Source: https://groups.oist.jp/light/fy2014-annual-report
Timestamp: 2019-04-25 07:47:41+00:00

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This year the group focussed on work related to particle trapping at the nanoscale, optical control of particles over a range of sizes and sensing using whispering gallery resonators. Amongst the major outputs were a proposal for atom trapping based on nanostructured optical fibres, the first demonstration of higher order optical mode propagation in optical nanofibres and the interaction of such modes with cold atoms, a demonstration of the Autler-Townes effect in an atomic system for ultralow powers, a model and demonstratioin of optical binding for micron sized particles next to optical nanofibres and the demonstration of nonlinear effects in a variety of whispering gallery resonators.
Following our previous results on the controlled generation of higher order modes in a micro- and nanofiber [Opt. Commun. 285, 4648, (2012), Rev. Sci. Instrum. 85, 111501 (2014)], we demonstrated in this work the capability to trap and propel particles based on the excitation of the first order of the higher order modes at the fibre waist. The propelling velocity of a 3 µm polystyrene particle were 8 times faster (as shown in Fig. 1) under the higher order mode (HOM) than the fundamental mode (FM) for a waist power of 25 mW. The hydrodynamic interaction between particles and fibre surface has also been investigated. We applied two correction factors (Faxen and Krishnan factors) of the hydrodynamic interaction effect to predict the particle speeds for the HOM and FM cases. Experimental data were supported by theoretical calculations.
Figure 1: Microgram of 3 µm polystyrene particle propulsion under (a) FM and (b) HOMs propagation for the waist power of 25 mW.The work can be applied for future trapping and control of laser-cooled atoms for quantum networks, to investigate molecular motions of cells and simultaneous trapping of multiple micro- and nanoparticles in complex systems.
In this work, we first investigated the optical properties of a hybrid gold nano-cavity disk and hole array design which demonstrates high plasmon resonances in the near-infrared regime (NIR). The enhancement in the NIR is in the biologically compatible part of the spectrum where low photo damage is desirable. The resonant modes of this hybrid design exhibit splitting to low and high energy modes caused by the electromagnetic interference between the disk and hole plasmons. We have characterized the design by calculating transmission spectra (Fig. 2a) and field distributions (Fig. 2b) for different array parameters using FDTD software. The Kretschmann configuration was then used to excite the plasmonics devices at a glass-water interface using evanescent fields. We preliminary demonstrated experimental results of trapped 100 nm polystyrene particles with this nano-plasmon array using a 950 nm laser source. The results demonstrate the potential of this configuration to be used for direct trapping and manipulation of matter such as cells, proteins and molecules down to atomic levels for biological science applications.
Figure 2: Transmission spectra for (a) single cell unit and (b) for periodic arrays with 350 nm pitch for different inner ring diameters. The transmission peak is shifted to the NIR by increasing the inner ring diameter. The same is observed in (b) but also the splitting of the resonance for larger inner ring diameters due to the interaction between the cells in the array.
Whispering gallery resonators continue to be a source of interest for research groups around the world. During FY2014, the Light–Matter Interactions group focused on the sensing capabilities and the non-linear optical behaviour of whispering gallery resonators. Our group has interest in a special type of optical microcavity called the microbubble or microbottle whispering gallery resonator. These are hollow microcavities where the optical modes propagate inside a thin spherical shell. By filling the microbubble with different materials we can control or alter the behaviour of the whispering gallery modes. In one such case we explore a polymer filled microbubble and found that regenerative oscillations can be sustained within the cavity due to the interplay between the glass and polymer’s thermal and optical coefficients (Fig. 1).
Fig. 1 Transmitted power from a PDMS microbubble when the pump laser is tuned near a WGM. The modulated output is sustained for a number of minutes.
By compressing the air inside an empty microbubble resonator we were able to control the coupling between modes of different order and observe coupled mode induced transparency (Fig. 2). From this experiment it was realised that different order modes shift at different rates due the application of stress and strain.
Using microbubbles with very thin walls can boost the interaction between the whispering gallery modes and the material in the core of the bubble. However ultra-thin walls induce optical loss and reduce the resolution of the sensor. We have shown that by careful fabrication it is possible can make microbubbles with 500 nm thick walls and still maintain Quality Factors close the theoretical limit even at long optical wavelengths around 1550 nm (Fig. 3).
Fig 3. (Left) A SEM of the microbubble snapped in the middle. The measured wall thickness varies from 563 nm down to 507 nm. (Right). Accurate Q factor calculated for different wall thickness by finite element method at 1550 nm. The red line is just for guiding of eyes.
For further improving the aerostatic pressure sensing capability, we filled the microbubble with acetone. It was found that the sensitivity was boosted by nearly 20% for a microbubble with a wall thickness of 1.3 μm. (Fig .4). This is due to the fact that elasto-optic coefficient of the liquid is 100 times higher than in the solid silica material. Such experiments show that by using the microbubble it is possible to measure the elasto-optic coefficient of the liquid.
Fig .4 Pressure tuning sensitivity measurement for a microbubble when it is empty (upper) and filled with acetone (bottom).
The use of microcavities for the generation of non-linear optical effects has been studied for decades but it still remains an area of intense study. We have observed Raman lasing in a hollow micobottle resonator (Fig. 5) and are working on characterisation of four-wave mixing in such structures (Fig. 6).
Fig. 5 (Left) Bottle whispering gallery mode resonator. The red lines represent the mode light traveling in the resonator. (Right) Spectrum of cascaded Raman scattering. Pump light at 771.6nm generates first-order Raman scattering around 802.0 nm; this generates the second order around 831.2 nm, which generates the third order around 861.3 nm.
Fig. 6 Parametric oscillation via four-wave-mixing in the hollow microbottle. The free spectrum range of the frequency comb generated here is about 5.4 nm.
To further improve the non-linearity in the microcavities, highly non-linear materials are required. In collaboration with the Dublin Institute of Technology and the Optoelectronics Research Center (University of Southampton), we successfully fabricated microbubbles from highly non-linear lead silicate glass (Fig 7.).
Fig 6. (Up) Single and double input lead silicate microbubble and their spectra (bottom).
In other work, our group has investigated the optomechanical interaction between the laser light in an optical waveguide and the optical modes in a free moving whispering gallery resonator. The nanoscale movement of the micocavity is transduced by the evanescent field of the waveguide. It was found that the amplitude of the transmitted signal depends on the detuning between the laser light and the whispering gallery mode resonance. The cause of this effect was found to be due to the interference between the dissipative and dispersive loss channels of the optical system. This observation is important for the study of centre of mass cooling of optical microcavities and optomechanical sensing.
Fig. 7 (left) Numerically calculated transduction response of WGMs to the micropendulum motion. The color bar shows the 1 kHz mechanical mode relative peak amplitudes. (Right) Transduction response profile for undercoupled system.
Finally we have published two review articles, one discussing the fabrication of a tapered optical fiber pulling rigs and the other discussing the state of the art of hollow whispering gallery resonators.
Sub-wavelength size diameter of an optical nanofiber (ONF) provides significant portion of propagating light in the evanescent field region. Also tight confinement of the light gives high intensities even at low powers. Atoms around the ONF experience this field and non-linear optics phenomena can be studied. Here, we use an optical nanofiber embedded in a cloud of laser-cooled 87Rb for near-infrared frequency up-conversion via a resonant two-photon process. Sub-nW powers of the two-photon radiation, at 780 (ω1) and 776 nm (ω2), co-propagate through the optical nanofiber and the generation of 420 nm photons is observed. At tens of nWs of power, a clear Autler-Townes splitting is observed which provides a direct measurement of the Rabi frequency of the ω1 transition. With the slightly modified set-up we observed electromagnetically induced transparency where presence of ω2 beam makes ω1 light transparent at the resonant transitions. We have also developed a laser operating at 482 nm and integrated it with the existing system in order to address the nonlinear interactions in highly excited cold atoms around the ONF.
Figure 1: Blue fluorescence from atoms collected via the ONF for different powers in ω1, which is 14 MHz red detuned from the 5S1/2 F=2 to 5P3/2 F̍̍̍̍'=3 transition, while ω2 is scanned across the 5P3/2 F̍̍' =3 to 5D5/2 hyperfine levels. The power for ω2 is fixed at 0.5 nW. δp is the detuning of ω2 from 5P3/2 F̍̍'=3 to 5D5/2 F″=4. ω1 is held at the same frequency as the cooling beams. Asymmetry in the observed A-T doublet is due to the fact that ω1 is not on resonance. Solid lines are theoretical fits to the data.
Daly, M., Truong, V. G., Phelan, C. F., Deasy, K. & Nic Chormaic, S. Nanostructured optical nanofibres for atom trapping New Journal of Physics 16, 053052, doi:10.1088/1367-2630/16/5/053052 (2014).
Frawley, M. C., Gusachenko, I., Truong, V. G., Sergides, M. & Nic Chormaic, S. Selective particle trapping and optical binding in the evanescent field of an optical nanofiber. Optics Express 22, 16322-16334, doi:10.1364/OE.22.016322 (2014).
Gusachenko, I., Sergides, M., Truong, V. G. & Nic Chormaic, S. Towards polarization-sensitive trapping of nanoparticles in nanoring apertures. Proc. SPIE 9164, Optical Trapping and Optical Micromanipulation XI, 91642Y 9164, 91642Y-91641-91645, doi:10.1117/12.2061521 (2014).
Kumar, R., Gokhroo, V., Deasy, K., Maimaiti, A., Frawley, M. C., Phelan, C. & Nic Chormaic, S. Interaction of laser-cooled 87Rb atoms with higher order modes of an optical nanofibre. New Journal of Physics 17, doi:10.1088/1367-2630/17/1/013026 (2015).
Maimaiti, A., Truong, V. G., Sergides, M., Gusachenko, I. & Nic Chormaic, S. Higher order microfibre modes for dielectric particle trapping and propulsion. Scientific Reports 5, doi:10.1038/srep09077 (2015).
Wang, P., Ward, J., Yang, Y., Feng, X., Brambilla, G., Farrell, G. & Nic Chormaic, S. Lead-silicate glass optical microbubble resonator. Applied Physics Letters 106, 061101, doi:10.1063/1.4908054 (2015).
Ward, J. M., Madugani, R., Yang, Y. & Nic Chormaic, S. Asymmetric response function of the transduction spectrum for a microsphere pendulum. SPIE Proceedings, Laser Resonators, Microresonators, and Beam Control XVII 9343, 1-6, doi:10.1117/12.2077323 (2015).
Ward, J. M., Yang, Y. & Nic Chormaic, S. PDMS quasi-droplet microbubble resonator. SPIE Proceedings, Laser Resonators, Microresonators, and Beam Control XVII 9343, 1-7, doi:10.1117/12.2078658 (2015).
Hosseini, E., Kasamatsu, K., Nic Chormaic, S., Takui, T., Kondo, Y., Nakahara, M. & Ohmi, T. Physics, Mathematics, and All that Quantum Jazz Two-qubit gate operation on selected nearest neighboring qubits in a neutral atom quantum computer, in Kinki University Series on Quantum Computing Vol. Volume 9 (ed S. Tanaka, Bando, M., Güngördü, U. ), Ch. Physics, Mathematics, and All that Quantum Jazz pages 175-177, World Scientific Publishing Co. (2014).
Nic Chormaic, S. Breaking the trend in Japanese universities - viewpoint of a female and foreign faculty member (invited) in Symposium Series: My Work and Career Design 8: Global Perspectives on Diversity in Japanese Universities - Benefits and Challenges, Kyoto University Gender Equality Promotion Center, Japan (2014).
Daly, M., Truong, V. G., Phelan, C., Deasy, K. & Nic Chormaic, S. Nanostructured nanofiber for atom trapping, in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Deasy, K., Daly, M., Truong, V. G., Phelan, C. & Nic Chormaic, S. Atom trapping in a slotted optical nanofibre, in Photon14, London, UK (2014).
Deasy, K., Kumar, R., Gokhroo, V., Maimaiti, A., Frawley, M. C. & Nic Chormaic, S. Excitation and absorption of optical nanofibre higher order modes by 87Rb atoms, in Photon14, London, UK (2014).
Kumar, R., Gokhroo, V., Deasy, K. & Nic Chormaic, S. Optical nanofiber mediated frequency up-conversion in cold 87Rb atoms, in ASPC 2014, Kolkata, India (2014).
Kumar, R., Gokhroo, V., Maimaiti, A., Deasy, K. & Nic Chormaic, S. Excitation of higher-order modes of an optical nanofiber by laser-cooled Rb-87 atoms, in CLEO2014, San Jose, USA (2014).
Madugani, R., Yang, Y., Ward, J., Le, V. H. & Nic Chormaic, S. Microsphere pendulum optomechanics, in Workshop on Hierarchy of Quantum Mechanics, Okazaki, Japan (2015).
Nic Chormaic, S. Microbubble whispering gallery mode resonators (invited), in 560. WE-Heraeus-Seminar - Taking Detection to the Limit: Biosensing wtih Optical Microcavities, Bad Honnef, Germany (2014).
Nic Chormaic, S. Optical nanofibres as quantum interface tools for atoms and light (invited), in ASPC 2014, Kolkata, India (2014).
Nic Chormaic, S. Manipulating cold atoms with optical nanofiber guided light (invited) in Shortcuts to Adiabaticity 2014, Shanghai, China (2014).
Nic Chormaic, S. Light-matter interactions research at OIST in OIST-University of Tokyo Joint Symposium, Okinawa, Japan (2014).
Nic Chormaic, S. Optical nanofibres for particle traping and manipulation (invited), in International Seminar on Optical Nanofibres in Applications, Chicheley Hall, United Kingdom (2014).
Nic Chormaic, S. A hybrid system based on optical nanofibres for probing and trapping atoms, in QCLM2015: Quantum Control of Light and Matter, Okinawa, Japan (2015).
Nic Chormaic, S., Kumar, R., Gokhroo, V. & Deasy, K. A hybrid system based on optical nanofibres for probing and trapping atoms, in Topical Research Meeting on Hybrid Quantum Systems, Nottingham, UK (2014).
Truong, V. G., Maimaiti, A., Daly, M., Gusachenko, I., Sergides, M. & Nic Chormaic, S. Ultrathin optical fibres for particle trapping and manipulation (invited), in IEICE General Conference 2015, Kusatsu, Japan (2015).
Ward, J. M., Yang, Y., Madugani, R. & Nic Chormaic, S. Asymmetric response function of the transduction spectrum for a microsphere pendulum, in LASE, SPIE Photonics West, San Francisco, USA (2015).
Ward, J. M., Yang, Y. & S., N. C. PDMS quasi-droplet microbubble resonator, in LASE, SPIE Photonics West, San Francisco, USA (2015).
Daly, M., Truong, V. G. & Nic Chormaic, S. Local field enhancements for particle trapping, in IONS-Asia 5, Sapporo, Japan (2014).
Deasy, K., Kumar, R., Gokhroo, V., Maimaiti, A., Frawley, M. & Nic Chormaic, S. Fluorescent excitation of nanofibre higher order modes, in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Dhasmana, N., Yang, Y. & Nic Chormaic, S. Four-wave mixing in microsphere resonator, in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Gokhroo, V., Kumar, R., Deasy, K. & Nic Chormaic, S. Probing 2-photon absorption in cold atoms using an optical nanofiber in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Gokhroo, V., Kumar, R., Deasy, K. & Nic Chormaic, S. Very low power 2-photon absorption in cold 87Rb atoms using an optical nanofiber in ICAP 2014, Washington DC, USA (2014).
Gokhroo, V., Kumar, R., Maimaiti, A., Deasy, K. & Nic Chormaic, S. Probing evanescent field couping between laser-cooled 87Rb atoms and the fundamental and higher order modes of an optical nanofiber, in ICAP 2014, Washington DC, USA (2014).
Gusachenko, I., Frawley, M., Truong, V. G. & Nic Chormaic, S. Optical nanofiber intergrated into an optical tweezers for particle mainpulation and in-situ fiber probing, in SPIE Optics & Photonics - Optical Trapping and Optical Micromanipulation XI, San Diego, USA (2014).
Gusachenko, I., Sergides, M., Truong, V. G. & Nic Chormaic, S. Towards polarization-sensitive traping of nanoparticles in nanoring apertures, in SPIE Optics & Photonics - Optical Trapping and Optical Micromanipulation XI, San Diego, USA (2014).
Kumar, R., Gokhroo, V., Deasy, K. & Nic Chormaic, S. Optical nanofiber mediated frequency up-conversion in cold 87Rb atoms, in Okinawa School in Physics: Coherent Quantum Dynamics, Okinawa, Japan (2014).
Kumar, R., Gokhroo, V., Deasy, K. & Nic Chormaic, S. Autler-Townes splitting in cold Rb atoms at ultra-low power using an optical nanofibre, in Topical Research Meeting on Hybrid Quantum Systems, Nottingham, UK (2014).
Kumar, R., Gokhroo, V., Deasy, K., Russell, L. & Nic Chormaic, S. Sensing cold atoms with a hot sensor, in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Madugani, R., Yang, Y., Ward, J. & Nic Chormaic, S. Microsphere pendulum optomechanical transduction and characterization via evanescent light, in Okinawa School in Physics: Coherent Quantum Dynamics, Okinawa, Japan (2014).
Madugani, R., Yang, Y., Ward, J. M. & Nic Chormaic, S. Microsphere pendulum optomechanical trasnduction and characterization via evanescent light in 560. WE-Heraeus-Seminar - Taking Detection to the Limit: Biosensing wtih Optical Microcavities, Bad Honnef, Germany (2014).
Maimaiti, A., Truong, V. G., Sergides, M., Gusachenko, I. & Nic Chormaic, S. Manipulation of dielectric particles using higher order microfiber modes, in IONS-Asia 5, Sapporo, Japan (2014).
Nic Chormaic, S., Daly, M., Phelan, C., Deasy, K. & Truong, V. G. A nanostructured tapered optical fiber for cold atom trapping, in ICAP 2014, Washington DC, USA (2014).
Nieddu, T., Deasy, K., Kumar, R., Gokhroo, V. & Nic Chormaic, S. Fluorescent excitation of nanofiber higher order modes, in Topical Research Meeting on Hybrid Quantum Systems, Nottingham, UK (2014).
Phelan, C., Daly, M., Truong, V. G., Deasy, K. & Nic Chormaic, S. Cold atom trapping with a nanostructured optical nanofiber, in C3QS 2014, Seaside House, Okinawa, Japan (2014).
Truong, V. G., Maimaiti, A., Gusachenko, I., Sergides, M., Frawley, M. & Nic Chormaic, S. Optical micro- and nanofibres: Particle trapping, self-assembly and higher order mode generation for particle manipulation, in Trends in Optical Manipulation III, Obergurgl, Austria (2015).
Yang, Y., Madugani, R., Ward, J. & Nic Chormaic, S. Optomechanical response of a tapered fiber coupled microsphere pendulum, in CLEO: QELS Fundamental Science, San Jose, USA (2014).
Yang, Y., Ward, J. M. & Nic Chormaic, S. Optimization of quasi-droplet microbubble resonators for sensing, in 560. WE-Heraeus-Seminar - Taking Detection to the Limit: Biosensing wtih Optical Microcavities, Bad Honnef, Germany (2014).
Gokhroo, V. Experiments on two-photon absorption in cold 87Rb atoms using an optical nanofiber, JQI, University of Maryland, USA (2014).
Nic Chormaic, S. Manipulating particles with light, Dept. Experimental Physics, NUIM, Maynooth, Ireland (2014).
Nic Chormaic, S. Probing particles with light Faculty of Physics and Mathematics, University of Latvia, Riga, Latvia (2014).
Nic Chormaic, S. Optical micro- and nanofibres for particle trapping and manipulation, St Andrews University, Scotland (2014).
Nic Chormaic, S. Optical nanofibres as manipulation tools for cold atoms, Université Paris-Sud, France (2014).
Nic Chormaic, S. Optical micro- and nanofibres for particle trapping and manipulation Acharya Narendra Dev College (University of Delhi), India (2014).
Nic Chormaic, S. Optical micro- and nanofibres for particle traping and manipulation Trinity College Dublin, Ireland (2014).
Yang, Y. & Nic Chormaic, S. A Brief Introduction of Whispering Gallery Mode Resonator Research in Light-Matter Interactions Unit Micro/Nano Photonics Lab, Washington University, St Louis, USA (2014).
One PhD student, Mary Frawley, graduated from the unit through University College Cork (Ireland).

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