84 research outputs found
Photothermal effects in ultra-precisely stabilized tunable microcavities
We study the mechanical stability of a tunable high-finesse microcavity under
ambient conditions and investigate light-induced effects that can both suppress
and excite mechanical fluctuations. As an enabling step, we demonstrate the
ultra-precise electronic stabilization of a microcavity. We then show that
photothermal mirror expansion can provide high-bandwidth feedback and improve
cavity stability by almost two orders of magnitude. At high intracavity power,
we observe self-oscillations of mechanical resonances of the cavity. We explain
the observations by a dynamic photothermal instability, leading to parametric
driving of mechanical motion. For an optimized combination of electronic and
photothermal stabilization, we achieve a feedback bandwidth of kHz and a
noise level of m rms
Dielectric response of light, heavy and heavy-oxygen water: isotope effects on the hydrogen-bonding network's collective relaxation dynamics
Ion-pairing equilibria and kinetics of dimethyl phosphate: A model for counter-ion binding to the phosphate backbone of nucleic acids
Glasslike Behavior in Aqueous Electrolyte Solutions
When salts are added to water, the viscosity generally increases suggesting
the ions increase the strength of the water's hydrogen-bond network. However,
infrared pump-probe measurements on electrolyte solutions have found that ions
have no influence on the rotational dynamics of water molecules implying no
enhance-ment or breakdown of the hydrogen-bond network. Here we report optical
Kerr-effect and dielectric relaxa-tion spectroscopic measurements, which have
enabled us to separate the effects of rotational and transitional motions of
the water molecules. These data show that electrolyte solutions behave like a
supercooled liquid approaching a glass transition in which rotational and
translational molecular motions are decoupled. It is now possible to understand
previously conflicting viscosity data, nuclear magnetic resonance relaxation,
and ultrafast infrared spectroscopy in a single unified picture
Comparing systemic therapy and cognitive behavioral therapy for social anxiety disorders: study protocol for a randomized controlled pilot trial
Background: Social anxiety disorders are among the most prevalent anxiety disorders in the general population. The efficacy of cognitive behavioral therapy (CBT) for social anxiety disorders is well demonstrated. However, only three studies point to the efficacy of systemic therapy (ST) in anxiety disorders, and only two of them especially focus on social anxiety disorders. These ST studies either do not use a good comparator but minimal supportive therapy, they do not use a multi-person ST but a combined therapy, or they do not especially focus on social anxiety disorders but mood and anxiety disorders in general. Though ST was approved as evidence based in Germany for a variety of disorders in 2008, evidence did not include anxiety disorders. This is the first pilot study that will investigate multi-person ST, integrating a broad range of systemic methods, specifically for social anxiety disorders and that will compare ST to the "gold standard" CBT. Design: This article describes the rationale and protocol of a prospective, open, interventive, balanced, bi-centric, pilot randomized controlled trial (RCT). A total of 32 patients with a primary SCID diagnosis of social anxiety disorder will be randomized to either CBT or ST. Both treatments will be manualized. The primary outcome will include social anxiety symptoms at the end of therapy. Therapy will be restricted to no more than 26 hours (primary endpoint). Secondary outcomes will include psychological, social systems and interpersonal functioning, symptom adjustment, and caregiver burden, in addition to change measures, therapist variables and treatment adherence. At the secondary endpoints, 9 and 12 months after the beginning of therapy, we will again assess all outcomes. Discussion: The study is expected to pilot test a RCT which will be the first to directly compare CBT and multi-person ST, integrating a broad range of systemic methods, for social anxiety disorders, and it will provide empirical evidence for the calculation of the number of patients needed for a confirmatory RCT. Trial registration; ClinicalTrials.gov: NCT02360033; date of registration: 21 January 2015
Laser written mirror profiles for open-access fiber Fabry-P\'erot microcavities
We demonstrate laser-written concave hemispherical structures produced on the
endfacets of optical fibers that serve as mirror substrates for tunable
open-access microcavities. We achieve finesse values of up to 250, and a mostly
constant performance across the entire stability range. This enables cavity
operation also close to the stability limit, where a peak quality factor of
is reached. Together with a small mode waist of , the cavity achieves a Purcell factor of , which is
useful for experiments that require good lateral optical access or otherwise
large separation of the mirrors. Laser-written mirror profiles can be produced
with a tremendous flexibility in shape and on various surfaces, opening new
possibilities for microcavities.Comment: 8 pages, 3 figure
Dielectric Response of Light, Heavy and Heavy-Oxygen water: Isotope Effects on the Hydrogen-Bonding Network's Collective Relaxation Dynamics
Ion-pairing equilibria and kinetics of dimethyl phosphate: A model for counter-ion binding to the phosphate backbone of nucleic acids
Dimethyl phosphate (DMP–) is the simplest model ion to assess ion-pairing phenomena between metal ions and the phosphate backbone of nucleic acids. Yet, the equilibria and dynamics of ion binding to DMP– have not been fully uncovered. Here, we study the interaction of DMP– with different cations and water in aqueous solutions of NaDMP using dielectric relaxation and nuclear magnetic resonance spectroscopies. We find DMP– to be weakly hydrated and weakly associated with Na+ in the absence of added salt. Upon addition of NaCl, MgCl2, or CaCl2 to solutions of NaDMP, we detect the formation of solvent-shared (NaDMP0) and contact (MgDMP+, CaDMP+) ion-pairs; the degree of ion association is 20–27 % at 2:1 salt:DMP molar ratio for the bivalent ions. Comparison to literature results suggests the formation constant of MgDMP+ to be a good estimate for the binding of Mg2+ to RNA. From the concentration dependence of the rotational relaxation time of the ion-pairs, we find ion-pair dissociation rates to follow the order Mg2+ ≪ Ca2+ < Na+. Strikingly, our data suggest that the overall ion-pair dissociation dynamics are governed by an ion-pair metathesis reaction, which provides a different pathway for the binding of ions by DMP–
Open-Cavity in Closed-Cycle Cryostat as a Quantum Optics Platform
The introduction of an optical resonator can enable efficient and precise interaction between a photon and a solid-state emitter. It facilitates the study of strong light-matter interaction, polaritonic physics and presents a powerful interface for quantum communication and computing. A pivotal aspect in the progress of light-matter interaction with solid-state systems is the challenge of combining the requirements of cryogenic temperature and high mechanical stability against vibrations while maintaining sufficient degrees of freedom for in situ tunability. Here, we present a fiber-based open Fabry-Pérot cavity in a closed-cycle cryostat exhibiting ultrahigh mechanical stability while providing wide-range tunability in all three spatial directions. We characterize the setup and demonstrate the operation with the root-mean-square cavitylength fluctuation of less than 90 pm at temperature of 6.5 K and integration bandwidth of 100 kHz. Finally, we benchmark the cavity performance by demonstrating the strong-coupling formation of exciton polaritons in monolayer WSe2 with a cooperativity of 1.6. This set of results manifests the open cavity in a closed-cycle cryostat as a versatile and powerful platform for low-temperature cavity QED experiments
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