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Diamonds containing the negatively charged nitrogen-vacancy centre are a promising system for room-temperature magnetometry. The combination of nano- and micro-diamond particles with optical fibres provides an option for deploying nitrogen-vacancy magnetometers in harsh and challenging environments. Here we numerically explore the coupling efficiency from nitrogen-vacancy centres within a diamond doped at the core/clad interface across a range of commercially available fibre types so as to inform the design process for a diamond in fibre magnetometers. We determine coupling efficiencies from nitrogen-vacancy centres to the guided modes of a step-index fibre and predict the optically detected magnetic resonance (ODMR) generated by a ensemble of four nitrogen-vacancy centres in this hybrid fibre system. Our results show that the coupling efficiency is enhanced with a high refractive index difference between the fibre core and cladding and depends on the radial position of the nitrogen-vacancy centres in the fibre core. Our ODMR simulations show that due to the preferential coupling of the nitrogen-vacancy emission to the fibre guided modes, certain magnetometry features such as ODMR contrast can be enhanced and lead to improved sensitivity in such diamond-fibre systems, relative to conventional diamond only ensemble geometries.

We experimentally demonstrate a single-layer terahertz dielectric metasurface. The metasurface consists of an array of sub-wavelength fibers. It is shown that this single-layer terahertz metasurface has high transmission window and can also behave like a terahertz magnetic or electric mirror due to the excitation of resonances in the fibers. It is also observed that changing the excitation angle ( \phi >5{\circ }) leads to appearance of new resonances, which narrows and widens the transmission window for s- and p- polarizations, respectively. By exploring the variation of resonances due to excitation of single, double or array of fibers, we have demonstrated that the individual element resonances can interact and lead to high transmission when the fibers are arranged in an array. The proposed single-layer metasurface that can operate both in transmission and reflection mode, opens new opportunities to develop single-layer terahertz devices for wavefront engineering.

Diamond containing the nitrogen-vacancy (NV) center is emerging as a significant sensing platform. However, most NV sensors require microscopes to collect the fluorescence signals and therefore are limited to laboratory settings. By embedding micron-scale diamond particles at an annular interface within the cross section of a silicate glass fiber, we demonstrate a robust fiber material capable of sensing magnetic fields. Luminescence spectroscopy and electron spin resonance characterization reveal that the optical properties of NV centers in the diamond microcrystals are well preserved throughout the fiber drawing process. The hybrid fiber presents a low propagation loss of ∼4.0 dB/m in the NV emission spectral window, permitting remote monitoring of the optically detected magnetic resonance signals. We demonstrate NV-spin magnetic resonance readout through 50 cm of fiber. This study paves a way for the scalable fabrication of fiber-based diamond sensors for field-deployable quantum metrology applications.

Precision glass tubes for analytical instrumentation often require tight tolerances in their inner and outer diameter, which makes them cumbersome to fabricate. The extrusion method is a potential method for the fabrication of precision glass tubes, however, the effects of die swell and taper which occur during the extrusion process can distort the final product. This work aims to determine the tolerances that can be achieved for glass tubes fabricated using the extrusion method by comparing the extent of the die swell and tapering on tubes extruded under a variety of extrusion parameters. Lead-silicate glass tubes of 6.5 mm outer diameter and 0.50 mm inner diameter were fabricated with a taper of <1% for the outer diameter and <5% for the inner diameter over 200 mm lengths. This target geometry was achieved using a volume flow rate of 4.7 mm 3 /s, a glass viscosity of 10 7.2 Pa.s and a die geometry that accommodated a 8%-10% offset due to die swell. This result indicates the extrusion method is a viable method for producing glass tubes with tight tolerances for applications in analytical instrumentation.

The probing of physiological processes in living organisms is a grand challenge that requires bespoke analytical tools. Optical fiber probes offer a minimally invasive approach to report physiological signals from specific locations inside the body. This perspective article discusses a wide range of such fiber probes developed at the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics. Our fiber platforms use a range of sensing modalities, including embedded nanodiamonds for magnetometry, interferometric fiber cavities for refractive index sensing, and tailored metal coatings for surface plasmon resonance sensing. Other fiber probes exploit molecularly sensitive Raman scattering or fluorescence where optical fibers have been combined with chemical and immunosensors. Fiber imaging probes based on interferometry and computational imaging are also discussed as emerging in vivo diagnostic devices. We provide examples to illustrate how the convergence of multiple scientific disciplines generates opportunities for the fiber probes to address key challenges in real-time in vivo diagnostics. These future fiber probes will enable the asking and answering of scientific questions that were never possible before.

We experimentally demonstrate that an enhanced THz magnetic source can be achieved by placing a subwavelength fiber in front of a sub-wavelength aperture illuminated by a THz plane wave. This hybrid system can be considered as a unit cell of metasurfaces for THz wave manipulation and can also be scaled to optical frequencies opening up avenues for developing fiber based optical devices such as nanoantenna and laser.

Novel approaches for digital data storage are imperative, as storage capacities are drastically being outpaced by the exponential growth in data generation. Optical data storage represents the most promising alternative to traditional magnetic and solid-state data storage. In this paper, a novel and energy efficient approach to optical data storage using rare-earth ion doped inorganic insulators is demonstrated. In particular, the nanocrystalline alkaline earth halide BaFCl:Sm is shown to provide great potential for multilevel optical data storage. Proof-of-concept demonstrations reveal for the first time that these phosphors could be used for rewritable, multilevel optical data storage on the physical dimensions of a single nanocrystal. Multilevel information storage is based on the very efficient and reversible conversion of Sm3+ to Sm2+ ions upon exposure to UV-C light. The stored information is then read-out using confocal optics by employing the photoluminescence of the Sm2+ ions in the nanocrystals, with the signal strength depending on the UV-C fluence used during the write step. The latter serves as the mechanism for multilevel data storage in the individual nanocrystals, as demonstrated in this paper. This data storage platform has the potential to be extended to 2D and 3D memory for storage densities that could potentially approach petabyte/cm3 levels.

Dielectric sub-wavelength particles have opened up a new platform for realization of magnetic light. Recently, we have demonstrated that a dipole emitter by a sub-wavelength fiber leads to an enhanced magnetic response. Here, we experimentally demonstrate an enhanced magnetic dipole source in the terahertz frequency range. By placing the fiber next to the hole in a metal screen, we find that the radiation power can be enhanced more than one order of magnitude. The enhancement is due to the excitation of the Mie-type resonances in the fiber. We demonstrate that such a system is equivalent to a double-fiber system excited by a magnetic source. This coupled magnetic dipole and optical fiber system can be considered a unit cell of metasurfaces for manipulation of terahertz radiation and is a proof-of-concept of a possibility to achieve enhanced radiation of a dipole source in proximity of a sub-wavelength fiber. It can also be scaled down to optical frequencies opening up promising avenues for developing integrated nanophotonic devices such as nanoantennas or lasers on fibers.

Traditional optical fibers are insensitive to magnetic fields, however many applications would benefit from fiber-based magnetometry devices. In this work, we demonstrate a magnetically sensitive optical fiber by doping nanodiamonds containing nitrogen vacancy centers into tellurite glass fibers. The fabrication process provides a robust and isolated sensing platform as the magnetic sensors are fixed in the tellurite glass matrix. Using optically detected magnetic resonance from the doped nanodiamonds, we demonstrate detection of local magnetic fields via side excitation and longitudinal collection. This is a first step towards intrinsically magneto-sensitive fiber devices with future applications in medical magneto-endoscopy and remote mineral exploration sensing.

© OSA 2016. A new versatile method of integrating upconversion nanocrystals into a glassy matrix is presented, which opens up exciting possibilities for new hybrid glass materials and multifunctional fiber devices with tailored nanoscale properties and high transparency.

We have developed a technique for creating high quality tellurite microspheres with embedded nanodiamonds (NDs) containing nitrogen-vacancy (NV) centres. This hybrid method allows fluorescence of the NVs in the NDs to be directly, rather than evanescently, coupled to the whispering gallery modes of the tellurite microspheres at room temperature. As a demonstration of its sensing potential, shifting of the resonance peaks is also demonstrated by coating a sphere surface with a liquid layer. This new approach is a robust way of creating cavities for use in quantum and sensing applications.