Loss of Oxygen Atoms on Well-Oxidized Cobalt by Heterogeneous Surface Recombination.

Calorimetry is a commonly used method in plasma characterization, but the accuracy of the method is tied to the accuracy of the recombination coefficient, which in turn depends on a number of surface effects. Surface effects also govern the kinetics in advanced methods such as atomic layer oxidation of inorganic materials and functionalization of organic materials. The flux of the reactive oxygen atoms for the controlled oxidation of such materials depends on the recombination coefficient of materials placed into the reaction chamber, which in turn depends on the surface morphology, temperature, and pressure in the processing chamber.

A Microfluidic, Flow-Through, Liquid Reagent Fluorescence Sensor Applied to Oxygen Concentration Measurement.

A concept of a microfluidic fluorescent chemical sensing system is presented and demonstrated as a sensor for measurement of dissolved oxygen in water. The system utilizes on-line mixing of a fluorescent reagent with the analyzed sample, while it measures the fluorescence decay time of the mixture. The system is built entirely out of silica capillaries and optical fibers, and allows for very low consumption of the reagent (of the order of mL/month) and the analyzed sample (of the order of L/month).

A Review of Recombination Coefficients of Neutral Oxygen Atoms for Various Materials.

Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations.

An All-Fiber Fabry-Pérot Sensor for Emulsion Concentration Measurements.

This paper describes a Fabry-Pérot sensor-based measuring system for measuring fluid composition in demanding industrial applications. The design of the sensor is based on a two-parametric sensor, which enables the simultaneous measurement of temperature and refractive index (RI). The system was tested under real industrial conditions, and enables temperature-compensated online measurement of emulsion concentration with a high resolution of 0.

Nano-strain resolution fiber-optic Fabry-Perot sensors compatible with moderate/low resolution VIS-NIR spectrometers.

This paper reports on nano-strain resolution fiber-optic Fabry-Perot sensors produced by an improved selective etching method. The presented sensors exhibit high spectral sensitivity, low intrinsic temperature response, small size and mounting comparable to conventional Fiber Bragg gratings. Furthermore, the proposed sensors can be read-out by a combination of cost-efficient and widely available VIS/NIR spectrometers and LEDs used in lighting/automotive applications.

Miniature magneto-optic angular position sensor.

This Letter describes a miniature Fabry-Perot, contactless, magneto-optic sensor for angular position measurement. The sensor utilizes a magneto-optic fluid comprising barium hexaferrite nanoplatelets that become birefringent in the presence of an external magnetic field and a compact fiber-optic sensor system for tracking the liquid's optical axis direction. An efficient temperature compensation system is provided which allows the use of otherwise highly temperature-sensitive magneto-optic liquids.

Resonant-Opto-Thermomechanical Oscillator (ROTMO): A Low-Power, Large Displacement, High-Frequency Optically Driven Microactuator.

A light-driven micromechanical oscillator is presented, which can be operated by a low optical power (in the mW, or even the µW range), can produce large mechanical displacements (>5-100 µm), and can be designed to operate at frequencies from sub-kHz up to more than 200 kHz. The actuation of the oscillator is achieved by an asymmetrically metal-coated optical microwire configured into a silica micromechanical oscillator. The metalized optical microwire confines and absorbs the light strongly over a short distance, which results in a controlled optical power conversion into heat, and, consequently, into mechanical actuation through the temperature rise and the difference in thermal expansions of the silica microwire and the asymmetrically applied metal layer.

Optical Micro-Wire Flow-Velocity Sensor.

This paper presents a short response time, all-silica, gas-flow-velocity sensor. The active section of the sensor consists of a 16 µm diameter, highly optically absorbing micro-wire, which is heated remotely by a 980 nm light source. The heated microwire forms a Fabry-Perot interferometer whose temperature is observed at standard telecom wavelengths (1550 nm).

All Silica Micro-Fluidic Flow Injection Sensor System for Colorimetric Chemical Sensing.

This paper presents a miniature, all-silica, flow-injection sensor. The sensor consists of an optical fiber-coupled microcell for spectral absorption measurements and a microfluidic reagent injection system. The proposed sensor operates in back reflection mode and, with its compact dimensions, (no more than 200 µm in diameter) enables operation in small spaces and at very low flow rates of analyte and reagent, thus allowing for on-line or in-line colorimetric chemical sensing.

Optical flow sensor based on the thermal time-of-flight measurement.

This paper presents a dielectric, all-optical thermal time-of-flight fluid flow velocity sensor. The proposed sensor utilizes a sequence of three short sections of optical fibers, which are positioned in a direction perpendicular to the measured fluid flow. One of these three fiber sections is highly doped with vanadium and acts as an optically controlled heater, while the other two fiber sections contain fiber Bragg gratings (FBG) that act as dynamic temperature sensors.

Miniature all-fiber force sensor.

A miniature all-fiber Fabry-Perot sensor for measurement of force is presented in this Letter. The sensor consists of a thin silica diaphragm created at the tip of the fiber. The central part of the diaphragm is extended into a silica pole, which is ended with a round-shaped probe or a sensing cylinder apt for asserting measured force.

THz Signal Generator Using a Single DFB Laser Diode and the Unbalanced Optical Fiber Interferometer.

This paper presents a frequency-modulated optical signal generator in the THz band. The proposed method is based on a fast optical frequency sweep of a single narrowband laser diode used together with an optical fiber interferometer. The optical frequency sweep using a single laser diode is achieved by generating short current pulses with a high amplitude, which are driving the laser diode.

A Fiber-Optic Gas Sensor and Method for the Measurement of Refractive Index Dispersion in NIR.

This paper presents a method for gas concentration determination based on the measurement of the refractive index dispersion of a gas near the gas resonance in the near-infrared region (NIR). The gas refractive index dispersion line shape is reconstructed from the variation in the spectral interference fringes' periods, which are generated by a low-finesse Fabry-Perot interferometer during the DFB diode's linear-over-time optical frequency sweep around the gas resonance frequency. The entire sensing system was modeled and then verified experimentally, for an example of a low concentration methane-air mixture.

PECVD of Hexamethyldisiloxane Coatings Using Extremely Asymmetric Capacitive RF Discharge.

An extremely asymmetric low-pressure discharge was used to study the composition of thin films prepared by PECVD using HMDSO as a precursor. The metallic chamber was grounded, while the powered electrode was connected to an RF generator. The ratio between the surface area of the powered and grounded electrode was about 0.

Deposition Kinetics of Thin Silica-Like Coatings in a Large Plasma Reactor.

An industrial size plasma reactor of 5 m volume was used to study the deposition of silica-like coatings by the plasma-enhanced chemical vapor deposition (PECVD) method. The plasma was sustained by an asymmetrical capacitively coupled radio-frequency discharge at a frequency of 40 kHz and power up to 7 kW. Hexamethyldisilioxane (HMDSO) was introduced continuously at different flows of up to 200 sccm upon pumping with a combination of roots and rotary pumps at an effective pumping speed between 25 and 70 L/s to enable suitable gas residence time in the plasma reactor.

Miniature, micro-machined, fiber-optic Fabry-Perot voltage sensor.

This paper presents a miniature Fabry-Perot voltage sensor created at the tip of an optical fiber. The sensor utilizes a micro-machined, all-silica, opto-mechanical structure that is flexed under the presence of attractive forces generated among charged bodies. The small dimensions and short response times of the structure provide an opportunity for measurement of the DC and AC voltages within the range of power grid frequencies.

Optically controlled fiber-optic micro-gripper for sub-millimeter objects.

A miniature, fully optically controlled, dielectric, opto-thermally actuated tweezer/micro-gripper that is suitable for the manipulation of small objects is presented. The tweezer/micro-gripper is formed at the tip of an optical fiber and utilizes a mid-power laser diode for its actuation. The manipulation of small objects such as short pieces of optical fibers is demonstrated.

A Miniature Fabry Perot Sensor for Twist/Rotation, Strain and Temperature Measurements Based on a Four-Core Fiber.

In this article, a novel miniature Fabry-Perot twist/rotation sensor using a four core fiber and quadruple interferometer setup is presented and demonstrated. Detailed sensor modeling, analytical evaluation and test measurement assessment were conducted in this contribution. The sensor structure comprises a single lead-in multicore fiber, which has four eccentrically positioned cores, a special asymmetrical microstructure, and an inline semi-reflective mirror, all packed in a glass capillary housing.

Miniature fiber-optic Fabry-Perot refractive index sensor for gas sensing with a resolution of 5x10 RIU.

This paper presents a micro-machined, high-resolution refractive index sensor suitable for monitoring of small changes in the composition of gases. Experimentally demonstrated measurement resolution, induced by gas composition variation, proved to be in the range of 5x10-9 of a Refractive Index Unit (RIU). The proposed all-silica, all-fiber sensor consists of an open-path Fabry-Perot micro-cavity that includes an in-fiber collimation and temperature-sensing segment.

All-fiber, thermo-optic liquid level sensor.

This paper proposes an all-optical-fiber sensor for continuous measurements of liquid levels. The proposed sensor utilizes an optically absorbing vanadium doped optical fiber, which is configured as a long-gauge, optically-heated, fiber-optic, Fabry-Perot interferometer that is immersed into the measured liquid. The sensor is excited cyclically by a medium-power 980 nm optical source, which induces periodic temperature variation and, consequently, optical path length modulation within the vanadium doped fiber.

Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review.

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research.

Quasi-distributed twist/torsion sensor.

This paper presents a fiber-optic quasi-distributed in-line twist/rotation sensor. The presented sensor consists of a polarization maintaining lead-in fiber and series of in-line fiber polarizers with integrated semi-reflective mirrors that are interconnected by a standard single mode fiber. Sections of interconnecting single mode define multiple twist/rotation sensitive sensor segments, which can be interrogated individually by a simple optical time domain reflectometer.

Miniature all-silica fiber-optic sensor for simultaneous measurement of relative humidity and temperature.

This Letter presents a miniature fiber-optic sensor created at the tip of an optical fiber suitable for simultaneous measurement of relative humidity and temperature. The proposed sensor is based on two cascaded Fabry-Perot interferometers, the first configured as a relative humidity sensing element made from silica micro-wire coated with thin porous SiO2 layer, and the second as a temperature sensing element made from a segment of a standard single-mode fiber. The sensor has linear characteristics for both measurement parameters and a sensitivity of 0.

Miniature fiber-optic sensor for simultaneous measurement of pressure and refractive index.

This Letter presents a fiber-optic sensor created at the tip of an optical fiber for simultaneous measurements of pressure and refractive index. The sensor diameter does not exceed the standard fiber diameter and is shorter than 300 μm. Measurement resolutions of 0.

High resolution, all-fiber, micro-machined sensor for simultaneous measurement of refractive index and temperature.

This paper presents a highly-sensitive, miniature, all-silica, dual parameter fiber-optic Fabry-Perot sensor, which is suitable for independent measurement of the refractive index and the temperature of the fluid surrounding the sensor. The experimental sensor was produced by a micromachining process based on the selective etching of doped silica glass and a simple assembly procedure that included fiber cleaving, splicing and etching of optical fibers. The presented sensor also allows for direct compensation of the temperature's effect on the fluid's refractive index change and consequently provides opportunities for the detection of very small changes in the surrounding fluid's composition.