning (ML) process applied to the preprocessed and parametrized flotation froth images. The ML procedure can be conducted on the basis of Artificial Neural Network (ANN) or Linear Discriminant Analysis (LDA). This paper presents the LDA application in a ML process. The ML algorithms have their origins in the family of classification algorithms. They are constructed on the basis of training groups of data and enable us to classify the unknown data to one of the training groups. Theoretically, if we have more training groups, we should be able to obtain more accurate estimation of data. However, such approach is not efficient. Each training group should have a high number of data sets, which in most cases is difficult to obtain. This paper presents the estimation of the flotation froth content in the mineral processing plant on the basis of images of the froth surface. The experiment was performed in the Pb Mineral Processing Plant. The images of the flotation froth surface were registered for seven different configurations of the flotation process parameters. The flotation parameters were stabilized 30 minutes before the image registration process. The images registered in the stabilized technological conditions constituted the training group of images for the ML process. For each of the technological configurations of the flotation process, ten collective froth samples were collected for direct chemical analysis. This means that each of seven training groups of the froth images contained ten subgroups of images with well-defined froth content. The ML process enabled us to construct the froth content estimation algorithms for the flotation process in the experiment.