Ultrahigh and persistent optical depths of cesium in Kagomé-type hollow-core photonic crystal fibers.

Alkali-filled hollow-core fibers are a promising medium for investigating light-matter interactions, especially at the single-photon level, due to the tight confinement of light and high optical depths achievable by light-induced atomic desorption (LIAD). However, until now these large optical depths could only be generated for seconds, at most once per day, severely limiting the practicality of the technology. Here we report the generation of the highest observed transient (>10(5) for up to a minute) and highest observed persistent (>2000 for hours) optical depths of alkali vapors in a light-guiding geometry to date, using a cesium-filled Kagomé-type hollow-core photonic crystal fiber (HC-PCF).

A new transducer receive transfer function calibration method: application to microbubble backscattering cross-section measurements at high frequency.

When comparing acoustic scattering experiments with theory, the relationship between the pressure generated by a scatterer at the surface of a transducer and the induced voltage must be known. Methods have been previously proposed to measure the receive transfer function that rely on several assumptions. A new, experimental method for measuring the acoustic response of a spherically-focused transducer, using a hydrophone at twice the focal distance, is proposed that requires a minimum number of assumptions and calculations.

Nonlinear emission from individual bound microbubbles at high frequencies.

Targeted microbubbles detected with high-frequency ultrasound can establish the molecular expression of blood vessels with submillimeter resolution. To improve microbubble-specific imaging at high frequencies, the subharmonic and second harmonic signal from individual microbubbles were measured as a function of size and pressure. Single phospholipid-shell microbubbles (1.

Reflection from bound microbubbles at high ultrasound frequencies.

Targeted contrast agents and ultrasound imaging are now used in combination for the assessment and tracking of biomarkers in animal models in vivo. These applications have triggered interest in the understanding and prediction of the ultrasound echoes from contrast agents attached to cells. This study describes the reflection enhancement due to microbubbles bound on a gelatin surface.