Laser Spectroscopy

Demtröder, Wolfgang

doi:10.1007/978-3-662-08257-7

Cited by 531 publications

(445 citation statements)

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“…High-speed imaging (around 10 5 images/s at a resolution 200 × 200 px) allows to probe the global spatio-temporal dynamics of plasma density fluctuations (Oldenbürger et al 2010). Ion velocimetry from Laser Induced Fluorescence of Argon ions (ArII) lines will shortly be installed to probe the details of the plasma flows with non-intrusive diagnostics (Demtröder 1981;Bieber et al 2011). …”

Section: Plasma Diagnosticsmentioning

confidence: 99%

Flow dynamics and magnetic induction in the von-Kármán plasma experiment

et al. 2014

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The von-Kármán plasma experiment is a novel versatile experimental device designed to explore the dynamics of basic magnetic induction processes and the dynamics of flows driven in weakly magnetized plasmas. A high-density plasma column (10 16 -10 19 particles. m −3 ) is created by two radio-frequency plasma sources located at each end of a 1 m long linear device. Flows are driven through J × B azimuthal torques created from independently controlled emissive cathodes. The device has been designed such that magnetic induction processes and turbulent plasma dynamics can be studied from a variety of time-averaged axisymmetric flows in a cylinder. MHD simulations implementing volume-penalization support the experimental development to design the most efficient flow-driving schemes and understand the flow dynamics. Preliminary experimental results show that a rotating motion of up to nearly 1 km/s is controlled by the J × B azimuthal torque.

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Section: Plasma Diagnosticsmentioning

confidence: 99%

Flow dynamics and magnetic induction in the von-Kármán plasma experiment

et al. 2014

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“…Both V and υ t are random variables. Following the argu ment which led to the Voigt profile, 2,4 it is easy to show that the spectral line profile of a turbulent gas is the following convolution:…”

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Spectral line profile of turbulent gas

Zhi

Qian²

1987

Appl. Opt.

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“…In conventional dual-beam LAS detection, the incident and transmitted beams are independently detected to deliver a photocurrent of I and T , respectively [15,25]. Any commonmode laser intensity fluctuations are removed by constructing the ratio T /I .…”

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confidence: 99%

“…At such low probe intensities, the transmitted probe power P (f ) can be modeled using the Beer-Lambert law [25,29],…”

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confidence: 99%

“…In this same low intensity limit, we can write σ = αV (f − f 0 ), where α is the on-resonance optical depth, f 0 is the optical frequency of the transition, and V (f ) is a Voigt function [10,25] where k is the Boltzmann constant, T Cs is the temperature of the cesium vapor, m Cs is the atomic mass of cesium, and c is the speed of light. Line-shape broadening associated with the linewidth of the probe laser (<1 kHz) is negligible in this experiment, while conventional power broadening amounts to just a 5% change in the homogeneous linewidth over the range of probe intensities [29].…”

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confidence: 99%

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Absolute absorption line-shape measurements at the shot-noise limit

et al. 2012

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Here, we report a measurement scheme for determining an absorption profile with an accuracy imposed solely by photon shot noise. We demonstrate the power of this technique by measuring the absorption of cesium vapor with an uncertainty at the 2-ppm level. This extremely high signal-to-noise ratio allows us to directly observe the homogeneous line-shape component of the spectral profile, even in the presence of Doppler broadening, by measuring the spectral profile at a frequency detuning more than 200 natural linewidths from the line center. We then use this tool to discover an optically induced broadening process that is quite distinct from the well-known power broadening phenomenon. The recent development of the optical frequency comb [1,2] has delivered a powerful new tool for absorption spectroscopy. The frequency comb allows us to determine the optical frequency of spectral features to astonishing new levels, which has paved the way for intriguing laboratory-scale tests of fundamental physics [3] as well as exciting applications in a wide variety of fields, including frequency metrology [1,4], direct optical frequency comb spectroscopy [5][6][7], and trace gas detection [8,9]. High-quality frequency measurement, however, represents only half the story. Many spectroscopic applications also demand absorbance measurements of high precision and accuracy in order to reveal subtle features of the spectral line shape. This requirement is of particular concern to the fields of precision line-shape measurement [10,11], precision line-shape analysis [12], and Doppler thermometry [13][14][15][16].The conventional quantum limit for precision in laser absorption spectroscopy (LAS) is set by shot noise of the probing light. In practice, though, this performance level has been exceedingly difficult to achieve because technical noise and instrumental limitations usually mask this quantum limit. These technical limitations are particularly acute for LAS because it is inherently a bright field [17] measurement; i.e., the absorbance is encoded in the ratio of two measurements of the incident and transmitted power. If one wishes to build a highly sensitive and accurate tool for probing optical absorbance, then there are three key challenges to overcome: First, one needs to suppress technical noise sources, which are usually much larger than fundamental sources; second, the resolution of the measurement can be limited because most of the dynamic range of the sensor is consumed in measuring small changes of relatively large signals; and third, the measurement technique needs to be inherently linear.

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Laser Spectroscopy

Cited by 531 publications

References 0 publications

Flow dynamics and magnetic induction in the von-Kármán plasma experiment

Flow dynamics and magnetic induction in the von-Kármán plasma experiment

Spectral line profile of turbulent gas

Absolute absorption line-shape measurements at the shot-noise limit

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