Showing papers by "David McGloin published in 2006"
TL;DR: A background in optical manipulation technologies and an overview of the applications of optical tweezers are provided and a critical discussion of where the future might lead this maturing technology is discussed.
Abstract: In 1986, Arthur Ashkin and colleagues published a seminal paper in Optics Letters, ‘Observation of a single-beam gradient force optical trap for dielectric particles’ which outlined a technique for trapping micrometre-sized dielectric particles using a focused laser beam, a technology which is now termed optical tweezers. This paper will provide a background in optical manipulation technologies and an overview of the applications of optical tweezers. It contains some recent work on the optical manipulation of aerosols and concludes with a critical discussion of where the future might lead this maturing technology.
122 citations
TL;DR: The ability of spatial light modulators to manipulate airborne droplets in real time as well as the difficulties associated with loading and trapping particles in such an environment are discussed.
Abstract: We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of some of the applications of such a technique.
122 citations
TL;DR: In this paper, a spatial light modulator (SLM) was used to create high quality Laguerre-Gaussian (LG) light beams, which have been used to study the guiding of cold rubidium atoms.
Abstract: A spatial light modulator (SLM) has been used to create high quality Laguerre–Gaussian (LG) light beams, which have been used to study the guiding of cold rubidium atoms. The SLM allows real-time variation of the hollow guiding beam and permits direct comparison of the guided atom fluxes for different LG modes with minimal adjustment of the other optical components. It is demonstrated that, by increasing the azimuthal index l of the Laguerre–Gaussian beam, the radiation pressure pushing the trapped atoms may be reduced while maintaining the same guided flux. This is the first comparative study of hollow beam atom guiding, and further demonstrates the versatility of the SLM for studies in atom optics.
62 citations
TL;DR: The use of a zeroth-order Bessel beam, which has a non-diffracting thin core, is shown to improve guiding distances over a comparable Gaussian beam by more than three times with guiding distances of up to 2.75mm for dodecane droplets.
Abstract: We characterize the ability of Gaussian and Bessel beams to guide water, ethanol and dodecane aerosol droplets. Droplets produced from a nebuliser source are trapped using radiation pressure and then by varying the beam power are controllably guided in a vertical direction. The use of a zeroth-order Bessel beam, which has a non-diffracting thin core, is shown to improve guiding distances over a comparable Gaussian beam by more than three times with guiding distances of up to 2.75mm for dodecane droplets. We discuss the applications for this work in the context of tools for optically manipulating airborne particles.
55 citations
TL;DR: It is demonstrated that optical tweezers can be used to control and characterize the coagulation and mixing state of aerosols, and theCoagulation of different aerosol components can be compared and the mixingState of the final coagulated droplet can be investigated.
Abstract: We demonstrate that optical tweezers can be used to control and characterize the coagulation and mixing state of aerosols Liquid aerosol droplets of 2-14 mum in diameter are optically trapped and characterized by spontaneous and stimulated Raman scatterings, which together provide a unique signature of droplet size and composition From the conventional bright field image, the size of the trapped droplet can be estimated and compared with that determined from stimulated Raman scattering, and the motion of the particle within the trapping plane can be recorded A maximum of four droplets can be manipulated in tandem by forming multiple optical traps through rapid beam steering The coagulation of two droplets can be studied directly by controlling two droplets The limiting conditions under which optical forces and capillary forces dominate the aerosol coagulation event are explored by varying the relative optical trap strengths and characterizing the coagulation of different droplet sizes Finally, we demonstrate that the coagulation of different aerosol components can be compared and the mixing state of the final coagulated droplet can be investigated In particular, we compare the outcome of the coagulation of an aqueous sodium chloride aerosol droplet with a second aqueous droplet, with an ethanol droplet or with a decane droplet
51 citations
TL;DR: In this paper, phase conjugation is achieved by means of degenerate four-wave mixing from a colloidal crystal, which is provided by a periodic spatial refractive index grating created by dielectric microparticles trapped in the intensity distribution of two nearly copropagating interfering laser beams.
Abstract: We demonstrate phase conjugation by means of degenerate four-wave mixing from a colloidal crystal. The nonlinear medium is provided by a periodic spatial refractive index grating created in a colloidal suspension of dielectric microparticles trapped in the intensity distribution of two nearly copropagating interfering laser beams. Phase conjugation is achieved for a probe beam carrying orbital angular momentum as evidenced by the inversion of the topological charge of a phase singularity within the beam. The e ciency and nonlinear parameters of the colloidal crystal as well as its lattice properties are measured and compared to theoretical predictions and previous experimental work.
2 citations
TL;DR: In this article, the authors demonstrate the use of holographic optical tweezers for the optical trapping and manipulation of arrays of airborne water droplets (aerosols) making use of a phase-only spatial light modulator.
Abstract: We demonstrate the use of holographic optical tweezers for the optical trapping and manipulation of arrays of airborne water droplets (aerosols). Making use of a phase-only spatial light modulator we present evidence of stable, interactive manipulation of both single and multiple aerosol droplets, of the order of 10 microns in diameter, and also their controlled coagulation. We discuss the advantages, disadvantages, and limitations of using a spatial light modulator for droplet manipulation including the implications of the update speed of the device (a Holoeye LC-R2500 SLM), diffraction efficiency, and droplet growth and evaporation due to laser intensity variations. We will examine the generic difficulties of trapping in air, working in the absence of inertial damping. Finally we will discuss the applications of the above work in fields such as atmospheric chemistry and microfluidic microchemical reactors whilst presenting preliminary results on fusion of two or more droplets of differing phases.
2 citations
TL;DR: Aerosol droplets are guided over mm distances using single beam optical traps using micron-sized particles are confined in two dimensions and guided along the direction of beam propagation.
Abstract: Aerosol droplets are guided over mm distances using single beam optical traps. The micron-sized particles are confined in two dimensions and guided along the direction of beam propagation. Both Gaussian and Bessel beam geometries are compared for water, ethanol and dodecane droplets. The observed trapping of multiple droplets in 1-D arrays will also be discussed.
1 citations
TL;DR: In this article, the deegenerate four wave mixing and phase conjugation in a colloidal crystal were demonstrated using an artifical structure formed by the ordered arrangement of dielectric particles in colloidal suspension as the nonlinear medium.
Abstract: Degenerate four wave mixing and phase conjugation in a colloidal crystal are demonstrated using an artifical structure formed by the ordered arrangement of dielectric particles in a colloidal suspension as the nonlinear medium.