22 research outputs found
Investigation of dust grains by optical tweezers for space applications
Cosmic dust plays a dominant role in the universe, especially in the
formation of stars and planetary systems. Furthermore, the surface of cosmic
dust grains is the bench-work where molecular hydrogen and simple organic
compounds are formed. We manipulate individual dust particles in water solution
by contactless and non-invasive techniques such as standard and Raman tweezers,
to characterize their response to mechanical effects of light (optical forces
and torques) and to determine their mineral compositions. Moreover, we show
accurate optical force calculations in the T-matrix formalism highlighting the
key role of composition and complex morphology in optical trapping of cosmic
dust particles.This opens perspectives for future applications of optical
tweezers in curation facilities for sample return missions or in
extraterrestrial environments
The global dust SED: Tracing the nature and evolution of dust with DustEM
The Planck and Herschel missions are currently measuring the farIR-mm
emission of dust, which combined with existing IR data, will for the first time
provide the full SED of the galactic ISM dust emission with an unprecedented
sensitivity and angular resolution. It will allow a systematic study of the
dust evolution processes that affect the SED. Here we present a versatile
numerical tool, DustEM, that predicts the emission and extinction of dust given
their size distribution and their optical and thermal properties. In order to
model dust evolution, DustEM has been designed to deal with a variety of grain
types, structures and size distributions and to be able to easily include new
dust physics. We use DustEM to model the dust SED and extinction in the diffuse
interstellar medium at high-galactic latitude (DHGL), a natural reference SED.
We present a coherent set of observations for the DHGL SED. The dust components
in our DHGL model are (i) PAHs, (ii) amorphous carbon and (iii) amorphous
silicates. We use amorphous carbon dust, rather than graphite, because it
better explains the observed high abundances of gas-phase carbon in shocked
regions of the interstellar medium. Using the DustEM model, we illustrate how,
in the optically thin limit, the IRAS/Planck HFI (and likewise Spitzer/Herschel
for smaller spatial scales) photometric band ratios of the dust SED can
disentangle the influence of the exciting radiation field intensity and
constrain the abundance of small grains relative to the larger grains. We also
discuss the contributions of the different grain populations to the IRAS,
Planck and Herschel channels. Such information is required to enable a study of
the evolution of dust as well as to systematically extract the dust thermal
emission from CMB data and to analyze the emission in the Planck polarized
channels. The DustEM code described in this paper is publically available.Comment: accepted for publication in A&
Roadmap for Optical Tweezers 2023
Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration
Position locking of a resonant gain-assisted metallic/dielectric nano-shell in Optical Tweezers
We calculate optical forces on dye-enriched resonant nano-shells in dual-beam Optical Tweezers. We investigate the non-linear gain-assisted enhancement of their optomechanics and study their behaviour through Brownian dynamics simulations. When the wavelength is red detuned with respect to the plasmon resonance, we observe that the particles are efficiently trapped at the laser beam
intensity maxima of the dual beam standing wave. Conversely, for blue-detuned wavelengths the nano-shells are channelled through the standing wave antinodes due to the sign reversal of the optical force. This open perspectives for gain-assisted optomechanics where non-linear optical forces are finely tuned to manipulate controlled nano-photonic systems
Preface: Introducing ELS XIII
Electromagnetic and Light Scattering crosses the boundaries of many science and engineering disciplines. It is central to both fundamental and applied research in astrophysics, atmospheric physics, geophysics, materials science, nano-optics, biology, and medicine