182 research outputs found
Theory of self-induced back-action optical trapping in nanophotonic systems
Optical trapping is an indispensable tool in physics and the life sciences.
However, there is a clear trade off between the size of a particle to be
trapped, its spatial confinement, and the intensities required. This is due to
the decrease in optical response of smaller particles and the diffraction limit
that governs the spatial variation of optical fields. It is thus highly
desirable to find techniques that surpass these bounds. Recently, a number of
experiments using nanophotonic cavities have observed a qualitatively different
trapping mechanism described as "self-induced back-action trapping" (SIBA). In
these systems, the particle motion couples to the resonance frequency of the
cavity, which results in a strong interplay between the intra-cavity field
intensity and the forces exerted. Here, we provide a theoretical description
that for the first time captures the remarkable range of consequences. In
particular, we show that SIBA can be exploited to yield dynamic reshaping of
trap potentials, strongly sub-wavelength trap features, and significant
reduction of intensities seen by the particle, which should have important
implications for future trapping technologiesComment: 7 pages, 5 figure
Strong Optomechanical Coupling at Room Temperature by Coherent Scattering
Quantum control of a system requires the manipulation of quantum states
faster than any decoherence rate. For mesoscopic systems, this has so far only
been reached by few cryogenic systems. An important milestone towards quantum
control is the so-called strong coupling regime, which in cavity optomechanics
corresponds to an optomechanical coupling strength larger than cavity decay
rate and mechanical damping. Here, we demonstrate the strong coupling regime at
room temperature between a levitated silica particle and a high finesse optical
cavity. Normal mode splitting is achieved by employing coherent scattering,
instead of directly driving the cavity. The coupling strength achieved here
approaches three times the cavity linewidth, crossing deep into the strong
coupling regime. Entering the strong coupling regime is an essential step
towards quantum control with mesoscopic objects at room temperature
On-a-chip biosensing based on all-dielectric nanoresonators
Nanophotonics has become a key enabling technology in biomedicine with great
promises in early diagnosis and less invasive therapies. In this context, the
unique capability of plasmonic noble metal nanoparticles to concentrate light
on the nanometer scale has widely contributed to biosensing and enhanced
spectroscopy. Recently, high-refractive index dielectric nanostructures
featuring low loss resonances have been proposed as a promising alternative to
nanoplasmonics, potentially offering better sensing performances along with
full compatibility with the microelectronics industry. In this letter we report
the first demonstration of biosensing with silicon nanoresonators integrated in
state-of-the-art microfluidics. Our lab-on-a-chip platform enables detecting
Prostate Specific Antigen (PSA) cancer marker in human serum with a sensitivity
that meets clinical needs. These performances are directly compared with its
plasmonic counterpart based on gold nanorods. Our work opens new opportunities
in the development of future point-of-care devices towards a more personalized
healthcare
Unravelling the Role of Electric and Magnetic Dipoles in Biosensing with Si Nanoresonators
High refractive index dielectric nanoresonators are attracting much attention due to their ability to control both electric and magnetic components of light. Combining confined modes with reduced absorption losses, they have recently been proposed as an alternative to nanoplasmonic biosensors. In this context, we study the use of semi-random silicon nanocylinder arrays, fabricated with simple and scalable colloidal lithography for the efficient and reliable detection of biomolecules in biological samples. Interestingly, electric and magnetic dipole resonances are associated to two different transduction mechanisms: extinction decrease and resonance redshift, respectively. By contrasting both observables, we identify clear advantages in tracking changes in the extinction magnitude. Our data demonstrate that, despite its simplicity, the proposed platform is able to detect prostate specific antigen (PSA) in human serum with limits of detection meeting clinical needs.Peer ReviewedPostprint (author's final draft
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