20964607
Human breath analysis via cavity-enhanced optical frequency comb spectroscopy
To date, researchers have identified over 1000 different compounds contained in human breath. These molecules have both endogenous and exogenous origins and provide information about physiological processes occurring in the body as well as environment-related ingestion or absorption of contaminants1,2. While the presence and concentration of many of these molecules are poorly understood, many 'biomarker' molecules have been correlated to specific diseases and metabolic processes. Such correlations can result in non-invasive methods of health screening for a wide variety of medical conditions. In this article we present human breath analysis using an optical-frequency-comb-based trace detection system with excellent performance in all criteria: detection sensitivity, ability to identify and distinguish a large number of biomarkers, and measurement time. We demonstrate a minimum detectable absorption of 8 x 10-10 cm-1, a spectral resolution of 800 MHz, and 200 nm of spectral coverage from 1.5 to 1.7 micron where strong and unique molecular fingerprints exist for many biomarkers. We present a series of breath measurements including stable isotope ratios of CO2, breath concentrations of CO, and the presence of trace concentrations of NH3 in high concentrations of H2O.
119207145
Mid-Infrared Frequency Comb Fourier Transform Spectrometer
Optical frequency-comb-based-high-resolution spectrometers offer enormous potential for spectroscopic applications. Although various implementations have been demonstrated, the lack of suitable mid-infrared comb sources has impeded explorations of molecular fingerprinting. Here we present for the first time a frequency-comb Fourier transform spectrometer operating in the 2100-to-3700-cm-1 spectral region that allows fast and simultaneous acquisitions of broadband absorption spectra with up to 0.0056 cm-1 resolution. We demonstrate part-per-billion detection limits in 30 seconds of integration time for various important molecules including methane, ethane, isoprene, and nitrous oxide. Our system enables precise concentration measurements even in gas mixtures that exhibit continuous absorption bands, and it allows detection of molecules at levels below the noise floor via simultaneous analysis of multiple spectral features. This system represents a near real-time, high-resolution, high-bandwidth mid-infrared spectrometer which is ready to replace traditional Fourier transform spectrometers for many applications in trace gas detection, atmospheric science, and medical diagnostics.
25651519
New limits on coupling of fundamental constants to gravity using 87Sr optical lattice clocks.
The 1S0-3P0 clock transition frequency nuSr in neutral 87Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the 1 x 10(-15) level makes nuSr the best agreed-upon optical atomic frequency. We combine periodic variations in the 87Sr clock frequency with 199Hg+ and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant alpha, electron-proton mass ratio mu, and light quark mass. Furthermore, after 199Hg+, 171Yb+, and H, we add 87Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of alpha and mu.
8781619
Control of four-level quantum coherence via discrete spectral shaping of an optical frequency comb.
We present experiments demonstrating high-resolution and wide-bandwidth coherent control of a four-level atomic system in a diamond configuration. A femtosecond frequency comb is used to excite a specific pair of two-photon transitions in cold 87Rb. The optical-phase-sensitive response of the closed-loop diamond system is studied by controlling the phase of the comb modes with a pulse shaper. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.
2486417
Precision test of mass-ratio variations with lattice-confined ultracold molecules.
We propose a precision measurement of time variations of the proton-electron mass ratio using ultracold molecules in an optical lattice. Vibrational energy intervals are sensitive to changes of the mass ratio. In contrast to measurements that use hyperfine-interval-based atomic clocks, the scheme discussed here is model independent and does not require separation of time variations of different physical constants. The possibility of applying the zero-differential-Stark-shift optical lattice technique is explored to measure vibrational transitions at high accuracy.
31462099
Precision stabilization of femtosecond lasers to high-finesse optical cavities
We report on direct stabilization of a femtosecond laser by a high-finesse passive optical cavity. Detailed comparison of two distinct stabilization schemes leads to new understanding of the optimum conditions for cavity stabilization and limitations on the ability to transfer the frequency stability of the cavity to the microwave domain. The stability of the frequency comb is explored in both the optical and the radio frequency domain. With an independent, stable cw laser, we verify that the linewidth and stability of the optical comb components, respectively, reach below 300 Hz and 53 10 ˛14 at 1 s averaging time, both limited by the
18954058
Quality Control of Optical Transmitters for the ATLAS Liquid Argon Calorimeter
A quality control test is performed on nearly 2000 custom optical transmitters for use in the Liquid Argon Calorimeter of the ATLAS detector. More than 90% of these optical transmitters passed the test and have been installed in the calorimeter readout system. The acceptance criteria, measurement procedure, and results of the quality control test are presented in this note.
30481535
A compact apparatus for muon lifetime measurement and time dilation demonstration in the undergraduate laboratory
We describe a compact apparatus for measuring the charge-averaged lifetime of atmospheric muons in plastic scintillator using low-cost, low-power electronics. We present measurements of the stopping rate of atmospheric muons as a function of altitude to demonstrate relativistic time dilation. The apparatus is designed for the advanced undergraduate physics laboratory and is suitable for field measurements.
15040700
DEVELOPMENT OF RADIATION TOLERANT Gb / s OPTICAL LINKS FOR THE FRONT-END READOUT OF THE ATLAS LIQUID ARGON CALORIMETER
In the baseline readout solution for the ATLAS liquid argon calorimeter, approximately 1500 unidirectional Gigabit/s (Gb/s) fibre-optic links are used to transfer data from the calorimeter to receivers in data acquisition electronics situated up to 200 m away. In an architecture currently under study, ‘G-Link’ serialiser chips manufactured by Hewlett Packard are used to convert calorimeter data words into a 1.6 Gb/s serial data stream which is fed into a VCSEL (vertical cavity surface emitting laser diode) based emitter system operating at 850 nm. Graded index multimode optical fibres are used to couple the on-detector emitters to PIN-photodiodes located in receivers. In this note results from neutron irradiations of a complete GLink based link demonstrator are presented along with results from neutron and ionising irradiations of potential link components (packaged VCSEL’s and graded-index fibres).
55746504
The versatile link, a common project for super-LHC
A common project to develop a bi-directional, radiation tolerant, high speed (4.8 Gb/s) optical link for future high energy physics experiments is described. Due to be completed in 2012, it targets the upgrade programs of detectors installed at CERN's Large Hadron Collider (LHC). The development of radiation and magnetic field tolerant opto-electronic devices, fibre and connectors is described. Both Single-Mode and Multi-Mode versions of the system operating respectively at 850 nm and 1310 nm wavelength are proposed. First results at component and system level are presented, based mostly on commercially available devices.
15277817
Electronics of the ATLAS Liquid Argon calorimeter and its precision calibration
The Liquid Argon sampling calorimeter is a key detector component in the ATLAS experiment at the LHC, designed to provide precision measurements of electrons, photons, jets and missing transverse energy. In this note we present the detector readout electronics system and its precision calibration. The system has 182,468 channels with more than 16-bit dynamic range. The contribution to the relative energy resolution constant term due to the calibration uncertainty is below 0.25%. The radiation tolerant optical link between the detector front-end and the data acquisition back-end is also discussed.