Hollow Core Anti-resonant fibers allow for guidance of mid-infrared light at low attenuation and can be used for a variety of applications, such as high power laser transmission and gas sensing. Recent work has seen the integration of silicon into such fibers with linear losses potentially as low as 0.1dB/m. Due to the change in refractive index difference of silicon via for example the free carrier plasma dispersion effect, the prospect of an all optical modulator using such a fiber has been proposed. Here, further work has been undertaken on the integration of functional materials inside hollow core fibers via the deposition of the TMD semiconductor material MoS2, in its few-layered form. Through the use of a liquid precursor, a high quality MoS2 film can be deposited over 30cm length of fiber, as confirmed via Raman spectroscopy. The transmission spectra of these novel composite material hollow core fibers has also been analysed, showing additional loss of around 5dB/m, despite being only around 2nm in thickness. This implies that the refractive index of the integrated material is potentially able to modify the guidance properties of the fiber sample. We will present a comparison of the composite material hollow core fibers we have fabricated to date and discuss the prospects for using these novel waveguides in the active manipulation of light, including optical switching, sensing and frequency generation.
Thermal poling, a technique to create permanently effective second-order susceptibility in silica optical fibers, has a wide range of applications, such as frequency conversion, electro-optic modulation, switching and polarization-entangled photon pairs generation. After many works where a conventional configuration anode-cathode was used, in 2009 a new electrode configuration (double-anode) was adopted, which allows for a more temperature-stable depletion region formation and a higher value of effective Chi21, 2. In this work we demonstrate, via numerical simulations realized in COMSOL® Multiphysics, that in a double-anode configuration the effective value of Chi2 strongly depends on the relative position of the core with respect to the electrodes, requiring an accurate and precisely tailored geometry of the fiber, while in a single-anode configuration this value, for standard poling conditions1 is almost independent of the position of the core, offering the possibility of relaxing the manufacturing constraint of the fiber fabrication. We also demonstrate that, in the same experimental conditions, the maximum value of effective Chi2 induced by thermal poling in double-anode configuration is smaller than the one obtained in single-anode configuration for any position of the core in the range between the anodic surface and the geometric center of the fiber. Finally, we report the experimental observation of depletion region formation in a twin-hole fused silica fiber poled in single-anode configuration. Using a QPM SHG experimental set-up, we demonstrate that the value of Chi2 obtained in the single anode configuration is at least as large as for the double anode one.
UV generation via four-wave-mixing (FWM) in optical microfibres (OMFs) was demonstrated. This was achieved by exploiting the tailorable dispersion of the OMF in order to phase match the propagation constant of the four frequencies involved in the FWM process. In order to satisfy the frequency requirement for FWM, a Master Oscillator Power Amplifier (MOPA) working at the telecom C-band was connected to a periodically poled silica fibre (PPSF), producing a fundamental frequency (FF) at 1550.3 nm and a second harmonic (SH) frequency at 775.2 nm. A by-product of this second harmonic generation is the generation of a signal at the third harmonic (TH) frequency of 516.7 nm via degenerate FWM. This then allows the generation of the fourth harmonic (FH) at 387.6 nm and the fifth harmonic (5H) at 310nm via degenerate and nondegenerate FWM in the OMF.The output of the PPSF was connected to a pure silica core fibre which was being tapered using the modified flame brushing technique from an initial diameter of 125 μm to 0.5 μm. While no signal at any UV wavelength was initially observed, as the OMF diameter reached the correct phase matching diameters, signals at 387.6 nm appeared. Signals at 310 nm also appeared although it is not phase matched, as the small difference in the propagation constant is bridged by other nonlinear processes such as self-phase and cross phase modulation.
Thermal poling, a technique to introduce effective second-order nonlinearities in silica optical fibers, has found widespread applications in frequency conversion, electro-optic modulation, switching and polarization-entangled photon pair generation. Since its first demonstration around 25 years ago, studies into thermal poling were primarily based on anode-cathode electrode configurations. However, more recently, superior electrode configurations have been investigated that allow for robust and reliable thermally poled fibers with excellent second order nonlinear properties [1, 2]. Very recently, we experimentally demonstrated an electrostatic induction poling technique that creates a stable second-order nonlinearity in a twin-hole fiber without any direct physical contact to internal fiber electrodes whatsoever . This innovative technique lifts a number of restrictions on the use of complex microstructured optical fibers (MOF) for poling, as it is no longer necessary to individually contact internal electrodes and presents a general methodology for selective liquid electrode filling of complex MOF geometries. In order to systematically implement these more advanced device embodiments, it is first necessary to develop comprehensive numerical models of the induction poling mechanism itself. To this end, we have developed two-dimensional (2D) simulations of space-charge region formation using COMSOL finite element analysis, by building on current numerical models .
ZnSe and other zinc chalcogenide semiconductor materials can be doped with divalent transition metal ions to create a
mid-IR laser gain medium with active function in the wavelength range 2 - 5 microns and potentially beyond using
frequency conversion. As a step towards fiberized laser devices, we have manufactured ZnSe semiconductor fiber
waveguides with low (less than 1dB/cm at 1550nm) optical losses, as well as more complex ternary alloys with
ZnSxSe(1-x) stoichiometry to potentially allow for annular heterostructures with effective and low order mode corecladding
Integration of semiconductor and metal structures into optical fibers to enable fusion of semiconductor optoelectronic
function with glass optical fibers is discussed. A chemical vapor deposition (CVD)-like process, adapted for high pressure
flow within microstructured optical fibers allows for flexible fabrication of such structures. Integration of semiconductor
optoelectronic devices such as lasers, detectors, and modulators into fibers may now become possible.
In this paper we report the fabrication of microstructured optical fibers (MOFs) metallic metamaterials using a bottom-up
processing technique for surface enhanced Raman scattering (SERS) applications. The inner walls of the silica-based
holey optical fiber have been modified by depositing granular films of Ag nanoparticles from its organometallic
precursor at high pressure condition. The resulting fibers demonstrate strong SERS effect when analyte molecules are
infiltrated within the MOF due to large electromagnetic field enhancement and long interaction length. The chemically
modified MOFs with 3D patterning represent an exciting platform technology for next generation SERS sensors and
plasmonic in-fiber integrated devices.
We have recently fabricated continuous semiconducting micro and nanowires within the empty spaces of highly ordered microstructured (e.g., photonic crystal or holey) optical fibers (MOF's). These systems contain the highest aspect ratio semiconductor micro- and nanowires yet produced by any method: centimeters long and ~100 nm in diameter. These structures combine the flexible light guiding capabilities of an optical fiber with the electronic and optical functionalities of semiconductors and have many potential applications for in-fiber sensing, including in-fiber detection, modulation, and generation of light.