7,879 research outputs found
Scatterer induced mode splitting in poly(dimethylsiloxane) coated microresonators
We investigate scatterer induced mode splitting in a composite microtoroidal
resonator (Q ~ 10^6) fabricated by coating a silica microtoroid (Q ~ 10^7) with
a thin poly(dimethylsiloxane) layer. We show that the two split modes in both
coated and uncoated silica microtoroids respond in the same way to the changes
in the environmental temperature. This provides a self-referencing scheme which
is robust to temperature perturbations. Together with the versatile
functionalities of polymer materials, mode splitting in polymer and polymer
coated microresonators offers an attractive sensing platform that is robust to
thermal noise.Comment: 9 pages, 3 figures, 15 reference
Observation and characterization of mode splitting in microsphere resonators in aquatic environment
Whispering gallery mode (WGM) optical resonators utilizing resonance shift
(RS) and mode splitting (MS) techniques have emerged as highly sensitive
platforms for label-free detection of nano-scale objects. RS method has been
demonstrated in various resonators in air and liquid. MS in microsphere
resonators has not been achieved in aqueous environment up to date, despite its
demonstration in microtoroid resonators. Here, we demonstrate scatterer-induced
MS of WGMs in microsphere resonators in water. We determine the size range of
particles that induces MS in a microsphere in water as a function of resonator
mode volume and quality factor. The results are confirmed by the experimental
observations.Comment: 4 Pages, 5 Figures, 13 Reference
Estimation of Purcell factor from mode-splitting spectra in an optical microcavity
We investigate scattering process in an ultra-high-Q optical microcavity
coupled to subwavelength scatterers by introducing "splitting quality" Qsp, a
dimensionless parameter defined as the ratio of the scatterer-induced mode
splitting to the total loss of the coupled system. A simple relation is
introduced to directly estimate the Purcell factor from single-shot measurement
of transmission spectrum of scatterer-coupled cavity. Experiments with
polystyrene (PS) and gold (Au) nanoparticles, Erbium ions and Influenza A
virions show that Purcell-factor-enhanced preferential funneling of scattering
into the cavity mode takes place regardless of the scatterer type.
Experimentally determined highest Qsp for single PS and Au nanoparticles are
9.4 and 16.19 corresponding to Purcell factors with lower bounds of 353 and
1049, respectively. The highest observed Qsp was 31.2 for an ensemble of Au
particles. These values are the highest Qsp and Purcell factors reported up to
date.Comment: 5 Pages, 4 Figures, 12 Reference
Controlled Manipulation of Mode Splitting in an Optical Microcavity by Two Rayleigh Scatterers
We report controlled manipulation of mode splitting in an optical
microresonator coupled to two nanoprobes. It is demonstrated that, by
controlling the positions of the nanoprobes, the split modes can be tuned
simultaneously or individually and experience crossing or anti-crossing in
frequency and linewidth. A tunable transition between standing wave mode and
travelling wave mode is also observed. Underlying physics is discussed by
developing a two-scatterer model which can be extended to multiple scatterers.
Observed rich dynamics and tunability of split modes in a single microresonator
will find immediate applications in optical sensing, opto-mechanics, filters
and will provide a platform to study strong light-matter interactions in
two-mode cavities.Comment: 9 pages, 5 figures, 14 references. Major revision. Published version
in Optics Expres
Cooperativity and the origins of rapid, single-exponential kinetics in protein folding
The folding of naturally occurring, single domain proteins is usually
well-described as a simple, single exponential process lacking significant
trapped states. Here we further explore the hypothesis that the smooth energy
landscape this implies, and the rapid kinetics it engenders, arises due to the
extraordinary thermodynamic cooperativity of protein folding. Studying
Miyazawa-Jernigan lattice polymers we find that, even under conditions where
the folding energy landscape is relatively optimized (designed sequences
folding at their temperature of maximum folding rate), the folding of
protein-like heteropolymers is accelerated when their thermodynamic
cooperativity enhanced by enhancing the non-additivity of their energy
potentials. At lower temperatures, where kinetic traps presumably play a more
significant role in defining folding rates, we observe still greater
cooperativity-induced acceleration. Consistent with these observations, we find
that the folding kinetics of our computational models more closely approximate
single-exponential behavior as their cooperativity approaches optimal levels.
These observations suggest that the rapid folding of naturally occurring
proteins is, at least in part, consequences of their remarkably cooperative
folding
- …