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Controlled transfer of transverse optical angular momentum to optically trapped birefringent particles
Alexander B. Stilgoe, Timo A. Nieminen, Halina Rubinsztein-Dunlop
We report on the observation and measurement of the transfer of transverse angular momentum to birefringent particles several wavelengths in size. A trapped birefringent particle i…
Machine learning reveals complex behaviours in optically trapped particles
Isaac C. D. Lenton, Giovanni Volpe, Alexander B. Stilgoe +2
Since their invention in the 1980s [1], optical tweezers have found a wide range of applications, from biophotonics and mechanobiology to microscopy and optomechanics [2, 3, 4, 5].…
Orientation of Swimming Cells with Annular Beam Optical Tweezers
Isaac C. D. Lenton, Declan J. Armstrong, Alexander B. Stilgoe +2
Optical tweezers are a versatile tool that can be used to manipulate small particles including both motile and non-motile bacteria and cells. The orientation of a non-spherical par…
Theory and practice of simulation of optical tweezers
Ann A. M. Bui, Alexander B. Stilgoe, Isaac C. D. Lenton +5
Computational modelling has made many useful contributions to the field of optical tweezers. One aspect in which it can be applied is the simulation of the dynamics of particles in…
Visual guide to optical tweezers
Isaac C. D. Lenton, Alexander B. Stilgoe, Halina Rubinsztein-Dunlop +1
It is common to introduce optical tweezers using either geometric optics for large particles or the Rayleigh approximation for very small particles. These approaches are successful…
T-matrix calculation via discrete-dipole approximation, point matching and exploiting symmetry
Vincent L. Y. Loke, Timo A. Nieminen, N. R. Heckenberg +1
We present a method of incorporating the discrete dipole approximation (DDA) method with the point matching method to formulate the T-matrix for modeling arbitrarily shaped micro-s…
Symmetry and the generation and measurement of optical torque
Timo A. Nieminen, Theodor Asavei, Vincent L. Y. Loke +2
A key element in the generation of optical torque in optical traps, which occurs when electromagnetic angular momentum is transferred from the trapping beam to the trapped particle…
Fabrication of micro-structures for optically driven micromachines using two-photon photopolymerization of UV curing resins
Theodor Asavei, Timo A. Nieminen, Norman R. Heckenberg +1
Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We hav…
Picolitre viscometry using optically rotated particles
Simon J. Parkin, Gregor Knoener, Timo A. Nieminen +2
Important aspects in the field of microrheology are the studies of the viscosity of fluids within structures with micron dimensions and fluid samples where only microlitre volumes…
Refractometry of organosilica microspheres
Katrina Y. T. Seet, Robert Vogel, Timo A. Nieminen +4
The refractive index of novel organosilica (nano/micro)material is determined using two methods. The first method is based on analysis of optical extinction efficiency of organosil…
Forces from highly focused laser beams: modeling, measurement and application to refractive index measurements
G. Knoener, S. Parkin, T. A. Nieminen +2
The optical forces in optical tweezers can be robustly modeled over a broad range of parameters using generalsed Lorenz-Mie theory. We describe the procedure, and show how the comb…
Nanotrapping and the thermodynamics of optical tweezers
W. Singer, T. A. Nieminen, N. R. Heckenberg +1
Particles that can be trapped in optical tweezers range from tens of microns down to tens of nanometres in size. Interestingly, this size range includes large macromolecules. We sh…
Optical trapping of a cube
A. M. Branczyk, T. A. Nieminen, N. R. Heckenberg +1
The successful development and optimisation of optically-driven micromachines will be greatly enhanced by the ability to computationally model the optical forces and torques applie…
Collecting single molecules with conventional optical tweezers
Wolfgang Singer, Timo A. Nieminen, Norman R. Heckenberg +1
The size of particles which can be trapped in optical tweezers ranges from tens of nanometres to tens of micrometres. This size regime also includes large single molecules. Here we…
Measurement of refractive index of single microparticles
Gregor Knoener, Simon Parkin, Timo A. Nieminen +2
The refractive index of single microparticles is derived from precise measurement and rigorous modeling of the stiffness of a laser trap. We demonstrate the method for particles of…
Modelling optical micro-machines
Vincent L. Y. Loke, Timo A. Nieminen, Agata M. Branczyk +2
A strongly focused laser beam can be used to trap, manipulate and exert torque on a microparticle. The torque is the result of transfer of angular momentum by scattering of the las…
Towards efficient modelling of optical micromanipulation of complex structures
T. A. Nieminen, V. L. Y. Loke, A. M. Branczyk +2
Computational methods for electromagnetic and light scattering can be used for the calculation of optical forces and torques. Since typical particles that are optically trapped or…
Measurement of the total optical angular momentum transfer in optical tweezers
Simon Parkin, Gregor Knoener, Timo A. Nieminen +2
We describe a way to determine the total angular momentum, both spin and orbital, transferred to a particle trapped in optical tweezers. As an example an LG02 mode of a laser beam…
Resonant coupling between bulk waves and guided modes in a dielectric slab with a thick holographic grating
D. R. Mason, S. J. Goodman, D. K. Gramotnev +1
What we believe to be a new type of resonant coupling of an incident bulk wave into guided modes of a slab with a thick holographic grating is shown to occur in the presence of str…
Orientation of optically trapped nonspherical birefringent particles
Wolfgang Singer, Timo A. Nieminen, Ursula J. Gibson +2
While the alignment and rotation of microparticles in optical traps have received increased attention recently, one of the earliest examples has been almost totally neglected the a…
Rigorous analysis of extremely asymmetrical scattering of electromagnetic waves in slanted periodic gratings
T. A. Nieminen, D. K. Gramotnev
Extremely asymmetrical scattering (EAS) is a new type of Bragg scattering in thick, slanted, periodic gratings. It is realised when the scattered wave propagates parallel to the fr…
Extremely asymmetrical scattering in gratings with varying mean structural parameters
D. K. Gramotnev, T. A. Nieminen, T. A. Hopper
Extremely asymmetrical scattering (EAS) is an unusual type of Bragg scattering in slanted periodic gratings with the scattered wave (the +1 diffracted order) propagating parallel t…
Non-steady-state double-resonant extremely asymmetrical scattering of waves in periodic gratings
Dmitri K. Gramotnev, Timo A. Nieminen
Double-resonant extremely asymmetrical scattering (DEAS) is a strongly resonant type of Bragg scattering in two joint or separated uniform gratings with different phases. It is cha…
Rigorous analysis of grazing-angle scattering of electromagnetic waves in periodic gratings
D. K. Gramotnev, T. A. Nieminen
Grazing-angle scattering (GAS) is a type of Bragg scattering of waves in slanted non-uniform periodic gratings, when the diffracted order satisfying the Bragg condition propagates…