Cavity optomechanical liquid level meter using a twin-microbottle resonator

Cavity optomechanical devices can be made to have good compatibility with optical fiber technology by utilizing fiber-based waveguides and cavities and can be used in high-performance optical sensor applications. Such optomechanical microsensors have a great potential for exploring the properties of liquids, such as density, viscosity, and masses of included nanoparticles. However, as yet, there is no cavity optomechanical architecture that can be used to sense the liquid's shape, e.g., liquid level. In this paper, we report a demonstration of a liquid-level meter using a twin-microbottle resonator that can make measurements at arbitrary positions and depths in the liquid. The twin-microbottle resonator has a maximum diameter of 68 $\mu$m and length of 800 $\mu$m. By immersing one part of it in water and keeping the other part in air, the mechanical radial breathing mode can be read out sensitively while maintaining a high optical quality factor of the optical whispering gallery mode regardless of the water immersion. This high mechanical displacement sensitivity provides a frequency resolution that is high enough to measure the mechanical frequency shift due to the water immersion and resolves the water level to 2.6$\pm$0.9 pm. This unique liquid-level meter based on a highly sensitive cavity optomechanical setup can be used to detect tiny fluctuations of various air-liquid and liquid-liquid interfaces

Near-field optomechanical transduction enhanced by Raman gain

Raman-gain-enhanced near-field optomechanical transduction between a movable optical cavity and SiN-membrane resonator is demonstrated. The Raman gain compensates for the intrinsic loss of the cavity and amplifies the optomechanical transduction, through which the membrane vibration is sensed using a high-Q whispering-gallery-mode optical cavity evanescently. The optical Q of the cavity resonance is improved with respect to the optical pump power, which results in an increase in the optomechanically transduced vibration signals of the mechanical resonator. Our near-field optomechanical coupling approach with optical gain realizes highly sensitive displacement measurement in nano- and micro-mechanical resonators consisting of arbitrary materials and structures

Effect of Surface Defects on Auger Recombination in Colloidal CdS Quantum Dots

The effect of surface states originating from surface defects and capping reagents on Auger recombination in CdS quantum dots (QDs) are investigated by femtosecond transient absorption spectroscopy. Because of the strong size-dependent nature of Auger recombination and surface defects, the size dependence of Auger recombination is also conducted to reveal the effect of surface states. The lifetime of Auger recombination is very similar irrespective of surface states in all size regions and was proportional to <i>D</i>⁶ (<i>D</i>: QD diameter). This result clearly shows that Auger recombination in CdS QDs does not depend on interfacial electronic structures originating from the surface defects and capping reagents of one monolayer level

Hypoxia Imaging Endoscopy Equipped with Laser Light Source from Preclinical Live Animal Study to First-In-Human Subject Research

<div><p>A goal in next-generation endoscopy is to develop functional imaging techniques to open up new opportunities for cancer diagnosis. Although spatial and temporal information on hypoxia is crucial for understanding cancer physiology and expected to be useful for cancer diagnosis, existing techniques using fluorescent indicators have limitations due to low spatial resolution and invasive administration. To overcome these problems, we developed an imaging technology based on hemoglobin oxygen saturation in both the tumor and surrounding mucosa using a laser endoscope system, and conducted the first human subject research for patients with aero-digestive tract cancer. The oxygen saturation map overlapped the images of cancerous lesions and indicated highly heterogeneous features of oxygen supply in the tumor. The hypoxic region of the tumor surface was found in both early cancer and cancer precursors. This technology illustrates a novel aspect of cancer biology as a potential biomarker and can be widely utilized in cancer diagnosis.</p></div

Mechanism of hemoglobin oxygen saturation imaging and schematic illustration of prototype endoscope system.

<p>(A) Illustration of the mechanism (see text for details.) (B) The 445-nm laser excited a phosphor equipped at the tip of the endoscope and emitted white light. The 473-nm laser light was emitted without the phosphor excitation. These two lights alternately illuminated the mucosal surface and the reflected lights were sequentially detected with a colour CCD in synchronization with light switching. The obtained images were processed and transformed into a StO₂ map.</p

Clinicopathological findings of the study with gastric cancer patients.

<p>Clinicopathological findings of the study with gastric cancer patients.</p

Verification of hemoglobin oxygen saturation imaging by observing a phantom.

<p>(A) Blood vessel phantom consisted of a glass tube filled with diluted blood and aqueous solution of intralipid. The intralipid solution strongly scattered incident light to simulate the living tissue around blood vessel. (B) The observed optical densities of the blood vessel at the three bands were dependent on StO2(T) (left) and Hct (right). Here, StO2(T) denotes the supposedly correct value of StO2 derived by analyzing the transmittance spectrum of blood. (C) StO2(I) map (derived by image processing) of the vessel. (D) Comparison of StO2(I) with StO2(T) (derived by measurement of transmittance spectra).</p

Patients Characteristics.

<p>Patients Characteristics.</p

StO₂ maps obtained in human subject research.

<p>(A) White light image by endoscopic observation in rectal adenocarcinoma (left). Line (L-R) corresponds to cross-section of pathological diagnosis. StO₂ map visualized by laser endoscope system (middle: pseudocolor StO₂ image; right: StO₂ overlay image). (B) Cross-section appearance stained with H&E (upper) and HIF1 alpha antibody (lower) corresponding to the hypoxic area visualized with StO₂ map. (C) Endoscopic images of a colorectal adenoma (upper) showing clear hypoxia: white light image (upper left), pseudocolor StO₂ map (upper middle) and overlayed image (upper right). Another case of a colonic lesion (lower) consisting of an adenoma (red arrow) and a hyperplasia (blue arrow): white light image (lower left), pseudocolor StO₂ map (lower middle) and overlayed image (lower right). Only the adenoma was detected as hypoxia. (D) Observed StO₂ differences between neoplastic and non-neoplastic areas: For comparing pathology specimens and endoscope images, the line on the endoscopic image corresponding to the cross-section was determined. StO₂ levels at neoplasic and non-neoplasic areas along this line were then calculated using this StO₂ map.</p

The Metallic State in Neutral Radical Conductors: Dimensionality, Pressure and Multiple Orbital Effects

Pressure-induced changes in the solid-state structures and transport properties of three oxobenzene-bridged bisdithiazolyl radicals <b>2</b> (R = H, F, Ph) over the range 0–15 GPa are described. All three materials experience compression of their π-stacked architecture, be it (i) 1D ABABAB π-stack (R = Ph), (ii) quasi-1D slipped π-stack (R = H), or (iii) 2D brick-wall π-stack (R = F). While R = H undergoes two structural phase transitions, neither of R = F, Ph display any phase change. All three radicals order as spin-canted antiferromagnets, but spin-canted ordering is lost at pressures <1.5 GPa. At room temperature, their electrical conductivity increases rapidly with pressure, and the thermal activation energy for conduction <i>E</i>_act is eliminated at pressures ranging from ∼3 GPa for R = F to ∼12 GPa for R = Ph, heralding formation of a highly correlated (or bad) metallic state. For R = F, H the pressure-induced Mott insulator to metal conversion has been tracked by measurements of optical conductivity at ambient temperature and electrical resistivity at low temperature. For R = F compression to 6.2 GPa leads to a quasiquadratic temperature dependence of the resistivity over the range 5–300 K, consistent with formation of a 2D Fermi liquid state. DFT band structure calculations suggest that the ease of metallization of these radicals can be ascribed to their multiorbital character. Mixing and overlap of SOMO- and LUMO-based bands affords an increased kinetic energy stabilization of the metallic state relative to a single SOMO-based band system