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.
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.
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.
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.