29 results match your criteria Applied physics. B Lasers and optics[Journal]

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Are absorption and spontaneous or stimulated emission inverse processes? The answer is subtle!

Authors:
Markus Pollnau

Appl Phys B 2019 21;125(2):25. Epub 2019 Jan 21.

Department of Electrical and Electronic Engineering, Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH UK.

It is generally believed that absorption and stimulated emission are inverse processes, as both are driven by an external field, their strength is quantified by the same Einstein coefficient, and they occur with a defined phase, opposite to each other, namely in phase and in anti-phase with the driving field, whereas spontaneous emission is a different process that occurs with an arbitrary phase with respect to a potential incident field. Recently, the phase relation in absorption and emission was shown to differ from this believe. Here it is verified via the amplitude-phase diagram and via the interference of sine waves that, precisely speaking, only the absorption process, in which a number  + 1 of incident photons is decreased by one photon, and the emission process, in which a number of incident photons is increased by one photon, are truly inverse processes also in their phase. Read More

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http://dx.doi.org/10.1007/s00340-019-7133-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383760PMC
January 2019

Optical remote sensing for monitoring flying mosquitoes, gender identification and discussion on species identification.

Appl Phys B 2018 Mar 17;124(3). Epub 2018 Feb 17.

Department of Physics, New Jersey Institute of Technology, 323 Martin Luther King Jr Blvd, Newark, NJ, USA.

Mosquito-borne diseases are a major challenge for Human health as they affect nearly 700 million people every year and result in over 1 million deaths. Reliable information on the evolution of population and spatial distribution of key insects species is of major importance in the development of eco-epidemiologic models. This paper reports on the remote characterization of flying mosquitoes using a continuous-wave infrared optical remote sensing system. Read More

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http://dx.doi.org/10.1007/s00340-018-6917-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6269144PMC

Laser spectroscopy for breath analysis: towards clinical implementation.

Appl Phys B 2018 28;124(8):161. Epub 2018 Jul 28.

1Trace Gas Research Group, Molecular and Laser Physics, IMM, Radboud University, 6525 AJ Nijmegen, The Netherlands.

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. Read More

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http://dx.doi.org/10.1007/s00340-018-7030-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428385PMC

New avenues for matter-wave-enhanced spectroscopy.

Appl Phys B 2017 9;123(1). Epub 2016 Dec 9.

Faculty of Physics, VCQ, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.

We present matter-wave interferometry as a tool to advance spectroscopy for a wide class of nanoparticles, clusters and molecules. The high sensitivity of de Broglie interference fringes to external perturbations enables measurements in the limit of an individual particle absorbing only a single photon on average, or even no photon at all. The method allows one to extract structural and electronic information from the loss of the interference contrast. Read More

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http://dx.doi.org/10.1007/s00340-016-6573-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5148790PMC
December 2016
3 Reads

Pulsed Rydberg four-wave mixing with motion-induced dephasing in a thermal vapor.

Appl Phys B 2016;122:18. Epub 2016 Jan 22.

5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.

We report on time-resolved pulsed four-wave mixing (FWM) signals in a thermal Rubidium vapor involving a Rydberg state. We observe FWM signals with dephasing times up to 7 ns, strongly dependent on the excitation bandwidth to the Rydberg state. The excitation to the Rydberg state is driven by a pulsed two-photon transition on ns timescales. Read More

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http://dx.doi.org/10.1007/s00340-015-6277-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750283PMC
January 2016
1 Read

Autonomous field measurements of CO in the atmospheric column with the miniaturized laser heterodyne radiometer (Mini-LHR).

Appl Phys B 2015;120(4):609-615. Epub 2015 Jul 28.

Microwave Instrument and Technology Branch, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 USA.

We present column CO measurements taken by the passive miniaturized laser heterodyne radiometer (Mini-LHR) at 1611.51 nm at the Mauna Loa Observatory in Hawaii. The Mini-LHR was operated autonomously, during the month of May 2013 at this site, working in tandem with an AERONET sun photometer that measures aerosol optical depth at 15-min intervals during daylight hours. Read More

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http://dx.doi.org/10.1007/s00340-015-6172-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4551134PMC
July 2015
19 Reads

Time-resolved digital holographic microscopy of laser-induced forward transfer process.

Authors:
H Ma V Venugopalan

Appl Phys B 2014 Mar;114(3):361-366

Department of Chemical Engineering and Materials Science, University of California, 916 Engineering Tower, Irvine, CA 92697-2575, USA ; Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, CA 92697-1475, USA ; Department of Biomedical Engineering, University of California, Irvine, CA 92697-2715, USA.

We develop a method for time-resolved digital holographic microscopy to obtain time-resolved 3-D deformation measurements of laser induced forward transfer (LIFT) processes. We demonstrate nanometer axial resolution and nanosecond temporal resolution of our method which is suitable for measuring dynamic morphological changes in LIFT target materials. Such measurements provide insight into the early dynamics of the LIFT process and a means to examine the effect of laser and material parameters on LIFT process dynamics. Read More

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http://dx.doi.org/10.1007/s00340-013-5524-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990434PMC

Continuous-wave broadly tunable high-power Cr:CdS laser.

Appl Phys B 2014;117(4):1009-1014. Epub 2014 Sep 14.

Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway.

We report spectroscopic characteristics and laser properties of the mid-infrared active laser medium Cr:CdS. Temperature-dependent absorption, luminescence and lifetime measurements of the E exited state allow determination of peak emission cross section value of 1.35 × 10 cm in -polarization at room temperature. Read More

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http://dx.doi.org/10.1007/s00340-014-5921-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4372838PMC
September 2014
1 Read

Continuous-Wave Stimulated Raman Scattering (cwSRS) Microscopy.

Appl Phys B 2013 Aug;112(1):99-103

Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843,USA.

Stimulated Raman scattering (SRS) microscopy is a powerful tool for chemically-sensitive non-invasive optical imaging. However, ultrafast laser sources, which are currently employed, are still expensive and require substantial maintenance to provide temporal overlap and spectral tuning. SRS imaging, which utilizes continuous-wave laser sources, has a major advantage, as it eliminates the cell damage due to exposure to the high-intensity light radiation, while substantially reducing the cost and complexity of the set-up. Read More

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http://dx.doi.org/10.1007/s00340-013-5405-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775370PMC
August 2013
3 Reads

Multifocal multiphoton microscopy based on a spatial light modulator.

Appl Phys B 2013 Jun;107(3):653-657

College of Optoelectronic Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China.

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware. Read More

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http://dx.doi.org/10.1007/s00340-012-5027-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722068PMC

Active Wavelength Control of an External Cavity Quantum Cascade Laser.

Appl Phys B 2012 May 1;109(3):415-421. Epub 2012 Nov 1.

Electrical Engineering Dept., Princeton University, Princeton, NJ 08544 USA.

We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3σ precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm. Read More

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http://dx.doi.org/10.1007/s00340-012-5075-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3592968PMC
May 2012
1 Read

Cross-validation of theoretically quantified fiber continuum generation and absolute pulse measurement by MIIPS for a broadband coherently controlled optical source.

Appl Phys B 2012 Feb 11;106(2):379-384. Epub 2011 Oct 11.

Biophotonics Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

The predicted spectral phase of a fiber continuum pulsed source rigorously quantified by the scalar generalized nonlinear Schrödinger equation is found to be in excellent agreement with that measured by multiphoton intra-pulse interference phase scan (MIIPS) with background subtraction. This cross-validation confirms the absolute pulse measurement by MIIPS and the transform-limited compression of the fiber continuum pulses by the pulse shaper performing the MIIPS measurement, and permits the subsequent coherent control on the fiber continuum pulses by this pulse shaper. The combination of the fiber continuum source with the MIIPS-integrated pulse shaper produces compressed transform-limited 9. Read More

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http://dx.doi.org/10.1007/s00340-011-4746-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491074PMC
February 2012

Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

Appl Phys B 2012 Sep;108(4)

College of Optoelectronics Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China.

We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. Read More

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http://dx.doi.org/10.1007/s00340-012-5164-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3846096PMC
September 2012
6 Reads

Effect of multimodal coupling in imaging micro-endoscopic fiber bundle on optical coherence tomography.

Appl Phys B 2012 Jan;106(3):635-643

Department of Brain and Cognitive Engineering, Korea University, 145, Anam-Ro, Sungbuk-Ku, Seoul, 136-701, South Korea.

The effect of higher order modes in fiber bundle imager-based optical coherence tomography (OCT) has been theoretically modeled using coupled fiber mode analysis ignoring the polarization and core size variation in order to visualize the pure effect of multimodal coupling of the imaging bundle. In this model, the optical imaging fiber couples several higher order modes in addition to the fundamental one due to its high numerical aperture for achieving light confinement to the single core pixel. Those modes become evident in a distance domain using A-mode (depth) OCT based on a mirror sample experiment where multiple peaks are generated by the spatial convolution and coherence function of the light source. Read More

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http://dx.doi.org/10.1007/s00340-011-4847-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3286611PMC
January 2012

Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy.

Appl Phys B 2010 Aug;100(2):377-382

Toyohashi University of Technology, 1-1, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan.

The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring CO(2)-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength differ with the rate. Read More

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http://dx.doi.org/10.1007/s00340-009-3878-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2929129PMC

Investigation of gold-coated bare fiber probe for in situ intra-vitreous coherence domain optical imaging and sensing.

Appl Phys B 2010 Jun;99(4):741-746

Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA, .

We have investigated the usage of gold-plated bare fiber probes for in situ imaging of retinal layers and surrounding ocular tissues using time-domain common-path optical coherence tomography. The fabricated intra-vitreous gold-plated micro-fiber probe can be fully integrated with surgical tools working in close proximity to the tissue to provide subsurface images having a self-contained reference plane independent to the Fresnel reflection between the distal end of the probe and the following medium for achieving reference in typical common-path optical coherence tomography. We have fully characterized the probe in an aqueous medium equivalent to the vitreous humor in the eye and were able to differentiate various functional retinal tissue layers whose thickness is larger than the system's resolution. Read More

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http://dx.doi.org/10.1007/s00340-010-3910-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2887671PMC

Optimal strategy for trapping single fluorescent molecules in solution using the ABEL trap.

Authors:
Q Wang W E Moerner

Appl Phys B 2010 Apr;99(1-2):23-30

Departments of Electrical Engineering and Chemistry, Stanford University, Stanford, CA 94305, USA.

Trapping of 10-nm-sized single fluorescent bio-molecules in solution has been achieved using high-speed position sensing and electrokinetic feedback forces in the Anti-Brownian ELectrokinetic (ABEL) trap. The high diffusion coefficient of small objects in solution requires very fast, real-time sensing of position, and this has been previously achieved using a simple rotating beam, but improved strategies are needed for the smallest objects, such as single nanometer-sized fluorescent molecules. At the same time, single molecules are limited in photon emission rate and total number of photons, so each emitted photon must be used as efficiently as possible. Read More

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http://dx.doi.org/10.1007/s00340-009-3843-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850131PMC

K(alpha) x-ray emission characterization of 100 Hz, 15 mJ femtosecond laser system with high contrast ratio.

Appl Phys B 2008 Dec;94(4):569-575

INRS-EMT, Université du Québec, Varennes, J3X 1S2, Canada,

We report K(alpha) x-ray production with a high energy (110 mJ per pulse at 800 nm before compression/15 mJ at 400 nm after compression), high repetition rate (100 Hz), and high pulse contrast (better than 10(-9) at 400 nm) laser system. To develop laser-based x-ray sources for biomedical imaging requires to use high-energy and high-power ultra-fast laser system where compression is achieved under vacuum. Using this type of laser system, we demonstrate long-term stability of the x-ray yield, conversion efficiency higher than 1. Read More

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http://dx.doi.org/10.1007/s00340-008-3342-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2801139PMC
December 2008
1 Read

Raman effects in the infrared supercontinuum generation in soft-glass PCFs.

Appl Phys B 2007 Mar;87(1):37-44

Institut für Photonik, TU Wien, Gusshausstr. 27/387, A-1040 Vienna, Austria.

Measurements of the Raman gain spectra in the SF6 and SF57 highly-nonlinear-glasses demonstrated twice as high Raman shift in comparison with the fused silica. Numerical simulation predicted that a large Raman shift in combination with high nonlinearity can significantly reduce the required input pulse intensity for supercontinuum in these glasses, retaining the necessary degree of coherence. We found, that the degradation of the SC coherence due to Raman soliton jitter can be effectively controlled by a correct choice of input intensity and fiber length. Read More

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http://dx.doi.org/10.1007/s00340-006-2545-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958656PMC

13CO2/12CO2 isotopic ratio measurements using a difference frequency-based sensor operating at 4.35 micrometers.

Appl Phys B 2002 ;75(2-3):289-95

Rice Quantum Institute, Rice University, Houston, TX 77005, USA.

A portable modular gas sensor for measuring the 13C/12C isotopic ratio in CO2 with a precision of 0.8%(+/-1 sigma) was developed for volcanic gas emission studies. This sensor employed a difference frequency generation (DFG)-based spectroscopic source operating at 4. Read More

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Chemical sensing with pulsed QC-DFB lasers operating at 15.6 micrometers.

Appl Phys B 2002 ;75(2-3):351-7

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

Pulsed thermoelectrically cooled QC-DFB lasers operating at 15.6 micrometers were characterized for spectroscopic gas sensing applications. A new method for wavelength scanning based on repetition rate modulation was developed. Read More

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April 2003
1 Read

Development of a tunable mid-IR difference frequency laser source for highly sensitive airborne trace gas detection.

Appl Phys B 2002 ;75(2-3):281-8

National Center for Atmospheric Research, Boulder, CO 80305, USA.

The development of a compact tunable mid-IR laser system at 3.5 micrometers for quantitative airborne spectroscopic trace gas absorption measurements is reported. The mid-IR laser system is based on difference frequency generation (DFG) in periodically poled LiNbO3 and utilizes optical fiber amplified near-IR diode and fiber lasers as pump sources operating at 1083 nm and 1562 nm, respectively. Read More

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http://lasersci.blogs.rice.edu/files/2014/05/ApplPhysB-Richt
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April 2003
1 Read

Development of a cw-laser-based cavity-ringdown sensor aboard a spacecraft for trace air constituents.

Appl Phys B 2002 ;75(2-3):255-60

The George Washington University, Washington, DC 20052, USA.

The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous-wave (cw), external-cavity tunable diode laser centered at 1.55 micrometers is used to pump an optical cavity absorption cell in cw-cavity ringdown spectroscopy (cw-CRDS). Read More

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http://link.springer.com/content/pdf/10.1007/s00340-002-0969
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Ambient formaldehyde detection with a laser spectrometer based on difference-frequency generation in PPLN.

Appl Phys B 2001 ;72(8):947-52

Rice University, Department of Electrical and Computer Engineering, Houston, TX 77251-1892, USA.

A laser spectrometer based on difference-frequency generation in periodically poled LiNbO3 (PPLN) has been used to quantify atmospheric formaldehyde with a detection limit of 0.32 parts per billion in a given volume (ppbV) using specifically developed data-processing techniques. With state-of-the-art fiber-coupled diode-laser pump sources at 1083 nm and 1561 nm, difference-frequency radiation has been generated in the 3. Read More

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January 2003

Applications of Kalman filtering to real-time trace gas concentration measurements.

Appl Phys B 2002 Jan;74(1):85-93

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

A Kalman filtering technique is applied to the simultaneous detection of NH3 and CO2 with a diode-laser-based sensor operating at 1.53 micrometers. This technique is developed for improving the sensitivity and precision of trace gas concentration levels based on direct overtone laser absorption spectroscopy in the presence of various sensor noise sources. Read More

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January 2002

Detection of biogenic CO production above vascular cell cultures using a near-room-temperature QC-DFB laser.

Appl Phys B 2002 Jan;74(1):95-9

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

We report the first application of pulsed, near-room-temperature quantum cascade laser technology to the continuous detection of biogenic CO production rates above viable cultures of vascular smooth muscle cells. A computer-controlled sequence of measurements over a 9-h period was obtained, resulting in a minimum detectable CO production of 20 ppb in a 1-m optical path above a standard cell-culture flask. Data-processing procedures for real-time monitoring of both biogenic and ambient atmospheric CO concentrations are described. Read More

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January 2002

Spectroscopic detection of biological NO with a quantum cascade laser.

Appl Phys B 2001 May;72(7):859-63

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

Two configurations of a continuous wave quantum cascade distributed feedback laser-based gas sensor for the detection of NO at a parts per billion (ppb) concentration level, typical of biomedical applications, have been investigated. The laser was operated at liquid nitrogen temperature near lambda = 5.2 microns. Read More

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Mid-infrared trace gas detection using continuous-wave difference frequency generation in periodically poled RbTiOAsO4.

Appl Phys B 2001 May;72(7):873-6

MREID Universite du Littoral, Dunkerque, France.

A tunable mid-infrared continuous-wave (cw) spectroscopic source in the 3.4-4.5 micrometers region is reported, based on difference frequency generation (DFG) in a quasi-phase-matched periodically poled RbTiOAsO4 (PPRTA) crystal. Read More

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May 2001
1 Read

Portable fiber-coupled diode-laser-based sensor for multiple trace gas detection.

Appl Phys B 1999 Nov-Dec;69:459-65

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

Tunable narrowband mid-infrared radiation from 3.25 to 4.4 micrometers is generated by a compact fiber-coupled, difference-frequency-based spectroscopic source. Read More

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March 2000
4 Reads
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