Our latest work in softphotonics features the seamless integration of liquid-core fibers into standard fiber systems, achieving unprecedented advancements in nonlinear optics and signal processing. Utilizing liquids like CS2 and halocarbonates, we have developed a reliable splicing technique with standard fibers, enabling low-loss all-fiber interconnectivity. This breakthrough provides insights into intra-fiber thermodynamics and enables robust, long-term applications in optical signal processing in the near-infrared. Our method opens new avenues for exploring negative pressures and facilitating multi-laser excitation for cross-phase modulation, showcasing the potential of liquid-filled fibers in future optical technologies.
Surface alignment of liquid crystals (LCs) is key for optimizing their performance. Effective LC alignment strongly depends on the substrate used, which should promote strong local anchoring of the director field. Our work introduces a novel method using nanolithography to control the alignment of thermotropic LCs. Key to the approach is the use of 3D nanoprinting to create customized parallel nanogrooves on a glass substrate. These grooves yield azimuthal anchoring energies ranging from 10^-6 J/m² to 10^-5 J/m², partially surpassing values from other photopolymers. This approach offers high spatial resolution (~2µm) and allows for electro-optical switching, thus providing a flexible substrate platform for LC applications.
Meta-Fibers, which incorporate 3D-printed Metalens into optical fiber facets, are versatile technology with applications in imaging, optical trapping, and electromagnetic wave manipulation. Single-Mode Fiber (SMF) stands out for its defined output, but its limited mode field diameter poses a challenge, often requiring fusion splicing with Multi-Mode Fiber (MMF) or a 3D-printed structure to expand SMF's usable cross-section. However, these methods are complex and may damage the Meta-Fiber. This study introduces an alternative, replacing SMF with Thermally Expanded Core (TEC) fiber, featuring a significantly larger mode field diameter. This approach enables optical trapping and imaging via 3D laser-printed ultra-high numerical aperture metalens into TEC fibers, functioning effectively in diverse environments. The findings expand Meta-Fiber applications, providing an efficient, robust, and scalable solution for optical wavefront manipulation, highlighting the potential of TEC fibers in optics and photonics technology.
Hollow-core waveguides represent a promising type of on-chip waveguide, enabling strong light-matter interactions for guiding light directly in the medium of interest. Hollow-core waveguides are very established in fiber optics, while they receive much less attention in on-chip photonics.
Here, we will show how 3D nanoprinting is used to transfer hollow-core waveguide concepts from fiber optics to on-chip photonics. Two main types of nanoprinted waveguides are discussed, yielding a high-power fraction in the core and lateral access to the core region. We will explain applications of these waveguides in gas- and water-based spectroscopy, nanoparticle tracking analysis and optical fiber interconnection.
The integration of metasurfaces onto the end faces of optical fibers holds great promise for numerous applications. Traditional top-down fabrication struggles with optical fiber geometry. Our presentation reveals a solution: 3D nanoprinting via direct laser writing to create nanopillar metasurfaces on fiber end faces. This concept gives rise to a novel kind of fiber devices called meta-fibers, allowing for shaping the fiber's output properties. We showcase two applications: (i) achromatic fiber-interfaced metasurface lenses covering the entire telecommunication range, and (ii) meta-fibers generating structured light. These meta-fibers utilize dielectric nanopillars of varying heights, a capability unique to the nanoprinting process.
We demonstrate a metafiber platform capable of creating arbitrarily structured light on the hybrid-order Poincaré sphere. The metasurface is directly printed on the end face of a commercial polarization-maintaining optical fiber through 3D laser nanoprinting process. The release of height degree of freedom greatly expands the 3D meta-atom library, empowering metasurfaces to independently manipulate phase and polarization. Our work provides a paradigm for advancing optical fiber science and technology towards fiber-integrated light shaping, which may find important applications in fiber communications, fiber lasers and sensors, endoscopic imaging, fiber lithography, and lab-on-fiber technology.
On-chip hollow-core waveguides represent a promising platform for microfluidic analysis, nonlinear optics and quantum information processing, due to light guidance directly inside the medium of interest. Recently, we have introduced two types of 3D nanoprinted on-chip hollow-core waveguides, namely the hollow-core light cage and the microgap waveguide which have unique properties for on-chip sensing. Here we will present our results for water-based spectroscopy, refractive index sensing, nanoparticle tracking, and optical fiber interfacing.
We demonstrate the use of 3D direct laser writing method to fabricate large-scale 3D metasurfaces with unleashed height degree of freedom. We showcased multiple 3D laser-nanoprinted metasurfaces for a range of photonic applications, including ultrahigh-bandwidth holography, metafibre-enabled optical trapping, highly sensitive molecular sensing, achromatic fibre-optic focusing and imaging, and structured light generation on metafibres. The optical performance of our demonstrated 3D laser-nanoprinted metasurfaces surpass existing 2D metasurfaces fabricated from planar lithography. This metasurface fabrication platform allows superior integration with other photonic elements, such as optical fibres, holding great potential for advanced classical and quantum light manipulation.
Wavelength-tunable femtosecond light sources are essential in various research fields and technologies, including medical diagnostics, biophotonics, and metrology. Although fiber lasers have emerged as leaders in the development of such sources, achieving wide spectral tunability for femtosecond pulses remains a significant challenge. To address this challenge, dispersive wave generation offers a powerful solution. In this study, we exploit the concept of quasi-phase matching to enable multi-order dispersive wave formation with unprecedented spectral tunability and femtosecond durations. Here, liquid-core fibers (LCFs) with periodically controlled dispersion of a higher-order mode along the fiber are applied, achieved by axial modulation of the liquid core diameter, relying on the strong dependence of dispersion on the core diameter. Nonlinear optical experiments and simulations, as well as phase-mismatching considerations based on an effective dispersion, confirm the conversion process and reveal unique emission features This resonance-empowered approach provides a versatile photonic platform with unique dispersion control capabilities for efficient, coherent femtosecond multi-frequency conversion.
Here I will report on optical fibers that are interfaced with dielectric nanostructures and demonstrate their capabilities on the examples of achromatic light focussing and optical trapping. Both topics involve implementation of nanostructures on fibers through 3D nanoprinting. This has allowed for (i) the realization of an achromatic metasurface-based lens interfaced to a SMF-28, used for wavelength- and polarization-independent light focussing across the entire telecommunication range, and for (ii) trapping microspheres and bacteria with only one single-mode fiber containing a nanoprinted holographic metalens with a record-high numerical aperture of 0.88.
In this presentation, a new concept of an achromatic metafiber that focuses light coming out from the fiber facet over wavelengths of interest will be introduced. The achromatic metafiber consists of achromatic metalens microprinted on a telecommunication single-mode fiber. The 3D meta-atoms of which height is a geometric degree of freedom provide large variation of group delay, capable of realizing large time-bandwidth product. As a demonstration, direct scanning confocal imaging using the metafiber is facilitated over entire telecommunication wavelengths. Our compact achromatic metafiber may envisage many photonics applications such as hyperspectral imaging, in vivo deep-tissue imaging, and wavelength-multiplexed fiber communications.
Here I will report on optical fibers that are interfaced with dielectric nanostructures and demonstrate their properties on the examples of optical trapping and tracking of single nano-objects. The first topic addresses the implementation of nanostructures on fibers by 3D nanoprinting. This allows microspheres and bacteria to be trapped with only a single-mode fiber by integrating meta-lenses on the fiber end faces, achieving numerical apertures of up to 0.88. Through modified electron-beam lithography, I will show that incoupling efficiencies into fiber can be boosted by orders of magnitude.
On-chip hollow-core waveguides represent a promising platform for microfluidic analysis, nonlinear optics and quantum information processing, due to light guidance directly inside the medium of interest. Recently, we have reported a 3D printed hollow-core waveguide ⎯ light cage ⎯ which consists of a ring of high-aspect-ratio cylinders and combines a high fraction of field in the core (>99%) with transverse access. Here we will discuss our results on interfacing light cages with optical fibers, the measurement of electromagnetically induced transparency within light cages filled with alkali vapour, the potential of the light cage concept for spectroscopy and nanoparticle tracking analysis.
High-speed tracking of nano-objects is a gateway to understanding processes at the nanoscale. Here we will present our results on tracking single or ensembles of nano-objects inside optofluidic fibers and on-chip waveguides via elastic light scattering. The nano-objects diffuse inside a channel of a microstructured waveguide and the light scattered by the nano-object is detected transversely via a microscope. We will present the fundamentals of this approach and focus on selected results including 3D tracking in dual-core microstructured fibers and revealing the limits of the approach. We will also present first results on tracking inside nanoprinted on-chip waveguides.
High-speed tracking of nano-objects is a gateway to understanding biological processes at the nanoscale. Here we will present our results on tracking single or ensembles of nano-objects inside optofluidic fibers via elastic light scattering. The nano-objects diffuse inside a channel of a microstructured fiber and the light scattered by the nano-object is detected transversely via a microscope. We will present the fundamentals of this approach and focus on selected results including retrieval of the full 3D trajectory of a diffusing nano-sphere, the simultaneous detection of hundreds of nano-objects in hollow core anti-resonant fibers and first results on inactivated SARS-CoV-2.
Coupling of light into optical fibers is important for many applications, while for commonly used step-index optical fibers it massively drops for oblique incident angles <15 degrees, limiting their operational range to a narrow angle interval. In this work, we address this issue via inclusion of dielectric concentric ring-type nanostructures located in the core region of commercially available step-index fibers. Modification of fiber facet with the optimized ring-like nanostructure leads to polarization- and azimuthally-independent enhancement of in-coupling efficiency across the entire angle interval from 15 to 85 degrees. We develop the analytical model and show the percent-level of light in-coupling efficiency even at angles as large as 70 degrees, addressing a domain that is out-of-reach for fibers with unstructured end faces. The main result of this work is the enhancement of the in-coupling efficiency at large incident angles (<30 degrees) by several orders of magnitude with respect to a bare fiber. The results obtained are promising for any application that demands to remotely collect light under large angles, such as in-vivo spectroscopy, biosensing or quantum technology.
Quantum memories are a key tool for optical quantum information processing. Several physical implementations have been suggested. Photonic nano- and microstructures can significantly improve light matter interaction and in this way facilitate efficient photon storage. In this presentation we will introduce a photonics light cage as an engineered photonic structure to improve the performance of quantum memories based on warm atomic (Cs) vapor. Based on first results we derive the improved storage parameters of such a device and discuss prospect for integration into quantum networks.
High-speed tracking of nano-objects is a gateway to understanding biological processes at the nanoscale. Here we will present our results on tracking single or ensembles of nano-objects inside optofluidic fibers via elastic light scattering. The nano-objects diffuse inside a channel of a microstructured fiber and the light scattered by the nano-object is detected transversely via a microscope. We will present the fundamentals of this approach and focus on selected results including retrieval of the full 3D trajectory of a diffusing nano-sphere, the simultaneous detection of hundreds of nano-objects in hollow core anti-resonant fibers and first results on inactivated SARS-CoV-2.
One gateway to understanding physical, chemical, and biological processes at the nanoscale level is high-speed tracking of single nano-objects. Here I will present our recent results on tracking individual nano-objects inside optofluidic microstructured fibers via elastic light scattering. Conceptually, the nano-objects (e.g., gold nano-spheres, polymer beads, sub-20nm viruses) are located within a liquid environment inside a well-selected channel of respective microstructured fiber. Light elastically scattered by the freely diffusing nano-objects is transversely detected by a microscopic setup continuously imaging the liquid-filled channel from the side at very high frame rates. Here I will discuss (i) tracking of unlabeled virions at rates of over 2 kHz for durations of tens of seconds in nanobore optical fibers, (ii) retrieving full 3D information about the nano-object’s trajectory using modified step index fibers, and (iii) simultaneous detection and identification of hundreds of nano-objects in anti-resonant hollow core fibers. Any of the mentioned approaches addresses light scattering intensities and diffusion constants, allowing us to determine key properties of the nano-objects such as size or hydrodynamic radius. Together with the compatibility with fiber circuitry and microfluidics, the presented approach defines a new platform for fiber sensors and nano-scale physics with applications in a multitude of fields such as bioanalytics and soft matter material science.
High-speed tracking of single nanoobjects is a gateway to understanding physical, chemical, and biological processes at the nanoscale. Here I will present our recent results on tracking single individual nanoobjects inside optofluidic optical fibers via elastic light scattering. The nanoobjects are located within an aqueous environment inside a well-selected channel of microstructured optical fiber. Light from the core mode which hits the freely diffusing nano-object scatters off and can be detected transversely. Tracking of unlabeled dielectric particles as small as 20 nm as well as individual cowpea chlorotic mottle virus (CCMV) virions at rates of over 2 kHz for durations of tens of seconds has been achieved in nanobore optical fibers, whereas full 3D information about the nano-object’s trajectory are retrieved in modified step index fibers. From the light scattering intensities and the diffusion constants we were able to determine key properties of the particles such as size or hydrodynamic radius.
We report on OH diffusion effects at preparation of hollow core fibers with large central hexagonal and square shaped cores. The fibers with up to 30 μm central hole diameter are suitable for chemical sensor applications, especially for gases. We demonstrate the single mode guidance at selective bands in the UV, VIS and NIR region. Key feature of low loss in specific spectral windows of such fiber structures is the control of thickness and homogeneity of the web bridges. The fibers achieve a minimum loss of 2 dB/m and effective single mode propagation in the wavelength range between 270 nm and 1500 nm. The thinness of the bridges beneath one micrometer results in a deep impregnation of OH by diffusion from the cavities during thermal processing, e.g. fiber drawing. Up to 1000 ppm by weight of OH had been measured in the silica web surrounding the hollow core. Obviously, the OH sources are atmospheric humidity and condensed water originating from using a hydrogen-oxygen torch at final preform fabrication. The paper shows the good agreement between OH diffusion simulation and experimental observation of OH impregnation in the hollow core web.
Optical waveguides represent the key element of integrated planar photonic circuitry having revolutionized many fields of photonics ranging from telecommunications, medicine, environmental science and light generation. However, the use of solid cores imposes limitations on applications that demand controlling strong light-matter interaction within low permittivity media such as gases or liquids, which has triggered substantial interest towards the development of hollow core waveguides. Here, we introduce the concept of the on-chip hollow core light cage that consists of free standing arrays of cylindrical dielectric strands surrounding a central hollow core implemented by 3D nanoprinting. The cage operates by the anti-resonant guidance effect and exhibits extraordinary properties such as (1) diffraction-less propagation in “quasi-air” over more than a centimetre distance within the ultraviolet, visible and near-infrared spectral domains, (2) unique side-wise direct access to the hollow core via open spaces between the strands speeding up gas diffusion times by at least a factor of 10.000, and (3) an extraordinary high fraction of modal fields in the hollow section (> 99.9%). With these properties, the light cage can overcome the limitations of current planar hollow core waveguide technology, allowing unprecedented future on-chip applications within quantum technology, ultrafast spectroscopy, bioanalytics, acousto-optics, optofluidics and nonlinear optics.
Here we report a novel fabrication approach which enables to integrate 2D nanostructures on the facet of optical fibers by electron beam lithography. The general idea behind this fabrication approach is to planarize the fiber surface in order to fit planar fabrication technology, i.e., that the fibers can be treated in the same way as typical wafers. To demonstrate our approach, we have implemented two types of gold structures on the on the end face of 50 cm long standard single mode fibers (SMF-28): the one is gold nanotrimers lattice and the other is nanodots array. The former is employed as a novel refractive index sensor with a sensitivity of 390 nm/RIU, which represents the state-of-the-art for such a device type. The latter significantly improves the fiber light-collecting ability at an oblique incidence angle with a maximum acceptance angle of 80° breaking the limitation of conventional fiber. This fabrication method is not limited to the nanostructure geometry reported here and can also be applied to dielectric nanostructures, thus opening up the field of fiber optics for planar nanostructures within numerous application fields including bioanalytics, telecommunications, nonlinear photonics, optical trapping and beam shaping.
Integrating nanowires into microstructured fibers represent a promising pathway to include sophisticated functionalities into optical fibers which allowing to develop novel types of photonic devices with unprecedented properties. Beside solid materials such as plasmonic metals or soft glasses particular interesting is the combination of liquids and fibers, which allows to access new regimes for fiber optics.
The first part of my presentation is related to ultrafast nonlinear light generation inside liquid core optical fibers. I will discusses our recent results on a new kind of optical soliton inside carbon-disulphide (CS2) filled liquid core fibers, which results from the hybrid nonlinear response functions of inorganic liquids, consisting of both instantaneous and noninstantaneous contributions. Using this fiber system we have measured octave-spanning mid-IR supercontinuum generation ranging from 1.1 µm towards more than 2.8 µm, showing clear indications of an improved shot-to-shot correlation, i.e., higher degree of coherence across the entire generated bandwidth at soliton numbers solely instantaneous systems deliver highly incoherent spectra, i.e., are modulatin instability driven. I will also discuss the unique temperature tuning potential of liquid core fibers, allowing to shift the central wavelength of dispersive waves by more than 100nm by locally changing the temperature within an interval of 20°C only.
In the second part of the talk I will present our recent results on tracking single individual nanoobjects inside optofluidic optical fibers via elastic light scattering. The nanoobjects are located within an aqueous environment inside a well-selected channel of the microstructured optical fiber used. Light from the core mode which hits the freely diffusing nanoobject scatters off and can be detected transversely. Tracking of unlabeled dielectric particles as small as 20 nm as well as individual cowpea chlorotic mottle virus (CCMV) virions at rates of over 2 kHz for durations of tens of seconds has been achieved in nanobore optical fibers, whereas full 3D information about the nanoobject’s trajectory are retrieved in modified step index fibers. From the light scattering intensities and the diffusion constants we were able to determine key properties of the particles such as size or hydrodynamic radius.
Background: Extracellular vesicles, such as exosomes, are abundantly present in human body fluids. Since the size, concentration and composition of these vesicles change during disease, vesicles have promising clinical applications, including cancer diagnosis. However, since ~70% of the vesicles have a diameter <70 nm, detection of single vesicles remains challenging. Thus far, vesicles <70 nm have only be studied by techniques that require the vesicles to be adhered to a surface. Consequently, the majority of vesicles have never been studied in their physiological environment. We present a novel label-free optical technique to track single vesicles <70 nm in suspension.
Method: Urinary vesicles were contained within a single-mode light-guiding silica fiber containing a 600 nm nano-fluidic channel. Light from a diode laser (660 nm wavelength) was coupled to the fiber, resulting in a strongly confined optical mode in the nano-fluidic channel, which continuously illuminated the freely diffusing vesicles inside the channel. The elastic light scattering from the vesicles, in the direction orthogonal to the fiber axis, was collected using a microscope objective (NA=0.95) and imaged with a home-built microscope.
Results: We have tracked single urinary vesicles as small as 35 nm by elastic light scattering. Please note that vesicles are low-refractive index (n<1.4) particles, which we confirmed by combining data on thermal diffusion and light scattering cross section.
Conclusions: For the first time, we have studied vesicles <70 nm freely diffusing in suspension. The ease-of-use and performance of this technique support its potential for vesicle-based clinical applications.
Hybrid optical fibers are fiber-type waveguides including multimaterial large-aspect ratio nano- and microstructures. Using our pressure-assisted melt-filling approach various hybrid waveguides have been fabricated inside photonic crystal fibers by filling the air holes with materials such as noble metals, semiconductors, fluids or low-melting compound glasses. In this talk I will review our latest results on fiber-based plasmonics and nonlinear optics, with the focus on the basic physical working principle and of such novel nanophotonic structures.
KEYWORDS: Sapphire, Sensors, Temperature metrology, Fiber Bragg gratings, Data acquisition, Temperature sensors, Fiber optics sensors, Optical fibers, Crystals, Process control
We tested the long term stability of first order Sapphire Fiber Bragg gratings (SFBG) at 1400°C for a period of 28 days in air. During the whole period temperatures detected by the SFBG differed less than ±2K°C from the temperatures measured by a type B thermocouple. The spectra at the beginning and the end of the installation were identical. The reliable practical application of wavelength-multiplexed two-grating SFBG arrays for quasi-distributed sensing at very high temperatures has been demonstrated.
Fiber Bragg gratings (FBG) were inscribed in single crystalline sapphire fibers by fs-laser irradiation. Due to the used multi-mode air clad fiber a sapphire-FBG spectra showa a wide asymmetric peak with a half width of 7 nm. Different mathematical peak functions were tested to determine a fiber Bragg wavelength. It was shown that the shift of the calculated Bragg wavelengths in dependence on temperature is identical for the different peak functions. The determination of the fiber Bragg wavelength shift with a resolution of 10pm allows temperature measurements within an accuracy of ±1°C in the temperature range up to 1500°C. Sapphire FBG were used to measure the temperature distribution and thermal fluctuations within an inductive heated furnace in the range from 100°C to 1500°C.
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