Integrated modulators are key components for communications, quantum, spectroscopy or LIDAR. These components require high-speed modulation and low power consumption. Silicon modulators, which are mainly based on the plasma dispersion effect, consume a lot of power and are limited in bandwidth. To overcome these limitations, such modulators can also rely on Pockels effect, an inherently fast and pure phase modulation effect. Since silicon does not have a natural chi2 due to its centrosymmetric structure, pure phase modulators cannot be achieved directly with silicon waveguides. Nevertheless, pure phase modulation in silicon can be realized either by associating materials with high chi2 such as polymer, BTO, PZT, lithium niobate, by straining silicon, or by using DC Kerr effect to electrically induce an effective chi2. The latter is studied in this paper for light modulation in a silicon Mach-Zehnder modulator based on PIN junctions. A clear linear behavior of the dynamic electro-optic response has been demonstrated under a reverse bias applied across a PIN junction. A modulation at twice the RF frequency applied is also shown and assigned to Kerr effect.

We present an innovative waveguide based on the hybridization of a titanium dioxide nano-waveguide within a polymer strip. Through simulations and design, we demonstrate that the waveguide sustains principally the quasi-TM fundamental mode and that even in tight bends (radius smaller than 2 µm) light remains confined in the titania layer. Such a waveguide, in addition to enabling low loss propagation is a way towards efficient evanescent sensing in highly integrated scheme, i.e., small footprint. We also show that the fabrication, here based on electron beam lithography and atomic layer deposition, can be extended easily to large scale manufacturing using nanoimprinting technology.

We performed infrared optical characterization of polycrystalline MoO3 films deposited by pulsed laser deposition on fused silica substrates. Several samples have been fabricated using different parameters such as temperature and oxygen pressure. Our analysis shows that under appropriate fabrication conditions it is possible to obtain a dominant alpha-phase film, with a well-defined, normal to surface (z-axis) orientation. These results are confirmed by reflection spectra performed at 45° incidence angle revealing a strong modulation of the sharp z-phonon Reststrahlen band as a function of the incident field linear polarization.

Optical security is a promising application of metasurfaces because light has large degrees of freedom in metasurfaces. Although many different structures/materials have been proposed for this purpose, the fabrication of dynamic metasurfaces in a straightforward and scalable manner while maintaining a high security level remains a significant challenge. Herein, a metasurface consisting of a phase-changing GeSbTe layer and a thin metal back reflector is presented to space-selectively and dynamically control the infrared emission of the surface by a spatially modulated pulsed laser beam. Unlike conventional laser processes using a focused beam, the employed laser printing is an expanded beam-based parallel process that enables the fabrication of wafer-sized emission patterns. Owing to the multispectral responses of GeSbTe, mutually independent visible and infrared images can be printed in one region. Grayscale emission patterns can also be obtained by gradually modulating the spatial profile of the laser beam, which makes the replication of laser-printed emission patterns extremely difficult. These encouraging features are experimentally verified using banknote and ordinary paper substrates, indicating that the presented emissive metasurface has the potential for use as an effective platform for anti-counterfeiting

We present the operating range of Raman wavelength converters based on silica nanofibers immersed in liquids for the design of all fibered wavelength converters. This range is bounded on the lower limit by the pump energy necessary to reach the Raman threshold and on the upper limit by the laser induced breakdown of the nanofiber. These breakdown energies are measured in the ns regime for different liquids (water, ethanol, isopropanol) and for air. We finally define guidelines that open the way to a new family of low-cost compact and efficient all-fibered Raman converters that can be directly inserted in optical fibered networks with very low losses.

Lobster-eye type X-ray telescopes use reflecting plano mirrors under grazing incidence and can observe a large field of view. As part of a Bavarian-Czech cooperation, two telescopes were build, equipped with mirrors coated with gold and iridium. Their X-ray characterization was carried out at the PANTER test facility, which simulates parallel starlight incident on the telescopes. The telescopes have an angular resolution of about 4 arc minutes in X-rays and a focal length of about 2 meters. The used X-ray mirrors reflect and focus visible light as well; their functionality in the optical regime was checked in laboratory tests. Now another test campaign will be carried out to examine the telescope resolution for real objects of the visible night sky and the imaging properties for star constellations.

We demonstrate single-mode ZBLAN optical fiber couplers. A controlled tapering procedure leads to coupling ratios of 5%/95% and 14%/86% at a wavelength of 2200 nm, with insertion losses of 1.6 dB and 1.8 dB, respectively.

Modern optical systems utilize various degrees of freedom, such as polarization, for shaping and controlling the light. Common representative of such a component is spatial light modulator (SLM), consisting of liquid crystal display, allowing for imposing predetermined retardation with given orientation of optical axis of anisotropy. Therefore, it is widely used for polarization coded phase shifting, polarization splitting of wavefront in digital holography etc. Narrowing tolerance in optical experiments puts higher demands on precise setting of the modulator and the parameters set. Consequently, measuring such devices and their parameters is essential for proper functionality. We present a single shot, common path method for measuring retardance map of the modulator, based on spatial probing the modulator with point images of spatially coherent light source and transforming them to optical vortices.

Optical tweezers use light to trap and manipulate mesoscopic scaled particles with high precision making them a useful tool in a plethora of natural sciences, with emphasis on biological applications. In principle, the Brownian-like dynamics reflect trapped particle properties making it a robust source of information. In this work, we exploit this information by plotting histogram based images of 250ms of position or displacement used as input to a Convolution Neural Network. Results of 2-fold stratified cross-validation show satisfying classifications between sizes or types of particles: Polystyrene and Polymethilmethacrylate thus highlighting the potential of CNN approaches in faster and non-invasive applications in intelligent opto and microfluidic devices using optical trapping tools.

In this paper we describe the implementation of a secure key distribution system based on an ultra-long fiber laser with a bi-directional erbium doped fiber amplifier. The resilience of the system was tested against passive attacks from an eavesdropper, having been observed a similarity in spectrum for both secure configurations of the system.

Here, we study optically resonant substrates fabricated using the previously reported BLIN (biotemplated lithography of inorganic nanostructures) technique with single triangle and bowtie DNA origami as templates. We present the first optical characterization of BLIN-fabricated origami-shaped silver nanoparticle patterns on glass surfaces, comprising optical transmission measurements and surface-enhanced Raman spectroscopy. The formed nanoparticle patterns are examined by optical transmission measurements and used for surface-enhanced Raman spectroscopy (SERS) of Rhodamine 6G (R6G) dye molecules.

Whispering-gallery-mode (WGM) resonators are monolithic structures that guide light by total internal reflection.They exhibit ultra-high Q-factors and provide lossless in- and out-coupling of light in tapered optical fibres. Thus, WGM resonators can be realized in a fully integrated way and can be implemented as optical circuits on photonic chips. Furthermore, these resonators provide a chiral (i.e. direction dependent) light-matter interaction, which opens up new routes for photonic quantum information and communication applications.

We demonstrate, for the first time, trapping of single 85Rb atoms in the evanescent field of a WGM resonator by means of a tightly focused dipole trap retroreflected on the resonator surface. In order to compensate the trap-induced light shift of the atomic transition frequency, an additional light beam is employed to realize a dual-colour magic-wavelength trapping scheme. Using this method, we observe a vacuum Rabi splitting in the transmission spectrum of the coupled atom-resonator system, which indicates its operation in the strong coupling regime.

We are currently implementing a second generation trapping scheme, which will enable deterministic trap loading with improved trap lifetimes and a well-defined coupling strength.

Polarised emittance measurements are reported for a rutile-phase TiO2 single crystal up to 2000 K in a broad spectral range. Above 1000 K, strong opacification was observed for most of the investigated spectral range. This phenomenon was thermally activated, with a 1.25 eV activation energy close to that of DC conductivity. The sample became opaque at temperatures significantly below the melting point. This anomalous optical phenomenon can be explained by small-polaron conduction, which is particularly strong for this material. The transition from transparency to high and flat emissivities in a broad near- and mid-infrared region has important implications for the use of TiO2 materials at high temperatures.

Synchronization control of complex systems is a field that emerged with huge interest and aims to study new possible routes to synchronization in networks of non-locally coupled chemical oscillators. Light can be used to stimulate these systems and to be able to synchronize the different micro-reactors involved in the complex system. To this end, transparent reactors with good optical qualities are needed. Glass is the most appropriated material to be used for fabricating the micro-reactors. Subaquatic indirect Laser-Induced Plasma-Assisted Ablation is presented as a laser technique that combines underwater ablation with shock waves as a potential technique for fabricating these micro-reactors by using a Nd:YVO4 laser.

It is presented a study of the dependence between the free spectral range (FSR) and the cavity length in Fabry-Perot interferometers. Furthermore, the effect of frequency modulation on the FSR is studied when an optical spectrum analyser (OSA) is used as an interrogator. For low frequency range it is possible to observe this behaviour in the OSA and using an appropriate processing signal it is possible to use the white light interferometry technique.

The use of convolutional neuronal networks (CNN) for the treatment of interferometric fringes has been introduced in recent years. In this paper, we optimize and build a CNN model, based U-NET architecture, to maximize its performance processing electronic speckle interferometry fringes (ESPI)

Brillouin scattering has been widely exploited for advanced photonics functionalities such as microwave photonics, signal processing, sensing, lasing, and more recently in micro- and nano-photonic waveguides. Due to the small transverse dimension, the tapered optical fiber have a number of optical and mechanical properties that make them very attractive for both fundamental physics and technological applications. Contrary to standard telecom fiber where the Brillouin scattering effect is characterized by a single Lorentzian resonance centred at 10.86 GHz (@ 1550nm), in tapered silica fiber, we identified several Brillouin resonances at different frequencies from 5 GHz to 10 GHz coming from surface, shear and compression elastic waves. And for a large evanescent optical field surrounding the nanofiber, we observe an efficient Brillouin scattering in gas. We show drastic Brillouin scattering enhancement by increasing the gas pressure with a maximum Brillouin which is 79 times larger than in a standard single-mode fibre.

We demonstrated that the sensitivity of nanoparticle detection on surfaces can be substantially improved by implementing synthetic optical holography (SOH) in coherent Fourier scatterometry (CFS), resulting in a phase-sensitive confocal differential detection technique that operates at a very low power level (P = 0.016 mW). The improvement in sensitivity is due to two reasons: firstly, the boost in the signal at the detector due to the added reference beam, and secondly, the reduction of background noise caused by the electronics.

With this new system, we were able to detect a 60 nm polystyrene latex (PSL) particle at wavelength of 633 nm (\lambda/10) on a silicon wafer with an improvement in the signal-to-noise ratio (SNR) of about 4 dB.

The fused deposition modelling technique has been used in the production of strain sensors in which fibre Bragg gratings (FBGs) are encapsulated during the 3D printing process. This paper reports the study of the influence of the FBG position and the material filling, in this case a flexible polymer material, on the sensors’ sensitivity and overall performance. In addition, this study preliminarily evaluated the ability of the strain sensor to monitor (heart rate) HR and (respiratory rate) RR as a wearable on the wrist and as a non-intrusive solution on the back of an office chair

A new, simple digital holography-based polarization microscope for quantitative birefringence imaging of biological cells is presented. As a proof of concept, two different class of cells have been characterized by polarization sensitive digital holographic imaging (PSDHI). These two cases study reported are: differentiation of leukaemia cells and identification of reacted sperm cells. Although further experimentation is necessary, the suggested approach could represent a prospective label-free diagnostic tool for use in biological and medical research and diagnosis.

We demonstrate through numerical simulations the existence of a new type of nonlinear waves in optical media: structures of vortex solitons that remain static in certain configurations, which depend on their relative positions and topological charges. Several examples are presented to illustrate this surprising behavior.

Based on the fact that the degree of polarization of a light source is given in terms of the absolute value of its complex degree of coherence, we design a depolarization experiment using a variable retarder in which we measured the degree of polarization as a function of the retarder's birefringence. We show that if the incident light is previously linearly polarized we can perform a direct measurement of the light source's coherence using a Stokes meter.

We analyse the high harmonic emission from single-layer graphene driven by infrared vector beams. We demonstrate that graphene’s anisotropy offers a privileged scenario to explore non-trivial light spin-orbit couplings, which substantially extends the possibilities for the generation of high-harmonic structured beams currently studied in atomic and molecular targets. In our case, graphene’s crystal symmetry introduces a spin-dependent diffraction pattern that, coupled with the fundamental conservation of the driver’s topological phase, leads to the splitting of the harmonic field in a multi-beam structure, composed of spatially diverging vortices. Our work demonstrates that anisotropic targets are extraordinary tools to sculpt complex structured short-wavelength beams.

We present a new open-view dynamic double-pass (DP) system for the study of accommodative response in binocular natural viewing conditions. The DP point spread function (PSF) of the eye is analyzed to compute the Visual Strehl Ratio (VSR) fluctuation as a function of time at 50 Hz frame rate. Preliminary results showed that the proposed method can quantify the temporal dynamic of the optical and visual quality of both eyes simultaneously.

Recent developments in power electronics require the use of new wide bandgap compound semiconductor. We demonstrate the use of the ellipsometry and white light interference microscopy to detect defects in epitaxially grown SiC layers on SiC substrates. Such hybrid optical metrology methods can be used to better understand the mechanism of the development of the defects as well as their effects on the material´s optoelectronic properties.

Recent technological advancements in the past decades have been driven by the miniaturisation of devices using surfaces with nano-scale features. These advancements require fast, large area measurement techniques that can be used in process control to detect surface contaminations or to monitor fabrication quality. Here we present a modified version of the scanning coherent Fourier scatterometer with multiple beams that can be used to scan larger areas without increasing the scan time or decreasing the spatial resolution.

We present a system able to discriminate pulses according to their duration with potential applications in all-optical signal multiplexing. The device is based on a directional coupler with nonlinear cores and metallic claddings with dimensions in a nanometric scale. Simulations are carried out using the FDTD technique for ultrashort pulses of femtosecond order. It is shown that the device is able to separate such pulses respect to a time-width threshold which depends on the total energy of the pulse.

A whispering-gallery mode nanophotonic laser cavity having as active medium a transition-metal-dichalcogenide (TMD) bilayer is examined. The proposed system is analysed and designed utilizing a strict and rigorous computational framework based on the coupled-mode theory. Our framework is capable of accurately and efficiently handling the gain properties of two-dimensional materials, such as contemporary TMD monolayers, multilayers, and heterostructures. The presented lasing cavity exhibits an adequately low pump threshold and light emission in the order of milliwatts is predicted. Exploiting the capabilities of the developed framework, we were in position to efficiently design the cavity as well as to estimate quantitative lasing parameters such as the pumping threshold and the lasing frequency.

Fundamental numerical study on controlling chromaticity with the simplest diffractive structure is carried out. Observed various characteristics on transmission/reflection and dielectric/metal will be useful guidelines for practical optimisation of device structures.

We present the numerical modeling of two different randomization methods of photonic lattices. We compare the results of light propagation in disordered aperiodic and disordered periodic lattices. In disordered aperiodic lattice disorder always enhances light transport for both methods, contrary to the disordered periodic lattice. For the highest disorder levels, we detect Anderson localization for both methods and both disordered lattices. More pronounced localization is observed for disordered aperiodic lattice.

Ion traps are a promising platform for the realisation of high-performance quantum computers. To enable the future scalability of these systems, integrated photonic solutions for guiding and manipulating the laser light at chip level are a major step. Such passive optical components offer the great advantage of providing beam radii in the µm range at the location of the ions without increasing the number of bulk optics. Different wavelengths, from UV to NIR, as well as laser beam properties, such as angle or polarisation, are required for different cooling and readout processes of ions. We present simulation results for different optical photonic components, such as grating outcouplers or waveguide splitters and their applications on ion trap chips. Furthermore, we will introduce the experimental setup for the optical characterisation of the fabricated structures.

Beside Wolter I X-ray optics, which are used at most in currently operating X-ray space telescopes, there exist also other optical designs and their usability for space observations is still the matter of studies. This article covers preliminary testing results of an optical module which is based on a modified Kirkpatrick-Baez optics. This X-ray optics, consisting of four sub-modules, was assembled in Prague and tested at the PANTER test facility of MPE afterward. The sub-modules use different reflective coatings, in part developed by our research group, on complementary flat mirrors, which approximate the shape of a Kirkpatrick-Baez optical design. In this contribution we summarise the design of the optical modules, the details of applied coating layers, and the X-ray characterisation results at the PANTER test facility.

We address the problem of passive modelocking in class-B lasers with saturable abosrber taking into account the fast dynamics of both gain and absorption. Our model, which is derived from a delay differential equation model, treats in a rigorous way the definition of the fast and slow times which are typically used in the master equation approach. In that way all the dynamical variables obey exact periodic boundary conditions and this makes the model suitable for analytic and numerical treatment. The model accounts for behaviours different from fundamental modelocking, such as Q-switching modelocking and harmonic modelocking.

2D metasurfaces based on periodic nanoholes in metal have been proposed in various plasmonic platforms. Specifically, their resonant features have led to applications spanning in biosensing. Here we investigate additional degree of freedom in elliptical nanohole arrays with hexagonal geometry: chiro-optical effects. Namely, the in-plane asymmetry and a slightly elliptical shape of nanoholes were previously shown to differently extinct light of opposite handedness, even at normal incidence. We now fully characterize nanoholes in Ag, fabricated by low-cost nanosphere lithography. We first measure the dependence of the transmitted intensity for opposite handedness, in a broad spectral and angle of incidence range. We then resolve the circular polarization degree of the transmitted light when the nanohole array is excited with linear polarization. Finally, we numerically investigate the origin of the chiro-optical effect at the nanoscale. We believe that circular polarization resolving of the transmitted degree could be further adapted as a highly sensitive tool in chiral sensing.

We theoretically investigate a non-reciprocal magneto-optical integrated slab directional coupler.

The scattering parameters of the structure are derived in the frame of the Coupled-Mode Theory (CMT). By properly designing the coupler, it is possible to achieve a perfect non-reciprocity (with 100% contrast) between the two directions of propagation. Other operating points can also be defined, especially since modal dispersion in the spectral domain is naturally taken into consideration.

We present the design, fabrication, simulation and initial characterisation of tantalum pentoxide (Ta2O5) optical waveguides and micro-ring resonators for the purpose of supercontinuum and frequency comb generation. Spectral broadening results are presented for linear Ta2O5 waveguides for a range of central pump wavelengths between 900 nm and 1500 nm. These results are used as the basis for the dispersion engineering and development of Ta2O5 micro-ring resonators. The losses for sputtered and TEOS PECVD deposited SiO2 top cladded waveguides are characterised using a Fabry-Pérot loss measurement set-up. A solver based on the Lugiato-Lefever equation is presented and used to simulate the expected emission from the Ta2O5 micro-ring resonators. Promising initial experimental results show critical coupling and a Q-factor of 3.7×10^4.

This work describes the different steps of the design of a cylindric Optical Parametric Oscillator. It is based on a BBO nonlinear crystal shaped as a partial cylinder to be pumped by a commercial micro-laser at 0.355 µm for an energetic and sub-nanosecond emission continuously tunable between 0.4 µm and 0.9 µm.

We report on single-short laser crystallization of Ge/Si multilayer stacks consisting of alternating amorphous nanosized films of silicon and germanium using near- and mid-infrared femtosecond and picosecond laser pulses. The phase composition of the irradiated stacks was investigated by the Raman scattering technique. Several non-ablative regimes of crystallization were found, from partial crystallization of germanium without intermixing the Ge/Si layers to complete intermixing of the layers with formation of GexSi1-x solid alloys. The roles of one- and two-photon absorption, thermal and non-thermal (ultrafast) melting processes, and laser-induced stresses in selective pico- and femtosecond laser annealing are analysed based on theoretical estimations and comparison with experimental data. It is concluded that, due to a mismatch of the thermal expansion coefficients between the adjacent stack layers, efficient explosive solid-phase crystallization of the Ge layers is possible at relatively low temperatures, well below the melting point. The possibility of ultrafast non-thermal phase transition in germanium in the studied regimes is also discussed.