S. Nic Chormaic

Contributed Review: Optical micro- and nanofiber pulling rig

We review the method of producing adiabatic optical micro- and nanofibers using a hydrogen/oxygen flame brushing technique. The flame is scanned along the fiber, which is being simultaneously stretched by two translation stages. The tapered fiber fabrication is reproducible and yields highly adiabatic tapers with either exponential or linear profiles. Details regarding the setup of the flame brushing rig and the various parameters used are presented. Information available from the literature is compiled and further details that are necessary to have a functioning pulling rig are included. This should enable the reader to fabricate various taper profiles, while achieving adiabatic transmission of ∼99% for fundamental mode propagation. Using this rig, transmissions ranging from 85% to 95% for higher order modes in an optical nanofiber have been obtained.

Selective particle trapping and optical binding in the evanescent field of an optical nanofiber.

The evanescent field of an optical nanofiber presents a versatile interface for the manipulation of micron-scale particles in dispersion. Here, we present a detailed study of the optical binding interactions of a pair of 3.13 μm SiO(2) spheres in the nanofiber evanescent field. Preferred equilibrium positions for the spheres as a function of nanofiber diameter and sphere size are discussed. We demonstrated optical propulsion and self-arrangement of chains of one to seven 3.13 μm SiO(2) particles; this effect is associated with optical binding via simulated trends of multiple scattering effects. Incorporating an optical nanofiber into an optical tweezers setup facilitated the individual and collective introduction of selected particles to the nanofiber evanescent field for experiments. Computational simulations provide insight into the dynamics behind the observed behavior.

Hollow whispering gallery resonators

In recent years, whispering gallery mode (WGM) devices have extended their functionality across a number of research fields from photonics device development to sensing applications. Here, we will discuss some such recent applications using ultrahigh Q-factor hollow resonators fabricated from pretapered glass capillary. We will discuss device fabrication and different applications that can be pursued such as bandpass filtering, nanoparticle detection, and trapping. Finally, we will introduce our latest results on visible frequency comb generation.

Neutral 87 Rb atoms near the surface of optical nanofibres

Optical nanofibres (ONF), which are fabricated by tapering standard optical fibre over a heat source to subwavelength diameter [1], have recently come to the fore as ideal tools for atom-photon hybrid quantum systems. For a recent review on the topic the reader is referred to [2]. A sub-wavelength diameter ONF results in a large portion of the guided mode energy being contained within the evanescent field beyond the nanofibre surface. The tight confinement of the light provides a high intensity and field gradient even for very low input powers. The fibre-guided light can probe ensembles of atoms around the nanofibre and, equivalently, the nanofibre can be used to transfer light from one atomic system to another.

Characterization of periodic plasmonic nanoring devices for nanomanipulation

We study the optical properties of hybrid gold nanodisk and nanohole arrays and present experimental evidence of nanoparticle trapping using these devices. The fabrication procedure using electron beam lithography (EBL) is also discussed. This hybrid design exhibits a splitting of the resonance modes (low and high energy modes) due to the coupling of the electromagnetic interaction between nanohole and nanodisk plasmons. The devices demonstrate high plasmon resonance tunabilities from the visible to the near-infrared region (NIR) by varying the dimensions of the features of this design. This enhancement in the NIR is highly desirable for the purposes of biological sample manipulation where photo damage should be low. Additionally, these devices consist of grooves connecting the hybrid structures to each other. These regions provide further enhancement of the local electric fields and play the role of the trapping sites. We demonstrate multiple dielectric nanoparticle trapping in these grooves while the devices are excited by evanescent fields via the Kretschmann configuration. The results provide good evidence of the potential of this design to be used for the manipulation of biological samples with sub-diffraction limit sizes.

Submicron particle manipulation using slotted tapered optical fibers

The use of optical micro- and nanofibers has become commonplace in the areas of atom trapping using neutral atoms and, perhaps more relevantly, the optical trapping and propulsion of micro- and nanoscale particles. It has been shown that such fibers can be used to manipulate and trap silica and polystyrene particles in the 1-3 µm range using either the fundamental or higher order modes of the fibers, with the propulsion of smaller particle sizes also possible through the use of metallic and/or high index materials. We previously proposed using a focused ion beam nanostructured tapered optical fiber for improved atom trapping geometries; here, we present the details of how these nanostructured optical fibers can be used as a platform for submicron particle trapping. The optical fibers are tapered to approximately 1.2 µm waist diameters, using a custom-built, heat-and-pull fiber rig prior to processing using a focused ion beam. Slots of approximately 300 nm in width and 10-20 µm in length are milled clean though the waist regions of the tapered optical fibers. High fiber transmissions (> 80%) over a broad range of wavelengths (700-1100 nm) are observed. We present simulation results for the trapping of submicron particles and experimental results on the trapping of 200 nm particles. This work demonstrates even further the functionality of optical micro- and nanofibers as trapping devices across a range of regimes.

Advanced optics in an interdisciplinary graduate program

The Okinawa Institute of Science and Technology Graduate University, established in November 2011, provides a 5-year interdisciplinary PhD program, through English, within Japan. International and Japanese students entering the program undertake coursework and laboratory rotations across a range of topics, including neuroscience, molecular science, physics, chemistry, marine science and mathematics, regardless of previous educational background. To facilitate interdisciplinarity, the university has no departments, ensuring seamless interactions between researchers from all sectors. As part of the PhD program a course in Advanced Optics has been developed to provide PhD students with the practical and theoretical skills to enable them to use optics tools in any research environment. The theoretical aspect of the course introduces students to procedures for complex beam generation (e.g. Laguerre-Gaussian), optical trapping, beam analysis and photon optics, and is supported through a practical program covering introductory interference/diffraction experiments through to more applied fiber optics. It is hoped that, through early exposure to optics handling and measurement techniques, students will be able to develop and utilize optics tools regardless of research field. In addition to the formal course in Advanced Optics, a selection of students also undertakes 13 week laboratory rotations in the Light-Matter Interactions research laboratory, where they work side-by-side with physicists in developing optics tools for laser cooling, photonics or bio-applications. While currently in the first year, conclusive results about the success of such an interdisciplinary PhD training are speculative. However, initial observations indicate a rich cross-fertilization of ideas stemming from the diverse backgrounds of all participants.