Although there is a well-developed commercial offering for the detection of gaseous emissions in natural gas infrastructures, the same does not exist in the transport or transformation of liquid petroleum products. In the case of aromatics, UV DOAS using lamps and retroreflectors are amongst the only choices, along with UV-DIAL. But these are limited in sensitivity and depend on long absorption paths or are very complex. There are also large airborne lidars for the detection of liquid hydrocarbon spills on water or land that rely on UV induced fluorescence (LIF). But there is a lack of simple techniques for the remote detection of vapor plumes or spills involving liquid petroleum products. There have been proposals for the use of UV enhanced Raman for the detection of vapor plumes, but these require large laser powers and detection optics for poor sensitivity. On the other hand, recent developments in UV LEDs allows for simple techniques in the detection of aromatics, benzene and toluene in particular. These are found in most liquid petroleum products. Using these new commercially available UV LEDs and a gas correlation spectrometer set-up, benzene vapor is measured using the electronic transition at 258.9 nm and at other deep UV wavelengths. It is shown that while there is significant fluorescence in liquid benzene, oxygen in air severely quenches the fluorescence of the vapor phase benzene, rendering fluorescence unusable for the standoff detection of the vapor phase. Various implementations of standoff benzene/toluene detection using UV LEDs and gas correlation are discussed, along with pros and cons of the technique.
An electroluminescence test for a Concentrated PV system is presented with the objective of capturing high resolution pseudo-efficiency maps that highlight optical defects in the concentrator system. Key parameters of the experimental setup and imaging system are presented. Image processing is discussed, including comparison of experimental to nominal results and the quantitative estimation of optical efficiency. Efficiency estimates are validated using measurements under a collimated solar simulator and ray-tracing software. Further validation is performed by comparison of the electroluminescence technique to direct mapping of the optical efficiency. Initial results indicate the mean estimation error for Isc is -2.4% with a standard deviation is 6.9% and a combined measurement and analysis time of less than 5 seconds per optic. An extension of this approach to in-line quality control is discussed.
μMany fluorescent tools have been developed through the past decades in order to better understand the physiology at a
cellular level. They are generally used for microscopy or endoscopy, in vivo and in vitro, but they are also usable with
fluorescent sensors such as fiber optic sensors. Among these tools, fluorescent ion indicators have been widely used to
understand ionic dynamics into living cells. Indicators are mainly designed for Ca2+, although K+ is also an important
target for its role in maintaining cellular membrane potential and regulating many other electrophysiological phenomena.
Here we propose a technique to improve the use of a miniature fiber optic sensor to sense potassium dynamics in vivo.
Due to the lack of commercially available potassium indicators, we are using a UV excitable indicator (PBFI). The UV
excitation light induces unwanted fluorescence and/or luminescence from the optical components including the sensing
fiber, leading to a poor signal-to-noise ratio. Our technique uses a UV diode pumped Q-switched source from
CrystaLaser, a time gated acquisition system and a delay fiber that improve the signal-to-noise ratio and allow reducing
the sensor size and the light intensity provided to the tissue, thus diminishing UV induced photodamage. Using this
technique we have been able to record intracellular potassium fluctuations in vivo with fiber optic sensors of 10μm
diameter.
It has been observed that the optical noise of a Ti:sapphire laser is related to the optical noise of the laser used for its optical pumping. Argon ion lasers are largely used as optical pump for solid-state lasers, such as Ti:sapphire lasers. The intensity noise of Argon laser is transferred to the beam (or pulses) emitted by the pumped laser. In this paper, we report on the optical noise reduction of a Ti:sapphire laser, operated in continuous-wave (cw) and mode-locked regimes. This effect is achieved through the optical noise reduction of the pump laser by coupling it to a passive external cavity ended by a dielectric mirror. In the mode-locked regime, the noise reduction of the low-frequency noise components, as averaged over the interval from 100 kHz to 800 kHz, is larger than 20 dB and the maximum noise reduction is larger than 34 dB. We have also compared the noise level of the Ti:sapphire laser to the noise measured when it is pumped by a solid-state laser (diode-pumped, intracavity frequency-doubled, Nd:Vanadate laser).
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