New group members

Ewa Karczewska is joining the UCL Optical Tweezers Group today for an eight week research project funded by the Nuffield Foundation.  The foundation provides research bursaries for undergraduate students considering a career in research to gain experience in a research lab over the summer vacation.  The Optical Twezeers Group has peviously hosted three Nuffield bursary students: Muddassar Rashid (2008), Alex Dunning (2009) and Radhika Patel (2010).

Ewa is a second year undergraduate student at UCL, studying for an MSci degree in Physics.  She will be contributing to a number of different projects presently running in the group, and making regular updates of her progress on this blog.

Andrei Rode visit and seminar

This week Prof Andrei Rode from the Laser Physics Centre of the Australian National University, Canberra is visiting.  While here he will also be giving an AMOP Physics seminar on Optical vortices: Trapping of particles and material processing.

Abstract: In physics and biology, manipulation of microscopic objects achieved remarkable precision and functionality using very small radiation pressure of light and dipole-induced gradient forces, so called optical tweezers.  Stable trapping of absorbing particles in air was not achieved till now due to the dominance of forces from thermal interaction of the laser-irradiated particle with the molecules of ambient gas.  We address this challenge by developing a touch-free optical trapping of particles suspended in air with optical vortices.  The ability to guide absorbing particles along the vortex core in a stable and controlled manner can be employed further for high-accuracy manipulation of particles in three dimensions.

We also developed a femtosecond vortex beam converter where polarization singularities are created when the beam propagates through a birefringent crystal, to produce sub-micron ring structures on the surface of fused silica and glass samples. We employ this technique to generate optical vortex as well as radially (TM) and azimuthally (TE) polarized fs-laser pulses for sub-µm structuring of glass samples.

Interaction of tightly focused multiple fs-pulses with transparent media allows one to imprint their local polarization pattern with sub-wavelength resolution, including the presence of the longitudinal component of electric field.  The materials’ response to the state of polarization of high intensity light fields has been used to map the complex vector structure in the focal volume of radially and azimuthally polarized fs-laser pulses.

Nuffield Bursary Award

Ewa Karczewska has been awarded a Nuffield Foundation Undergraduate Research Bursary to work in the UCL Optical Tweezers Group this summer. This scheme allows UK undergraduates to gain research experience by providing funding for up to eight weeks to complete a research project during the summer vacation. We have hosted three previous Nuffield Foundation Bursary students: Muddassar Rashid (2008) who worked on synthesis and properties of polarisation vortex beams, Alex Dunning (2009) who performed calculations on the properties of optical nanofibres and is now studying for a PhD at Southampton University, and Radhika Patel (2010) who worked on photonic force microscopy experiments and is taking her final exams this year.

Optical Trapping Applications

Next week Phil, Susan and Marios will all be attending the OSA Optical Trapping Applications conference in Monterey, CA.  Phil will be giving a talk about our work on trapping with novel beams, and Susan and Marios will be presenting posters on their research projects.

Visit by Onofrio Marago

Onofrio Marago (NanoSoft Lab, IPCF-CNR, Messina) is visiting the group this week, 7-11 March 2011.

Onofrio has a long-running collaboration with the UCL Optical Tweezers Group and exchange visits between UCL and NanoSoft Lab are presently funded by our Royal Society International Joint Project.

Left: Onofrio adjusting the evanescent-wave optical binding experiment.

NPL Annual Review

The NPL-UCL Microbubble Project is featured in the latest NPL Annual Review, 110 Years of Impact.

Measuring with microbubbles

NPL is working with University College London on a fascinating project which investigates the dynamics of microbubbles, to see if they can be used as highly sensitive sensors in medical an industrial applications.

Microbubbles are specially-coated bubbles which are designed primarily to enhance ultrasound pulse-echo imagaing.  Their use significantly enhances sound echoes, thereby improving detection accuracy, and therefore diagnosis of 'difficult' cancers (e.g. liver, prostate).

Microbubbles (and specially designed ultrasonic fields) are being studied worldwide as possible vehicles for drug and gene delivery.  They promise to play a crucial role in fighting Alzheimer's disease, or cancers in which the use of chemotherapy is deemed too risky to the patient, and thus a targeted therapy is more effective.

NPL's work in this area is developing the measurement building blocks, to exploit the sensitivity of microbubbles to local changes in their environment, so extending their effectiveness in medical applications and beyond.

For more information about this project contact Phil Jones at UCL, or Gianluca Memoli at NPL.

UCL sp2 Carbon Group

Phil is giving a talk to the UCL sp2 Carbon Group on 'Optical Trapping of Carbon Nanomaterials'

This talk will give a brief overview of our experimants on optical tweezers for trapping and maniplation of carbon nanomaterials, including nanotubes and graphene flakes.  It will start with a description of
the experimental techniques of opical trapping and back focal plane interferometry for paricle tracking, then present results on trapping, tracking and the analysis of Brownian motion of trapped carbon nanotube bundles and graphene flakes, including centre-of-mass and angluar fluctuations and driven rotations, and combined optical tweezers and Raman spectroscopy.


References:
O. M. Maragò, F. Bonaccorso, R. Saija, G. Privitera, P. G. Gucciardi, M. A. Iatì, G. Calogero, P. H. Jones, F. Borghese, P. Denti, V. Nicolosi & A. C. Ferrari. 'Brownian motion of graphene', ACS Nano 4 7515-7523 (2010)

O. M. Maragò, R. Saija, F. Borghese, P. Denti, P. H. Jones, E. Messina, G. Compagnini, V. Amendola, M. Meneghetti, M. A. Iatì, and P. G. Gucciardi.  'Plasmon-enhanced optical trapping of metal nanoparticles: force calculations and light-driven rotations of nanoaggregates', Proc. SPIE Vol. 7762, 77622Z (2010)

O. M. Maragò, P. G. Gucciardi and P. H. Jones.  'Photonic Force Microscopy: from femtonewton force sensing to ultra-sensitive spectroscopy', in Scanning Probe Microscopy in Nanoscience and Nanotechnology 1 (Springer) B. Bushan (Ed.) (2010)

P. H. Jones, F. Palmisano, F. Bonaccorso, P. G. Gucciardi, G. Calogero, A. C. Ferrari & O. M. Maragò.  'Rotation detection in light-driven nanorotors',  ACS Nano 3 3077-3084 (2009)

O. M. Maragò, P. H. Jones and A. C. Ferrari. 'A light touch on nanotubes: femtonewton force sensing and nanometric spatial resolution', SPIE newsroom, doi 10.1117/2.1200901.1475 (2009)

O. M. Maragò, P. H. Jones, F. Bonaccorso, V. Scardaci, P. G. Gucciardi, A. Rozhin, and A. C. Ferrari.  'Femtonewton Force Sensing with Optically Trapped Nanotubes', Nano Letters 8 3211-3216 (2008)

O. M. Maragò, P. G. Gucciardi, F. Bonaccorso, G. Calogero, V. Scardaci, A. Rozhin, A. C. Ferrari, P. H. Jones, R. Saija, F. Borghese, P. Denti & M. A. Iatì.  'Optical trapping of carbon nanotubes’, Physica E 40 2347-2351 (2008)