Optical sorting and detection of sub-micron objects in a motional standing wave

An extended interference pattern close to surface may result in both a transmissive or evanescent surface fields for large area manipulation of trapped particles. The affinity of differing particle sizes to a moving standing wave light pattern allows us to hold and deliver them in a bi-directional manner and importantly demonstrate experimentally particle sorting in the sub-micron region. This is performed without the need of fluid flow (static sorting). Theoretical calculations experimentally confirm that certain sizes of colloidal particles thermally hop more easily between neighboring traps. A new generic method is also presented for particle position detection in an extended periodic light pattern and applied to characterization of optical traps and particle behaviorComment: 5 pages, 6 figures, Optical Trapping pape

All-optical sub-Kelvin sympathetic cooling of a levitated microsphere in vacuum

Funding: UK Engineering and Physical Sciences Research Council (EP/P030017/1).We demonstrate all-optical sympathetic cooling of a laser-trapped microsphere to sub-Kelvin temperatures, mediated by optical binding to a feedback-cooled adjacent particle. Our study opens prospects for multi-particle quantum entanglement and sensing in levitated optomechanics.Publisher PDFPeer reviewe

Rotating Gliding Arc: Innovative Source for VOC Remediation

The large-scale plasma treatment of waste gas in industrial or municipal conditions requires high efficiency of plasma conversion process at high processing speed, i.e., large volumetric flow. The integration of the plasma unit into existing systems puts demands on the pipe-system compatibility and minimal pressure drop due to adoption of plasma processing step. These conditions are met at the innovative rotating electrode gliding arc plasma unit described in this article. The system consists of propeller-shaped high voltage electrode inside grounded metallic tube. The design of HV electrode eliminates the pressure drop inside the air system, contrary the plasma unit itself is capable of driving the waste gas at volumetric flow up to 300 m3/hr for 20 cm pipe diameter. In the article the first results on pilot study of waste air treatment will be given for selected volatile organic compounds together with basic characteristic of the plasma unit used

Cooling the optical-spin driven limit cycle oscillations of a levitated gyroscope

Birefringent microspheres, trapped in vacuum and set into rotation by circularly polarised light, demonstrate remarkably stable translational motion. This is in marked contrast to isotropic particles in similar conditions. Here we demonstrate that this stability is obtained because the fast rotation of these birefringent spheres reduces the effect of azimuthal spin forces created by the inhomogeneous optical spin of circularly polarised light. At reduced pressures, the unique profile of these rotationally averaged, effective azimuthal forces results in the formation of nano-scale limit cycles. We demonstrate feedback cooling of these non-equilibrium oscillators, resulting in effective temperatures on the order of a milliKelvin. The principles we elaborate here can inform the design of high-stability rotors carrying enhanced centripetal loads or result in more efficient cooling schemes for autonomous limit cycle oscillations. Ultimately, this latter development could provide experimental access to non-equilibrium quantum effects within the mesoscopic regime.Yoshihiko Arita, Stephen H. Simpson, Graham D. Bruce, Ewan M. Wright, Pavel Zemánek, Kishan Dholaki

Stable optical trapping and sensitive characterization of nanostructures using standing- wave Raman tweezers

Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints

Dynamic size tuning of multidimensional optically bound matter

We generate and dynamically control one-, two- and three-dimensional optically bound structures of soft matter in the geometry of counter-propagating incoherent laser beams. We report results for the Bessel, Gaussian, and Laguerre-Gaussian laser modes and particularly focus on the influence of the lateral dimensions of the beam profile on the resulting self-arranged optically bound structures. Employing the transfer of the orbital angular momentum of light in the Laguerre-Gaussian beams, we show that optically bound structures can conserve their spatial arrangements even while orbiting along the beam circumference.Publisher PDFPeer reviewe

The cost efficiency of higher doses of compost application

Application of higher doses of compost has several technical problems at the same time. Compost application at higher doses required relatively high consumption of working time deployed machinery. That is mainly affected loading capacity of the spreaders. Standard is a spreader with a loading capacity of 5–10 t, for higher capacity it is necessary to monitor the influence of the chassis to a higher soil compaction, especially in wheel tracks. This paper deals with determination of the cost of application for spreading compost at high doses 60–100 t.ha−1. From the proven data of performance, acquisition costs of machinery and fuel consumption were determined hectare costs for the spreader of carrying capacity 5, 8, 10 a 15 t and transport distances corresponding to an area of 8–100 hectares of fertilized land. Costs were determined by using the program AGROTEKIS, by using the database machines, manufacturers data and other available data, direct measurements and related experiments. Application costs for the dose 60 t.ha−1 are 2 100–5 250 CZK.ha−1, for the dose 80 t.ha−1 are 2 750–7 000 CZK.ha−1and for the dose 100 t.ha−1 are 2 650–8 650 CZK.ha−1. The results are useful for quick and easy calculation of costs for fertilizing with higher doses of compost and deciding on the selection of used spreader