A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases

NASA Astrophysics Data System (ADS)

Robinson, Iain; Jack, James W.; Rae, Cameron F.; Moncrieff, John B.

2015-10-01

We report the development of a differential absorption lidar instrument (DIAL) designed and built specifically for the measurement of anthropogenic greenhouse gases in the atmosphere. The DIAL is integrated into a commercial astronomical telescope to provide high-quality receiver optics and enable automated scanning for three-dimensional lidar acquisition. The instrument is portable and can be set up within a few hours in the field. The laser source is a pulsed optical parametric oscillator (OPO) which outputs light at a wavelength tunable near 1.6 μm. This wavelength region, which is also used in telecommunications devices, provides access to absorption lines in both carbon dioxide at 1573 nm and methane at 1646 nm. To achieve the critical temperature stability required for a laserbased field instrument the four-mirror OPO cavity is machined from a single aluminium block. A piezoactuator adjusts the cavity length to achieve resonance and this is maintained over temperature changes through the use of a feedback loop. The laser output is continuously monitored with pyroelectric detectors and a custom-built wavemeter. The OPO is injection seeded by a temperature-stabilized distributed feedback laser diode (DFB-LD) with a wavelength locked to the absorption line centre (on-line) using a gas cell containing pure carbon dioxide. A second DFB-LD is tuned to a nearby wavelength (off-line) to provide the reference required for differential absorption measurements. A similar system has been designed and built to provide the injection seeding wavelengths for methane. The system integrates the DFB-LDs, drivers, locking electronics, gas cell and balanced photodetectors. The results of test measurements of carbon dioxide are presented and the development of the system is discussed, including the adaptation required for the measurement of methane.

Breath Analysis Using Laser Spectroscopic Techniques: Breath Biomarkers, Spectral Fingerprints, and Detection Limits

PubMed Central

Wang, Chuji; Sahay, Peeyush

2009-01-01

Breath analysis, a promising new field of medicine and medical instrumentation, potentially offers noninvasive, real-time, and point-of-care (POC) disease diagnostics and metabolic status monitoring. Numerous breath biomarkers have been detected and quantified so far by using the GC-MS technique. Recent advances in laser spectroscopic techniques and laser sources have driven breath analysis to new heights, moving from laboratory research to commercial reality. Laser spectroscopic detection techniques not only have high-sensitivity and high-selectivity, as equivalently offered by the MS-based techniques, but also have the advantageous features of near real-time response, low instrument costs, and POC function. Of the approximately 35 established breath biomarkers, such as acetone, ammonia, carbon dioxide, ethane, methane, and nitric oxide, 14 species in exhaled human breath have been analyzed by high-sensitivity laser spectroscopic techniques, namely, tunable diode laser absorption spectroscopy (TDLAS), cavity ringdown spectroscopy (CRDS), integrated cavity output spectroscopy (ICOS), cavity enhanced absorption spectroscopy (CEAS), cavity leak-out spectroscopy (CALOS), photoacoustic spectroscopy (PAS), quartz-enhanced photoacoustic spectroscopy (QEPAS), and optical frequency comb cavity-enhanced absorption spectroscopy (OFC-CEAS). Spectral fingerprints of the measured biomarkers span from the UV to the mid-IR spectral regions and the detection limits achieved by the laser techniques range from parts per million to parts per billion levels. Sensors using the laser spectroscopic techniques for a few breath biomarkers, e.g., carbon dioxide, nitric oxide, etc. are commercially available. This review presents an update on the latest developments in laser-based breath analysis. PMID:22408503

Atmospheric effects on CO2 laser propagation

NASA Technical Reports Server (NTRS)

Murty, S. S. R.; Bilbro, J. W.

1978-01-01

An investigation was made of the losses encountered in the propagation of CO2 laser radiation through the atmosphere, particularly as it applies to the NASA/Marshall Space Flight Center Pulsed Laser Doppler System. As such it addresses three major areas associated with signal loss: molecular absorption, refractive index changes in a turbulent environment, and aerosol absorption and scattering. In particular, the molecular absorption coefficients of carbon dioxide, water vapor, and nitrous oxide are calculated for various laser lines in the region of 10.6 mu m as a function of various pressures and temperatures. The current status in the physics of low-energy laser propagation through a turbulent atmosphere is presented together with the analysis and evaluation of the associated heterodyne signal power loss. Finally, aerosol backscatter and extinction coefficients are calculated for various aerosol distributions and the results incorporated into the signal-to-noise ratio equation for the Marshall Space Flight Center system.

He-Ne and CW CO2 laser long-path systems for gas detection

NASA Technical Reports Server (NTRS)

Grant, W. B.

1986-01-01

This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual CW carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.

Multi-Wavelength Measurement of Bus Exhausts Using a Four QC Laser Spectrometer

NASA Astrophysics Data System (ADS)

Hay, K. G.; Wilson, D.; Duxbury, G.; Langford, N.

2010-06-01

Using a portable, lightweight, four laser intra-pulse quantum cascade laser spectrometer we have measured the variation of the composition of exhaust gases emitted by diesel engined buses which are representative of the decades from the 1930's until the 1990's. The lasers and the fast detector used in the spectrometer are Peltier cooled, and the spectra are recorded using each laser in turn, in a repeated four laser cycle. The instrument is controlled via a ruggedised laptop computer. The wavelengths of the lasers used were 7.84 microns (methane, nitrous oxide and formaldehyde), 6.13 microns (nitrogen dioxide) 5.25 microns (nitric oxide and water) and 4.88 microns (carbon monoxide and carbon dioxide). The path length of the multiple pass absorption cell used was 77 m. The results we will present demonstrate the possibility of deploying this type of instrument for investigating gas emissions from a variety of sources.

Airborne Measurements of Atmospheric Methane Using Pulsed Laser Transmitters

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Wu, Stewart; Gonzalez, Brayler; Rodriguez, Michael; Hasselbrack, William; Fahey, Molly; Yu, Anthony; Stephen, Mark; Mao, Jianping;

United States Air Force Summer Faculty Research Program: Program Management Report

DTIC Science & Technology

1988-12-01

Laboratory 64 Realization of Sublayer Relative Dr. Lane Clark Shielding Order in Electromagnetic Topology 65 Diode Laser Probe of Vibrational Dr. David...given. In addition, all possible sublayer topologies with relative shielding order at most 5 are explicitly given. S863 Diode Laser Probe of...dioxide at 193 nm to prepare the SO radicals. High resolution diode laser absorption spectrometry will be used to obtain time-dependent concentrations

Progress on High-Energy 2-micron Solid State Laser for NASA Space-Based Wind and Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.

2011-01-01

Sustained research efforts at NASA Langley Research Center during last fifteen years have resulted in significant advancement of a 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurements from ground, air and space-borne platforms. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

Simultaneous sensing of temperature, CO, and CO2 in a scramjet combustor using quantum cascade laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Spearrin, R. M.; Goldenstein, C. S.; Schultz, I. A.; Jeffries, J. B.; Hanson, R. K.

2014-07-01

A mid-infrared laser absorption sensor was developed for gas temperature and carbon oxide (CO, CO2) concentrations in high-enthalpy, hydrocarbon combustion flows. This diagnostic enables non-intrusive, in situ measurements in harsh environments produced by hypersonic propulsion ground test facilities. The sensing system utilizes tunable quantum cascade lasers capable of probing the fundamental mid-infrared absorption bands of CO and CO2 in the 4-5 µm wavelength domain. A scanned-wavelength direct absorption technique was employed with two lasers, one dedicated to each species, free-space fiber-coupled using a bifurcated hollow-core fiber for remote light delivery on a single line of sight. Scanned-wavelength modulation spectroscopy with second-harmonic detection was utilized to extend the dynamic range of the CO measurement. The diagnostic was field-tested on a direct-connect scramjet combustor for ethylene-air combustion. Simultaneous, laser-based measurements of carbon monoxide and carbon dioxide provide a basis for evaluating combustion completion or efficiency with temporal and spatial resolution in practical hydrocarbon-fueled engines.

The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

DOE PAGES

Levine, Zachary H.; Pintar, Adam L.; Dobler, Jeremy T.; ...

2016-04-13

Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant ratemore » giving rise to a plume with a concentration and distribution that depend on the wind velocity. Lastly, we demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement.« less

Atmospheric transmission of CO2 laser radiation with application to laser Doppler systems

NASA Technical Reports Server (NTRS)

Murty, S. S. R.

1975-01-01

The molecular absorption coefficients of carbon dioxide, water vapor, and nitrous oxide are calculated at the P16, P18, P20, P22, and P24 lines of the CO2 laser for temperatures from 200 to 300 K and for pressures from 100 to 1100 mb. The temperature variation of the continuum absorption coefficient of water vapor is taken into account semi-empirically from Burch's data. The total absorption coefficient from the present calculations falls within + or - 20 percent of the results of McClatchey and Selby. The transmission loss which the CO2 pulsed laser Doppler system experiences was calculated for flight test conditions for the five P-lines. The total transmission loss is approximately 7 percent higher at the P16 line and 10 percent lower at the P24 line compared to the P20 line. Comparison of the CO2 laser with HF and DF laser transmission reveals the P2(8) line at 3.8 micrometers of the DF laser is much better from the transmission point of view for altitudes below 10 km.

Quantitative evaluation of the safety of mucosal incision and submucosal dissection for colon during endoscopic submucosal dissection using carbon dioxide laser

NASA Astrophysics Data System (ADS)

Noguchi, Takuma; Honda, Norihiro; Hazama, Hisanao; Morita, Yoshinori; Awazu, Kunio

2018-02-01

Since the increase in the overall mortality rate in patients with colon cancer is remarkably high in recent years, early treatment is required. For this reason, endoscopic submucosal dissection (ESD) has been at the forefront of international attention as a low invasive treatment for early digestive cancer. In current ESD procedure, an electrosurgical knife is used for mucosal incision and subsequent submucosal dissection. However, the perforation has been reported to occur by approximately 5%. Thus, to enhance the tissue selectivity of this modality, we focused on the application of laser for ESD. A carbon dioxide laser was chosen as a surgical knife because the saline or a sodium hyaluronate solution injected into the submucosal layer in current ESD procedure has a high absorption coefficient at the wavelength of the carbon dioxide laser. In this research, ex vivo experiment was performed at the output power of 3-7 W and discuss the optimum irradiation power of laser. As a result of ex vivo experiment using extracted porcine colon tissues, mucosal incision and submucosal dissection were safely and less invasively performed in every output power, without reaching the thermal damage to a muscular layer. This is because a carbon dioxide laser is strongly absorbed by saline injected into submucosa. ESD using a carbon dioxide laser is a safer method for the treatment of early colon cancer. We are planning to measure and compare the optical and thermal properties of porcine colon with those of human colon.

Carbon dioxide UV laser-induced fluorescence in high-pressure flames

NASA Astrophysics Data System (ADS)

Bessler, W. G.; Schulz, C.; Lee, T.; Jeffries, J. B.; Hanson, R. K.

2003-07-01

Laser-induced fluorescence (LIF) of carbon dioxide is investigated with excitation between 215 and 255 nm with spectrally resolved detection in 5-40 bar premixed CH 4/O 2/Ar and CH 4/air flat-flames at fuel/air ratios between 0.8 and 1.9. The LIF signal consists of a broad (200-450 nm) continuum with a faint superimposed structure, and this signal is absent in similar H 2/O 2/Ar flames. There is strong evidence this signal arises from CO 2, as the signal variations with excitation wavelength, equivalence ratio and flame temperature all correlate with CO 2 absorption cross-sections. The signal is linear with pressure and laser fluence within the investigated ranges.

Development of Double-Pulsed Two-Micron Laser for Atmospheric Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Petros, Mulugeta; Singh, Upendra N.; Yu, Jirong; Refaat, Tamer F.

2017-01-01

A CO2 lidar double-pulse two-micron high-energy transmitter, tuned to on- and off-line absorption wavelengths, has been developed. Transmitter operation and performance has been verified on ground and airborne platform.

[The study of CO2 cavity enhanced absorption and highly sensitive absorption spectroscopy].

PubMed

Pei, Shi-Xin; Gao, Xiao-Ming; Cui, Fen-Ping; Huang, Wei; Shao, Jie; Fan, Hong; Zhang, Wei-Jun

2005-12-01

Cavity enhanced absorption spectroscopy (CEAS) is a new spectral technology that is based on the cavity ring down absorption spectroscopy. In the present paper, a DFB encapsulation narrow line width tunable diode laser (TDL) was used as the light source. At the center output, the TDL radiation wavelength was 1.573 microm, and an optical cavity, which consisted of two high reflectivity mirrors (near 1.573 microm, the mirror reflectivity was about 0.994%), was used as a sample cell. A wavemeter was used to record the accurate frequency of the laser radiation. In the experiment, the method of scanning the optical cavity to change the cavity mode was used, when the laser frequency was coincident with one of the cavity mode; the laser radiation was coupled into the optical cavity and the detector could receive the light signals that escaped the optical cavity. As a result, the absorption spectrum of carbon dioxide weak absorption at low pressure was obtained with an absorption intensity of 1.816 x 10(-23) cm(-1) x (molecule x cm(-2)(-1) in a sample cell with a length of only 33.5 cm. An absorption sensitivity of about 3.62 x 10(-7) cm(-1) has been achieved. The experiment result indicated that the cavity enhanced absorption spectroscopy has the advantage of high sensivity, simple experimental setup, and easy operation.

JPRS Report. Science & Technology: Japan.

DTIC Science & Technology

1987-07-07

the mirror with this high reflectance is also provided with a function of cutting off return light. The method of cutting off return light which is...0.351 micron), far down from the planned level of 100 kJ, owing to a damage incurred in the laser glass by absorption and heating of a contaminant...a new project, is also underway, which involves a "two-laser method " wherein ions are produced by a carbon-dioxide laser and subseguently excited

A compact tunable diode laser absorption spectrometer to monitor CO2 at 2.7 μm wavelength in hypersonic flows.

PubMed

Vallon, Raphäel; Soutadé, Jacques; Vérant, Jean-Luc; Meyers, Jason; Paris, Sébastien; Mohamed, Ajmal

2010-01-01

Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship's Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.

Miniaturized Laser Heterodyne Radiometer for Measurements of CO2 in the Atmospheric Column

NASA Technical Reports Server (NTRS)

Wilson, E. L.; Mclinden, M. L.; Miller, J. H.; Allan, G. R.; Lott, L. E.; Melroy, H. R.; Clarke, G. B.

2013-01-01

We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H2O) and nitrous oxide (N2O).

Double-pulse 1.57  μm integrated path differential absorption lidar ground validation for atmospheric carbon dioxide measurement.

PubMed

Du, Juan; Zhu, Yadan; Li, Shiguang; Zhang, Junxuan; Sun, Yanguang; Zang, Huaguo; Liu, Dan; Ma, Xiuhua; Bi, Decang; Liu, Jiqiao; Zhu, Xiaolei; Chen, Weibiao

2017-09-01

A ground-based double-pulse integrated path differential absorption (IPDA) instrument for carbon dioxide (CO 2 ) concentration measurements at 1572 nm has been developed. A ground experiment was implemented under different conditions with a known wall located about 1.17 km away acting as the scattering hard target. Off-/offline testing of a laser transmitter was conducted to estimate the instrument systematic and random errors. Results showed a differential absorption optical depth (DAOD) offset of 0.0046 existing in the instrument. On-/offline testing was done to achieve the actual DAOD resulting from the CO 2 absorption. With 18 s pulses average, it demonstrated that a CO 2 concentration measurement of 432.71±2.42  ppm with 0.56% uncertainty was achieved. The IPDA ranging led to a measurement uncertainty of 1.5 m.

The airborne Laser Absorption Spectrometer - A new instrument of remote measurement of atmospheric trace gases

NASA Technical Reports Server (NTRS)

Shumate, M. S.; Menzies, R. T.

1978-01-01

The Laser Absorption Spectrometer is a portable instrument developed by JPL for remote measurement of trace gases from an aircraft platform. It contains two carbon dioxide lasers, two optical heterodyne receivers, appropriate optics to aim the lasers at the ground and detect the backscattered energy, and signal processing and recording electronics. Operating in the differential-absorption mode, it is possible to monitor one atmospheric gas at a time and record the data in real time. The system can presently measure ozone, ethylene, water vapor, and chlorofluoromethanes with high sensitivity. Airborne measurements were made in early 1977 from the NASA/JPL twin-engine Beechcraft and in May 1977 from the NASA Convair 990 during the ASSESS-II Shuttle Simulation Study. These flights resulted in measurements of ozone concentrations in the lower troposphere which were compared with ground-based values provided by the Air Pollution Control District. This paper describes the details of the instrument and results of the airborne measurements.

Solid-State 2-Micron Laser Transmitter Advancement for Wind and Carbon Dioxide Measurements From Ground, Airborne, and Space-Based Lidar Systems

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Kavaya, Michael J.; Koch, Grady; Yu, Jirong; Ismail, Syed

2008-01-01

NASA Langley Research Center has been developing 2-micron lidar technologies over a decade for wind measurements, utilizing coherent Doppler wind lidar technique and carbon dioxide measurements, utilizing Differential Absorption Lidar (DIAL) technique. Significant advancements have been made towards developing state-of-the-art technologies towards laser transmitters, detectors, and receiver systems. These efforts have led to the development of solid-state lasers with high pulse energy, tunablility, wavelength-stability, and double-pulsed operation. This paper will present a review of these technological developments along with examples of high resolution wind and high precision CO2 DIAL measurements in the atmosphere. Plans for the development of compact high power lasers for applications in airborne and future space platforms for wind and regional to global scale measurement of atmospheric CO2 will also be discussed.

Fiber-Based Laser Transmitter at 1.57 Micrometers for Remote Sensing of Atmospheric Carbon Dioxide from Satellites

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Abshire, James B.; Stephen, Mark A.; Chen, Jeffrey R.; Wu, Stewart; Gonzalez, Brayler; Han, Lawrence; Numata, Kenji; Allan, Graham R.; Hasselbrack, William;

Carbon dioxide sequestration monitoring and verification via laser based detection system in the 2 mum band

NASA Astrophysics Data System (ADS)

Humphries, Seth David

Carbon Dioxide (CO2) is a known contributor to the green house gas effect. Emissions of CO2 are rising as the global demand for inexpensive energy is placated through the consumption and combustion of fossil fuels. Carbon capture and sequestration (CCS) may provide a method to prevent CO2 from being exhausted to the atmosphere. The carbon may be captured after fossil fuel combustion in a power plant and then stored in a long term facility such as a deep geologic feature. The ability to verify the integrity of carbon storage at a location is key to the success of all CCS projects. A laser-based instrument has been built and tested at Montana State University (MSU) to measure CO2 concentrations above a carbon storage location. The CO2 Detection by Differential Absorption (CODDA) Instrument uses a temperature-tunable distributed feedback (DFB) laser diode that is capable of accessing a spectral region, 2.0027 to 2.0042 mum, that contains three CO2 absorption lines and a water vapor absorption line. This instrument laser is aimed over an open-air, two-way path of about 100 m, allowing measurements of CO2 concentrations to be made directly above a carbon dioxide release test site. The performance of the instrument for carbon sequestration site monitoring is studied using a newly developed CO2 controlled release facility. The field and CO2 releases are managed by the Zero Emissions Research Technology (ZERT) group at MSU. Two test injections were carried out through vertical wells simulating seepage up well paths. Three test injections were done as CO2 escaped up through a slotted horizontal pipe simulating seepage up through geologic fault zones. The results from these 5 separate controlled release experiments over the course of three summers show that the CODDA Instrument is clearly capable of verifying the integrity of full-scale CO2 storage operations.

A Compact Tunable Diode Laser Absorption Spectrometer to Monitor CO2 at 2.7 μm Wavelength in Hypersonic Flows

PubMed Central

Vallon, Raphäel; Soutadé, Jacques; Vérant, Jean-Luc; Meyers, Jason; Paris, Sébastien; Mohamed, Ajmal

2010-01-01

Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow. PMID:22219703

Computer Simulation of Global Profiles of Carbon Dioxide Using a Pulsed, 2-Micron, Coherent-Detection, Column-Content DIAL System

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Singh, Upendra N.; Koch, Grady J.; Yu, Jirong; Frehlich, Rod G.

2009-01-01

We present preliminary results of computer simulations of the error in measuring carbon dioxide mixing ratio profiles from earth orbit. The simulated sensor is a pulsed, 2-micron, coherent-detection lidar alternately operating on at least two wavelengths. The simulated geometry is a nadir viewing lidar measuring the column content signal. Atmospheric absorption is modeled using FASCODE3P software with the HITRAN 2004 absorption line data base. Lidar shot accumulation is employed up to the horizontal resolution limit. Horizontal resolutions of 50, 100, and 200 km are shown. Assuming a 400 km spacecraft orbit, the horizontal resolutions correspond to measurement times of about 7, 14, and 28 s. We simulate laser pulse-pair repetition frequencies from 1 Hz to 100 kHz. The range of shot accumulation is 7 to 2.8 million pulse-pairs. The resultant error is shown as a function of horizontal resolution, laser pulse-pair repetition frequency, and laser pulse energy. The effect of different on and off pulse energies is explored. The results are compared to simulation results of others and to demonstrated 2-micron operating points at NASA Langley.

Control of electromagnetically induced transparency via a hybrid semiconductor quantum dot-vanadium dioxide nanoparticle system

NASA Astrophysics Data System (ADS)

Zamani, Naser; Hatef, Ali; Nadgaran, Hamid; Keshavarz, Alireza

2017-07-01

We numerically investigate the electromagnetically induced transparency (EIT) of a hybrid system consisting of a three-level quantum dot (QD) in the vicinity of vanadium dioxide nanoparticle (VO2NP). VO2NP has semiconductor and metallic phases where the transition between the two phases occurs around a critical temperature. When the QD-VO2NP hybrid system interacts with continuous wave laser fields in an infrared regime, it supports a coherent coupling of exciton-polariton and exciton-plasmon polariton in semiconductor and metal phases of VO2NP, respectively. In our calculations a filling fraction factor controls the VO2NP phase transition. A probe and control laser field configuration is studied for the hybrid system to measure the absorption of QD through the filling fraction factor manipulations. We show that for the VO2NP semiconductor phase and proper geometrical configuration, the absorption spectrum profile of the QD represents an EIT with two peaks and a clear minimum. These two peaks merge to one through the VO2NP phase transition to metal. We also show that the absorption spectrum profile is modified by different orientations of the laser fields with the axis of the QD-VO2NP hybrid system. The innovation in comparison to other research in the field is that robust variation in the absorption profile through EIT is due to the phase transition in VO2NP without any structural change in the QD-VO2NP hybrid system. Our results can be employed to design nanothermal sensors, optical nanoswitches, and energy transfer devices.

Dual photon effects in nitrogen dioxide photolysis

NASA Technical Reports Server (NTRS)

Hakala, D.; Harteck, P.; Reeves, R. R.

1974-01-01

A previous study demonstrated two-photon consecutive absorption as being the most probable mechanism for the photodissociation of NO2 using a pulsed ruby laser at 6943 A. Additional data discussed here confirmed this and also examined an associated phenomenon, that of multiphoton induced fluorescence. The dissociation of NO2 by ON-O bond cleavage requires 3.4 eV, while the laser energy corresponds to 1.785 eV. The pooling of the energy of two photons would give more than enough energy to dissociate the NO2 into NO + O. Several mechanisms including (1) simultaneous absorption of two photons; (2) reaction of two singly excited NO2; (3) reaction of a singly excited NO2 with a ground state NO2; and (4) consecutive absorption of two photons were examined.

Wavelength Locking to CO2 Absorption Line-Center for 2-Micron Pulsed IPDA Lidar Application

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Petros, Mulugeta; Antill, Charles W.; Singh, Upendra N.; Yu, Jirong

2016-01-01

An airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is currently under development at NASA Langley Research Center (LaRC). This IPDA lidar system targets both atmospheric carbon dioxide (CO2) and water vapor (H2O) column measurements. Independent wavelength control of each of the transmitted laser pulses is a key feature for the success of this instrument. The wavelength control unit provides switching, tuning and locking for each pulse in reference to a 2-micron CW (Continuous Wave) laser source locked to CO2 line-center. Targeting the CO2 R30 line center, at 2050.967 nanometers, a wavelength locking unit has been integrated using semiconductor laser diode. The CO2 center-line locking unit includes a laser diode current driver, temperature controller, center-line locking controller and CO2 absorption cell. This paper presents the CO2 center-line locking unit architecture, characterization procedure and results. Assessment of wavelength jitter on the IPDA measurement error will also be addressed by comparison to the system design.

Double-Pulse Two-Micron IPDA Lidar Simulation for Airborne Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta

2015-01-01

An advanced double-pulsed 2-micron integrated path differential absorption lidar has been developed at NASA Langley Research Center for measuring atmospheric carbon dioxide. The instrument utilizes a state-of-the-art 2-micron laser transmitter with tunable on-line wavelength and advanced receiver. Instrument modeling and airborne simulations are presented in this paper. Focusing on random errors, results demonstrate instrument capabilities of performing precise carbon dioxide differential optical depth measurement with less than 3% random error for single-shot operation from up to 11 km altitude. This study is useful for defining CO2 measurement weighting, instrument setting, validation and sensitivity trade-offs.

Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

NASA Technical Reports Server (NTRS)

Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

2009-01-01

Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

Single-mode interband cascade laser multiemitter structure for two-wavelength absorption spectroscopy

NASA Astrophysics Data System (ADS)

Scheuermann, Julian; Weih, Robert; Becker, Steffen; Fischer, Marc; Koeth, Johannes; Höfling, Sven

2018-01-01

An interband cascade laser multiemitter with single-mode distributed feedback (DFB) emission at two wavelengths is presented. Continuous-wave laser operation is measured from 0°C to 40°C with threshold currents of around 25 mA and output powers of around 9 mW at 20°C. The ridge waveguide DFB structures are monolithically integrated with a spacing of 70 μm and each is provided with an individual metal DFB grating to select specific single-mode wavelengths of interest for absorption spectroscopy. The emission windows at 3.92 and 4.01 μm are targeting hydrogen sulfide and sulfur dioxide, which are of importance for industrial applications since both gases are reagents of the Claus process in sulfur recovery units, recovering elemental sulfur from gaseous hydrogen sulfide.

Particle agglomerated 3-d nanostructures for photon absorption

NASA Astrophysics Data System (ADS)

Sivayoganathan, Mugunthan

The main objective of this thesis is to investigate the photon absorption properties of particle agglomerated 3-D structures that are synthesized through femtosecond laser ablation of solids. The size and morphology of these particle agglomerated 3-D structures, which can be tailored through adjusting laser parameters, determine the photon absorption property. A systematic theoretical and experimental study was performed to identify the effect of lasers on the size of the formed particles. The literature survey showed that the amount of supersaturation influences the growth rate as well as the nucleation rate of vapour condensed nanoparticles. Based on this theory, a mechanism was formed to explain the control of laser parameters over the size of formed particles. Further, a theoretical explanation was proposed from the experimental results for the transition of particle size distribution modals. These proposed mechanisms and explanations show the variation in particle size in the particle agglomerated 3-D nanostructures with laser parameters. The effect of laser parameters on the formed ring size was studied. Based on the previous studies, a mechanism was proposed for the formation of ring nanoclusters. The laser pulse intensity dependent ponderomotive force was the key force to define the formation of ring nanoclusters. Then the effect of laser parameters on ring size was studied. Structures fabricated on several materials such as graphite, aluminosilicate ceramic, zinc ingot, gold, and titanium were analyzed to show the influence of material properties, laser parameters, and the environmental conditions on the size of ring formed. The studies performed on the structures showed a minimum absorption of 0.75 A.U. in the bandwidth from UV to IR. The absorption spectrum is much wider compared to existing nanomaterials, such as silicon nanostructures and titanium dioxide nanostructures. To the best of the author's knowledge, it is a very competitive absorption rate when compared with the previous nanostructures used in photovoltaic conversion. Several features of nanostructures contribute to the enhancement of this light absorption. The special feature of the structure is that ease to fabricate and modify the properties by varying the laser parameters could make it competitive among other nanostructures available for solar cells.

Advances in High Energy Solid-State 2-micron Laser Transmitter Development for Ground and Airborne Wind and CO2 Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Kavaya, Michael J.; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Modlin, Edward A.; Koch, Grady;

Ultraviolet absorption cross-sections of hot carbon dioxide

NASA Astrophysics Data System (ADS)

Oehlschlaeger, Matthew A.; Davidson, David F.; Jeffries, Jay B.; Hanson, Ronald K.

2004-12-01

The temperature-dependent ultraviolet absorption cross-section for CO 2 has been measured in shock-heated gases between 1500 and 4500 K at 216.5, 244, 266, and 306 nm. Continuous-wave lasers provide the spectral brightness to enable precise time-resolved measurements with the microsecond time-response needed to monitor thermal decomposition of CO 2 at temperatures above 3000 K. The photophysics of the highly temperature dependent cross-section is discussed. The new data allows the extension of CO 2 absorption-based temperature sensing methods to higher temperatures, such as those found in behind detonation waves.

Attosecond transient absorption instrumentation for thin film materials: Phase transitions, heat dissipation, signal stabilization, timing correction, and rapid sample rotation.

PubMed

Jager, Marieke F; Ott, Christian; Kaplan, Christopher J; Kraus, Peter M; Neumark, Daniel M; Leone, Stephen R

2018-01-01

We present an extreme ultraviolet (XUV) transient absorption apparatus tailored to attosecond and femtosecond measurements on bulk solid-state thin-film samples, specifically when the sample dynamics are sensitive to heating effects. The setup combines methodology for stabilizing sub-femtosecond time-resolution measurements over 48 h and techniques for mitigating heat buildup in temperature-dependent samples. Single-point beam stabilization in pump and probe arms and periodic time-zero reference measurements are described for accurate timing and stabilization. A hollow-shaft motor configuration for rapid sample rotation, raster scanning capability, and additional diagnostics are described for heat mitigation. Heat transfer simulations performed using a finite element analysis allow comparison of sample rotation and traditional raster scanning techniques for 100 Hz pulsed laser measurements on vanadium dioxide, a material that undergoes an insulator-to-metal transition at a modest temperature of 340 K. Experimental results are presented confirming that the vanadium dioxide (VO 2 ) sample cannot cool below its phase transition temperature between laser pulses without rapid rotation, in agreement with the simulations. The findings indicate the stringent conditions required to perform rigorous broadband XUV time-resolved absorption measurements on bulk solid-state samples, particularly those with temperature sensitivity, and elucidate a clear methodology to perform them.

Attosecond transient absorption instrumentation for thin film materials: Phase transitions, heat dissipation, signal stabilization, timing correction, and rapid sample rotation

NASA Astrophysics Data System (ADS)

Jager, Marieke F.; Ott, Christian; Kaplan, Christopher J.; Kraus, Peter M.; Neumark, Daniel M.; Leone, Stephen R.

2018-01-01

We present an extreme ultraviolet (XUV) transient absorption apparatus tailored to attosecond and femtosecond measurements on bulk solid-state thin-film samples, specifically when the sample dynamics are sensitive to heating effects. The setup combines methodology for stabilizing sub-femtosecond time-resolution measurements over 48 h and techniques for mitigating heat buildup in temperature-dependent samples. Single-point beam stabilization in pump and probe arms and periodic time-zero reference measurements are described for accurate timing and stabilization. A hollow-shaft motor configuration for rapid sample rotation, raster scanning capability, and additional diagnostics are described for heat mitigation. Heat transfer simulations performed using a finite element analysis allow comparison of sample rotation and traditional raster scanning techniques for 100 Hz pulsed laser measurements on vanadium dioxide, a material that undergoes an insulator-to-metal transition at a modest temperature of 340 K. Experimental results are presented confirming that the vanadium dioxide (VO2) sample cannot cool below its phase transition temperature between laser pulses without rapid rotation, in agreement with the simulations. The findings indicate the stringent conditions required to perform rigorous broadband XUV time-resolved absorption measurements on bulk solid-state samples, particularly those with temperature sensitivity, and elucidate a clear methodology to perform them.

High-Resolution Vibration-Rotation Spectroscopy of CO[subscript 2]: Understanding the Boltzmann Distribution

ERIC Educational Resources Information Center

Castle, Karen J.

2007-01-01

In this undergraduate physical chemistry laboratory experiment, students acquire a high-resolution infrared absorption spectrum of carbon dioxide and use their data to show that the rotational-vibrational state populations follow a Boltzmann distribution. Data are acquired with a mid-infrared laser source and infrared detector. Appropriate…

Random-modulation differential absorption lidar based on semiconductor lasers and single photon counting for atmospheric CO2 sensing

NASA Astrophysics Data System (ADS)

Quatrevalet, M.; Ai, X.; Pérez-Serrano, A.; Adamiec, P.; Barbero, J.; Fix, A.; Rarity, J. G.; Ehret, G.; Esquivias, I.

2017-09-01

Carbon dioxide (CO2) is the major anthropogenic greenhouse gas contributing to global warming and climate change. Its concentration has recently reached the 400-ppm mark, representing a more than 40 % increase with respect to its level prior to the industrial revolution.

Frequency Stabilization of DFB Laser Diodes at 1572 nm for Spaceborne Lidar Measurements of CO2

NASA Technical Reports Server (NTRS)

Numata, Kenji; Chen, Jeffrey R.; Wu, Stewart T.; Abshire, James B.; Krainak, Michael A.

2010-01-01

We report a fiber-based, pulsed laser seeder system that rapidly switches among 6 wavelengths across atmospheric carbon dioxide (CO2) absorption line near 1572.3 nm for measurements of global CO2 mixing ratios to 1-ppmv precision. One master DFB laser diode has been frequency-locked to the CO2 line center using a frequency modulation technique, suppressing its peak-to-peak frequency drifts to 0.3 MHz at 0.8 sec averaging time over 72 hours. Four online DFB laser diodes have been offset-locked to the master laser using phase locked loops, with virtually the same sub-MHz absolute accuracy. The 6 lasers were externally modulated and then combined to produce the measurement pulse train.

Measurement of Carbon Dioxide Column via Space Borne Laser Absorption

NASA Technical Reports Server (NTRS)

Heaps, WIlliam S.

2007-01-01

In order to better understand the budget of carbon dioxide in the Earth's atmosphere it is necessary to develop a global high precision understanding of the carbon dioxide column. In order to uncover the 'missing sink that is responsible for the large discrepancies in the budget as we presently understand it calculation has indicated that measurement accuracy on the order of 1 ppm is necessary. Because typical column average CO2 has now reached 380 ppm this represents a precision on the order of .25% for these column measurements. No species has ever been measured from space at such a precision. In recognition of the importance of understanding the CO2 budget in order to evaluate its impact on global warming the National Research Council in its decadal survey report to NASA recommended planning for a laser based total CO2 mapping mission in the near future. The extreme measurement accuracy requirements on this mission places very strong requirements on the laser system used for the measurement. This work presents an analysis of the characteristics necessary in a laser system used to make this measurement. Consideration is given to the temperature dependence, pressure broadening, and pressure shift of the CO2 lines themselves and how these impact the laser system characteristics Several systems for meeting these requirements that are under investigation at various institutions in the US as well as Europe will be discussed.

Development of an Eye-Safe Micro-Pulse Differential Absorption Lidar (DIAL) for Carbon Dioxide Profilings

NASA Astrophysics Data System (ADS)

Johnson, W.; Repasky, K. S.; Nehrir, A. R.; Carlsten, J.

2011-12-01

A differential absorption lidar (DIAL) for monitoring carbon dioxide (CO2) is under development at Montana State University using commercially available parts. Two distributed feedback (DFB) lasers, one at the on-line wavelength and one at the off-line wavelength are used to injection seed a fiber amplifier. The DIAL operates in the 1.57 micron carbon dioxide absorption band at an on-line wavelength of 1.5714060 microns. The laser transmitter produces 40 μJ pulses with a pulse duration of 1 μs and a pulse repetition frequency of 20 kHz. The scattered light from the laser transmitter is collected using a 28 cm diameter Schmidt-Cassegrain telescope. The light collected by the telescope is collimated and then filtered using a 0.8 nm FWHM narrowband interference filter. After the optical filter, the light is coupled into a multimode optical fiber with a 1000 μm core diameter. The output from the optical fiber is coupled into a photomultiplier tube (PMT) used to monitor the return signal. The analog output from the PMT is next incident on a discriminator producing TTL logic pulses for photon counting. The output from the PMT and discriminator is monitored using a multichannel scalar card allowing the counting of the TTL pulses as a function of range. Data from the DIAL instrument is collected in the following manner. The fiber amplifier is injection seeded first with the on-line DFB laser. The return signal as a function of range is integrated using the multichannel scalar for a user defined time, typically set at 6 s. The off-line DFB laser is then used to injection seed the fiber amplifier and the process is repeated. This process is repeated for a user defined period. The CO2 concentration as a function of range is calculated using the on-line and off-line return signals with the DIAL equation. A comparison of the CO2 concentration measured using the DIAL instrument at 1.5 km and a Li-Cor LI-820 in situ sensor located at 1.5 km from the DIAL over a 2.5 hour period indicate that the CO2 DIAL has an accuracy of ±20 parts per million (PPM).

A novel method of carbon dioxide clumped isotope analysis with tunable infra-red laser direct absorption spectroscopy

NASA Astrophysics Data System (ADS)

Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

2016-04-01

Precise clumped isotopes analysis of carbon dioxide opens up new horizons of atmospheric and biogeochemical research. Recent advances in laser and spectroscopic techniques provides us necessary instrumentation to access extremely low sub-permill variations of multiply-substituted isotopologues. We present an advanced analysis method of carbon dioxide clumped isotopes using direct absorption spectroscopy. Our assessments predict the ultimate precision of the new method on the sub-permill level comparable to state of the art mass spectrometry. Among the most auspicious intrinsic properties of this method we highlight genuine Δ16O13C18O and Δ16O13C18O measurements without isobaric interference, measurement cycle duration of several minutes versus hours for mass spectrometric analysis, reduced sample size of ˜ 10 μmol and high flexibility, allowing us to perform in-situ measurements. The pilot version of the instrument is being developed in an international collaboration framework between Heidelberg University, Germany and Pierre and Marie Curie University, Paris, France. It employs two continuous interband quantum cascade lasers tuned at 4.439 μm and 4.329 μm to measure doubly ( 16O13C18O, 16O13C17O) and singly ( 16O12C16O, 16O13C16O, 16O12C17O, 16O12C18O) substituted isotopologues, respectively. Two identical Herriot cells are filled with dry pure CO2 sample and reference gas at working pressure of 1 - 10 mbar. Cells provide optical path lengths of ˜ 17 m for the laser tuned at doubly substituted isotopologues lines and use a single pass for the laser tuned at the stronger lines of singly substituted isotopologues. Light outside of the gas cells is coupled into optical fiber to avoid absorption by ambient air CO2. Simulations predict sub-permill precision at working pressure of 1 mbar and room temperature stabilised at the ±10 mK level. Our prime target is to apply the proposed method for continuous in-situ analysis of CO2. We are foreseeing potential applications to the following environmental issues: assessments of distinct sources of atmospheric CO2, temperature reconstructions from terrestrial and marine archives, extra-terrestrial atmosphere studies, etc.

Development and Deployment of a Compact Eye-Safe Scanning Differential absorption Lidar (DIAL) for Spatial Mapping of Carbon Dioxide for Monitoring/Verification/Accounting at Geologic Sequestration Sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Repasky, Kevin

2014-03-31

A scanning differential absorption lidar (DIAL) instrument for monitoring carbon dioxide has been developed. The laser transmitter uses two tunable discrete mode laser diodes (DMLD) operating in the continuous wave (cw) mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto- optic modulator (AOM) is used to generate a pulse train used to injection seed an erbium doped fiber amplifier (EDFA) to produce eye-safe laser pulses with maximum pulse energies of 66more » {micro}J, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 {micro}m. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photo-multiplier tube (PMT) module operating in the photon counting mode. The DIAL instrument has been operated from a laboratory environment on the campus of Montana State University, at the Zero Emission Research Technology (ZERT) field site located in the agricultural research area on the western end of the Montana State University campus, and at the Big Sky Carbon Sequestration Partnership site located in north-central Montana. DIAL data has been collected and profiles have been validated using a co-located Licor LI-820 Gas Analyzer point sensor.« less

2-Micron Triple-Pulse Integrated Path Differential Absorption Lidar Development for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong

2016-01-01

For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

Laser spectrometer for CO2 clumped isotope analysis

NASA Astrophysics Data System (ADS)

Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

2017-04-01

Carbon dioxide clumped isotope thermometry has proven to be a reliable method for biogeochemical and atmospheric research. We present a new laser spectroscopic instrument for doubly-substituted isotopologues analysis. In contrast to a conventional isotope ratio mass spectrometry (IRMS), tunable laser direct absorption spectroscopy (TLDAS) has the advantage of isotopologue-specific determination free of isobaric interferences. Tunable infrared laser based spectrometer for clumped isotope analysis is being developed in collaboration between Heidelberg University, Germany, and LERMA-IPSL, CNRS, France. The instrument employs two continuous intraband cascade lasers (ICL) tuned at 4439 and 4329 nm. The spectral windows covered by the lasers contain absorption lines of the six most abundant CO2 isotopologues, including the two doubly substituted species 16O13C18O and 16O13C17O, and all singly substituted isotopologues with 13C, 18O and 17O. A Herriott-type multi-pass cell provides two different absorption pathlengths to compensate the abundance difference between singly- and doubly-substituted isotopologues. We have reached the sub-permill precision required for clumped isotope measurements within the integration time of several seconds. The test version of the instrument demonstrates a performance comparable to state of the art IRMS. We highlight the following features of the instrument that are strong advantages compared to conventional mass spectrometry: measurement cycle in the minute range, simplified sample preparation routine, table-top layout with a potential for in-situ applications.

Lidar detection of carbon dioxide in volcanic plumes

NASA Astrophysics Data System (ADS)

Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Maio, Giovanni; Del Franco, Mario; Aiuppa, Alessandro

2015-06-01

Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. Two differential absorption lidar instruments will be presented in this paper: BILLI (BrIdge voLcanic LIdar), based on injection seeded Nd:YAG laser, double grating dye laser, difference frequency mixing (DFM) and optical parametric amplifier (OPA), and VULLI (VULcamed Lidar), based on injection seeded Nd:YAG laser and optical parametric oscillator (OPO). The first one is funded by the ERC (European Research Council) project BRIDGE and the second one by the ERDF (European Regional Development Fund) project VULCAMED. While VULLI has not yet been tested in a volcanic site, BILLI scanned the gas emitted by Pozzuoli Solfatara (Campi Flegrei volcanic area, Naples, Italy) during a field campaign carried out from 13 to 17 October 2014. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater area. Lidar measurements were in good agreement with well-established techniques, based on different operating principles. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar, representing the first direct measurement of this kind ever performed on an active volcano and showing the high potential of laser remote sensing in geophysical research.

Measurement of nitrogen dioxide in cigarette smoke using quantum cascade tunable infrared laser differential absorption spectroscopy (TILDAS)

NASA Astrophysics Data System (ADS)

Shorter, Joanne H.; Nelson, David D.; Zahniser, Mark S.; Parrish, Milton E.; Crawford, Danielle R.; Gee, Diane L.

2006-04-01

Although nitrogen dioxide (NO 2) has been previously reported to be present in cigarette smoke, the concentration estimates were derived from kinetic calculations or from measurements of aged smoke, where NO 2 was formed some time after the puff was taken. The objective of this work was to use tunable infrared laser differential absorption spectroscopy (TILDAS) equipped with a quantum cascade (QC) laser to determine if NO 2 could be detected and quantified in a fresh puff of cigarette smoke. A temporal resolution of ˜0.16 s allowed measurements to be taken directly as the NO 2 was formed during the puff. Sidestream cigarette smoke was sampled to determine if NO 2 could be detected using TILDAS. Experiments were conducted using 2R4F Kentucky Reference cigarettes with and without a Cambridge filter pad. NO 2 was detected only in the lighting puff of whole mainstream smoke (without a Cambridge filter pad), with no NO 2 detected in the subsequent puffs. The measurement precision was ˜1.0 ppbV Hz -1/2, which allows a detection limit of ˜0.2 ng in a 35 ml puff volume. More NO 2 was generated in the lighting puff using a match or blue flame lighter (29 ± 21 ng) than when using an electric lighter (9 ± 3 ng). In the presence of a Cambridge filter pad, NO 2 was observed in the gas phase mainstream smoke for every puff (total of 200 ± 30 ng/cigarette) and is most likely due to smoke chemistry taking place on the Cambridge filter pad during the smoke collection process. Nitrogen dioxide was observed continuously in the sidestream smoke starting with the lighting puff.

Development of an advanced Two-Micron triple-pulse IPDA lidar for carbon dioxide and water vapor measurements

NASA Astrophysics Data System (ADS)

Petros, Mulugeta; Refaat, Tamer F.; Singh, Upendra N.; Yu, Jirong; Antill, Charles; Remus, Ruben; Taylor, Bryant D.; Wong, Teh-Hwa; Reithmaier, Karl; Lee, Jane; Ismail, Syed; Davis, Kenneth J.

2018-04-01

An advanced airborne triple-pulse 2-μm integrated path differential absorption (IPDA) lidar is under development at NASA Langley Research Center that targets both carbon dioxide (CO2) and water vapor (H2O) measurements simultaneously and independently. This lidar is an upgrade to the successfully demonstrated CO2 2-μm double-pulse IPDA. Upgrades include high-energy, highrepetition rate 2-μm triple-pulse laser transmitter, innovative wavelength control and advanced HgCdTe (MCT) electron-initiated avalanche photodiode detection system. Ground testing and airborne validation plans are presented.

Space-based active optical remote sensing of carbon dioxide column using high-energy two-micron pulsed ipda lidar

NASA Astrophysics Data System (ADS)

Singh, Upendra N.; Refaat, Tamer F.; Ismail, Syed; Petros, Mulugeta; Davis, Kenneth J.; Kawa, Stephan R.; Menzies, Robert T.

2018-04-01

Modeling of a space-based high-energy 2-μm triple-pulse Integrated Path Differential Absorption (IPDA) lidar was conducted to demonstrate carbon dioxide (CO2) measurement capability and to evaluate random and systematic errors. A high pulse energy laser and an advanced MCT e-APD detector were incorporated in this model. Projected performance shows 0.5 ppm precision and 0.3 ppm bias in low-tropospheric column CO2 mixing ratio measurements from space for 10 second signal averaging over Railroad Valley (RRV) reference surface.

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

Tunable diode lasers application for fully automated absolute measurements of CO and CO2 concentrations in human breath

NASA Astrophysics Data System (ADS)

Moskalenko, Konstantin L.; Sobolev, Nikolai V.; Adamovskay, Inna A.; Stepanov, Eugene V.; Nadezhdinskii, Alexander I.; McKenna-Lawlor, Susan

1994-01-01

Measurements of carbon monoxide and carbon dioxide concentrations by registration of high resolution absorption spectra are described. A fully automated diode laser system developed to simultaneously measure CO and CO2, with sensitivity for CO up to 50 ppb and CO2 up to 0.1 vol%, is described. Calculation of CO and CO2 concentrations was carried out on the base of a priori date on strength and broadening coefficients of detected absorption lines. Test procedures of such diode laser systems are described. Possible reasons affected on accuracy and reliability of obtained data (e.g., the value of diode lasers spontaneous radiation, the stability of CO content in a cell, etc.) for absolute and relative calibration procedure are discussed. The physiological level of CO concentration in the breath of non smokers and smokers under different ambient conditions of CO concentrations in the atmosphere (in Moscow and in Maynooth) are compared. Recent results on statistical studies of the behavior of CO concentrations as a function of breath holding time are represented.

Gas sensing using wavelength modulation spectroscopy

NASA Astrophysics Data System (ADS)

Viveiros, D.; Ribeiro, J.; Flores, D.; Ferreira, J.; Frazao, O.; Santos, J. L.; Baptista, J. M.

2014-08-01

An experimental setup has been developed for different gas species sensing based on the Wavelength Modulation Spectroscopy (WMS) principle. The target is the measurement of ammonia, carbon dioxide and methane concentrations. The WMS is a rather sensitive technique for detecting atomic/molecular species presenting the advantage that it can be used in the near-infrared region using optical telecommunications technology. In this technique, the laser wavelength and intensity are modulated applying a sine wave signal through the injection current, which allows the shift of the detection bandwidth to higher frequencies where laser intensity noise is reduced. The wavelength modulated laser light is tuned to the absorption line of the target gas and the absorption information can be retrieved by means of synchronous detection using a lock-in amplifier, where the amplitude of the second harmonic of the laser modulation frequency is proportional to the gas concentration. The amplitude of the second harmonic is normalised by the average laser intensity and detector gain through a LabVIEW® application, where the main advantage of normalising is that the effects of laser output power fluctuations and any variations in laser transmission, or optical-electrical detector gain are eliminated. Two types of sensing heads based on free space light propagation with different optical path length were used, permitting redundancy operation and technology validation.

Pulsed 2-micron Laser Transmitter For Carbon Dioxide Sensing From Space

NASA Astrophysics Data System (ADS)

Singh, U. N.; Yu, J.; Bai, Y.; Petros, M.

2011-12-01

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. Studies of the carbon cycle are limited by the tools available to precisely measure CO2 concentrations by remote sensing. Active sensing, using the Integrated Path Differential Absorption (IPDA) approach, permits measurements day and night, at all latitudes and seasons. The development of a high pulse energy 2-μm laser transmitter for high-precision CO2 measurements from space leverages years of NASA investment in solid-state laser technology. Under NASA Laser Risk Reduction Program, funded by Earth Science Technology Office, researchers at NASA Langley Research Center developed an injection seeded, high repetition rate, Q-switched Ho:YLF laser transmitter for CO2 Differential Absorption Lidar/IPDA (profile/column) measurements from ground and airborne platforms. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. NASA LaRC's 2-micron pulsed laser transmitter possesses advantages over current passive and CW active sensors. First, the pulsed format provides a built-in means for determining range to the scattering target and effectively filtering out the scattering from thin clouds and aerosols, thus eliminating a source of measurement bias. Second, by concentrating the laser energy into a pulse, sufficient backscatter signal strength can be obtained from aerosol scattering rather than relying on a hard target at a known distance. Third, the absorption line at the 2.05 μm band is ideally suited for the CO2 concentration measurement. In particular, the weighting function of 2 μm is optimum for measurement in the lower troposphere where the sources and sinks of CO2 are located. The planned laser transmitter development will lead to a Tm:Fiber pumped Ho:YLF laser transmitter capable of delivering 65 mJ at 50 Hz at on-line wavelength and 50 mJ at 50 Hz at off-line wavelength. The planned laser technology development and performance capabilities are a major step forward in the laser transmitter requirements called out in recent comprehensive system studies, e.g., the European Space Agency (ESA) exploration mission studies, A-SCOPE, for future CO2 column density measurements from space. The planned laser technology development is relevant to NASA's earth science priorities, such as NASA ASCENDS mission for space-based CO2 column density measurements. This presentation will provide an overview of the current status of laser transmitter development and describe future technology development to meet the transmitter requirement for a space-based column averaged measurement of CO2 concentration.

New Broadband LIDAR for Greenhouse Carbon Dioxide Gas Sensing in the Earth's Atmosphere

NASA Technical Reports Server (NTRS)

Georgieva, Elena; Heaps, William S.; Huang,Wen

2011-01-01

We present demonstration of a novel broadband lidar technique capable of dealing with the atmospherically induced variations in CO2 absorption using a Fabry-Perot based detector and a broadband laser. The Fabry-Perot solid etalon in the receiver part is tuned to match the wavelength of several CO2 absorption lines simultaneously. The broadband technique tremendously reduces the requirement for source wavelength stability, instead putting this responsibility on the Fabry- Perot based receiver. The instrument technology we are developing has a clear pathway to space and realistic potential to become a robust, low risk space measurement system.

Multicomponent Breath Analysis With Infrared Absorption Using Room-Temperature Quantum Cascade Lasers

PubMed Central

Shorter, Joanne H.; Nelson, David D.; Barry McManus, J.; Zahniser, Mark S.; Milton, Donald K.

2010-01-01

Breath analysis is a powerful noninvasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO) and carbon monoxide (CO) are markers of airway inflammation and can indicate the extent of respiratory diseases. We have developed a compact fast response laser system for analysis of multiple gases by infrared absorption. The instrument uses room temperature quantum cascade lasers to simultaneously measure NO, CO, carbon dioxide (CO2) and nitrous oxide (N2O) in exhaled breath. Four breath flow rates are employed to explore their exchange dynamics in the lungs and airways. We obtain 1-s detection precisions of 0.5-0.8 parts-per-billion (ppb) for NO, CO, and N2O with an instrument response time of less than 1 s. The breath analysis system has been demonstrated in a preliminary study of volunteers. It is currently deployed in a trial clinical study. PMID:20697459

Advancements in quantum cascade laser-based infrared microscopy of aqueous media.

PubMed

Haase, K; Kröger-Lui, N; Pucci, A; Schönhals, A; Petrich, W

2016-06-23

The large mid-infrared absorption coefficient of water frequently hampers the rapid, label-free infrared microscopy of biological objects in their natural aqueous environment. However, the high spectral power density of quantum cascade lasers is shifting this limitation such that mid-infrared absorbance images can be acquired in situ within signal-to-noise ratios of up to 100. Even at sample thicknesses well above 50 μm, signal-to-noise ratios above 10 are readily achieved. The quantum cascade laser-based microspectroscopy of aqueous media is exemplified by imaging an aqueous yeast solution and quantifying glucose consumption, ethanol generation as well as the production of carbon dioxide gas during fermentation.

Quantification of the dynamic changes in the absorption coefficient of liquid water at erbium:YAG and carbon dioxide laser wavelengths

NASA Astrophysics Data System (ADS)

Shori, Ramesh K.

The interaction of high-intensity, short-pulsed radiation with liquid water results in dynamic changes in the optical absorption coefficient of water. These changes and their implications, as related to mid-infrared laser ablation of tissue, were not investigated until the late 1980's and early 1990's. Classical models of absorption and heating do not explain the dynamic, non-linear changes in water. The objective of the present work was to quantify the dynamic changes in the absorption coefficient of liquid water as a function of incident energy at three clinically relevant infrared wavelengths (λ = 2.94, 9.6, 10.6 μm). To investigate the changes in the absorption spectrum of water in the 3-μm band, a stable, high-energy Q- switched Er:YAG laser emitting 2.94-μm radiation in a near-perfect TEMoo spatial beam profile was developed. Key to the development of this laser was careful attention to the gain medium, optical pump system, system optics, and the thermal system. The final system design was capable of emitting 110 mJ/pulse at of 2-4 Hz with a lamp lifetime exceeding 12 million pulses The laser was used in two sets of experiments in order to quantify the above changes. First, the laser was used to measure the velocity of the shock front produced by vaporizing a gelatin-based tissue phantom. The measured shock velocity was related to the optical energy absorbed by the tissue phantom and the absorption coefficient, based on the pressure relationships derived using a 1-D piston model for an expanding plume. The shock front velocity measurements indicate that the absorption coefficient is constant for incident fluences less than 20 J/cm2, a result consistent with transmission data. For higher fluences, the data indicate a decrease in the absorption coefficient, which is again consistent with transmission data. Quantification of the absorption coefficient can, however, not be made without violating assumptions that form the basis for the 1-D piston model. Second, the laser was used to measure the optical transmission across water layers of known thicknesses. The data were used to develop a Dynamic Saturable Absorption (DSA) model to predict the dynamic changes in the absorption coefficient of water as a function of incident energy. The DSA model, based in part upon the homogeneous broadening of an atomic transition in a laser gain medium, accurately predicts the absorption coefficient of water over a wide range of incident fluences. One sees saturation of the absorption at both high and low fluence with a monotonic decrease in absorption with increasing fluence. Transmission measurements were also made at 9.6 and 10.6 μm using a TEA CO2 laser. The data show essentially no change in the absorption coefficient as the fluence is varied. The results from the experiments make a significant contribution towards an understanding of the relationship among the dynamic optical properties of water and clinically relevant properties such as ablation rate and residual thermal damage.

Ultrasensitive, real-time trace gas detection using a high-power, multimode diode laser and cavity ringdown spectroscopy.

PubMed

Karpf, Andreas; Qiao, Yuhao; Rao, Gottipaty N

2016-06-01

We present a simplified cavity ringdown (CRD) trace gas detection technique that is insensitive to vibration, and capable of extremely sensitive, real-time absorption measurements. A high-power, multimode Fabry-Perot (FP) diode laser with a broad wavelength range (Δλ_laser∼0.6  nm) is used to excite a large number of cavity modes, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. When detecting molecular species with broad absorption features (Δλ_absorption≫Δλ_laser), the laser's broad linewidth removes the need for precision wavelength stabilization. The laser's power and broad linewidth allow the use of on-axis cavity alignment, improving the signal-to-noise ratio while maintaining its vibration insensitivity. The use of an FP diode laser has the added advantages of being inexpensive, compact, and insensitive to vibration. The technique was demonstrated using a 1.1 W (λ=400  nm) diode laser to measure low concentrations of nitrogen dioxide (NO₂) in zero air. A sensitivity of 38 parts in 10¹² (ppt) was achieved using an integration time of 128 ms; for single-shot detection, 530 ppt sensitivity was demonstrated with a measurement time of 60 μs, which opens the door to sensitive measurements with extremely high temporal resolution; to the best of our knowledge, these are the highest speed measurements of NO₂ concentration using CRD spectroscopy. The reduced susceptibility to vibration was demonstrated by introducing small vibrations into the apparatus and observing that there was no measurable effect on the sensitivity of detection.

Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

2015-01-01

The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-micron laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-micron integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

Nonlinear optical properties of thick composite media with vanadium dioxide nanoparticles. I. Self-defocusing of radiation in the visible and near-IR regions

NASA Astrophysics Data System (ADS)

Ostrosablina, A. A.; Sidorov, A. I.

2005-07-01

This paper presents the experimental and theoretical results of a study of the interaction of pulsed laser radiation with thick composite media containing nanoparticles of vanadium dioxide (VO2). It establishes that the reversible semiconductor-metal phase transition that occurs in VO2 nanoparticles under the action of radiation can produce self-defocusing of radiation in the visible and near-IR regions because of the formation of a photoinduced dynamic lens. An analysis is carried out of how the radiation intensity affects the dynamics of these processes. It is shown that photoinduced absorption and scattering play a role in forming the nonlinear optical response.

Short-pulse laser interactions with disordered materials and liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phinney, L.M.; Goldman, C.H.; Longtin, J.P.

High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regimemore » in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.« less

New approach of Co2 laser use in plastic and dermo-cosmetic surgery

NASA Astrophysics Data System (ADS)

Trelles, Mario A.; Trelles, O. R.; Romero, L. F.

1996-01-01

Laboratory and mathematical skin examination has played an important role in defining the clinical usefulness and limitations of laser, developing concepts and techniques that have further improved the effectiveness of laser treatment. In addition to this, new technological developments over the years, have helped define the specificity of laser-tissue interaction. Instantaneous conversion by thermal energy of water in a liquid state to a gaseous state when irradiation of skin is done by high power density carbon dioxide laser in short pulses, occurs so quickly that there is minimal thermal conduction to the adjacent tissues structures. The zone of thermal injury could be minimized to the order of only 50 micron thick. In spite of the limited effects of heat conduction, coagulation in vessels can be obtained as well, since small blood vessels are immediately sealed by the laser. Modern carbon dioxide systems can be programmed and make it possible to reproduce shots precisely to vaporize identically thin layers of soft tissue, since absorption by intracellular water limits the depth of penetration. Moreover, collimated handpieces make it possible to deliver a fixed beam diameter and a constant power density as the handpiece is steadily moved over lesions situated on uneven facial contours. The use of large spot sizes gives a more uniform vaporization thus damaging adjacent tissues to a lesser degree, but enlarging of the spot size requires higher energy levels per pulse so that the whole surface can reach a sufficiently high fluence for clean vaporization to take place. For this to be achieved, the fluence required is about 4 - 5 J/cm2 and so UltraPulseR carbon dioxide laser with a 3 mm spot size may be operated with optimal parameters for clean ablation. The resulting surface, covered by dry debris, can be removed by gently scrubbing to avoid thermal build-up, otherwise this remaining tissue can act as a refracting surface as the practical absence of water content means that the carbon dioxide laser light is not efficiently absorbed. This process is repeated layer-by-layer using the same laser parameters until all remaining abnormal tissue has been grossly removed. Utilized as a chain of rapid, short (approx. 1 ms) pulses, with high peak power, tissue can be effectively eliminated, taking advantage of the concept of the known thermal relaxation time of soft tissue. The current laser systems which are built according to the new concept of high technology based upon the knowledge of laser tissue interaction, known as UltraPulsedR Carbon Dioxide Laser, are capable of precise ablation and also of being used in cosmetically sensitive areas with minimal thermal damage. Although the precise clinical role for this laser has yet to be accurately defined, the potential benefits offered by its use appear to be substantial.

Research on the trace detection of carbon dioxide gas and modulation parameter optimization based on the TDLAS technology

NASA Astrophysics Data System (ADS)

Zhao, Peng; Tao, Jun; Yu, Chang-rui; Li, Ye

2014-02-01

Based on the technology of tunable diode laser absorption spectroscopy, modulation of the center wavelength of 2004 nm distributed feedback laser diode at a room-temperature, the second harmonic amplitude of CO2 at 2004nm can be obtained. The CO2 concentration can be calculated via the Beer-Lambert law. Sinusoidal modulation parameter is an important factor that affects the sensitivity and accuracy of the system, through the research on the relationship between sinusoidal modulation signal frequency, amplitude and Second harmonic linetype, we finally achieve the detection limit of 10ppm under 12 m optical path.

Pseudorandom Noise Code-Based Technique for Thin Cloud Discrimination with CO2 and O2 Absorption Measurements

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudo noise (PN) code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

Airborne Lidar for Simultaneous Measurement of Column CO2 and Water Vapor in the Atmosphere

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Antill, Charles W.; Remus, Ruben; Yu, Jirong

2016-01-01

The 2-micron wavelength region is suitable for atmospheric carbon dioxide (CO2) measurements due to the existence of distinct absorption feathers for the gas at this particular wavelength. For more than 20 years, researchers at NASA Langley Research Center (LaRC) have developed several high-energy and high repetition rate 2-micron pulsed lasers. This paper will provide status and details of an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar. The development of this active optical remote sensing IPDA instrument is targeted for measuring both CO2 and water vapor (H2O) in the atmosphere from an airborne platform. This presentation will focus on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of seed laser locking, wavelength control, receiver telescope, detection system and data acquisition. Future plans for the IPDA lidar system for ground integration, testing and flight validation will also be presented.

Measurement of Trace Water Vapor in a Carbon Dioxide Removal Assembly Product Stream

NASA Technical Reports Server (NTRS)

Wormhoudt, Joda; Shorter, Joanne H.; McManus, J. Barry; Nelson, David D.; Zahniser, Mark S.; Freedman, Andrew; Campbell, Melissa; Chang, Clarence T.; Smith, Frederick D.

2004-01-01

The International Space Station Carbon Dioxide Removal Assembly (CDRA) uses regenerable adsorption technology to remove carbon dioxide (COP) from cabin air. Product water vapor measurements from a CDRA test bed at the NASA Marshall Space Flight Center were made using a tunable infrared diode laser differential absorption spectrometer (TILDAS) provided by NASA Glenn Research Center. The TILDAS instrument exceeded all the test specifications, including sensitivity, dynamic range, time response, and unattended operation. During the COP desorption phase, water vapor concentrations as low as 5 ppmv were observed near the peak of CO2 evolution, rising to levels of approx. 40 ppmv at the end of a cycle. Periods of high water concentration (>100 ppmv) were detected and shown to be caused by an experimental artifact. Measured values of total water vapor evolved during a single desorption cycle were as low as 1 mg.

Hydrazine Detection with a Tunable Diode Laser Spectrometer

NASA Technical Reports Server (NTRS)

Houseman, John; Webster, C. R.; May, R. D.; Anderson, M. S.; Margolis, J. S.; Jackson, Julie R.; Brown, Pamela R.

1999-01-01

Several instruments have been developed to measure low concentrations of hydrazine but none completely meet the sensitivity requirements while satisfying additional criteria such as quick response, stable calibration, interference free operation, online operation, reasonable cost, etc. A brief review is presented of the current technology including the electrochemical cell, the ion mobility spectrometer, the mass spectrometer, and the gas chromatograph. A review of the advantages and disadvantages of these instruments are presented here. The review also includes commercially unavailable technology such as the electronic nose and the Tunable Diode Laser (TDL) IR Spectrometer. It was found that the TDL could meet the majority of these criteria including fast response, minimum maintenance, portability, and reasonable cost. An experiment was conducted to demonstrate the feasibility of such a system using an existing (non-portable) instrument. A lead-salt tunable diode laser, cooled to 85 degrees Kelvin was used to record direct absorption and second-derivative spectra of Hydrazine at several pressures to study the sensitivity to low levels of Hydrazine. Spectra of NH3 and CO2 were used for wavelength identification of the scanned region. With a pathlength of 80 m, detection sensitivities of about 1 ppb were achieved for hydrazine in dry nitrogen at a cell pressure of 100 mbar. For spectroscopic detection of Hydrazine, spectral regions including strong Ammonia or Carbon Dioxide lines must be avoided. Strong Hydrazine absorption features were identified at 940/cm showing minimal contribution from Ammonia interferences as suitable candidates for Hydrazine gas detection. For the studies reported here, the particular laser diode could only cover the narrow regions near 962/cm and 965/cm where strong Ammonia interferences were expected. However, the high resolution (0.001/cm) of the TDL spectrometer allowed individual lines of Hydrazine to be identified away from interferences from either Ammonia or Carbon Dioxide, especially at lower pressures. A Hydrazine line was identified at 961.75/cm which was free from Ammonia absorption and would be suitable to monitor hydrazine levels. This paper also shows data on the degradation of the detectivity of Hydrazine with increasing pressure. Several design options for a portable unit are presented, including designs with near IR and Quantum Cascade laser components which do not require liquid nitrogen cooling.

Recent advances in the study of the UO2-PuO2 phase diagram at high temperatures

NASA Astrophysics Data System (ADS)

Böhler, R.; Welland, M. J.; Prieur, D.; Cakir, P.; Vitova, T.; Pruessmann, T.; Pidchenko, I.; Hennig, C.; Guéneau, C.; Konings, R. J. M.; Manara, D.

2014-05-01

Recently, novel container-less laser heating experimental data have been published on the melting behaviour of pure PuO2 and PuO2-rich compositions in the uranium dioxide-plutonium dioxide system. Such data showed that previous data obtained by more traditional furnace heating techniques were affected by extensive interaction between the sample and its containment. It is therefore paramount to check whether data so far used by nuclear engineers for the uranium-rich side of the pseudo-binary dioxide system can be confirmed or not. In the present work, new data are presented both in the UO2-rich part of the phase diagram, most interesting for the uranium-plutonium dioxide based nuclear fuel safety, and in the PuO2 side. The new results confirm earlier furnace heating data in the uranium-dioxide rich part of the phase diagram, and more recent laser-heating data in the plutonium-dioxide side of the system. As a consequence, it is also confirmed that a minimum melting point must exist in the UO2-PuO2 system, at a composition between x(PuO2) = 0.4 and x(PuO2) = 0.7 and 2900 K ⩽ T ⩽ 3000 K. Taking into account that, especially at high temperature, oxygen chemistry has an effect on the reported phase boundary uncertainties, the current results should be projected in the ternary U-Pu-O system. This aspect has been extensively studied here by X-ray diffraction and X-ray absorption spectroscopy. The current results suggest that uncertainty bands related to oxygen behaviour in the equilibria between condensed phases and gas should not significantly affect the qualitative trend of the current solid-liquid phase boundaries.

TDLAS a laser diode sensor for the in situ monitoring of H2O, CO2 and their isotopes in the Martian atmosphere

NASA Astrophysics Data System (ADS)

Le Barbu, T.; Vinogradov, I.; Durry, G.; Korablev, O.; Chassefière, E.; Bertaux, J.-L.

2006-01-01

Within the framework of Pasteur-Exomars, we have proposed to measure in situ water vapor (H2O, HDO, H218O, H217O) and carbon dioxide (CO2, 13C16O2, 16O12C18O, 16O12C17O) isotopes and also CO, CH4 and N2O by absorption spectroscopy using near infrared laser diodes. The Service d’Aéronomie has a relevant experience in trace-gas detection with laser diodes. We have developed, with the support of the CNES and the CNRS, the SDLA diode laser spectrometer to measure in situ H2O (at 1.39 μm), CH4 (1.65 μm) and CO2 (at 1.60 μm) in the middle atmosphere from stratospheric balloons. The concentrations are obtained with a precision error of a few percent and with a high temporal resolution that ranges from 10 ms to 1 s. The developed laser probing technique should be also highly efficient to study the Martian atmosphere as there are much higher amounts of water vapor and carbon dioxide in the Martian atmosphere than in the lower stratosphere (H2O: 200 ppmv at 6 hPa on Mars, 5 ppmv at 10 hPa in the low stratosphere (LS); CO2 95% on Mars, 360 ppmv in the LS). Hence, we propose to adapt the laser probing technique to the Martian atmosphere. The main objectives are to determine water vapor and carbon dioxide fluxes and to study boundary layer properties. The sensor will provide in situ daily, diurnally resolved measurements of near-surface H2O and CO2 concentrations over seasonal time scales. The additional isotopic measurements will provide quantitative constraints on the evolution of atmospheric composition and on the history of water on Mars.

MASERATI: a RocketBorne tunable diode laser absorption spectrometer.

PubMed

Lübken, F J; Dingler, F; von Lucke, H; Anders, J; Riedel, W J; Wolf, H

1999-09-01

The MASERATI (middle-atmosphere spectrometric experiment on rockets for analysis of trace-gas influences) instrument is, to our knowledge, the first rocket-borne tunable diode laser absorption spectrometer that was developed for in situ measurements of trace gases in the middle atmosphere. Infrared absorption spectroscopy with lead salt diode lasers is applied to measure water vapor and carbon dioxide in the altitude range from 50 to 90 km and 120 km, respectively. The laser beams are directed into an open multiple-pass absorption setup (total path length 31.7 m) that is mounted on top of a sounding rocket and that is directly exposed to ambient air. The two species are sampled alternately with a sampling time of 7.37 ms, each corresponding to an altitude resolution of approximately 15 m. Frequency-modulation and lock-in techniques are used to achieve high sensitivity. Tests in the laboratory have shown that the instrument is capable of detecting a very small relative absorbance of 10(-4)-10(-5) when integrating spectra for 1 s. The instrument is designed and qualified to resist the mechanical stress occurring during the start of a sounding rocket and to be operational during the cruising phase of the flight when accelerations are very small. Two almost identical versions of the MASERATI instrument were built and were launched on sounding rockets from the Andøya Rocket Range (69 degrees N) in northern Norway on 12 October 1997 and on 31 January 1998. The good technical performance of the instruments during these flights has demonstrated that MASERATI is indeed a new suitable tool to perform rocket-borne in situ measurements in the upper atmosphere.

Peculiarities of light absorption by spherical microcapsules

NASA Astrophysics Data System (ADS)

Geints, Yurii E.; Panina, Ekaterina K.; Zemlyanov, Alexander A.

2018-04-01

Optical radiation absorption in the poly-layer spherical microparticles simulating the inorganic/organic polyshell absorbing microcapsules is considered. With the aim of the finite-difference time-domain technique, the spatial distribution of the absorbed light power in microcapsules of various sizes and internal structure is numerically calculated. For the purpose of light absorption enhancement, we have engineered the optimal structure of a capsule consisting of a strong-refracting transparent outer coating and an absorbing layer which covers a liquid core. The proposed microcapsule prototype provides for a manifold increase in the absorbed light power density in comparison with the usual single-layer absorbing capsule. We show that for light-wavelengths-scaled microcapsules it is optimal to use a material with the refractive index larger than two as an outer shell, for example, titanium dioxide (TiO2). The highest values of the absorbed power density can be obtained in microcapsules with absorbing shell thickness of approximately a tenth of a laser wavelength. When laser radiation is scattered by a dimer constituted by two identical absorbing microcapsules the absorbed power density can be maximized by the choosing of proper dimer spatial configuration. In the case of strongly absorbing particles, the absorption maximum corresponds to a shift of the capsules to a distance of about their diameter, and in the case of weakly absorbing particles the absorption is maximal when particles are in geometrical shades of each other.

Three Dimensional Reconstruction Algorithm for Imaging Pathophysiological Signals Within Breast Tissue Using Near Infrared Light

DTIC Science & Technology

2006-07-01

of water, gelatin (G2625, Sigma Inc.), India ink (for absorption), and titanium dioxide powder (for scatter) (TiO2, Sigma Inc.) is poured into a mold...R. C., Ference, R. J, Refractive index of some mammalian tissue using a fiber optic cladding method. Applied Optics, 1989. 28(12): p. 2297-2303. 3...scans. The NIR system utilizes six optical wavelengths from 660 to 850 nm using intensity modulated diode lasers nominally working at 100 MHz

2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Bai, Yingxin; Yu, Jirong

2009-01-01

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam size is suitable for high efficiency. For Q-switched operation, the optimal energy extraction relies on the pump intensity, pump volume, and pump duration which is inversely proportion to the repetition rate. CW and Q-switched Ho:YLF lasers with different linear cavity configurations have been designed and demonstrated for a 30 W Tm:fiber pump laser. The CW Ho laser slope efficiency and optical-to-optical efficiencies reach 65% and 55%, respectively. The pulsed laser efficiency depends on the repetition rate. For 1 kHz operation, the optical-to-optical efficiency is 39% when the pump power is 14.5W. Currently, the injection seeding success rate is between 99.4% and 99.95%. After a ten thousand pulses, the standard deviation of the laser frequency jitter is about 3 MHz. It meets the requirements of highly precise CO2 concentration measurement. In conclusion, an injection seeded, high repetition rate, Q-switched Ho:YLF laser has been developed for a coherent CO2 differential absorption lidar. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. It can potentially meet the requirements of the coherent detection of CO2 concentration by a differential absorption lidar technique.

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

NASA Technical Reports Server (NTRS)

Leleux, D. P.; Claps, R.; Chen, W.; Tittel, F. K.; Harman, T. L.

2002-01-01

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. Filter performance is demonstrated to be adaptive to real-time noise and data statistics. Additionally, filter operation is successfully performed with dynamic ranges differing by three orders of magnitude. Details of Kalman filter theory applied to the acquired spectroscopic data are discussed. The effectiveness of this technique is evaluated by performing NH3 and CO2 concentration measurements and utilizing it to monitor varying ammonia and carbon dioxide levels in a bioreactor for water reprocessing, located at the NASA-Johnson Space Center. Results indicate a sensitivity enhancement of six times, in terms of improved minimum detectable absorption by the gas sensor.

High-Speed Multiplexed Spatiotemporally Resolved Measurements of Exhaust Gas Recirculation Dynamics in a Multi-Cylinder Engine Using Laser Absorption Spectroscopy.

PubMed

Yoo, Jihyung; Prikhodko, Vitaly; Parks, James E; Perfetto, Anthony; Geckler, Sam; Partridge, William P

2016-04-01

The need for more environmentally friendly and efficient energy conversion is of paramount importance in developing and designing next-generation internal combustion (IC) engines for transportation applications. One effective solution to reducing emissions of mono-nitrogen oxides (NOx) is exhaust gas recirculation (EGR), which has been widely implemented in modern vehicles. However, cylinder-to-cylinder and cycle-to-cycle variations in the charge-gas uniformity can be a major barrier to optimum EGR implementation on multi-cylinder engines, and can limit performance, stability, and efficiency. Precise knowledge and fine control over the EGR system is therefore crucial, particularly for optimizing advanced engine concepts such as reactivity controlled compression ignition (RCCI). An absorption-based laser diagnostic was developed to study spatiotemporal charge-gas distributions in an IC engine intake manifold in real-time. The laser was tuned to an absorption band of carbon dioxide (CO2), a standard exhaust-gas marker, near 2.7 µm. The sensor was capable of probing four separate measurement locations simultaneously, and independently analyzing EGR fraction at speeds of 5 kHz (1.2 crank-angle degree (CAD) at 1 k RPM) or faster with high accuracy. The probes were used to study spatiotemporal EGR non-uniformities in the intake manifold and ultimately promote the development of more efficient and higher performance engines. © The Author(s) 2016.

21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

Code of Federal Regulations, 2011 CFR

2011-04-01

... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear, nose...

21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

Code of Federal Regulations, 2010 CFR

2010-04-01

... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear, nose...

21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

Code of Federal Regulations, 2013 CFR

2013-04-01

... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear, nose...

21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

Code of Federal Regulations, 2012 CFR

2012-04-01

... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear, nose...

21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

Code of Federal Regulations, 2014 CFR

2014-04-01

... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear, nose...

Ablation of dermal and mucosal lesions with a new CO2 laser application system

NASA Astrophysics Data System (ADS)

Jovanovic, Sergije; Sedlmaier, Benedikt W.; Fuehrer, Ariane

1997-05-01

Laser treatment of skin changes has become common practice in recent years. The high absorption of the wavelength of the carbon-dioxide laser (10600 nm) is responsible for its low penetration depth in biological tissue. Shortening the exposure time minimizes thermic side effects such as carbonization and coagulation. This effect can be achieved with the SilkTouchTM scanner 767, since the focused laser beam is moved over a defined area by rapidly rotating mirrors. This enables controlled and reliable removal of certain dermal lesions, particularly hypertrophic scars, scars after common acne, wrinkles, rhinophyma and benign neoplasms like verruca vulgaris. Cosmetically favorable reepithelialization of the lasered surfaces results within a very short period of time. Benign mucosal changes of the upper aerodigestive tract can also be treated. Ablation is less traumatic for papillomas, fibromas, hyperplasias in the area of Waldeyer's tonsillar ring and certain laryngotracheal pathologies. Clinical examples demonstrate the advantages of this new mode of application.

Ultrafast X-Ray Absorption Spectroscopy of Isochorically Heated Warm Dense Matter

NASA Astrophysics Data System (ADS)

Engelhorn, Kyle Craig

This dissertation will present a series of new tools, together with new techniques, focused on the understanding of warm and dense matter. We report on the development of a high time resolution and high detection efficiency x-ray camera. The camera is integrated with a short pulse laser and an x-ray beamline at the Advanced Light Source synchrotron. This provides an instrument for single shot, broadband x-ray absorption spectroscopy of warm and dense matter with 2 picosecond time resolution. Warm and dense matter is created by isochorically heating samples of known density with an ultrafast optical laser pulse, and X-ray absorption spectroscopy probes the unoccupied electronic density of states before the onset of hydrodynamic expansion and electron-ion equilibrium is reached. Measured spectra from a variety of materials are compared with first principle molecular dynamics and density functional theory calculations. In heated silicon dioxide spectra, two novel pre-edge features are observed, a peak below the band gap and absorption within the band gap, while a reduction was observed in the features above the edge. From consideration of the calculated spectra, the peak below the gap is attributed to valence electrons that have been promoted to the conduction band, the absorption within the gap is attributed to broken Si-O bonds, and the reduction above the edge is attributed to an elevated ionic temperature. In heated copper spectra, a time-dependent shift and broadening of the absorption edge are observed, consistent with and elevated electron temperature. The temporal evolution of the electronic temperature is accurately determined by fitting the measured spectra with calculated spectra. The electron-ion equilibration is studied with a two-temperature model. In heated nickel spectra, a shift of the absorption edge is observed. This shift is found to be inconsistent with calculated spectra and independent of incident laser fluence. A shift of the chemical potential is applied to the calculated spectra to obtain satisfactory agreement with measured spectra.

CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang Hu

A new process called phase enhanced gas-liquid absorption has been developed in its early stage. It was found that adding another phase into the absorption system of gas/aqueous phase could enhance the absorption rate. A system with three phases was studied. In the system, gas phase was carbon dioxide. Two liquid phases were used. One was organic phase. Another was aqueous phase. By addition of organic phase into the absorption system of CO{sub 2}-aqueous phase, the absorption rate of CO{sub 2} was increased significantly. CO{sub 2} finally accumulated into aqueous phase. The experimental results proved that (1) Absorption rate ofmore » carbon dioxide was enhanced by adding organic phase into gas aqueous phase system; (2) Organic phase played the role of transportation of gas solute (CO{sub 2}). Carbon dioxide finally accumulated into aqueous phase.« less

Infrared Hollow Optical Fiber Probe for Localized Carbon Dioxide Measurement in Respiratory Tracts.

PubMed

Katagiri, Takashi; Shibayama, Kyosuke; Iida, Takeru; Matsuura, Yuji

2018-03-27

A real-time gas monitoring system based on optical absorption spectroscopy is proposed for localized carbon dioxide (CO₂) measurement in respiratory tracts. In this system, a small gas cell is attached to the end of a hollow optical fiber that delivers mid-infrared light with small transmission loss. The diameters of the fiber and the gas cell are smaller than 1.2 mm so that the probe can be inserted into a working channel of common bronchoscopes. The dimensions of the gas cell are designed based on absorption spectra of CO₂ standard gases in the 4.2 μm wavelength region, which are measured using a Fourier-transform infrared spectrometer. A miniature gas cell that is comprised of a stainless-steel tube with slots for gas inlet and a micro-mirror is fabricated. A compact probing system with a quantum cascade laser (QCL) light source is built using a gas cell with a hollow optical fiber for monitoring CO₂ concentration. Experimental results using human breaths show the feasibility of the system for in-situ measurement of localized CO₂ concentration in human airways.

Plasmonic enhancement of the vanadium dioxide phase transition induced by low-power laser irradiation

NASA Astrophysics Data System (ADS)

Ferrara, Davon W.; MacQuarrie, Evan R.; Diez-Blanco, Victor; Nag, Joyeeta; Kaye, Anthony B.; Haglund, Richard F.

2012-08-01

Nanocomposites consisting of gold nanoparticle (NP) arrays and vanadium dioxide (VO2) thin films are noteworthy for the tunability of both their thermal and optical properties. The localized surface plasmon resonance (LSPR) of the Au can be tuned when its dielectric environment is modulated by the semiconducting-to-metal phase transition (SMT) of the VO2; the LSPR itself can be altered by changing the shape of the NPs and the pitch of the NP array. In principle, then it should be possible to choose a combination of VO2 film and Au LSPR properties that maximizes the overall optical response of the nanocomposite. To demonstrate this effect, transient transmission measurements were conducted on lithographically fabricated arrays of Au NPs of diameter 140 nm, array spacing 350 nm, and covered with a 60 nm thick films of VO2 via pulsed laser deposition. Both Au::VO2 nanocomposites and bare VO2 film were irradiated with a shuttered 785 nm pump laser, and their optical response was probed at 1550 nm by a fixed-frequency diode laser. The Au::VO2 nanocomposite exhibited an increased effective absorption coefficient 1.5 times that of the plain film and required 37 % less laser power to induce the SMT. The time-dependent temperature rise in the film as a function of laser intensity was calculated from these measurements and compared with both analytic and finite-element models. Our results suggest that Au::VO2 nanocomposites may be useful in applications such as thermal-management coatings for energy efficient "smart" windows.

Method of determining pH by the alkaline absorption of carbon dioxide

DOEpatents

Hobbs, David T.

1992-01-01

A method for measuring the concentration of hydroxides in alkaline solutions in a remote location using the tendency of hydroxides to absorb carbon dioxide. The method includes the passing of carbon dioxide over the surface of an alkaline solution in a remote tank before and after measurements of the carbon dioxide solution. A comparison of the measurements yields the absorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to absorption fraction.

Triple-Pulse Integrated Path Differential Absorption Lidar for Carbon Dioxide Measurement - Novel Lidar Technologies and Techniques with Path to Space

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta

2017-01-01

The societal benefits of understanding climate change through identification of global carbon dioxide sources and sinks led to the desired NASA's active sensing of carbon dioxide emissions over nights, days, and seasons (ASCENDS) space-based missions of global carbon dioxide measurements. For more than 15 years, NASA Langley Research Center (LaRC) have developed several carbon dioxide active remote sensors using the differential absorption lidar (DIAL) technique operating at the two-micron wavelength. Currently, an airborne two-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development. This IPDA lidar measures carbon dioxide as well as water vapor, the dominant interfering molecule on carbon dioxide remote sensing. Advancement of this triple-pulse IPDA lidar development is presented.

Characterization of the surfaces of platinum/tin oxide based catalysts by Fourier transform spectroscopy (FTIR)

NASA Technical Reports Server (NTRS)

Keiser, Joseph T.

1989-01-01

The Laser Atmospheric Wind Sounder (LAWS) Program has as one of its goals the development of a satellite based carbon dioxide laser for making wind velocity measurements. The specifications for this laser include the requirement that the laser operate at a repetition rate of 10 Hertz continuously for three years. Earth-based carbon dioxide lasers can operate for only a short time on a single charge of gas because the lasing action causes the CO2 to break down into CO and O2. Therefore, earth-based CO2 lasers are generally operated in a flow through mode in which the spent gas is continually exhausted and fresh gas is continually added. For a satellite based system, however, a recirculation system is desired because it is not practical to send up extra tanks of CO2. A catalyst which could enable a recirculating CO2 laser to function continuously for three years needs to be developed. In the development of a catalyst system there are many variables. Obviously, not all possible formulations can be tested for three years, therefore, an accurate model which is based on the reaction mechanism is needed. The construction of a multistep reaction mechanism is similar to the construction of a jigsaw puzzle. Different techniques each supply a piece of the puzzle and the researcher must put the pieces together. Transmission infrared spectroscopy was shown to be very useful in supplying some of the information needed to elucidate reaction mechanisms. The purpose was to see what kind of information might be obtained about the NASA catalyst using infrared absorption spectroscopy. Approximately 200 infrared spectra of the prototype Pt/tin oxide catalyst and its precursor components are observed under a variety of different conditions. The most significant observations are summarized.

Corona Preionization Technique for Carbon Dioxide TEA Lasers.

DTIC Science & Technology

1982-11-30

34’" " " " "- -. .. " "I~ 82R8O701-02 CORONA PREIONIZATION TECHNIQUE FOR CARBON DIOXIDE TEA LASERS W after R. Kamnki SUnited Technologiles Research Center C...TITLE (and Subtitle) S. TYPE OF REPORT a PERIOD COVERED CORONA PREIONIZATION TECHNIQUE FOR CARBON Final Report DIOXIDE TEA LASERS May 5, 1981...Preionization Laser UV Preionization Pulsed CO2 Laser Corona Preionization CO2 TEA Laser 10. ABSTRACT (Continue on reverse side If neceeeiny md Identify

Simultaneous and Independent Measurement of Atmospheric Water Vapor and Carbon Dioxide using a Triple-Pulsed, 2-micron Airborne IPDA Lidar - A Feasibility Study

NASA Astrophysics Data System (ADS)

Singh, U. N.; Refaat, T. F.; Yu, J.; Petros, M.

2013-12-01

Water vapor (H2O) and carbon dioxide (CO2) are dominant greenhouse gases that are critical for Earth's radiation budget and global warming through the eco-system and the carbon cycle. NASA Langley Research Center (LaRC) has a strong heritage in atmospheric remote sensing of both gases using several instruments adopting various DIAL techniques. This communication presents a feasibility study for measuring both H2O and CO2 simultaneously and independently using a single instrument. This instrument utilizes the Integrated Path Differential Absorption (IPDA) lidar technique to measure the weighted-average column dry-air mixing ratios of CO2 (XCO2) and H2O (XH2O) independently and simultaneously from an airborne platform. The key component of this instrument is a tunable triple-pulse 2-micron laser. The three laser pulses are transmitted sequentially within a short time interval of 200 microsec. The wavelength of each of the laser pulses can be tuned separately. The IPDA receiver design is based on low-risk, commercially available components, including 300-micron diameter InGaAs 2-micron pin detector, a low-noise, high speed trans-impedance amplifier (TIA) and 12-bit 400 MHz digitizer.

Endoscopic Carbon Dioxide Laser Photocoagulation Of Bleeding Canine Gastric Ulcers

NASA Astrophysics Data System (ADS)

Gal, Dov; Ron, Nimrod; Orgad, Uri; Katzir, Abraham

1987-04-01

This is the first report which describes carbon dioxide laser photocoagulation of upper gastrointestinal bleeding via a flexible endoscope, using an infrared transmitting siver nalide fiber. Various laser parameters were checked to determine the optimal conditions for hemostasis. Both the acute effects of laser irradiation on tissue and the chronic effects on healing process were examined. Preliminary results indicate that carbon dioxide laser beam can successfully photocoagulate moderately bleeding ulcers.

Novel utilisation of a circular multi-reflection cell applied to materials ageing experiments

NASA Astrophysics Data System (ADS)

Knox, D. A.; King, A. K.; McNaghten, E. D.; Brooks, S. J.; Martin, P. A.; Pimblott, S. M.

2015-04-01

We report on the novel utilisation of a circular multi-reflection (CMR) cell applied to materials ageing experiments. This enabled trace gas detection within a narrow interfacial region located between two sample materials and remotely interrogated with near-infrared sources combined with fibre-optic coupling. Tunable diode laser absorption spectroscopy was used to detect water vapour and carbon dioxide at wavelengths near 1,358 and 2,004 nm, respectively, with corresponding detection limits of 7 and 1,139 ppm m Hz-0.5. The minimum detectable absorption was estimated to be 2.82 × 10-3 over a 1-s average. In addition, broadband absorption spectroscopy was carried out for the detection of acetic acid, using a super-luminescent light emitting diode centred around 1,430 nm. The 69 cm measurement pathlength was limited by poor manufacturing tolerances of the spherical CMR mirrors and the consequent difficulty of collecting all the cell output light.

Semiconductor-metal phase transition of vanadium dioxide nanostructures on silicon substrate: Applications for thermal control of spacecraft

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leahu, G. L., E-mail: roberto.livoti@uniroma1.it; Li Voti, R., E-mail: roberto.livoti@uniroma1.it; Larciprete, M. C., E-mail: roberto.livoti@uniroma1.it

2014-06-19

We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The VO2 phase transition is studied in the mid-infrared (MIR) region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO2 which has been explained by applying the Maxwell Garnett effective medium approximation theory, together with a strong hysteresis phenomenon, both useful to design tunable thermal devices to be applied for the thermal control of spacecraft. Wemore » have also applied the photothermal radiometry in order to study the changes in the modulated emissivity induced by laser. Experimental results show how the use of these techniques represent a good tool for a quantitative measurement of the optothermal properties of vanadium dioxide based structures.« less

Method of determining pH by the alkaline absorption of carbon dioxide

DOEpatents

Hobbs, D.T.

1992-10-06

A method is described for measuring the concentration of hydroxides in alkaline solutions in a remote location using the tendency of hydroxides to absorb carbon dioxide. The method includes the passing of carbon dioxide over the surface of an alkaline solution in a remote tank before and after measurements of the carbon dioxide solution. A comparison of the measurements yields the absorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to absorption fraction. 2 figs.

The new method of real-time detection of 129I2, 129I127I, 127I2 and NO2 in gases using tunable diode laser operating in the range of 632-637 nm

NASA Astrophysics Data System (ADS)

Kireev, S. V.; Shnyrev, S. L.

2018-02-01

This paper develops the new selective real-time method of 129I2, 129I127I, 127I2 and NO2 detection in gases. Measuring concentrations of molecular iodine is based on fluorescence exciting by the radiation of a tunable diode laser, operating in the red spectral region (632-637 nm), at two or three wavelengths corresponding to the centers of the absorption lines of 129I2, 129I127I and 127I2. Detection of NO2 is performed by measuring the intensity of the tunable diode laser radiation, which passed through the measuring cell. Measured simultaneously, boundary ratios of iodine molecule concentrations measured simultaneously are about 10-6. The sensitivity of nitrogen dioxide detection is 1016 cm-3.

Greenlite™: a year of carbon dioxide monitoring over paris, france, and recent progress in monitoring methane

NASA Astrophysics Data System (ADS)

Dobler, Jeremy; Zaccheo, T. Scott; Pernini, Timothy; Blume, Nathan; Braun, Michael

2018-04-01

GreenLITE™ is a ground-based laser absorption spectroscopy system capable of measuring and mapping CO2 concentrations over areas up to 25 km2. The system was deployed for COP21 as a demonstration and has now completed a year of CO2 measurements over the city of Paris, France. We will discuss lessons learned and relevant data from the year-long deployment. Recently, the system has demonstrated the same measurement capability for CH4, and results from preliminary testing are presented.

Preliminary results of an aircraft system based on near-IR diode lasers for continuous measurements of the concentration of methane, carbon dioxide, water and its isotopes

NASA Astrophysics Data System (ADS)

Nadezhdinsky, A. I.; Ponurovsky, Ya. Ya.; Shapovalov, Y. P.; Popov, I. P.; Stavrovsky, D. B.; Khattatov, V. U.; Galaktionov, V. V.; Kuzmichev, A. S.

2012-11-01

The Federal Agency for Hydrometeorology of the Russian Federation created the flying laboratory on board the passenger airplane Yak-42D for geophysical monitoring of the environment, including aircraft measurements of vertical concentrations of greenhouse gases in the troposphere. Within the limits of this project, General Physics Institute of the Russian Academy of Science developed airborne tunable diode laser spectrometer (TDLS) on the basis of diode lasers of a near-IR range for measurement of the altitude profiles of CO2, CH4, H2O and its isotopes. TDLS complex was integrated aboard in standard 19-in. rack. Air samples, taken over an aircraft on the pipeline, were injected into the optical cell. Using the system of inflow and heating, the air was set laminar with a flowrate of 0.2 l/s at a reduced pressure of 100 mbar for detecting narrow absorption lines of water vapor isotopes. For registration of the absorption spectra and for the measurement of greenhouse gas concentrations in online mode, modulation-correlation technique was used. Diode laser spectrometer output data were transferred to the airborne central computer. Sensitivity of TDLS measurements was 20-30 ppm for water, 3-4 ppm for CO2 and 20-25 ppb for CH4. Time of one-unit measurement is about 30 ms.

Low-Cost Miniaturized Laser Heterodyne Radiometer for Highly Sensitive Detection of CO2 and CH4 in the Atmospheric Column

NASA Technical Reports Server (NTRS)

Wilson, Emily L.; McLinden, Matthew L.; Miller, J. Houston

2011-01-01

We present a new passive ground-network instrument capable of measuring carbon dioxide (CO2) at 1.57 microns and methane (CH4) at 1.62 microns -- key for validation of OCO-2, ASCENDS, OCO-3, and GOSAT. Designed to piggy-back on an AERONET sun tracker (AERONET is a global network of more than 450 aerosol sensing instruments), this instrument could be rapidly deployed into the established AERONET network of ground sensors. Because aerosols induce a radiative effect that influences terrestrial carbon exchange, this simultaneous measure of aerosols and carbon cycle gases offers a uniquely comprehensive approach. This instrument is a variation of a laser heterodyne radiometer (LHR) that leverages recent advances in telecommunications lasers to miniaturize the instrument (the current version fits in a carry-on suitcase). In this technique, sunlight that has undergone absorption by the trace gas is mixed with laser light at a frequency matched to a trace gas absorption feature in the infrared (IR). Mixing results in a beat signal in the RF (radio frequency) region that can be related to the atmospheric concentration. By dividing this RF signal into a filter bank, concentrations at different altitudes can be resolved. For a one second integration, we estimate column sensitivities of 0.1 ppmv for CO2, and <1 ppbv for CH4.

Optical Parametric Technology for Methane Measurements

NASA Technical Reports Server (NTRS)

Dawsey, Martha; Numata, Kenji; Wu, Stewart; Riris, Haris

2015-01-01

Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas, with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. Yet, lack of understanding of the processes that control CH4 sources and sinks and its potential release from stored carbon reservoirs contributes significant uncertainty to our knowledge of the interaction between carbon cycle and climate change. At Goddard Space Flight Center (GSFC) we have been developing the technology needed to remotely measure CH4 from orbit. Our concept for a CH4 lidar is a nadir viewing instrument that uses the strong laser echoes from the Earth's surface to measure CH4. The instrument uses a tunable, narrow-frequency light source and photon-sensitive detector to make continuous measurements from orbit, in sunlight and darkness, at all latitudes and can be relatively immune to errors introduced by scattering from clouds and aerosols. Our measurement technique uses Integrated Path Differential Absorption (IPDA), which measures the absorption of laser pulses by a trace gas when tuned to a wavelength coincident with an absorption line. We have already demonstrated ground-based and airborne CH4 detection using Optical Parametric Amplifiers (OPA) at 1651 nm using a laser with approximately 10 microJ/pulse at 5kHz with a narrow linewidth. Next, we will upgrade our OPO system to add several more wavelengths in preparation for our September 2015 airborne campaign, and expect that these upgrades will enable CH4 measurements with 1% precision (10-20 ppb).

Natural deep eutectic solvents (NADES) as green solvents for carbon dioxide capture

NASA Astrophysics Data System (ADS)

Mulia, Kamarza; Putri, Sylvania; Krisanti, Elsa; Nasruddin

2017-03-01

This study was conducted to determine the effectiveness of Natural Deep Eutectic Solvent (NADES), consisting of choline chloride and a hydrogen bonding donor (HBD) compound, in terms of carbon dioxide absorption. Solubility of carbon dioxide in NADES was found to be influenced HBD compound used and choline chloride to HBD ratio, carbon dioxide pressure, and contact time. HBD and choline/HBD ratios used were 1,2-propanediol (1:2), glycerol (1:2), and malic acid (1:1). The carbon dioxide absorption measurement was conducted using an apparatus that utilizes the volumetric method. Absorption curves were obtained up to pressures of 30 bar, showing a linear relationship between the amount absorbed and the final pressure of carbon dioxide. The choline and 1,2-propanediol eutectic mixture absorbs the highest amount of carbon dioxide, approaching 0.1 mole-fraction at 3.0 MPa and 50°C. We found that NADES ability to absorb carbon dioxide correlates with its polarity as tested using Nile Red as a solvatochromic probe.

Nitrogen dioxide sensing using a novel gas correlation detector

NASA Astrophysics Data System (ADS)

Kebabian, Paul L.; Annen, Kurt D.; Berkoff, Timothy A.; Freedman, Andrew

2000-05-01

A nitrogen dioxide point sensor, based on a novel nondispersive gas filter spectroscopic scheme, is described. The detection scheme relies on the fact that the absorption spectrum of nitrogen dioxide in the 400-550 nm region consists of a complicated line structure superimposed on an average broadband absorption. A compensating filter is used to remove the effect of the broadband absorption, making the sensor insensitive both to small particles in the optical path and to potentially interfering gases with broadband absorption features in the relevant wavelength region. Measurements are obtained using a remote optical absorption cell that is linked via multimode fibre optics to the source and detection optics. The incorporation of blue light emitting diodes which spectrally match the nitrogen dioxide absorption allows the employment of electronic (instead of mechanical) switching between optical paths. A sensitivity of better than 1.0 ppm m column density (1 s integration time) has been observed; improvements in electronics and thermal stabilization should increase this sensitivity.

Determination of exhaled nitric oxide distributions in a diverse sample population using tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Namjou, K.; Roller, C. B.; Reich, T. E.; Jeffers, J. D.; McMillen, G. L.; McCann, P. J.; Camp, M. A.

2006-11-01

A liquid-nitrogen free mid-infrared tunable diode laser absorption spectroscopy (TDLAS) system equipped with a folded-optical-path astigmatic Herriott cell was used to measure levels of exhaled nitric oxide (eNO) and exhaled carbon dioxide (eCO2) in breath. Quantification of absolute eNO concentrations was performed using NO/CO2 absorption ratios measured by the TDLAS system coupled with absolute eCO2 concentrations measured with a non-dispersive infrared sensor. This technique eliminated the need for routine calibrations using standard cylinder gases. The TDLAS system was used to measure eNO in children and adults (n=799, ages 5 to 64) over a period of more than one year as part of a field study. Volunteers for the study self-reported data including age, height, weight, and health status. The resulting data were used to assess system performance and to generate eNO and eCO2 distributions, which were found to be log-normal and Gaussian, respectively. There were statistically significant differences in mean eNO levels for males and females as well as for healthy and steroid naïve asthmatic volunteers not taking corticosteroid therapies. Ambient NO levels affected measured eNO concentrations only slightly, but this effect was not statistically significant.

13CO2/12CO2 ratio analysis in exhaled air by lead-salt tunable diode lasers for noninvasive diagnostics in gastroenterology

NASA Astrophysics Data System (ADS)

Stepanov, Eugene V.; Zyrianov, Pavel V.; Miliaev, Valerii A.; Selivanov, Yurii G.; Chizhevskii, Eugene G.; Os'kina, Svetlana; Ivashkin, Vladimir T.; Nikitina, Elena I.

1999-07-01

An analyzer of 13CO2/12CO2 ratio in exhaled air based on lead-salt tunable diode lasers is presented. High accuracy of the carbon isotope ratio detection in exhaled carbon dioxide was achieved with help of very simple optical schematics. It was based on the use of MBE laser diodes operating in pulse mode and on recording the resonance CO2 absorption at 4.2 micrometers . Special fast acquisition electronics and software were applied for spectral data collection and processing. Developed laser system was tested in a clinical train aimed to assessment eradication efficiency in therapy of gastritis associated with Helicobacter pylori infection. Data on the 13C-urea breath test used for P.pylori detection and obtained with tunable diode lasers in the course of the trail was compared with the results of Mass-Spectroscopy analysis and histology observations. The analyzer can be used also for 13CO2/12CO2 ratio detection in exhalation to perform gastroenterology breath test based on using other compounds labeled with stable isotopes.

Visible light-harvesting of TiO2 nanotubes array by pulsed laser deposited CdS

NASA Astrophysics Data System (ADS)

Bjelajac, Andjelika; Djokic, Veljko; Petrovic, Rada; Socol, Gabiel; Mihailescu, Ion N.; Florea, Ileana; Ersen, Ovidiu; Janackovic, Djordje

2014-08-01

Titanium dioxide (TiO2) nanotubes arrays, obtained by anodization technique and annealing, were decorated with CdS using pulsed laser deposition method. Their structural, morphological and chemical characterization was carried out by electron microscopy in scanning (SEM) and transmission (TEM) modes, combined with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). It was demonstrated that the quantity of deposited CdS can be controlled by varying the number of laser pulses. The chemical mapping of the elements of interest was performed using the energy filtered mode of the electron microscope. The results showed that pulse laser deposition is an adequate technique for deposition of CdS inside and between 100 nm wide TiO2 nanotubes. The diffuse reflectance spectroscopy investigation of selected samples proved that the absorption edge of the prepared CdS/TiO2 nanocomposites is significantly extended to the visible range. The corresponding band gaps were determinated from the Tauc plot of transformed Kubelka-Munk function. The band gap reduction of TiO2 nanotubes by pulsed laser deposition of CdS was put in evidence.

Infrared Hollow Optical Fiber Probe for Localized Carbon Dioxide Measurement in Respiratory Tracts

PubMed Central

Katagiri, Takashi; Shibayama, Kyosuke; Iida, Takeru

2018-01-01

A real-time gas monitoring system based on optical absorption spectroscopy is proposed for localized carbon dioxide (CO2) measurement in respiratory tracts. In this system, a small gas cell is attached to the end of a hollow optical fiber that delivers mid-infrared light with small transmission loss. The diameters of the fiber and the gas cell are smaller than 1.2 mm so that the probe can be inserted into a working channel of common bronchoscopes. The dimensions of the gas cell are designed based on absorption spectra of CO2 standard gases in the 4.2 μm wavelength region, which are measured using a Fourier-transform infrared spectrometer. A miniature gas cell that is comprised of a stainless-steel tube with slots for gas inlet and a micro-mirror is fabricated. A compact probing system with a quantum cascade laser (QCL) light source is built using a gas cell with a hollow optical fiber for monitoring CO2 concentration. Experimental results using human breaths show the feasibility of the system for in-situ measurement of localized CO2 concentration in human airways. PMID:29584666

Intraindividual comparison of 1,470 nm diode laser versus carbon dioxide laser for tonsillotomy: a prospective, randomized, double blind, controlled feasibility trial.

PubMed

Havel, Miriam; Sroka, Ronald; Englert, Elsa; Stelter, Klaus; Leunig, Andreas; Betz, Christian S

2012-09-01

The need for reduction of post-tonsillectomy hemorrhage has led to promotion of tonsillotomy techniques for tonsil tissue reduction in obstructive tonsillar hypertrophy. This trial compares ablative tissue effects using 1,470 nm diode laser and carbon dioxide laser for tonsillotomy in an intraindividual design. 21 children aged 3-13 years (mean age 6.3 years) underwent laser tonsillotomy for obstructive tonsillar hypertrophy in this double blind, prospective, randomized, clinical feasibility trial. In each of the blinded patients, tonsillotomy was performed using fiber guided 1,470 nm diode laser (contact mode, 15 W power) on the one side and carbon dioxide laser (12 W power) on the other side. An independent, blinded physician documented clinical presentation and patients' symptoms preoperatively and on Days 1, 3, 7, 14, and 21 post-operatively using standardized questionnaire including VAS for each side separately. The mean duration of operative treatment was 2.7 min using 1,470 nm laser and 4.9 min using carbon dioxide laser respectively. Intraoperative bleeding and the frequency of bipolar forceps use for intraoperative bleeding control was significantly less using 1,470 nm diode laser system. There was no difference in post-operative pain scores between the carbon dioxide laser treated and the 1,470 nm fiber guided diode laser treated side. No infections, hemorrhages or other complications occurred in the course of the 3 weeks post-operative period. A fiber-guided 1,470 nm diode laser system offers an efficient and safe method for tonsillotomy as treatment of obstructive tonsillar hypertrophy. Compared to our standard practice (carbon dioxide laser), 1,470 nm laser application provides comparable tissue ablation effects with less intraoperative bleeding and shorter operation time. Copyright © 2012 Wiley Periodicals, Inc.

Color vision deficits and laser eyewear protection for soft tissue laser applications.

PubMed

Teichman, J M; Vassar, G J; Yates, J T; Angle, B N; Johnson, A J; Dirks, M S; Thompson, I M

1999-03-01

Laser safety considerations require urologists to wear laser eye protection. Laser eye protection devices block transmittance of specific light wavelengths and may distort color perception. We tested whether urologists risk color confusion when wearing laser eye protection devices for laser soft tissue applications. Subjects were tested with the Farnsworth-Munsell 100-Hue Test without (controls) and with laser eye protection devices for carbon dioxide, potassium titanyl phosphate (KTP), neodymium (Nd):YAG and holmium:YAG lasers. Color deficits were characterized by error scores, polar graphs, confusion angles, confusion index, scatter index and color axes. Laser eye protection device spectral transmittance was tested with spectrophotometry. Mean total error scores plus or minus standard deviation were 13+/-5 for controls, and 44+/-31 for carbon dioxide, 273+/-26 for KTP, 22+/-6 for Nd:YAG and 14+/-8 for holmium:YAG devices (p <0.001). The KTP laser eye protection polar graphs, and confusion and scatter indexes revealed moderate blue-yellow and red-green color confusion. Color axes indicated no significant deficits for controls, or carbon dioxide, Nd:YAG or holmium:YAG laser eye protection in any subject compared to blue-yellow color vision deficits in 8 of 8 tested with KTP laser eye protection (p <0.001). Spectrophotometry demonstrated that light was blocked with laser eye protection devices for carbon dioxide less than 380, holmium:YAG greater than 850, Nd:YAG less than 350 and greater than 950, and KTP less than 550 and greater than 750 nm. The laser eye protection device for KTP causes significant blue-yellow and red-green color confusion. Laser eye protection devices for carbon dioxide, holmium:YAG and Nd:YAG cause no significant color confusion compared to controls. The differences are explained by laser eye protection spectrophotometry characteristics and visual physiology.

Development of carbon dioxide laser doppler instrumentation detection of clear air turbulence

NASA Technical Reports Server (NTRS)

Sonnenschein, C.; Jelalian, A.; Keene, W.

1970-01-01

The analytical, experimental, and developmental aspects of an airborne, pulsed, carbon dioxide laser-optical radar system are described. The laser detects clear air turbulence and performs Doppler measurements of this air-motion phenomenon. Conclusions and recommendations arising from the development of the laser system are presented.

Carbon dioxide laser laparoscopy performed with a flexible fiber in humans.

PubMed

Baggish, M S; Baltoyannis, P; Badawy, S; Laurey, D

1987-11-01

A flexible carbon dioxide laser fiber delivery system was used in conjunction with the laparoscope to treat 12 women. The 77 by 2 mm hollow fiber could subtend an arc of 90 degrees without significant loss of power or unfavorably affecting the delivery mode. As many as 20 W of power was transmitted through the fiber; however, carbon dioxide gas flow rates as high as 2000 cc/min reduced power by approximately 25%. Replaceable tips preserved fiber integrity to the extent that a single fiber could be reused repeatedly and gas sterilized without jeopardizing laser transmission. Of the 12 cases, endometriotic implants were vaporized in eight women, adhesiolysis was performed in four women, endometrial cysts were drained in two women, and vaporization of myomata was accomplished in two patients. The fiber was also used as a manipulating instrument and could be internally bent with a grasping forceps to better site the laser beam on a lesion. No complications related to the use of the carbon dioxide laser fiber were observed. The safety aspects of carbon dioxide laser fiber technology are not inconsiderable and could provide laser laparoscopy with an extra margin of security.

Field Results from Three Campaigns to Validate the Performance of the Miniaturized Laser Heterodyne Radiometer (Mini-LHR) for Measuring Carbon Dioxide and Methane in the Atmospheric Column

NASA Technical Reports Server (NTRS)

Miller, J. Houston; Clarke, Greg B.; Melroy, Hilary; Ott, Lesley; Steel, Emily Wilson

2014-01-01

In a collaboration between NASA GSFC and GWU, a low-cost, surface instrument is being developed that can continuously monitor key carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). The instrument is based on a miniaturized, laser heterodyne radiometer (LHR) using near infrared (NIR) telecom lasers. Despite relatively weak absorption line strengths in this spectral region, spectrallyresolved atmospheric column absorptions for these two molecules fall in the range of 60-80% and thus sensitive and precise measurements of column concentrations are possible. In the last year, the instrument was deployed for field measurements at Park Falls, Wisconsin; Castle Airport near Atwater, California; and at the NOAA Mauna Loa Observatory in Hawaii. For each subsequent campaign, improvement in the figures of merit for the instrument has been observed. In the latest work the absorbance noise is approaching 0.002 optical density (OD) noise on a 1.8 OD signal. An overview of the measurement campaigns and the data retrieval algorithm for the calculation of column concentrations will be presented. For light transmission through the atmosphere, it is necessary to account for variation of pressure, temperature, composition, and refractive index through the atmosphere that are all functions of latitude, longitude, time of day, altitude, etc. For temperature, pressure, and humidity profiles with altitude we use the Modern-Era Retrospective Analysis for Research and Applications (MERRA) data. Spectral simulation is accomplished by integrating short-path segments along the trajectory using the SpecSyn spectral simulation suite developed at GW. Column concentrations are extracted by minimizing residuals between observed and modeled spectrum using the Nelder-Mead simplex algorithm. We will also present an assessment of uncertainty in the reported concentrations from assumptions made in the meteorological data, LHR instrument and tracker noise, and radio frequency bandwidth and describe additional future goals in instrument development and deployment target

Progress on development of an airborne two-micron IPDA lidar for water vapor and carbon dioxide column measurements

NASA Astrophysics Data System (ADS)

Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong; Antill, Charles W.; Taylor, Bryant D.; Bowen, Stephen C.; Welters, Angela M.; Remus, Ruben G.; Wong, Teh-Hwa; Reithmaier, Karl; Lee, Jane; Ismail, Syed

2017-09-01

An airborne 2-μm triple-pulse integrated path differential absorption (IPDA) lidar is currently under development at NASA Langley Research Center (LaRC). This lidar targets both atmospheric carbon dioxide (CO2) and water vapor (H2O) column measurements, simultaneously. Advancements in the development of this IPDA lidar are presented in this paper. Updates on advanced two-micron triple-pulse high-energy laser transmitter will be given including packaging and lidar integration status. In addition, receiver development updates will also be presented. This includes a state-of-the-art detection system integrated at NASA Goddard Space Flight Center. This detection system is based on a newly developed HgCdTe (MCT) electron-initiated avalanche photodiode (e-APD) array. Future plan for IPDA lidar system for ground integration, testing and flight validation will be discussed.

Progress on Development of an Airborne Two-Micron IPDA Lidar for Water Vapor and Carbon Dioxide Column Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong; Antill, Charles W.; Taylor, Bryant D.; Bowen, Stephen C.; Welters, Angela M.; Remus, Ruben G.; Wong, Teh-Hwa;

Depolarisation of light scattered by disperse systems of low-dimensional potassium polytitanate nanoparticles in the fundamental absorption band

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimnyakov, D A; Yuvchenko, S A; Pravdin, A B

2014-07-31

The results of experimental studies of depolarising properties of disperse systems on the basis of potassium polytitanate nanoplatelets and nanoribbons in the visible and near-UV spectral regions are presented. It is shown that in the fundamental absorption band of the nanoparticle material the increase in the depolarisation factor takes place for the radiation scattered perpendicularly to the direction of the probing beam. For nanoribbons a pronounced peak of depolarisation is observed, which is caused by the essential anisotropy of the particles shape and the peculiarities of the behaviour of the material dielectric function. The empirical data are compared with themore » theoretical results for 'nanodiscs' and 'nanoneedles' with the model dielectric function, corresponding to that obtained from optical constants of the titanium dioxide dielectric function. (laser biophotonics)« less

A comparative evaluation of APF gel, CPP/ACP paste alone and in combination with carbon dioxide laser on human enamel resistance to acid solubility using atomic absorption spectrometry: an in-vitro study.

PubMed

Nozari, Ali; Rafiee, Azade; Dehghan Khalili, Sara; Fekrazad, Reza

2018-04-01

The aim of this study was to compare the effects of acidulated phosphate fluoride (APF) gel, calcium phosphopeptide-amorphous calcium phosphate (CPP/ACP) paste alone and in combination with CO2 laser on the resistance of enamel to acid solubility. Ninety enamel sections were obtained from 15 extracted teeth and were randomly assigned to six groups: 1) control group; 2) APF group; 3) CPP-ACP group; 4) CO2 laser group; 5) APF + CO2 group; and 6) CPP-ACP + CO2 group. The specimens were individually demineralized in 0.1 M lactic acid solution with adjusted pH of 4.8 for 24h at 37 ºC. The acid solubility was determined using atomic absorption spectrometry. Statistical analysis was done using one-way ANOVA and Tukey-Kramer post hoc test (P<0.05). The average extent of calcium ion released (ppm) was estimated as follow: group 1: 6.974±1.757, group 2: 5.363±1.383, group 3: 6.962±1.489, group 4: 6.890±1.560, group 5: 4.803±1.080 and group 6: 6.789±1.218. Based on the between-group comparison results, group 2 and group 5 showed significant differences with the other groups. Under the studied conditions, only, the APF group alone and in combination with CO2 laser could decrease enamel acid solubility.

A high-pressure carbon dioxide gasdynamic laser

NASA Technical Reports Server (NTRS)

Kuehn, D. M.

1973-01-01

A carbon dioxide gasdynamic laser was operated over a range of reservoir pressure and temperature, test-gas mixture, and nozzle geometry. A significant result is the dominant influence of nozzle geometry on laser power at high pressure. High reservoir pressure can be effectively utilized to increase laser power if nozzle geometry is chosen to efficiently freeze the test gas. Maximum power density increased from 3.3 W/cu cm of optical cavity volume for an inefficient nozzle to 83.4 W/cu cm at 115 atm for a more efficient nozzle. Variation in the composition of the test gas also caused large changes in laser power output. Most notable is the influence of the catalyst (helium or water vapor) that was used to depopulate the lower vibrational state of the carbon dioxide. Water caused an extreme deterioration of laser power at high pressure (100 atm), whereas, at low pressure the laser for the two catalysts approached similar values. It appears that at high pressure the depopulation of the upper laser level of the carbon dioxide by the water predominates over the lower state depopulation, thus destroying the inversion.

DOUBLE SHELL TANK (DST) HYDROXIDE DEPLETION MODEL FOR CARBON DIOXIDE ABSORPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

OGDEN DM; KIRCH NW

2007-10-31

This document generates a supernatant hydroxide ion depletion model based on mechanistic principles. The carbon dioxide absorption mechanistic model is developed in this report. The report also benchmarks the model against historical tank supernatant hydroxide data and vapor space carbon dioxide data. A comparison of the newly generated mechanistic model with previously applied empirical hydroxide depletion equations is also performed.

Carbon Dioxide Absorption in a Membrane Contactor with Color Change

ERIC Educational Resources Information Center

Pantaleao, Ines; Portugal, Ana F.; Mendes, Adelio; Gabriel, Joaquim

2010-01-01

A pedagogical experiment is described to examine the physical absorption of gases, in this case carbon dioxide, in a hollow fiber membrane contactor (HFMC) where the absorption concentration profile can be followed by a color change. The HFMC is used to teach important concepts and can be used in interesting applications for students, such as…

The Successful Treatment of Elephantiasis Nostras Verrucosa With Ablative Carbon Dioxide Laser.

PubMed

Robinson, Caitlin G; Lee, Kory R; Thomas, Valencia D

2018-03-01

Elephantiasis nostras verrucosa (ENV) is a disfiguring skin condition that is difficult to treat. Existing treatment modalities serve to improve cosmesis or treat symptoms. Herein, we report a case of ENV with lymphocutaneous fistula successfully treated with ablative carbon dioxide laser. A 57-year-old woman with biopsy-proven ENV with lymphocutaneous fistula was treated with ablative carbon dioxide laser to the symptomatic area of her right thigh in 3 treatment sessions over 6 months. The patient had resolution of lymphocutaneous drainage as well as 90% improvement in the appearance of ENV lesions at the 1-month follow-up visit. Ablative carbon dioxide laser may provide cosmetic, symptomatic, and medical benefit for patients with localized ENV.

Parametric presentation of dielectric function of laser pumped wide-zone semiconductor material: Does this function satisfy the Kramers-Kronig relations?

NASA Astrophysics Data System (ADS)

Zimnyakov, D. A.; Yuvchenko, S. A.; Volchkov, S. S.; Samorodina, T. V.

2018-04-01

Dielectric function of wide-zone semiconductor nanoparticles (titanium dioxide) was studied under the condition of laser pumping at various wavelengths. A closed-aperture z-scan method with simultaneous measurements of the right-anglescattered intensity was used to retrieve the real and imaginary parts of dielectric function in the dependence on the pump intensity. It was found that the efficiency of dielectric function modulation by pumping light strongly depends on detuning of the wavelength of pumping light with respect to the fundamental absorption band of nanoparticles. The ColeCole diagrammatic technique was applied for interpretation of the pump-induced changes of the dielectric function in the optical range. Applicability of the Kramers-Kronig relations for description of the observed behavior of the dielectric function is discussed.

A light-emitting diode- (LED-) based absorption sensor for simultaneous detection of carbon monoxide and carbon dioxide

DOE PAGES

Thurmond, Kyle; Loparo, Zachary; Partridge, Jr., William P.; ...

2016-04-18

Here, a sensor was developed for simultaneous measurements of carbon monoxide (CO) and carbon dioxide (CO 2) fluctuations in internal combustion engine exhaust gases. This sensor utilizes low-cost and compact light-emitting diodes (LEDs) that emit in the 3–5 µm wavelength range. An affordable, fast response sensor that can measure these gases has a broad application that can lead to more efficient, fuel-flexible engines and regulation of harmful emissions. Light emission from LEDs is spectrally broader and more spatially divergent when compared to that of lasers, which presented many design challenges. Optical design studies addressed some of the non-ideal characteristics ofmore » the LED emissions. Measurements of CO and CO 2 were conducted using their fundamental absorption bands centered at 4.7 µm and 4.3 µm, respectively, while a 3.6 µm reference LED was used to account for scattering losses (due to soot, window deposits, etc.) common to the three measurement LEDs. Instrument validation and calibration was performed using a laboratory flow cell and bottled-gas mixtures. The sensor was able to detect CO 2 and CO concentration changes as small as 30 ppm and 400 ppm, respectively. Because of the many control and monitor species with infra-red absorption features, which can be measured using the strategy described, this work demonstrates proof of concept for a wider range of fast (250 Hz) and low-cost sensors for gas measurement and process monitoring.« less

Evaluation of an airborne triple-pulsed 2 μm IPDA lidar for simultaneous and independent atmospheric water vapor and carbon dioxide measurements.

PubMed

Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Ismail, Syed; Kavaya, Michael J; Davis, Kenneth J

2015-02-20

Water vapor and carbon dioxide are the most dominant greenhouse gases directly contributing to the Earth's radiation budget and global warming. A performance evaluation of an airborne triple-pulsed integrated path differential absorption (IPDA) lidar system for simultaneous and independent monitoring of atmospheric water vapor and carbon dioxide column amounts is presented. This system leverages a state-of-the-art Ho:Tm:YLF triple-pulse laser transmitter operating at 2.05 μm wavelength. The transmitter provides wavelength tuning and locking capabilities for each pulse. The IPDA lidar system leverages a low risk and technologically mature receiver system based on InGaAs pin detectors. Measurement methodology and wavelength setting are discussed. The IPDA lidar return signals and error budget are analyzed for airborne operation on-board the NASA B-200. Results indicate that the IPDA lidar system is capable of measuring water vapor and carbon dioxide differential optical depth with 0.5% and 0.2% accuracy, respectively, from an altitude of 8 km to the surface and with 10 s averaging. Provided availability of meteorological data, in terms of temperature, pressure, and relative humidity vertical profiles, the differential optical depth conversion into weighted-average column dry-air volume-mixing ratio is also presented.

Pseudorandom Noise Code-Based Technique for Cloud and Aerosol Discrimination Applications

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.; Harrison, Fenton Wallace

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a PN code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths. Keywords: ASCENDS, CO2 sensing, O2 sensing, PN codes, CW lidar

Technology Advancement for Active Remote Sensing of Carbon Dioxide from Space Using the ASCENDS CarbonHawk Experiment Simulator: First Results

NASA Technical Reports Server (NTRS)

Obland, Michael D.; Nehrir, Amin R.; Lin, Bing; Harrison, F. Wallace; Kooi, Susan; Choi, Yonghoon; Plant, James; Yang, Melissa; Antill, Charles; Campbell, Joel;

Clinical study on 71 anorectal cases treated by carbon dioxide laser

NASA Astrophysics Data System (ADS)

Li, Gui-hua

1993-03-01

This paper describes the effective result of carbon dioxide laser on type I and II internal hemorrhoids, mixed hemorrhoids, anal fissure or fistula, etc. At present, simple hemorrhoidectomy is less acceptable to patients for its excessive bleeding and severe pain during and after the operation. Therefore, the results of 71 anorectal cases of hemorrhoidectomy using carbon dioxide laser have been observed in our hospital. The rates of effective treatment and cure were 100% and 94.3%, respectively.

Novel Technique and Technologies for Active Optical Remote Sensing of Greenhouse Gases

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta

2017-01-01

The societal benefits of understanding climate change through identification of global carbon dioxide sources and sinks led to the desired NASA's active sensing of carbon dioxide emissions over nights, days, and seasons (ASCENDS) space-based missions of global carbon dioxide measurements. For more than 15 years, NASA Langley Research Center (LaRC) have developed several carbon dioxide active remote sensors using the differential absorption lidar (DIAL) technique operating at the two-micron wavelength. Currently, an airborne two-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development. This IPDA lidar measures carbon dioxide as well as water vapor, the dominant interfering molecule on carbon dioxide remote sensing. Advancement of this triple-pulse IPDA lidar development is presented.

The near-UV absorber OSSO and its isomers.

PubMed

Wu, Zhuang; Wan, Huabin; Xu, Jian; Lu, Bo; Lu, Yan; Eckhardt, André K; Schreiner, Peter R; Xie, Changjian; Guo, Hua; Zeng, Xiaoqing

2018-05-01

Disulfur dioxide, OSSO, has been proposed as the enigmatic "near-UV absorber" in the yellowish atmosphere of Venus. However, the fundamentally important spectroscopic properties and photochemistry of OSSO are scarcely documented. By either condensing gaseous SO or 266 laser photolysis of an S2O2 complex in Ar or N2 at 15 K, syn-OSSO, anti-OSSO, and cyclic OS([double bond, length as m-dash]O)S were identified by IR and UV/Vis spectroscopy for the first time. The observed absorptions (λmax) for OSSO at 517 and 390 nm coincide with the near-UV absorption (320-400 nm) found in the Venus clouds by photometric measurements with the Pioneer Venus orbiter. Subsequent UV light irradiation (365 nm) depletes syn-OSSO and anti-OSSO and yields a fourth isomer, syn-OSOS, with concomitant dissociation into SO2 and elemental sulfur.

Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

NASA Astrophysics Data System (ADS)

Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

2018-05-01

Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

A Carbon Dioxide Laser Bibliography, 1964-1969,

DTIC Science & Technology

A bibliography concerning carbon dioxide lasers has been compiled covering the period 1964 through 1969. The chronologically listed references have also been catalogued into an author index and a subject index. (Author)

Advances in Fabry-Perot and tunable quantum cascade lasers

NASA Astrophysics Data System (ADS)

Patel, C. Kumar N.

2017-05-01

Quantum cascade lasers (QCLs) are becoming mature infrared emitting devices that convert electrical power directly into optical power and generate laser radiation in the mid wave infrared (MWIR) and long wave infrared (LWIR) regions. These lasers operate at room temperature in the 3.5 μm to >12.0 μm region. QCLs operate at longer wavelengths into the terahertz region; however, these require some level of cryogenic cooling. Nonetheless, QCLs are the only solid-state sources that convert electrical power into optical power directly in these spectral regions. Three critical advances have contributed to the broad range of applications of QCLs, since their first demonstration in 1994 [1]. The first of these was the utilization of two phonon resonance for deexcitation of electrons from the lower lasing level [2]; the second is the utilization of epi-down mounting with hard solder of QCLs for practical applications [3]; and the third is the invention of nonresonant extraction for deexciting electrons from the lower laser level and simultaneously removing constraints on QCL structure design for extending high power room temperature operation to a broad range of wavelengths [4]. Although QCLs generate CW radiation at room temperature at wavelengths ranging from 3.5 μm to <12.0 μm, two spectral regions are very important for a broad range of applications. These are the first and the second atmospheric transmission windows from 3.5 μm to 5.0 μm and from 8.0 μm to 12.0 μm, respectively. Both of these windows (except for the spectral region near 4.2 μm, which is dominated by the infrared absorption from atmospheric carbon dioxide) are relatively free from atmospheric absorption and have a range of applications that involve long distance propagation.

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials

NASA Astrophysics Data System (ADS)

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R.; Hao, Xiaotao; Chen, Feng

2017-04-01

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS2) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO2 as low-cost saturable absorber for subnanosecond laser generation.

A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4-μm with a pulse duration of 26-μs

PubMed Central

Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

2016-01-01

Several studies over the past 20 years have shown that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-μs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase. The pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds which is short enough to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for transverse excited atmospheric pressure (TEA) lasers and too short for radio-frequency (RF) excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the Diamond J5-V laser for microvia drilling which can produce laser pulses greater than 100-mJ in energy at 9.4-μm with a pulse duration of 26-μs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate dental enamel. Efficient ablation of dental enamel is possible at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions. PMID:27006521

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials.

PubMed

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R; Hao, Xiaotao; Chen, Feng

2017-04-06

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO 4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO 2 ). The unique feature of VO 2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO 4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO 2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS 2 ) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO 2 as low-cost saturable absorber for subnanosecond laser generation.

Laser Energy Monitor for Double-Pulsed 2-Micrometer IPDA Lidar Application

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong; Singh, Upendra N.

2014-01-01

Integrated path differential absorption (IPDA) lidar is a remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. 2-micron double-pulsed IPDA lidar is best suited for atmospheric carbon dioxide measurements. In such case, the transmitter produces two successive laser pulses separated by short interval (200 microseconds), with low repetition rate (10Hz). Conventional laser energy monitors, based on thermal detectors, are suitable for low repetition rate single pulse lasers. Due to the short pulse interval in double-pulsed lasers, thermal energy monitors underestimate the total transmitted energy. This leads to measurement biases and errors in double-pulsed IPDA technique. The design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on a high-speed, extended range InGaAs pin quantum detectors suitable for separating the two pulse events. Pulse integration is applied for converting the detected pulse power into energy. Results are compared to a photo-electro-magnetic (PEM) detector for impulse response verification. Calibration included comparing the three detection technologies in single-pulsed mode, then comparing the pin and PEM detectors in double-pulsed mode. Energy monitor linearity will be addressed.

Laser-absorption effect on pulse-compression under Ohmic and weak-relativistic ponderomotive nonlinearity in plasmas

NASA Astrophysics Data System (ADS)

Singh, Mamta; Gupta, D. N.

2018-01-01

The inclusion of laser absorption in plasmas plays an important role in laser-plasma interactions. In this work, the laser pulse compression in weakly relativistic plasmas has been revisited by incorporating the collision-based laser absorption effects. By considering the role of laser absorption in plasmas, a set of coupled nonlinear equations is derived to describe the evolution of pulse compression. The laser pulse compression is reduced due to the collisional absorption in the plasmas. Fast dispersion is also observed with increasing the absorption coefficient, which is obviously due to the strong energy attenuation in plasmas. Using our theoretical model, the involvement and importance of a particular absorption mechanism for pulse compression in plasmas is analyzed.

Comparison of Carbon Dioxide Airborne Measurement over Land and Ocean using 2-μm Double-Pulse Integrated Path Differential Absorption Lidar

NASA Astrophysics Data System (ADS)

Refaat, T. F.; Singh, U. N.; Petros, M.; Yu, J.; Remus, R.; Ismail, S.

2017-12-01

An airborne Integrated Path Differential Absorption (IPDA) lidar has been developed and validated at NASA Langley Research Center for atmospheric carbon dioxide column measurements. The instrument consists of a tunable, high-energy 2-μm double pulse laser transmitter and 0.4 m telescope receiver coupled to an InGaAs pin detection system. The instrument was validated for carbon dioxide (CO2) measurements from ground and airborne platforms, using a movable lidar trailer and the NASA B-200 aircraft. Airborne validation was conducted over the ocean by comparing the IPDA CO2 optical depth measurement to optical depth model derived using NOAA airborne CO2 air-sampling. Another airborne validation was conducted over land vegetation by comparing the IPDA measurement to a model derived using on-board in-situ measurements using an absolute, non-dispersive infrared gas analyzer (LiCor 840A). IPDA range measurements were also compared to rangefinder and Global Positioning System (GPS) records during ground and airborne validation, respectively. Range measurements from the ground indicated a 0.93 m IPDA range measurement uncertainty, which is limited by the transmitted laser pulse and detection system properties. This uncertainty increased to 2.80 and 7.40 m over ocean and land, due to fluctuations in ocean surface and ground elevations, respectively. IPDA CO2 differential optical depth measurements agree with both models. Consistent CO2 optical depth biases were well correlated with the digitizer full scale input range settings. CO2 optical depth measurements over ocean from 3.1 and 6.1 km altitudes indicated 0.95% and 0.83% uncertainty, respectively, using 10 second (100 shots) averaging. Using the same averaging 0.40% uncertainty was observed over land, from 3.4 km altitude, due to higher surface reflectivity, which increases the return signal power and enhances the signal-to-noise ratio. However, less uncertainty is observed at higher altitudes due to reduced signal shot noise, indicating that detection system noise-equivalent-power dominates the error. These results show that the IPDA technique is well suited for space-based platforms, which includes larger column content integration that enhances the measurement sensitivity.

Performance characteristics and modeling of carbon dioxide absorption by amines in a packed column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, S.H.; Shyu, C.T.

1999-01-01

Carbon dioxide (CO[sub 2]) is widely recognized as a major greenhouse gas contributing to global warming. To mitigate the global warming problem, removal of CO[sub 2] from the industrial flue gases is necessary. Absorption of carbon dioxide by amines in a packed column was experimentally investigated. The amines employed in the present study were the primary mono-ethanolamine (MEA) and tertiary N-methyldiethanolamine (MDEA), two very popular amines widely used in the industries for gas purification. The CO[sub 2] absorption characteristics by these two amines were experimentally examined under various operating conditions. A theoretical model was developed for describing the CO[sub 2]more » absorption behavior. Test data have revealed that the model predictions and the observed CO[sub 2] absorption breakthrough curves agree very well, validating the proposed model. Preliminary regeneration tests of exhausted amine solution were also conducted. The results indicated that the tertiary amine is easier to regenerate with less loss of absorption capacity than the primary one.« less

Examination of contrast mechanisms in optoacoustic imaging of thermal lesions

NASA Astrophysics Data System (ADS)

Richter, Christian; Spirou, Gloria; Oraevsky, Alexander A.; Whelan, William M.; Kolios, Michael C.

2006-02-01

Optoacoustic Imaging is based on the thermal expansion of tissue caused by a temperature rise due to absorption of short laser pulses. At constant laser fluence, optoacoustic image contrast is proportional to differences in optical absorption and the thermoacoustic efficiency, expressed by the Grueuneisen parameter, Γ. Γ is proportional to the thermal expansion coefficient, the sound velocity squared and the inverse heat capacity at constant pressure. In thermal therapies, these parameters may be modified in the treated area. In this work experiments were performed to examine the influence of these parameters on image contrast. A Laser Optoacoustic Imaging System (LOIS, Fairway Medical Technologies, Houston, Texas) was used to image tissue phantoms comprised of cylindrical Polyvinyl Chloride Plastisol (PVCP) optical absorbing targets imbedded in either gelatin or PVCP as the background medium. Varying concentrations of Black Plastic Color (BPC) and titanium dioxide (TiO II) were added to targets and background to yield desired tissue relevant optical absorption and effective scattering coefficients, respectively. In thermal therapy experiments, ex-vivo bovine liver was heated with laser fibres (805nm laser at 5 W for 600s) to create regions of tissue coagulation. Lesions formed in the liver tissue were visible using the LOIS system with reasonable correspondence to the actual region of tissue coagulation. In the phantom experiments, contrast could be seen with low optical absorbing targets (μ a of 0.50cm -1 down to 0.13cm-1) embedded in a gelatin background (see manuscript for formula). Therefore, the data suggest that small objects (< 5mm) with low absorption coefficients (in the range < 1cm -1) can be imaged using LOIS. PVCP-targets in gelatin were visible, even with the same optical properties as the gelatin, but different Γ. The enhanced contrast may also be caused by differences in the mechanical properties between the target and the surrounding medium. PVCP-targets imbedded in PVCP produced poorer image contrast than PVCP-targets in gelatin with comparable optical properties. The preliminary investigation in tissue equivalent phantoms indicates that in addition to tissue optical properties, differences in mechanical properties between heated and unheated tissues may be responsible for image contrast. Furthermore, thermal lesions in liver tissue, ex-vivo, can be visualized using an optoacoustic system.

Development of laser transmission system

NASA Astrophysics Data System (ADS)

Song, Jiawu; Zhang, Yulan; Yang, Jiandong; Zhang, Xinming

1998-08-01

This paper discusses a light transfer system of therapeutic machine using carbon-dioxide laser. This system is based on imitating human being arm motion principle, consists of optical cardans mainly and can move in three-D space freely. Through it carbon-dioxide laser (which wavelength is 10.6 micrometer) is reflected, focused or diverged and transferred to the different therapeutic part of body to realize the purpose of cutting operation, gasification, cauterization and irradiation. This system includes an indicating system using He-Ne laser, by which carbon-dioxide laser can arrive therapeutic part accurately. This system possesses some advantages e.g. an accurate transfer, large moving range, small power consumption, high power density and easy operation. At present the occupancy in home market of this kind laser transfer system products is over 95%. Some products have been exported to other countries.

Laser Ablation of Poly(methylmethacrylate) Doped with Aromatic Compounds: Laser Intensity Dependence of Absorption Coefficient

NASA Astrophysics Data System (ADS)

Wang, Jun; Niino, Hiroyuki; Yabe, Akira

1999-02-01

We developed a novel method of obtaining an absorption coefficient which depends on the laser intensity, since a single-photon absorption coefficient of a polymer could not be applied to laser ablation. The relationship between the nonlinear absorption coefficient and the laser intensity was derived from experimental data of transmission and incident laser intensities. Using the nonlinear absorption coefficient of poly(methylmethacrylate) doped with benzil and pyrene, we succeeded in fitting the relationship of etch depth and laser intensity, obtained experimentally, and discussed the energy absorbed by the polymer at the threshold fluence.

Simplification of the laser absorption process in the particle simulation for the laser-induced shockwave processing

NASA Astrophysics Data System (ADS)

Shimamura, Kohei

2016-09-01

To reduce the computational cost in the particle method for the numerical simulation of the laser plasma, we examined the simplification of the laser absorption process. Because the laser frequency is sufficiently larger than the collision frequency between the electron and heavy particles, we assumed that the electron obtained the constant value from the laser irradiation. First of all, the simplification of the laser absorption process was verified by the comparison of the EEDF and the laser-absorptivity with PIC-FDTD method. Secondary, the laser plasma induced by TEA CO2 laser in Argon atmosphere was modeled using the 1D3V DSMC method with the simplification of the laser-absorption. As a result, the LSDW was observed with the typical electron and neutral density distribution.

Carbon dioxide (CO2) laser treatment of cutaneous papillomas in a common snapping turtle, Chelydra serpentina.

PubMed

Raiti, Paul

2008-06-01

Carbon dioxide (CO2) laser was used to treat multiple cutaneous papillomas on an adult female common snapping turtle, Chelydra serpentina serpentina. A combination of excisional and ablative techniques provided excellent intraoperative visibility and postoperative results due to the laser's unique ability to incise and vaporize soft tissue.

A Light-Emitting Diode- (LED-) Based Absorption Sensor for Simultaneous Detection of Carbon Monoxide and Carbon Dioxide.

PubMed

Thurmond, Kyle; Loparo, Zachary; Partridge, William; Vasu, Subith S

2016-06-01

A sensor was developed for simultaneous measurements of carbon monoxide (CO) and carbon dioxide (CO2) fluctuations in internal combustion engine exhaust gases. This sensor utilizes low-cost and compact light-emitting diodes (LEDs) that emit in the 3-5 µm wavelength range. An affordable, fast response sensor that can measure these gases has a broad application that can lead to more efficient, fuel-flexible engines and regulation of harmful emissions. Light emission from LEDs is spectrally broader and more spatially divergent when compared to that of lasers, which presented many design challenges. Optical design studies addressed some of the non-ideal characteristics of the LED emissions. Measurements of CO and CO2 were conducted using their fundamental absorption bands centered at 4.7 µm and 4.3 µm, respectively, while a 3.6 µm reference LED was used to account for scattering losses (due to soot, window deposits, etc.) common to the three measurement LEDs. Instrument validation and calibration was performed using a laboratory flow cell and bottled-gas mixtures. The sensor was able to detect CO2 and CO concentration changes as small as 30 ppm and 400 ppm, respectively. Because of the many control and monitor species with infra-red absorption features, which can be measured using the strategy described, this work demonstrates proof of concept for a wider range of fast (250 Hz) and low-cost sensors for gas measurement and process monitoring. © The Author(s) 2016.

Investigation of acetone, butanol and carbon dioxide as new breath biomarkers for convenient and noninvasive diagnosis of obstructive sleep apnea syndrome.

PubMed

Bayrakli, Ismail; Öztürk, Önder; Akman, Hatice

2016-12-01

The objective of the present study was to investigate whether analysis of carbon dioxide, acetone and/or butanol present in human breath can be used as a simple and noninvasive diagnosis method for obstructive sleep apnea syndrome (OSAS). For this purpose, overnight changes in the concentrations of these breath molecules were measured before and after sleep in 10 patients who underwent polysomnography and were diagnosed with OSAS, and were compared with the levels of these biomarkers determined after sleep in 10 healthy subjects. The concentrations of exhaled carbon dioxide were measured using external cavity laser-based off-axis cavity enhanced absorption spectroscopy, whereas the levels of exhaled acetone and butanol were determined using thermal desorption gas chromatography mass spectrometry. We observed no significant changes in the levels of exhaled acetone and carbon dioxide in OSAS patients after sleep compared with pre-sleep values and compared with those in healthy control subjects. However, for the first time, to our knowledge, analyses of expired air showed an increased concentration of butanol after sleep compared with that before sleep and compared with that in healthy subjects. These results suggest that butanol can be established as a potential biomarker to enable the convenient and noninvasive diagnosis of OSAS in the future. Copyright © 2016 John Wiley & Sons, Ltd.

Laser versus traditional techniques in cerebral and brain stem gliomas

NASA Astrophysics Data System (ADS)

Lombard, Gian F.

1996-01-01

In medical literature no significant studies have been published on the effectiveness of laser compared with traditional procedures in two series of cerebral gliomas; for this reason we have studied 220 tumors (200 supratentorial -- 20 brain stem gliomas), 110 operated upon with laser, 100 with conventional techniques. Four surgical protocols have been carried out: (1) traditional techniques; (2) carbon dioxide laser free hand; (3) carbon dioxide laser plus microscope; (4) multiple laser sources plus microscope plus neurosector plus CUSA. Two laser sources have been used alone or in combination (carbon dioxide -- Nd:YAG 1.06 or 1.32). Patients have been monitored for Karnofsky scale before and after operation, 12 - 24 and 36 months later; and for survival rate. Tumors were classified by histological examination, dimensions, vascularization, topography (critical or non critical areas). Results for supratentorial gliomas: survival time is the same in both series (laser and traditional). Post- op morbidity is significantly improved in the laser group (high grade sub-group); long term follow-up shows an improvement of quality of life until 36 months in the low grade sub-group.

Finite Element Analysis of Interaction of Laser Beam with Material in Laser Metal Powder Bed Fusion Process.

PubMed

Fu, Guang; Zhang, David Z; He, Allen N; Mao, Zhongfa; Zhang, Kaifei

2018-05-10

A deep understanding of the laser-material interaction mechanism, characterized by laser absorption, is very important in simulating the laser metal powder bed fusion (PBF) process. This is because the laser absorption of material affects the temperature distribution, which influences the thermal stress development and the final quality of parts. In this paper, a three-dimensional finite element analysis model of heat transfer taking into account the effect of material state and phase changes on laser absorption is presented to gain insight into the absorption mechanism, and the evolution of instantaneous absorptance in the laser metal PBF process. The results showed that the instantaneous absorptance was significantly affected by the time of laser radiation, as well as process parameters, such as hatch space, scanning velocity, and laser power, which were consistent with the experiment-based findings. The applicability of this model to temperature simulation was demonstrated by a comparative study, wherein the peak temperature in fusion process was simulated in two scenarios, with and without considering the effect of material state and phase changes on laser absorption, and the simulated results in the two scenarios were then compared with experimental data respectively.

Efficacy of autologous platelet-rich plasma combined with fractional ablative carbon dioxide resurfacing laser in treatment of facial atrophic acne scars: A split-face randomized clinical trial.

PubMed

Faghihi, Gita; Keyvan, Shima; Asilian, Ali; Nouraei, Saeid; Behfar, Shadi; Nilforoushzadeh, Mohamad Ali

2016-01-01

Autologous platelet-rich plasma has recently attracted significant attention throughout the medical field for its wound-healing ability. This study was conducted to investigate the potential of platelet-rich plasma combined with fractional laser therapy in the treatment of acne scarring. Sixteen patients (12 women and 4 men) who underwent split-face therapy were analyzed in this study. They received ablative fractional carbon dioxide laser combined with intradermal platelet-rich plasma treatment on one half of their face and ablative fractional carbon dioxide laser with intradermal normal saline on the other half. The injections were administered immediately after laser therapy. The treatment sessions were repeated after an interval of one month. The clinical response was assessed based on patient satisfaction and the objective evaluation of serial photographs by two blinded dermatologists at baseline, 1 month after the first treatment session and 4 months after the second. The adverse effects including erythema and edema were scored by participants on days 0, 2, 4, 6, 8, 15 and 30 after each session. Overall clinical improvement of acne scars was higher on the platelet-rich plasma-fractional carbon dioxide laser treated side but the difference was not statistically significant either 1 month after the first treatment session (P = 0.15) or 4 months after the second (P = 0.23). In addition, adverse effects (erythema and edema) on the platelet-rich plasma-fractional carbon dioxide laser-treated side were more severe and of longer duration. Small sample size, absence of all skin phototypes within the study group and lack of objective methods for the evaluation of response to treatment and adverse effects were the limitations. This study demonstrated that adding platelet-rich plasma to fractional carbon dioxide laser treatment did not produce any statistically significant synergistic effects and also resulted in more severe side effects and longer downtime.

Improvement of water resistance and dimensional stability of wood through titanium dioxide coating

Treesearch

Qingfeng Sun; Haipeng Yu; Yixing Liu; Jian Li; Yun Lu; John F. Hunt

2010-01-01

Moisture absorption and dimensional distortion are the major drawbacks of wood utilization as building material. In this study, poplar wood coated with a thin layer of titanium dioxide (TiO2) was prepared by the cosolvent-controlled hydrothermal method. Subsequently, its moisture absorption and dimensional stability were examined. Scanning...

New CO2 laser waveguide systems: advances in surgery of tracheal stenosis

NASA Astrophysics Data System (ADS)

Stasche, Norbert; Bernecker, Frank; Hoermann, Karl

1996-01-01

The carbon dioxide laser is a well established tool in the surgical treatment of laryngeal and tracheal stenosis. Usually the laser beam is applied by a microscope/micromanipulator device. Different types of rigid laryngoscopes and bronchoscopes provide access to nearly every area of larynx, trachea and main bronchi. In order to be treated with this equipment the target tissue has to be in a straight optical axis with the laser beam output at the micromanipulator. We report about one patient who presented with severe dyspnea due to granulation tissue directly below his left vocal cord. He was suffering from tracheomalacia for several years and was successfully treated by tracheostomy and a Montgomery's silicone T-tube as a stent. Then granulation tissue blocked the upper orifice of the Montgomery's T-tube. First removal by a carbon dioxide laser beam through the laryngoscope would have required sacrificing his intact left vocal cord. We removed the obstructing tissue by using the ArthroLaseTM System: the carbon dioxide laser beam was conducted through a 90 degree bent rigid probe, using the tracheostomy as an access. This ArthroLaseTM System was originally designed for arthroscopic surgery. In this special case however it successfully extends the use of the carbon dioxide laser in otolaryngology.

Structure and properties of nanoparticles fabricated by laser ablation of Zn metal targets in water and ethanol

NASA Astrophysics Data System (ADS)

Svetlichnyi, V. A.; Lapin, I. N.

2013-10-01

Size characteristics, structure, and spectral and luminescent properties of nanoparticles fabricated by laser ablation of zinc metal targets in water and ethanol are experimentally investigated upon excitation by Nd:YAG-laser radiation (1064 nm, 7 ns, and 15 Hz). It is demonstrated that zinc oxide nanoparticles with average sizes of 10 nm (in water) and 16 nm (in ethanol) are formed in the initial stage as a result of ablation. The kinetics of the absorption and luminescence spectra, transmission electron microscopy, and x-ray structural analysis demonstrate that during long storage of water dispersions and their drying, nanoparticles efficiently interact with carbon dioxide gas of air that leads to the formation of water-soluble Zn(CO3)2(OH)6. In ethanol, Zn oxidation leads to the formation of stable dispersions of ZnO nanoparticles with 99% of the wurtzite phase; in this case, the fluorescence spectra of ZnO nanoparticles change with time, shifting toward longer wavelength region from 550 to 620 nm, which is caused by the changed nature of defects.

Dental hard tissue characterization using laser-based ultrasonics

NASA Astrophysics Data System (ADS)

Blodgett, David W.; Massey, Ward L.

2003-07-01

Dental health care and research workers require a means of imaging the structures within teeth in vivo. One critical need is the detection of tooth decay in its early stages. If decay can be detected early enough, the process can be monitored and interventional procedures, such as fluoride washes and controlled diet, can be initiated to help re-mineralize the tooth. Currently employed x-ray imaging is limited in its ability to visualize interfaces and incapable of detecting decay at a stage early enough to avoid invasive cavity preparation followed by a restoration. To this end, non-destructive and non-contact in vitro measurements on extracted human molars using laser-based ultrasonics are presented. Broadband ultrasonic waves are excited in the extracted sections by using a pulsed carbon-dioxide (CO2) laser operating in a region of high optical absorption in the dental hard tissues. Optical interferometric detection of the ultrasonic wave surface displacements in accomplished with a path-stabilized Michelson-type interferometer. Results for bulk and surface in-vitro characterization of caries are presented on extracted molars with pre-existing caries.

Field-based stable isotope analysis of carbon dioxide by mid-infrared laser spectroscopy for carbon capture and storage monitoring.

PubMed

van Geldern, Robert; Nowak, Martin E; Zimmer, Martin; Szizybalski, Alexandra; Myrttinen, Anssi; Barth, Johannes A C; Jost, Hans-Jürg

2014-12-16

A newly developed isotope ratio laser spectrometer for CO2 analyses has been tested during a tracer experiment at the Ketzin pilot site (northern Germany) for CO2 storage. For the experiment, 500 tons of CO2 from a natural CO2 reservoir was injected in supercritical state into the reservoir. The carbon stable isotope value (δ(13)C) of injected CO2 was significantly different from background values. In order to observe the breakthrough of the isotope tracer continuously, the new instruments were connected to a stainless steel riser tube that was installed in an observation well. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10 day carbon stable isotope data set with 30 min resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within analytical precision. This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time stable isotope data directly in the field. The laser spectroscopy data revealed for the first time a prior to this experiment unknown, intensive dynamic with fast changing δ(13)C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The short-term variances as observed in this study might have been missed during previous works that applied laboratory-based IRMS analysis. The new technique could contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long-term integrity of the reservoir.

Superpulsed carbon dioxide laser: an update on cutaneous surgical applications

NASA Astrophysics Data System (ADS)

Wheeland, Ronald G.

1990-06-01

Superpulsing the carbon dioxide laser allows delivery of high energy pulses separated by short pauses during which tissue cooling can occur.1 This new technology can provide several important advantages in cutaneous surgery over similar procedures performed with conventional continuous discharge carbon dioxide laser systems. In the excisional mode, there is a two-thirds reduction in thermal necrosis of the wound edge.2 This should translate into more rapid healing3 and increased rate of gain in tensile strength. In the vaporizational mode, precise, superficial and bloodless ablation of multiple benign appendigeal tumors is possible with less thermal damage yielding excellent cosmetic results. The establishment through additional research of accurate laser parameters, pulse duration, peak energy levels, and frequency of pulses, will help improve the specificity of the laser-tissue interaction to provide even better surgical results.

Carbon Dioxide Laser Fiber Optics In Endoscopy

NASA Astrophysics Data System (ADS)

Fuller, Terry A.

1982-12-01

Carbon dioxide laser surgery has been limited to a great extent to surgical application on the integument and accessible cavities such as the cervix, vagina, oral cavities, etc. This limitation has been due to the rigid delivery systems available to all carbon dioxide lasers. Articulating arms (series of hollow tubes connected by articulating mirrors) have provided an effective means of delivery of laser energy to the patient as long as the lesion was within the direct line of sight. Even direct line-of-sight applications were restricted to physical dimension of the articulating arm or associated hand probes, manipulators and hollow tubes. The many attempts at providing straight endoscopic systems to the laser only stressed the need for a fiber optic capable of carrying the carbon dioxide laser wavelength. Rectangular and circular hollow metal waveguides, hollow dielectric waveguides have proven ineffective to the stringent requirements of a flexible surgical delivery system. One large diameter (1 cm) fiber optic delivery system, incorporates a toxic thalliumAbased fiber optic material. The device is an effective alternative to an articulating arm for external or conventional laser surgery, but is too large and stiff to use as a flexible endoscopic tool. The author describes the first highly flexible inexpensive series of fiber optic systems suitable for either conventional or endoscopic carbon dioxide laser surgery. One system (IRFLEX 3) has been manufactured by Medlase, Inc. for surgical uses capable of delivering 2000w, 100 mJ pulsed energy and 15w continuous wave. The system diameter is 0.035 inches in diameter. Surgically suitable fibers as small as 120 um have been manufactured. Other fibers (IRFLEX 142,447) have a variety of transmission characteristics, bend radii, etc.

[Analysis of UV-visible absorption spectrum on the decolorization of industrial wastewater by disinfection].

PubMed

Huang, Xin; Wang, Long-Yong; Gao, Nai-Yun; Li, Wei-Guo

2012-10-01

The UV-Visible absorption spectrum of industrial wastewater was explored to introduce a substituting method determining the color of water, and to compare the decolorization efficacy of different disinfectants. The results show that the visible absorption spectrum(350-600 nm), instead of ultraviolet absorption spectrum, should be applied to characterize the color of wastewater. There is a good correlation between the features of visible absorption spectrum and the true color of wastewater. Both ozone and chlorine dioxide has a better decolorization performance than chlorine. However, the color of chlorine dioxide itself has a negative effect on decolorization. The changes in the features of visible absorption spectrum effectively reflect the variations in the color of wastewater after disinfection.

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials

PubMed Central

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R.; Hao, Xiaotao; Chen, Feng

2017-01-01

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS2) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO2 as low-cost saturable absorber for subnanosecond laser generation. PMID:28383017

Exposure to nano-size titanium dioxide causes oxidative damages in human mesothelial cells: The crystal form rather than size of particle contributes to cytotoxicity.

PubMed

Hattori, Kenji; Nakadate, Kazuhiko; Morii, Akane; Noguchi, Takumi; Ogasawara, Yuki; Ishii, Kazuyuki

2017-10-14

Exposure to nanoparticles such as carbon nanotubes has been shown to cause pleural mesothelioma similar to that caused by asbestos, and has become an environmental health issue. Not only is the percutaneous absorption of nano-size titanium dioxide particles frequently considered problematic, but the possibility of absorption into the body through the pulmonary route is also a concern. Nevertheless, there are few reports of nano-size titanium dioxide particles on respiratory organ exposure and dynamics or on the mechanism of toxicity. In this study, we focused on the morphology as well as the size of titanium dioxide particles. In comparing the effects between nano-size anatase and rutile titanium dioxide on human-derived pleural mesothelial cells, the anatase form was shown to be actively absorbed into cells, producing reactive oxygen species and causing oxidative damage to DNA. In contrast, we showed for the first time that the rutile form is not easily absorbed by cells and, therefore, does not cause oxidative DNA damage and is significantly less damaging to cells. These results suggest that with respect to the toxicity of titanium dioxide particles on human-derived mesothelial cells, the crystal form rather than the particle size has a greater effect on cellular absorption. Also, it was indicated that the difference in absorption is the primary cause of the difference in the toxicity against mesothelial cells. Copyright © 2017 Elsevier Inc. All rights reserved.

Absorption of Carbon Dioxide in Aqueous Solutions of N-methyldiethanolamine Mixtures

NASA Astrophysics Data System (ADS)

Ma’mun, S.; Svendsen, H. F.

2018-05-01

Carbon dioxide (CO2) is one of the greenhouse gases (GHG) that has contributed to the global warming problem. Carbon dioxide is produced in large quantity from coal-fired power plants, iron and steel production, cement production, chemical and petrochemical industries, natural gas purification, and transportation. Some efforts to reduce the CO2 emissions to the atmosphere are then required. Amine-based absorption may be an option for post-combustion capture. The objective of this study is to measure the effect of promoter addition as well as MDEA concentration for the CO2 absorption into the aqueous solutions of MDEA to improve its performances, i.e. increasing the absorption rate and the absorption capacity. Absorption of CO2 in aqueous solutions of MDEA mixtures were measured at 40 °C in a bubble tank reactor. The systems tested were the mixtures of 30 wt% MDEA with 5 and 10 wt% BEA and the mixtures of 40 and 50 wt% MDEA with 6 wt% AEEA. It was found that for MDEA-BEA-H2O mixtures, the higher the promoter concentraation the higher the CO2 absorption rate, while for the MDEA-AEEA-H2O mixtures, the higher the MDEA concentration the lower the CO2 absorption rate.

Manufacturing Methods and Technology (MM&T) program. 10.6 micrometer carbon dioxide TEA (Transverely Excited Atmospheric) lasers

NASA Astrophysics Data System (ADS)

Luck, C. F.

1983-06-01

This report documents the efforts of Raytheon Company to conduct a manufacturing methods and technology (MM&T) program for 10.6 micrometer carbon dioxide TEA lasers. A set of laser parameters is given and a conforming tube design is described. Results of thermal and mechanical stress analyses are detailed along with a procedure for assembling and testing the laser tube. Also provided are purchase specifications for optics and process specifications for some of the essential operations.

Ablative Fractional Carbon Dioxide Laser in the Treatment of Chronic, Posttraumatic, Lower-Extremity Ulcers in Elderly Patients.

PubMed

Phillips, Tania J; Morton, Laurel M; Uebelhoer, Nathan S; Dover, Jeffrey S

2015-08-01

Treating posttraumatic lower extremity wounds can be challenging, especially in elderly patients. Recently, the use of fractional carbon dioxide laser has been shown to improve wound healing in scar-related wounds. We used this treatment modality in posttraumatic wounds that were slow to heal in 3 elderly patients. Each wound underwent one fractional carbon dioxide laser treatment. The wound base was treated at 30 mJ and 5% density. The entire wound edge and 1 to 2 cm into the normal surrounding skin were treated at 50 mJ and 5% density. One pass was completed at 150 Hz per treatment. Treatments were well tolerated with only mild discomfort. Each wound healed by 60% or greater within 3 weeks. No adverse events were reported aside from mild and transient erythema at site of treatment. Fractional carbon dioxide laser treatment appeared to accelerate healing in each of these posttraumatic wounds. It may be a helpful adjunct in nonhealing posttraumatic wounds.

Off-line-locked laser diode species monitor system

NASA Technical Reports Server (NTRS)

Lee, Jamine (Inventor); Goldstein, Neil (Inventor); Richtsmeier, Steven (Inventor); Bien, Fritz (Inventor); Gersh, Michael (Inventor)

1995-01-01

An off-line-locked laser diode species monitor system includes: reference means for including at least one known species having a first absorption wavelength; a laser source for irradiating the reference means and at least one sample species having a second absorption wavelength differing from the first absorption wavelength by a predetermined amount; means for locking the wavelength of the laser source to the first wavelength of the at least one known species in the reference means; a controller for defeating the means for locking and for displacing the laser source wavelength from said first absorption wavelength by said predetermined amount to the second absorption wavelength; and a sample detector device for determining laser radiation absorption at the second wavelength transmitted through the sample to detect the presence of the at least one sample species.

Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method.

PubMed

Nechayev, Sergey; Reusswig, Philip D; Baldo, Marc A; Rotschild, Carmel

2016-12-07

High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump absorption below the maximal value, which is in contrast to conventional lasers for which full pump absorption is desired. Numerical results are compared to experimental data on a sensitized Nd 3+ :YAG cavity, and quantitative agreement with theoretical models is found. Our work modularizes the gain and sensitizing components and paves the way for the optimal design of broadband-pumped high-quality micro-lasers and efficient solar-pumped lasers.

Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method

PubMed Central

Nechayev, Sergey; Reusswig, Philip D.; Baldo, Marc A.; Rotschild, Carmel

2016-01-01

High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump absorption below the maximal value, which is in contrast to conventional lasers for which full pump absorption is desired. Numerical results are compared to experimental data on a sensitized Nd3+:YAG cavity, and quantitative agreement with theoretical models is found. Our work modularizes the gain and sensitizing components and paves the way for the optimal design of broadband-pumped high-quality micro-lasers and efficient solar-pumped lasers. PMID:27924844

Development and Preliminary Tests of an Open-Path Airborne Diode Laser Absorption Instrument for Carbon Dioxide

NASA Technical Reports Server (NTRS)

Diskin, Glenn S.; DiGangi, Joshua P.; Yang, Melissa; Slate, Thomas A.; Rana, Mario

2015-01-01

Carbon dioxide (CO2) is well known for its importance as an atmospheric greenhouse gas, with many sources and sinks around the globe. Understanding the fluxes of carbon into and out of the atmosphere is a complex and daunting challenge. One tool applied by scientists to measure the vertical flux of CO2 near the surface uses the eddy covariance technique, most often from towers but also from aircraft flying specific patterns over the study area. In this technique, variations of constituents of interest are correlated with fluctuations in the local vertical wind velocity. Measurement requirements are stringent, particularly with regard to precision, sensitivity to small changes, and temporal sampling rate. In addition, many aircraft have limited payload capability, so instrument size, weight, and power consumption are also important considerations. We report on the development and preliminary application of an airborne sensor for the measurement of atmospheric CO2. The instrument, modeled on the successful DLH (Diode Laser Hygrometer) series of instruments, has been tested in the laboratory and on the NASA DC-8 aircraft. Performance parameters such as accuracy, precision, sensitivity, specificity, and temporal response are discussed in the context of typical atmospheric variability and suitability for flux measurement applications. On-aircraft, in-flight data have been obtained and are discussed as well. Performance of the instrument has been promising, and continued flight testing is planned during 2016.

Carbon Dioxide Absorption Heat Pump

NASA Technical Reports Server (NTRS)

Jones, Jack A. (Inventor)

2002-01-01

A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

Phase-selective vanadium dioxide (VO2) nanostructured thin films by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Masina, B. N.; Lafane, S.; Wu, L.; Akande, A. A.; Mwakikunga, B.; Abdelli-Messaci, S.; Kerdja, T.; Forbes, A.

2015-10-01

Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO2) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ˜43 °C, without any doping, paving the way to switchable transparency in optical materials at room temperature.

Analysis of plume emissions after papovavirus irradiation with the carbon dioxide laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellina, J.H.; Stjernholm, R.L.; Kurpel, J.E.

1982-05-01

This study was undertaken to evaluate potential inhalation hazards to operating room personnel after irradiation of tumors with the carbon dioxide laser. Cellular debris was analyzed for viability using labeled nucleotides and labeled glucose. In this way the plume was investigated for the presence of material with oncogenic potential. Most surgeons who have ablated venereal warts or certain tumors with the carbon dioxide laser have worried about possible hazards of inhaling the vapor that is produced as a result of their work. We utilized three methods to determine whether viable particles exist in the laser plume. Fortunately, it is mostmore » comforting that the metabolic studies, DNA and RNA studies and cytologic studies seem to indicate that the plume is biologically inactive.« less

Discovery of natural gain amplification in the 10-micrometer carbon dioxide laser bands on Mars - A natural laser

NASA Technical Reports Server (NTRS)

Mumma, M. J.; Buhl, D.; Chin, G.; Deming, D.; Espenak, F.; Kostiuk, T.; Zipoy, D.

1981-01-01

Fully resolved intensity profiles of various lines in the carbon dioxide band at 10.4 micrometers have been measured on Mars with an infrared heterodyne spectrometer. Analysis of the line shapes shows that the Mars atmosphere exhibits positive gain in these lines. The detection of natural optical gain amplification enables identification of these lines as a definite natural laser.

Collision and radiative processes in emission of atmospheric carbon dioxide

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2018-05-01

The peculiarities of the spectroscopic properties of CO2 molecules in air due to vibration-rotation radiative transitions are analyzed. The absorption coefficient due to atmospheric carbon dioxide and other atmospheric components is constructed within the framework of the standard atmosphere model, on the basis of classical molecular spectroscopy and the regular model for the spectroscopy absorption band. The radiative flux from the atmosphere toward the Earth is represented as that of a blackbody, and the radiative temperature for emission at a given frequency is determined with accounting for the local thermodynamic equilibrium, a small gradient of the tropospheric temperature and a high optical thickness of the troposphere for infrared radiation. The absorption band model with an absorption coefficient averaged over the frequency and line-by-line model are used for evaluating the radiative flux from the atmosphere to the Earth which values are nearby for these models and are equal W m‑2 for the contemporary concentration of atmospheric CO2 molecules and W m‑2 at its doubled value. The absorption band model is not suitable to calculate the radiative flux change at doubling of carbon dioxide concentration because averaging over oscillations decreases the range where the atmospheric optical thickness is of the order of one, and just this range determines this change. The line-by-line method gives the change of the global temperature K as a result of doubling the carbon dioxide concentration. The contribution to the global temperature change due to anthropogenic injection of carbon dioxide in the atmosphere, i.e. resulted from combustion of fossil fuels, is approximately 0.02 K now.

Laser absorption of carbon fiber reinforced polymer with randomly distributed carbon fibers

NASA Astrophysics Data System (ADS)

Hu, Jun; Xu, Hebing; Li, Chao

2018-03-01

Laser processing of carbon fiber reinforced polymer (CFRP) is a non-traditional machining method which has many prospective applications. The laser absorption characteristics of CFRP are analyzed in this paper. A ray tracing model describing the interaction of the laser spot with CFRP is established. The material model contains randomly distributed carbon fibers which are generated using an improved carbon fiber placement method. It was found that CFRP has good laser absorption due to multiple reflections of the light rays in the material’s microstructure. The randomly distributed carbon fibers make the absorptivity of the light rays change randomly in the laser spot. Meanwhile, the average absorptivity fluctuation is obvious during movement of the laser. The experimental measurements agree well with the values predicted by the ray tracing model.

Carbon dioxide laser for de-epithelialization of periodontal flaps.

PubMed

Centty, I G; Blank, L W; Levy, B A; Romberg, E; Barnes, D M

1997-08-01

Regeneration of mineralized and soft connective tissue components of the attachment apparatus is the main goal in the treatment of periodontal diseases. Often, apical migration of epithelium (long junctional epithelium) effectively prevents the formation of bone and connective tissue attachment after periodontal surgery. The purpose of the present study was to compare conventional periodontal surgery combined with carbon dioxide laser and conventional periodontal surgery alone with respect to epithelial elimination and degree of necrosis of mucoperiosteal flaps. After signing a consent form, five patients with at least two comparable bilateral periodontal defects needing pocket elimination surgery participated in this study. The investigators randomly divided each side into test and control sites. Each patient received oral hygiene instruction and initial therapy prior to surgery. At surgery, the test site received a sulcular incision and carbon dioxide laser de-epithelialization of the outer and inner aspects of the flap. The control group received reverse bevel incision only. The surgeon performed open flap debridement on all teeth. At the time of surgery, the surgeon did a biopsy of each site and submitted specimens for histologic evaluation. A matched pairs t-test was used to analyze the data. The results show significant differences between the carbon dioxide laser and reverse bevel incision with respect to sulcular (P < or = 0.025) and gingival (external) (P < or = 0.01) flap surface epithelial elimination and tissue necrosis (P < or = 0.005). These results should be replicated with a larger number of subjects. The carbon dioxide laser eliminated sulcular and gingival (external) epithelium without disturbing underlying connective tissue. This finding supports the concept that the carbon dioxide wavelength has little or no effect on tissues beyond the target. However, neither laser nor blade eliminated all the epithelium. Researchers observed chronic inflammation in the control and test sites, with a predominance of plasma cells. Lining the sulcular and gingival (external) lased areas, investigators found coagulation necrosis covered by fibrin and coagulated blood. The laser appears to effectively remove epithelium at the time of surgery; however, future long-term, well-controlled quantitative histologic studies are needed to evaluate the effect of repeated carbon dioxide laser de-epithelialization of the gingival (external) surface of mucoperiosteal flaps at intervals during the healing period.

An audit of the use of the CO2 laser in oral and maxillofacial surgery

NASA Astrophysics Data System (ADS)

Pinheiro, Antonio L. B.; Santos de Almeida, Darcy

2004-09-01

The use of the Carbon dioxide Laser to perform surgical procedures in the oral cavity has been described as a successful method for the treatment of several conditions affecting the maxillofacial region. Several benefits of the use of the CO2 Laser have been reported and includes reduction of postoperative pain and edema, local hemosthasis, reduction of scaring and wound contraction and infection. The aim of this work is to present our clinical experience in performing several surgical procedures using the CO2 Laser to treat soft tissue pathologies of both benign and malign origin as well as on performing pre-prosthetic surgery, apical surgery and on the treatment of pre-malignancies. Our experience demonstrate that the use of the Carbon dioxide Laser in treating oral soft-tissue pathology presents advantages over conventional techniques and local discomfort and pain are the most common complaints after Laser surgery. The Carbon dioxide Laser does not offer any enhanced cure-rate for oral pathology, but rather it is a precise means of removing soft tissue lesions with little upset afterwards.

Selective removal of dental composite using a rapidly scanned carbon dioxide laser

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Fried, Daniel

2011-03-01

Dental restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants or removing composite adhesives such as residual composite left after debonding orthodontic brackets. In this study a carbon dioxide laser operating at high laser pulse repetition rates integrated with a galvanometer based scanner was used to selectively remove composite from tooth surfaces. A diode array spectrometer was used to measure the plume emission after each laser pulse and determine if the ablated material was tooth mineral or composite. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. The laser was able to rapidly remove the composites rapidly from both surfaces with minimal damage to the underlying sound enamel.

Two-dimensional temperature and carbon dioxide concentration profiles in atmospheric laminar diffusion flames measured by mid-infrared direct absorption spectroscopy at 4.2 μm

NASA Astrophysics Data System (ADS)

Liu, Xunchen; Zhang, Guoyong; Huang, Yan; Wang, Yizun; Qi, Fei

2018-04-01

We present a multi-line flame thermometry technique based on mid-infrared direct absorption spectroscopy of carbon dioxide at its v_3 fundamental around 4.2 μm that is particularly suitable for sooting flames. Temperature and concentration profiles of gas phase molecules in a flame are important characteristics to understand its flame structure and combustion chemistry. One of the standard laboratory flames to analyze polycyclic aromatic hydrocarbons (PAH) and soot formation is laminar non-premixed co-flow flame, but PAH and soot introduce artifact to most non-contact optical measurements. Here we report an accurate diagnostic method of the temperature and concentration profiles of CO2 in ethylene diffusion flames by measuring its v_3 vibrational fundamental. An interband cascade laser was used to probe the R-branch bandhead at 4.2 μm, which is highly sensitive to temperature change, free from soot interference and ambient background. Calibration measurement was carried out both in a low-pressure Herriott cell and an atmospheric pressure tube furnace up to 1550 K to obtain spectroscopic parameters for high-temperature spectra. In our co-flow flame measurement, two-dimensional line-of-sight optical depth of an ethylene/N2 laminar sooting flame was recorded by dual-beam absorption scheme. The axially symmetrical attenuation coefficient profile of CO2 in the co-flow flame was reconstructed from the optical depth by Abel inversion. Spatially resolved flame temperature and in situ CO2 volume fraction profiles were derived from the calibrated CO2 spectroscopic parameters and compared with temperature profiles measured by two-line atomic fluorescence.

The carbon dioxide laser surgical unit as an instrument for surgery of brain tumours--its advantages and disadvantages.

PubMed

Takizawa, T

1984-01-01

The author started in 1969 his studies on developing the practical models of the carbon dioxide laser surgical units and produced Medilaser-S, Model MEL-42 and MEL-444. By the end of 1982 the author had operated on 143 cases of brain tumour with the laser. Most of those cases were brain tumours which were difficult or impossible to remove by conventional means. The major points of this paper are as follows: The principle of the laser, the mechanism of the CO2 laser, the biomedical features of the CO2 laser, the advantages and disadvantages of the CO2 laser, indications and contraindications for the use of the CO2 laser, development of the CO2 laser surgical units, surgical procedures and techniques of brain tumour laser surgery, adjuvant methods of laser surgery and comparison between the CO2 laser and the Nd-YAG laser.

Sensitivity studies for a space-based methane lidar mission

NASA Astrophysics Data System (ADS)

Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

2011-10-01

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1% over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

Sensitivity studies for a space-based methane lidar mission

NASA Astrophysics Data System (ADS)

Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

2011-06-01

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in Polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1 % over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

NASA Astrophysics Data System (ADS)

Gerdel, Katharina; Spielmann, Felix M.; Hammerle, Albin; Wohlfahrt, Georg

2016-04-01

Carbonyl sulfide (COS) is the most abundant sulfur containing trace gas present in the troposphere at concentrations of around 500 ppt. Recent interest in COS by the ecosystem-physiological community has been sparked by the fact that COS co-diffuses into plant leaves pretty much the same way as carbon dioxide (CO2) does, but in contrast to CO2, COS is not known to be emitted by plants. Thus uptake of COS by vegetation has the potential to be used as a tracer for canopy gross photosynthesis, which cannot be measured directly, however represents a key term in the global carbon cycle. Since a few years, quantum cascade laser absorption spectrometers (QCLAS) are commercially available with the precision, sensitivity and time response suitable for eddy covariance (EC) flux measurements. While there exist a handful of published reports on EC flux measurements in the recent literature, no rigorous investigation of the applicability of QCLAS for EC COS flux measurements has been carried out so far, nor have been EC processing and QA/QC steps developed for carbon dioxide and water vapor flux measurements within FLUXNET been assessed for COS. The aim of this study is to close this knowledge gap, to discuss critical steps in the post-processing chain of COS EC flux measurements and to devise best-practice guidelines for COS EC flux data processing. To this end we collected EC COS (and CO2, H2O and CO) flux measurements above a temperate mountain grassland in Austria over the vegetation period 2015 with a commercially available QCLAS. We discuss various aspects of EC data post-processing, in particular issues with the time-lag estimation between sonic anemometer and QCLAS signals and QCLAS time series detrending, as well as QA/QC, in particular flux detection limits, random flux uncertainty, the interaction of various processing steps with common EC QA/QC filters (e.g. detrending and stationarity tests), u*-filtering, etc.

Infrared Lasers in Chemistry.

ERIC Educational Resources Information Center

John, Phillip

1982-01-01

Selected infrared laser chemistry topics are discussed including carbon dioxide lasers, infrared quanta and molecules, laser-induced chemistry, structural isomerization (laser purification, sensitized reactions, and dielectric breakdown), and fundamental principles of laser isotope separation, focusing on uranium isotope separation. (JN)

Low-debris, efficient laser-produced plasma extreme ultraviolet source by use of a regenerative liquid microjet target containing tin dioxide (SnO2) nanoparticles

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Dojyo, Naoto; Hamada, Masaya; Sasaki, Wataru; Kubodera, Shoichi

2006-05-01

We demonstrated a low-debris, efficient laser-produced plasma extreme ultraviolet (EUV) source by use of a regenerative liquid microjet target containing tin-dioxide (SnO2) nanoparticles. By using a low SnO2 concentration (6%) solution and dual laser pulses for the plasma control, we observed the EUV conversion efficiency of 1.2% with undetectable debris.

Laser Heterodyne Radiometer for Sensitive Detection of CO2 and CH4

NASA Technical Reports Server (NTRS)

Wilson, Emily L.; Miller, J. Houston

2011-01-01

We propose to develop an inexpensive, miniaturized, passive laser heterodyne radiometer (LHR) using commercially available telecommunications laser components to measure two significant carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). This instrument would operate in tandem with the passive aerosol sensor currently used in AERONET (an established network of more than 450 ground aerosol monitoring instruments worldwide). Because aerosols induce a radiative effect that influences terrestrial carbon exchange, simultaneous detection of aerosols with these key carbon cycle gases offers a uniquely comprehensive measurement approach that supports the Decadal Survey. Laser heterodyne radiometry is a technique for detecting weak signals that was adapted from radio receiver technology. In a radio receiver, a weak input signal from a radio antenna is mixed with a stronger local oscillator signal. The mixed signal (beat note, or intermediate frequency) has a frequency equal to the difference between the input signal and the local oscillator. The intermediate frequency is amplified and sent to a detector that extracts the audio from the signal. In a laser heterodyne radiometer, the weak input signal is light that has undergone absorption by a trace gas. The local oscillator is a laser at a near-by frequency - in this case a low-cost distributed feedback (DFB) telecommunications laser. These two light waves are superimposed in either a beamsplitter or in a fiber coupler (as is the case in this design). The signals are mixed in the detector, and the RF beat frequency is extracted. Changes in concentration of the trace gas are realized through analyzing changes in the beat frequency amplitude. A schematic of the progression of the LHR development project is shown in the figure below. At the center (within the dashed line), light from the local oscillator is superimposed upon light that has undergone absorption by a trace gas, in a single mode fiber coupler. Superimposed light is mixed in a fast photoreceiver, and the beat signal is analyzed for changes in absorption. The left portion of the figure depicts a progression of light sources that pass through the trace gas, increasing in complexity in the downward direction. On the right side of the figure, RF signal processing progresses from a commercially available spectrum analyzer to a RF receiver, and finally to an RF filter bank to deconvolute portions of the beat frequency more heavily weighted for different altitudes.

Prospects of target nanostructuring for laser proton acceleration.

PubMed

Lübcke, Andrea; Andreev, Alexander A; Höhm, Sandra; Grunwald, Ruediger; Ehrentraut, Lutz; Schnürer, Matthias

2017-03-14

In laser-based proton acceleration, nanostructured targets hold the promise to allow for significantly boosted proton energies due to strong increase of laser absorption. We used laser-induced periodic surface structures generated in-situ as a very fast and economic way to produce nanostructured targets capable of high-repetition rate applications. Both in experiment and theory, we investigate the impact of nanostructuring on the proton spectrum for different laser-plasma conditions. Our experimental data show that the nanostructures lead to a significant enhancement of absorption over the entire range of laser plasma conditions investigated. At conditions that do not allow for efficient laser absorption by plane targets, i.e. too steep plasma gradients, nanostructuring is found to significantly enhance the proton cutoff energy and conversion efficiency. In contrast, if the plasma gradient is optimized for laser absorption of the plane target, the nanostructure-induced absorption increase is not reflected in higher cutoff energies. Both, simulation and experiment point towards the energy transfer from the laser to the hot electrons as bottleneck.

Prospects of target nanostructuring for laser proton acceleration

NASA Astrophysics Data System (ADS)

Lübcke, Andrea; Andreev, Alexander A.; Höhm, Sandra; Grunwald, Ruediger; Ehrentraut, Lutz; Schnürer, Matthias

2017-03-01

In laser-based proton acceleration, nanostructured targets hold the promise to allow for significantly boosted proton energies due to strong increase of laser absorption. We used laser-induced periodic surface structures generated in-situ as a very fast and economic way to produce nanostructured targets capable of high-repetition rate applications. Both in experiment and theory, we investigate the impact of nanostructuring on the proton spectrum for different laser-plasma conditions. Our experimental data show that the nanostructures lead to a significant enhancement of absorption over the entire range of laser plasma conditions investigated. At conditions that do not allow for efficient laser absorption by plane targets, i.e. too steep plasma gradients, nanostructuring is found to significantly enhance the proton cutoff energy and conversion efficiency. In contrast, if the plasma gradient is optimized for laser absorption of the plane target, the nanostructure-induced absorption increase is not reflected in higher cutoff energies. Both, simulation and experiment point towards the energy transfer from the laser to the hot electrons as bottleneck.

Application of a flexible CO(2) laser fiber for neurosurgery: laser-tissue interactions.

PubMed

Ryan, Robert W; Wolf, Tamir; Spetzler, Robert F; Coons, Stephen W; Fink, Yoel; Preul, Mark C

2010-02-01

The CO(2) laser has an excellent profile for use in neurosurgery. Its high absorption in water results in low thermal spread, sparing adjacent tissue. Use of this laser has been limited to line-of-sight applications because no solid fiber optic cables could transmit its wavelength. Flexible photonic bandgap fiber technology enables delivery of CO(2) laser energy through a flexible fiber easily manipulated in a handheld device. The authors examined and compared the first use of this CO(2) laser fiber to conventional methods for incising neural tissue. Carbon dioxide laser energy was delivered in pulsed or continuous wave settings for different power settings, exposure times, and distances to cortical tissue of 6 anesthetized swine. Effects of CO(2) energy on the tissue were compared with bipolar cautery using a standard pial incision technique, and with scalpel incisions without cautery. Tissue was processed for histological analysis (using H & E, silver staining, and glial fibrillary acidic protein immunohistochemistry) and scanning electron microscopy, and lesion measurements were made. Light microscopy and scanning electron microscopy revealed laser incisions of consistent shape, with central craters surrounded by limited zones of desiccated and edematous tissue. Increased laser power resulted in deeper but not significantly wider incisions. Bipolar cautery lesions showed desiccated and edematous zones but did not incise the pia, and width increased more than depth with higher power. Incisions made without using cautery produced hemorrhage but minimal adjacent tissue damage. The photonic bandgap fiber CO(2) laser produced reliable cortical incisions, adjustable over a range of settings, with minimal adjacent thermal tissue damage. Ease of application under the microscope suggests this laser system has reached true practicality for neurosurgery.

Blackbody absorption efficiencies for six lamp pumped Nd laser materials

NASA Technical Reports Server (NTRS)

Cross, Patricia L.; Barnes, Norman P.; Skolaut, Milton W., Jr.; Storm, Mark E.

1990-01-01

Utilizing high resolution spectra, the absorption efficiencies for six Nd laser materials were calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO4, Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

An intercomparison of airborne nitrogen dioxide instruments

NASA Technical Reports Server (NTRS)

Gregory, G. L.; Hoell, J. M., Jr.; Carroll, M. A.; Ridley, B. A.; Davis, D. D.; Bradshaw, J.; Rodgers, M. O.; Sandholm, S. T.; Schiff, H. I.; Torres, A. L.

1990-01-01

Results on NO2 instruments are reported from the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instruments tested were (1) a two-photon LIF system using a laser for NO2-NO photolysis, (2) a chemiluminescence (CL) detector using FeSO4 for NO2-NO conversion, (3) a CL detector using an arc lamp for NO2-NO photolysis, and (4) a tunable-laser-diode multipath-absorption system. The procedures for the CITE 2 ground-based and flight tests are described in detail, and the results are presented in extensive graphs. Instrument (2) was eliminated because the FeSO4 converted atmospheric PAN to NO, resulting in spuriously high NO2 values. The remaining instruments gave readings in 30-40-percent agreement at NO2 mixing ratios of 100-200 parts per trillion by volume (pptv). At ratios below 50 pptv, the correlation among the measurements was very poor, with a tendency for system (4) to give higher values than (1) or (3).

Methods and apparatus for measuring small leaks from carbon dioxide sequestration facilities

DOEpatents

Nelson, Jr., David D.; Herndon, Scott C.

2018-01-02

In one embodiment, a CO.sub.2 leak detection instrument detects leaks from a site (e.g., a CO.sub.2 sequestration facility) using rapid concentration measurements of CO.sub.2, O.sub.2 and optionally water concentration that are achieved, for example, using laser spectroscopy (e.g. direct absorption laser spectroscopy). Water vapor in the sample gas may not be removed, or only partially removed. The sample gas may be collected using a multiplexed inlet assembly from a plurality of locations. CO.sub.2 and O.sub.2 concentrations may be corrected based on the water concentration. A resulting dataset of the CO.sub.2 and O.sub.2 concentrations is analyzed over time intervals to detect any changes in CO.sub.2 concentration that are not anti-correlated with O.sub.2 concentration, and to identify a potential CO.sub.2 leak in response thereto. The analysis may include determining eddy covariance flux measurements of sub-surface potential carbon.

[Absorption spectrum of Quasi-continuous laser modulation demodulation method].

PubMed

Shao, Xin; Liu, Fu-Gui; Du, Zhen-Hui; Wang, Wei

2014-05-01

A software phase-locked amplifier demodulation method is proposed in order to demodulate the second harmonic (2f) signal of quasi-continuous laser wavelength modulation spectroscopy (WMS) properly, based on the analysis of its signal characteristics. By judging the effectiveness of the measurement data, filter, phase-sensitive detection, digital filtering and other processing, the method can achieve the sensitive detection of quasi-continuous signal The method was verified by using carbon dioxide detection experiments. The WMS-2f signal obtained by the software phase-locked amplifier and the high-performance phase-locked amplifier (SR844) were compared simultaneously. The results show that the Allan variance of WMS-2f signal demodulated by the software phase-locked amplifier is one order of magnitude smaller than that demodulated by SR844, corresponding two order of magnitude lower of detection limit. And it is able to solve the unlocked problem caused by the small duty cycle of quasi-continuous modulation signal, with a small signal waveform distortion.

Performance of an exhaled nitric oxide and carbon dioxide sensor using quantum cascade laser-based integrated cavity output spectroscopy.

PubMed

McCurdy, Matthew R; Bakhirkin, Yury; Wysocki, Gerard; Tittel, Frank K

2007-01-01

Exhaled nitric oxide (NO) is an important biomarker in asthma and other respiratory disorders. The optical performance of a NOCO(2) sensor employing integrated cavity output spectroscopy (ICOS) with a quantum cascade laser operating at 5.22 microm capable of real-time NO and CO(2) measurements in a single breath cycle is reported. A NO noise-equivalent concentration of 0.4 ppb within a 1-sec integration time is achieved. The off-axis ICOS sensor performance is compared to a chemiluminescent NO analyzer and a nondispersive infrared (NDIR) CO(2) absorption capnograph. Differences between the gas analyzers are assessed by the Bland-Altman method to estimate the expected variability between the gas sensors. The off-axis ICOS sensor measurements are in good agreement with the data acquired with the two commercial gas analyzers. This work demonstrates the performance characteristics and merits of mid-infrared spectroscopy for exhaled breath analysis.

Carbon dioxide laser microsurgery of the uterine tube.

PubMed

Baggish, M S; Chong, A P

1981-07-01

The carbon dioxide (CO2) laser was used to perform microsurgical excision of obstructed tubal segments in rabbit and human subjects. Approximation of the freshly severed tubes by means of laser "welding" was evaluated in both groups investigated. More important, the laser beam cuts accurately and atraumatically while sealing small vascular channels. Scanning electron microscopic studies of the human fallopian tube following laser surgery were done to determine the extent of tissue injury. At a distance of 1 mm distal to the vaporization and necrotic impact zone, normal tubal anatomy was observed. Follow-up data are presented for 7 women who underwent laser beam tuboplasty between 1979 and 1980. The principle advantages of the CO2 laser are its precise control, minimal tissue injury, and hemostatic properties.

Phase-selective vanadium dioxide (VO{sub 2}) nanostructured thin films by pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masina, B. N., E-mail: BMasina@csir.co.za, E-mail: slafane@cdta.dz; School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000; Lafane, S., E-mail: BMasina@csir.co.za, E-mail: slafane@cdta.dz

2015-10-28

Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO{sub 2}) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ∼43 °C, withoutmore » any doping, paving the way to switchable transparency in optical materials at room temperature.« less

Characterization of laser damage performance of fused silica using photothermal absorption technique

NASA Astrophysics Data System (ADS)

Wan, Wen; Shi, Feng; Dai, Yifan; Peng, Xiaoqiang

2017-06-01

The subsurface damage and metal impurities have been the main laser damage precursors of fused silica while subjected to high power laser irradiation. Light field enhancement and thermal absorption were used to explain the appearance of damage pits while the laser energy is far smaller than the energy that can reach the intrinsic threshold of fused silica. For fused silica optics manufactured by magnetorheological finishing or advanced mitigation process, no scratch-related damage site occurs can be found on the surface. In this work, we implemented a photothermal absorption technique based on thermal lens method to characterize the subsurface defects of fused silica optics. The pump beam is CW 532 nm wavelength laser. The probe beam is a He-Ne laser. They are collinear and focused through the same objective. When pump beam pass through the sample, optical absorption induces the local temperature rise. The lowest absorptance that we can detect is about the order of magnitude of 0.01 ppm. When pump beam pass through the sample, optical absorption induces the local temperature rise. The photothermal absorption value of fused silica samples range from 0.5 to 10 ppm. The damage densities of the samples were plotted. The damage threshold of samples at 8J/cm2 were gived to show laser damage performance of fused silica.The results show that there is a strong correlation between the thermal absorption and laser damage density. The photothermal absorption technique can be used to predict and evaluate the laser damage performance of fused silica optics.

The NASA high power carbon dioxide laser: A versatile tool for laser applications

NASA Technical Reports Server (NTRS)

Lancashire, R. B.; Alger, D. L.; Manista, E. J.; Slaby, J. G.; Dunning, J. W.; Stubbs, R. M.

1976-01-01

A closed-cycle, continuous wave, carbon dioxide high power laser has been designed and fabricated to support research for the identification and evaluation of possible high power laser applications. The device is designed to generate up to 70 kW of laser power in annular shape beams from 1 to 9 cm in diameter. Electric discharge, either self sustained or electron beam sustained, is used for excitation. This laser facility provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams. The facility provides a well defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.

Quad quantum cascade laser spectrometer with dual gas cells for the simultaneous analysis of mainstream and sidestream cigarette smoke

NASA Astrophysics Data System (ADS)

Baren, Randall E.; Parrish, Milton E.; Shafer, Kenneth H.; Harward, Charles N.; Shi, Quan; Nelson, David D.; McManus, J. Barry; Zahniser, Mark S.

2004-12-01

A compact, fast response, infrared spectrometer using four pulsed quantum cascade (QC) lasers has been applied to the analysis of gases in mainstream (MS) and sidestream (SS) cigarette smoke. QC lasers have many advantages over the traditional lead-salt tunable diode lasers, including near room temperature operation with thermoelectric cooling and single mode operation with improved long-term stability. The new instrument uses two 36 m, 0.3 l multiple pass absorption gas cells to obtain a time response of 0.1 s for the MS smoke system and 0.4 s for the SS smoke system. The concentrations of ammonia, ethylene, nitric oxide, and carbon dioxide for three different reference cigarettes were measured simultaneously in MS and SS smoke. A data rate of 20 Hz provides sufficient resolution to determine the concentration profiles during each 2 s puff in the MS smoke. Concentration profiles before, during and after the puffs also have been observed for these smoke constituents in SS smoke. Also, simultaneous measurements of CO 2 from a non-dispersive infrared (NDIR) analyzer are obtained for both MS and SS smoke. In addition, during this work, nitrous oxide was detected in both the MS and SS smoke for all reference cigarettes studied.

Applications of absorption spectroscopy using quantum cascade lasers.

PubMed

Zhang, Lizhu; Tian, Guang; Li, Jingsong; Yu, Benli

2014-01-01

Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

Temperature and pressure dependence of dichloro-difluoromethane (CF2C12) absorption coefficients for CO2 waveguide laser radiation

NASA Technical Reports Server (NTRS)

Harward, C. N.

1977-01-01

Measurements were performed to determine the pressure and temperature dependence of CFM-12 absorption coefficients for CO2 waveguide laser radiation. The absorption coefficients of CFM-12 for CO2 waveguide laser radiation were found to have no spectral structure within small spectral bandwidths around the CO2 waveguide laser lines in the CO2 spectral band for pressures above 20 torr. All of the absorption coefficients for the CO2 laser lines studied are independent of pressure above 100 torr, except for the P(36) laser CO2 spectral band. The absorption coefficients associated with the P(42) line in the same band showed the greatest change with temperature, and it also has the largest value of all the lines studied.

21 CFR 179.43 - Carbon dioxide laser for etching food.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Carbon dioxide laser for etching food. 179.43 Section 179.43 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF...

21 CFR 179.43 - Carbon dioxide laser for etching food.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Carbon dioxide laser for etching food. 179.43 Section 179.43 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources...

Fast-axial turbulent flow CO2 laser output characteristics and scaling parameters

NASA Astrophysics Data System (ADS)

Dembovetsky, V. V.; Zavalova, Valentina Y.; Zavalov, Yuri N.

1996-04-01

The paper presents the experimental results of evaluating the output characteristics of TLA- 600 carbon-dioxide laser with axial turbulent gas flow, as well as the results of numerical modeling. The output characteristic and spatial distribution of laser beam were measured with regard to specific energy input, working mixture pressure, active media length and output mirror reflection. The paper presents the results of experimental and theoretical study and design decisions on a succession of similar type industrial carbon-dioxide lasers with fast-axial gas-flow and dc discharge excitation of active medium developed at NICTL RAN. As an illustration, characteristics of the TLA-600 laser are cited.

Direct quantitative comparison of molecular responses in photodamaged human skin to fractionated and fully ablative carbon dioxide laser resurfacing.

PubMed

Orringer, Jeffrey S; Sachs, Dana L; Shao, Yuan; Hammerberg, Craig; Cui, Yilei; Voorhees, John J; Fisher, Gary J

2012-10-01

Fractionated ablative laser resurfacing has become a widely used treatment modality. Its clinical results are often found to approach those of traditional fully ablative laser resurfacing. To directly compare the molecular changes that result from fractionated and fully ablative carbon dioxide (CO(2)) laser resurfacing in photodamaged human skin. Photodamaged skin of 34 adult volunteers was focally treated at distinct sites with a fully ablative CO(2) laser and a fractionated CO(2) laser. Serial skin samples were obtained at baseline and several time points after treatment. Real-time reverse transcriptase polymerase chain reaction technology and immunohistochemistry were used to quantify molecular responses to each type of laser treatment. Fully ablative and fractionated CO(2) laser resurfacing induced significant dermal remodeling and collagen induction. After a single treatment, fractionated ablative laser resurfacing resulted in collagen induction that was approximately 40% to 50% as pronounced as that induced by fully ablative laser resurfacing. The fundamental cutaneous responses that result from fully ablative and fractionated carbon dioxide laser resurfacing are similar but differ in magnitude and duration, with the fully ablative procedure inducing relatively greater changes including more pronounced collagen induction. However, the molecular data reported here provide substantial support for fractionated ablative resurfacing as an effective treatment modality for improving skin texture. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work

NASA Astrophysics Data System (ADS)

Muniz, German; Alum, Jorge

1996-02-01

In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.

Pulsed CO2 laser for intra-articular cartilage vaporization and subchondral bone perforation in horses

NASA Astrophysics Data System (ADS)

Nixon, Alan J.; Roth, Jerry E.; Krook, Lennart P.

1991-05-01

A pulsed carbon dioxide laser was used to vaporize articular cartilage in four horses, and perforate the cartilage and subchondral bone in four horses. Both intercarpal joints were examined arthroscopically and either a 1 cm cartilage crater or a series of holes was created in the third carpal bone of one joint. The contralateral carpus served as a control. The horses were evaluated clinically for 8 weeks, euthanatized and the joints examined radiographically, grossly, and histologically. Pulsed carbon dioxide laser vaporized cartilage readily but penetrated bone poorly. Cartilage vaporization resulted in no greater swelling, heat, pain on flexion, lameness, or synovial fluid reaction than the sham procedure. Laser drilling resulted in a shallow, charred hole with a tenacious carbon residue, and in combination with the thermal damage to deeper bone, resulted in increased swelling, mild lameness and a low-grade, but persistent synovitis. Cartilage removal by laser vaporization resulted in rapid regrowth with fibrous and fibrovascular tissue and occasional regions of fibrocartilage at week 8. The subchondral bone, synovial membrane, and draining lymph nodes appeared essentially unaffected by the laser cartilage vaporization procedure. Conversely, carbon dioxide laser drilling of subchondral bone resulted in poor penetration, extensive areas of thermal necrosis of bone, and significant secondary damage to the apposing articular surface of the radial carpal bone. The carbon dioxide laser is a useful intraarticular instrument for removal of cartilage and has potential application in inaccessible regions of diarthrodial joints. It does not penetrate bone sufficiently to have application in subchondral drilling.

Development of a tunable Fabry-Perot interferometer UV camera for monitoring sulfur dioxide emissions

NASA Astrophysics Data System (ADS)

Tamminen, J.; Kujanpää, J.; Ojanen, H.; Saari, H.; Näkki, I.; Tukiainen, S.; Kyrölä, E.

2017-12-01

We present a novel UV camera for sulfur dioxide emission monitoring.The camera is equipped with a piezo-actuated Fabry-Perot interferometer allowing thefilter transmission to be tuned to match the differential absorption features ofsulfur dioxide in the wavelength region 305-320 nm. The differential absorption structuresare exploited to reduce the interfering effects of weakly wavelength dependent absorbers, suchas aerosols and black carbon, present in the exhaust gas. A data processing algorithm basedon two air gaps of the filter is presented allowing collection of a sufficient signal-to-noise ratio fordetecting sulfur dioxide in the ship plumes even in the designated emission control areas, such as the Baltic Seawhere the sulfur content limit of fuel oil is 0.1 %. First field tests performed inLänsisatama harbour, Helsinki Finland, indicate that sulfur dioxide can be detectedin ship plumes. The camera is light-weight and can be mounted to a drone.

Near-IR imaging of erbium laser ablation with a water spray

NASA Astrophysics Data System (ADS)

Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

2008-02-01

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO2 and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water.

Prospects of target nanostructuring for laser proton acceleration

PubMed Central

Lübcke, Andrea; Andreev, Alexander A.; Höhm, Sandra; Grunwald, Ruediger; Ehrentraut, Lutz; Schnürer, Matthias

2017-01-01

In laser-based proton acceleration, nanostructured targets hold the promise to allow for significantly boosted proton energies due to strong increase of laser absorption. We used laser-induced periodic surface structures generated in-situ as a very fast and economic way to produce nanostructured targets capable of high-repetition rate applications. Both in experiment and theory, we investigate the impact of nanostructuring on the proton spectrum for different laser–plasma conditions. Our experimental data show that the nanostructures lead to a significant enhancement of absorption over the entire range of laser plasma conditions investigated. At conditions that do not allow for efficient laser absorption by plane targets, i.e. too steep plasma gradients, nanostructuring is found to significantly enhance the proton cutoff energy and conversion efficiency. In contrast, if the plasma gradient is optimized for laser absorption of the plane target, the nanostructure-induced absorption increase is not reflected in higher cutoff energies. Both, simulation and experiment point towards the energy transfer from the laser to the hot electrons as bottleneck. PMID:28290479

High precision measurements of 16O12C17O using a new type of cavity ring down spectrometer

NASA Astrophysics Data System (ADS)

Daëron, M.; Stoltmann, T.; Kassi, S.; Burkhart, J.; Kerstel, E.

2016-12-01

Laser absorption techniques for the measurement of isotopologue abundances in gases have been dripping into the geoscientific community over the past decade. In the field of carbon dioxide such instruments have mostly been restricted to measurements of the most abundant stable isotopologues. Distinct advantages of CRDS techniques are non-destructiveness and the ability to resolve isobaric isotopologues. The determination of low-abundance isotopologues is predominantly limited by the linewidth of the probing laser, laser jitter, laser drift and system stability. Here we present first measurements of 16O12C17O abundances using a new type of ultra-precise cavity ring down spectrometer. By the use of Optical Feedback Frequency Stabilization, we achieved a laser line width in the sub-kHz regime with a frequency drift of less than 20 Hz/s. A tight coupling with an ultra-stable ring down cavity combined with a frequency tuning mechanism which enables us to arbitrarily position spectral points (Burkart et al., 2013) allowed us to demonstrate a single-scan (2 minutes) precision of 40 ppm on the determination of the 16O12C17O abundance. These promising results imply that routine, direct, high-precision measurements of 17O-anomalies in CO2 using this non-destructive method are in reach. References:Burkart J, Romanini D, Kassi S; Optical feedback stabilized laser tuned by single-sideband modulation; Optical Letters 12:2062-2063 (2013)

Petawatt laser absorption bounded

PubMed Central

Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

2014-01-01

The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

Manganese dioxide causes spurious gold values in flame atomic-absorption readings from HBr-Br2 digestions

USGS Publications Warehouse

Campbell, W.L.

1981-01-01

False readings, apparently caused by the presence of high concentrations of manganese dioxide, have been observed in our current flame atomic-absorption procedure for the determination of gold. After a hydrobromic acid (HBr)-bromine (Br2) leach, simply heating the sample to boiling to remove excess Br2 prior to extraction with methyl-isobutyl-ketone (MIBK) eliminates these false readings. ?? 1981.

Development of differential absorption lidar (DIAL) for detection of CO2, CH4 and PM in Alberta

NASA Astrophysics Data System (ADS)

Wojcik, Michael; Crowther, Blake; Lemon, Robert; Valupadas, Prasad; Fu, Long; Leung, Bonnie; Yang, Zheng; Huda, Quamrul; Chambers, Allan

2005-05-01

Rapid expansion of the oil and gas industry in Alberta, including the oil sands, has challenged the Alberta Government to keep pace in its efforts to monitor and mitigate the environmental impacts of development. The limitations of current monitoring systems has pushed the provincial government to seek out advanced sensing technologies such as satellite imagery and laser based sensors. The Space Dynamics Laboratory (SDL) of Utah State University, in cooperation with Alberta Environmental Monitoring, Evaluation and Reporting Agency (AEMERA), has developed North America's first mobile differential absorption lidar (DIAL) system designed specifically for emissions measurement. This instrument is housed inside a 36' trailer which allows for mobility to travel across Alberta to characterize source emissions and to locate fugitive leaks. DIAL is capable of measuring concentrations for carbon dioxide (CO2) and methane (CH4) at ranges of up to 3 km with a spatial resolution of 10 meters. DIAL can map both CO2 and CH4, as well as particulate matter (PM) in a linear fashion; by scanning the laser beam in both azimuth and elevation DIAL can create images of emissions in two dimensions. DIAL imagery may be used to understand and control production practices, characterize source emissions, determine emission factors, locate fugitive leaks, assess plume dispersion, and confirm air dispersion modeling. A system overview of the DIAL instrument and some representative results will be discussed.

Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents

NASA Astrophysics Data System (ADS)

Gray, R. J.; Wilson, R.; King, M.; Williamson, S. D. R.; Dance, R. J.; Armstrong, C.; Brabetz, C.; Wagner, F.; Zielbauer, B.; Bagnoud, V.; Neely, D.; McKenna, P.

2018-03-01

The absorption of laser energy and dynamics of energetic electrons in dense plasma is fundamental to a range of intense laser-driven particle and radiation generation mechanisms. We measure the total reflected and scattered laser energy as a function of intensity, distinguishing between the influence of pulse energy and focal spot size on total energy absorption, in the interaction with thin foils. We confirm a previously published scaling of absorption with intensity by variation of laser pulse energy, but find a slower scaling when changing the focal spot size. 2D particle-in-cell simulations show that the measured differences arise due to energetic electrons recirculating within the target and undergoing multiple interactions with the laser pulse, which enhances absorption in the case of large focal spots. This effect is also shown to be dependent on the laser pulse duration, the target thickness and the electron beam divergence. The parameter space over which this absorption enhancement occurs is explored via an analytical model. The results impact our understanding of the fundamental physics of laser energy absorption in solids and thus the development of particle and radiation sources driven by intense laser–solid interactions.

Eruptive keratoacanthomas following carbon dioxide laser resurfacing.

PubMed

Gewirtzman, A; Meirson, D H; Rabinovitz, H

1999-08-01

Skin resurfacing with the carbon dioxide (CO2) laser is currently a popular means of improving rhytides and scars. Scarring, hyperpigmentation, hypopigmentation, and infection are among the complications that have been known to occur in some patients treated with the CO2 laser. We wish to communicate a previously unreported complication of CO2 laser resurfacing-multiple eruptive keratoacanthomas. We describe a 61-year-old woman who presented with multiple eruptive keratoacanthomas subsequent to CO2 laser resurfacing. Her lesions were cultured for fungus and bacteria. Biopsy specimens of two lesions were taken. Cultures were negative for pathogens. Biopsy specimens revealed atypical squamous epithelial proliferation and changes consistent with eruptive keratoacanthomas. Multiple eruptive keratoacanthomas should be considered as a rare complication of CO2 laser resurfacing.

[Animal experiment comparison of the therapeutic efficacy of tumor excision with a scalpel or with a CO2 laser in subcutaneously implanted Lewis lung cancer].

PubMed

Mahn, H R; Nowak, C; Audring, H; Liebetruth, J; Lindenau, K F

1982-02-01

An animal experimental study was carried out in order to compare the therapeutical value of two different surgical methods for excising the subcutaneous implanted Lewis lung carcinoma - tumor excision with scalpel or with carbon dioxide laser. The radicalism of operation methods, the survival time, and the tumor local recurrences were performed. The therapeutic effectivity of tumor excision with the carbon dioxide laser is more favourable than the scalpel method.

Carbon dioxide gas sensor based on optical control of color in liquid indicator

NASA Astrophysics Data System (ADS)

Oblov, K. Yu; Ivanova, A. V.; Soloviev, S. A.; Zhdanov, S. V.; Voronov, Yu A.; Florentsev, V. V.

2016-10-01

A new optical carbon dioxide sensor based on the change in glow intensity of the Europium-III complex, caused by CO2 absorption to various pH-indicators (thymol blue, phenol red and cresol red) of carbon dioxide was developed, and its sensitive properties were studied.

The Modeling of Coupled Electromagnetic-Thermo-Mechanical Laser Interactions and Microstructural Behavior of Energetic Aggregates

DTIC Science & Technology

2015-01-01

analytical Beer - Lambert absorption profile to model laser heating of pure energetic crystals without considering any EM wave propagation effects...temperature. These aggregates were studied using both an analytical distribution for laser heating following Beer - Lambert absorption and the full EM finite...surface (ysurface - y) and material absorption coefficient, α, following a Beer - Lambert absorption relation given by , = !()

Airborne Lidar measurements of the atmospheric pressure profile with tunable Alexandrite lasers

NASA Technical Reports Server (NTRS)

Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Milrod, J.; Walden, H.

1986-01-01

The first remote measurements of the atmospheric pressure profile made from an airborne platform are described. The measurements utilize a differential absorption lidar and tunable solid state Alexandrite lasers. The pressure measurement technique uses a high resolution oxygen A band where the absorption is highly pressure sensitive due to collision broadening. Absorption troughs and regions of minimum absorption were used between pairs of stongly absorption lines for these measurements. The trough technique allows the measurement to be greatly desensitized to the effects of laser frequency instabilities. The lidar system was set up to measure pressure with the on-line laser tuned to the absorption trough at 13147.3/cm and with the reference laser tuned to a nonabsorbing frequency near 13170.0/cm. The lidar signal returns were sampled with a 200 range gate (30 vertical resoltion) and averaged over 100 shots.

Laser ablation of PMMA doped with benzyl

NASA Astrophysics Data System (ADS)

Wang, Jun; Niino, Hiroyuki; Yabe, Akira

1998-08-01

KrF-laser ablation of poly(methylmethacrylate) (PMMA) doped with benzil was studied from the viewpoint of nonlinear absorption of the PMMA film during the laser irradiation. After measuring the relationship between the transmission and incident laser intensity, we developed a novel method to obtain absorption coefficient depending on laser intensity. Using the nonlinear absorption coefficient of PMMA doped with benzil, we succeeded in fitting the relationship of etch depth and laser intensity. The dependence of concentration of benzil in PMMA film and the difference between benzil and pyrene were also discussed.

Method of and apparatus for measuring temperature and pressure. [atmospheric sounding

NASA Technical Reports Server (NTRS)

Korb, C. L.; Kalshoven, J. E., Jr. (Inventor)

1985-01-01

Laser beams are transmitted through gas to a reflecting target, which may be either a solid surface or particulate matter in gas or the gas molecules. The return beams are measured to determine the amount of energy absorbed by the gas. For temperature measurements, the laser beam has a wavelength at which the gas exhibits a relatively temperature sensitive and pressure insensitive absorption characteristic for pressure measurements, the laser beam has a wavelength at which the gas has a relatively pressure sensitive and temperature insensitive absorption characteristic. To reduce the effects of scattering on the absorption measurements a reference laser beam with a weak absorption characteristic is transmitted colinearly with the data beam having a strong absorption characteristic. The two signals are processed as a ratio to eliminate back scattering. Embodiments of transmitters and receivers described include a sequential laser pulse transmitter and receiver, a simultaneous laser pulse transmitter and receiver.

Nonequilibrium gas absorption in rotating permeable media

NASA Astrophysics Data System (ADS)

Baev, V. K.; Bazhaikin, A. N.

2016-08-01

The absorption of ammonia, sulfur dioxide, and carbon dioxide by water and aqueous solutions in rotating permeable media, a cellular porous disk, and a set of spaced-apart thin disks has been considered. The efficiency of cleaning air to remove these impurities is determined, and their anomalously high solubility (higher than equilibrium value) has been discovered. The results demonstrate the feasibility of designing cheap efficient rotor-type absorbers to clean gases of harmful impurities.

Non-invasive multiwavelength photoplethysmography under low partial pressure of oxygen.

PubMed

Fang, Yung Chieh; Tai, Cheng-Chi

2016-08-01

A reduction in partial pressure of oxygen in the environment may be caused by a gain in altitude, which reduces the atmospheric pressure; it may also be caused by the carbon dioxide generated from breathing in an enclosed space. Does inhaling oxygen of lower partial pressure affect the oxygen-carrying function of haemoglobin in vivo? This study uses non-invasive multiwavelength photoplethysmography to measure the effects that inhaling this type of oxygen can have on the plethysmography of the appendages of the body (fingertips). The results indicate that under low partial pressure of oxygen, be it the result of a gain in carbon dioxide concentration or altitude, the change in visible light absorption is the biggest for short wavelengths (approximately 620 or 640 nm) near deoxyhaemoglobin, which has higher absorption coefficient. Moreover, increasing carbon dioxide concentration from 5000 to 10,000 ppm doubly reduces the absorption rate of these short wavelengths.

Advancements for Active Remote Sensing of Carbon Dioxide from Space using the ASCENDS CarbonHawk Experiment Simulator: First Results

NASA Astrophysics Data System (ADS)

Obland, M. D.; Nehrir, A. R.; Lin, B.; Harrison, F. W.; Kooi, S. A.; Choi, Y.; Plant, J.; Yang, M. M.; Antill, C.; Campbell, J. F.; Ismail, S.; Browell, E. V.; Meadows, B.; Dobler, J. T.; Zaccheo, T. S.; Moore, B., III; Crowell, S.

2014-12-01

The ASCENDS CarbonHawk Experiment Simulator (ACES) is an Intensity-Modulated Continuous-Wave lidar system recently developed at NASA Langley Research Center that seeks to advance technologies and techniques critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. These advancements include: (1) increasing the power-aperture product to approach ASCENDS mission requirements by implementing multi-aperture telescopes and multiple co-aligned laser transmitters; (2) incorporating high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) developing and incorporating a high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration operation on Global Hawk aircraft, and (4) advancing algorithms for cloud and aerosol discrimination. The ACES instrument architecture is being developed for operation on high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. ACES simultaneously transmits five laser beams: three from commercial EDFAs operating near 1571 nm, and two from the Exelis oxygen (O2) Raman fiber laser amplifier system operating near 1260 nm. The Integrated-Path Differential Absorption (IPDA) lidar approach is used at both wavelengths to independently measure the CO2 and O2 column number densities and retrieve the average column CO2 mixing ratio. The outgoing laser beams are aligned to the field of view of ACES' three fiber-coupled 17.8-cm diameter athermal telescopes. The backscattered light collected by the three telescopes is sent to the detector/TIA subsystem, which has a bandwidth of 4.7 MHz and operates service-free using a tactical dewar and cryocooler. Two key laser modulation approaches are being tested to significantly mitigate the effects of thin clouds on the retrieved CO2 column amounts. Full instrument development concluded in the spring of 2014. After ground range tests of the instrument, ACES successfully completed six test flights on the Langley Hu-25 aircraft in July, 2014, and recorded data at multiple altitudes over land and ocean surfaces with and without intervening clouds. Preliminary results from these flights will be presented in this paper.

Diode Laser Sensor for Scramjet Inlet

DTIC Science & Technology

2010-05-11

This work presents the development of an oxygen -based diode laser absorption sensor designed to be used in a supersonic combustion ramjet engine inlet...ADFA Abstract This work presents development of an oxygen -based diode laser absorption sensor designed to be used in a supersonic combustion ramjet... sensor needs to use oxygen as the absorbing species, as this is the only option for absorption measurements in inlet air. Oxygen absorption lines

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1976-01-01

Techniques for the gas phase absorption of laser radiation for ultimate conversion to gas kinetic energy are discussed. Particular emphasis is placed on absorption by the vibration rotation bands of diatomic molecules at high pressures. This high pressure absorption appears to offer efficient conversion of laser energy to gas translational energy. Bleaching and chemical effects are minimized and the variation of the total absorption coefficient with temperature is minimal.

Laser absorption phenomena in flowing gas devices

NASA Technical Reports Server (NTRS)

Chapman, P. K.; Otis, J. H.

1976-01-01

A theoretical and experimental investigation is presented of inverse Bremsstrahlung absorption of CW CO2 laser radiation in flowing gases seeded with alkali metals. In order to motivate this development, some simple models are described of several space missions which could use laser powered rocket vehicles. Design considerations are given for a test call to be used with a welding laser, using a diamond window for admission of laser radiation at power levels in excess of 10 kW. A detailed analysis of absorption conditions in the test cell is included. The experimental apparatus and test setup are described and the results of experiments presented. Injection of alkali seedant and steady state absorption of the laser radiation were successfully demonstrated, but problems with the durability of the diamond windows at higher powers prevented operation of the test cell as an effective laser powered thruster.

Cadmium Telluride-Titanium Dioxide Nanocomposite for Photodegradation of Organic Substance.

PubMed

Ontam, Areeporn; Khaorapapong, Nithima; Ogawa, Makoto

2015-12-01

Cadmium telluride-titanium dioxide nanocomposite was prepared by hydrothermal reaction of sol-gel derived titanium dioxide and organically modified cadmium telluride. The crystallinity of titanium dioxide in the nanocomposite was higher than that of pure titanium dioxide obtained by the reaction under the same temperature and pressure conditions, showing that cadmium telluride induced the crystallization of titanium dioxide. Diffuse reflectance spectrum of the nanocomposite showed the higher absorption efficiency in the UV-visible region due to band-gap excitation of titanium dioxide. The nanocomposite significantly showed the improvement of photocatalytic activity for 4-chlorophenol with UV light.

Absorption of the laser radiation by the laser plasma with gas microjet targets

NASA Astrophysics Data System (ADS)

Borisevichus, D. A.; Zabrodskii, V. V.; Kalmykov, S. G.; Sasin, M. E.; Seisyan, R. P.

2017-01-01

An upper limit of absorption of the laser radiation in the plasma produced in a gas jet Xe target with the average density of (3-6) × 1018 cm-3 and the effective diameter of 0.7 mm is found. It is equal to ≈50% and remains constant under any variation in this range of densities. This result contradicts both theoretical assessments that have predicted virtually complete absorption and results of earlier experiments with the laser spark in an unlimited stationary Xe gas with the same density, where the upper limit of absorption was close to 100%. An analysis shows that nonlinearity of absorption and plasma nonequilibrium lead to the reduction of the absorption coefficient that, along with the limited size of plasma, can explain the experimental results.

Formation of porous silicon oxide from substrate-bound silicon rich silicon oxide layers by continuous-wave laser irradiation

NASA Astrophysics Data System (ADS)

Wang, Nan; Fricke-Begemann, Th.; Peretzki, P.; Ihlemann, J.; Seibt, M.

2018-03-01

Silicon nanocrystals embedded in silicon oxide that show room temperature photoluminescence (PL) have great potential in silicon light emission applications. Nanocrystalline silicon particle formation by laser irradiation has the unique advantage of spatially controlled heating, which is compatible with modern silicon micro-fabrication technology. In this paper, we employ continuous wave laser irradiation to decompose substrate-bound silicon-rich silicon oxide films into crystalline silicon particles and silicon dioxide. The resulting microstructure is studied using transmission electron microscopy techniques with considerable emphasis on the formation and properties of laser damaged regions which typically quench room temperature PL from the nanoparticles. It is shown that such regions consist of an amorphous matrix with a composition similar to silicon dioxide which contains some nanometric silicon particles in addition to pores. A mechanism referred to as "selective silicon ablation" is proposed which consistently explains the experimental observations. Implications for the damage-free laser decomposition of silicon-rich silicon oxides and also for controlled production of porous silicon dioxide films are discussed.

Comparison of the effect of the carbon dioxide laser and the bipolar coagulator on the cat brain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cozzens, J.W.; Cerullo, L.J.

The carbon dioxide laser has recently received clinical acceptance in neurosurgical practice. There are, however, few studies reported in the neurosurgical literature, either clinical or experimental, concerning its safety or efficacy on a physiological level by comparison to a more conventional tool. This study is not a description of a surgical technique, but is rather a basic physiological comparison of two surgical instruments. In this study, 11 cats were pretreated with the protein-bound dye, Evans blue. A corticotomy was performed in one hemisphere with the carbon dioxide laser and in the other with a microbipolar coagulator and a sharp blade.more » The subsequent extravasation of dye was presumed to be proportional to the amount of blood-brain barrier disruption associated with each lesion. When effective power settings for the two devices were compared, the laser lesions had significantly less extravasation of blue dye. This indicated that there was less damage to the blood-brain barrier surrounding laser corticotomy than surrounding conventional bipolar coagulation and sharp dissection at comparable power settings for each modality.« less

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1975-01-01

Techniques for the gas phase absorption of laser radiation for conversion to gas kinetic energy are discussed. Absorption by inverse Bremsstrahlung, in which laser energy is converted at a gas kinetic rate in a spectrally continuous process, is briefly described, and absorption by molecular vibrational rotation bands is discussed at length. High pressure absorption is proposed as a means of minimizing gas bleaching and dissociation, the major disadvantages of the molecular absorption process. A band model is presented for predicting the molecular absorption spectra in the high pressure absorption region and is applied to the CO molecule. Use of a rare gas seeded with Fe(CO)5 for converting vibrational modes to translation modes is described.

Applications of lasers and electro-optics

NASA Astrophysics Data System (ADS)

Tan, B. C.; Low, K. S.; Chen, Y. H.; Ahmad, Harith; Tou, T. Y.

Supported by the IRPA Programme on Laser Technology and Applications, many types of lasers have been designed, constructed and applied in various areas of science, medicine and industries. Amongst these lasers constructed were high power carbon dioxide lasers, rare gas halide excimer lasers, solid state Neodymium-YAG lasers, nitrogen lasers, flashlamp pumped dye lasers and nitrogen and excimer laser pumped dye lasers. These lasers and the associated electro-optics system, some with computer controlled, are designed and developed for the following areas of applications: (1) industrial applications of high power carbon dioxide lasers for making of i.c. components and other materials processing purposes -- prototype operational systems have been developed; (2) Medical applications of lasers for cancer treatment using the technique of photodynamic therapy -- a new and more effective treatment protocol has been proposed; (3) agricultural applications of lasers in palm oil and palm fruit-fluorescence diagnostic studies -- fruit ripeness signature has been developed and palm oil oxidation level were investigated; (4) development of atmospheric pollution monitoring systems using laser lidar techniques -- laboratory scale systems were developed; and (5) other applications of lasers including laser holographic and interferometric methods for the non destructive testing of materials.

Laboratory studies of stratospheric bromine chemistry: Kinetics of the reactions of bromine monoxide with nitrogen dioxide and atomic oxygen

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton

A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k(sub 16)) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k(sub 16)(P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k(sub 16)(P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k(sub 14)) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k(sub 14)(T) is k(sub 14)(T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k(sub 14)(T) at any temperature within the range studied is estimated to be +/- 25%. Possible kinetic interferences from production of vibrationally or electronically excited O2 are discussed. The effect of the faster reaction rate coefficients that are reported for the BrO + NO2 + M and BrO + O(P-3) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Laboratory Studies of Stratospheric Bromine Chemistry: Kinetics of the Reactions of Bromine Monoxide with Nitrogen Dioxide and Atomic Oxygen.

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton, Jr.

A laser flash photolysis - long path absorption technique has been employed to study the kinetics of the reaction rm BrO + NO_2 + M{k _{16}atopto} products as a function of temperature (248-346 K), pressure (16 -800 Torr), and buffer gas identity (rm N _2,CF_4). 351 nm photolysis of rm NO_2/Br_2/N_2 mixtures generated BrO. The BrO decay in the presence of excess NO_2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k_{16} (P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k_{16}(P,T) for use in modeling stratospheric BrO_{rm x} chemistry. The kinetics of the important stratospheric reaction rm BrO+O(^3P)_sp{to }{k_{14}}Br+O_2 in N_2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25 -150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of rm Br_2/O _3/N_2 mixtures produces O atoms in excess over Br_2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolyses a small fraction of the O_3 to generate O(^3P). The decay of O(^3P) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resolved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k_{14}(T) is given below.rm k_{14 }(T) = 1.64times 10^{-11} exp (263/T) cm^3 molecule ^{-1} s^{-1} The absolute accuracy of k_{14 }(T) at any temperature within the range studied is estimated to be +/-25%. Possible kinetic interferences from production of vibrationally or electronically excited O_2 are discussed. The effect of the faster reaction rate coefficients that are reported for the rm BrO + NO_2 + M and BrO + O(^3P) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Regeneration of 2-amino-2-methyl-1-propanol used for carbon dioxide absorption.

PubMed

Zhang, Pei; Shi, Yao; Wei, Jianwen; Zhao, Wei; Ye, Qing

2008-01-01

To improve the efficiency of the carbon dioxide cycling process and to reduce the regeneration energy consumption, a sterically hindered amine of 2-amino-2-methyl-1-propranol (AMP) was investigated to determine its regeneration behavior as a CO2 absorbent. The CO2 absorption and amine regeneration characteristics were experimentally examined under various operating conditions. The regeneration efficiency increased from 86.2% to 98.3% during the temperature range of 358 to 403 K. The most suitable regeneration temperature for AMP was 383 K, in this experiment condition, and the regeneration efficiency of absorption/regenerationruns descended from 98.3% to 94.0%. A number of heat-stable salts (HSS) could cause a reduction in CO2 absorption capacity and regeneration efficiency. The results indicated that aqueous AMP was easier to regenerate with less loss of absorption capacity than other amines, such as, monoethanolamine (MEA), diethanolamine (DEA), diethylenetriamine (DETA), and N-methyldiethanolamine (MDEA).

Characterization of absorption and degradation on optical components for high power excimer lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, K.; Eva, E.; Granitza, B.

1996-12-31

At Laser-Laboratorium Goettingen, the performance of UV optical components for high power excimer lasers is characterized, aiming to employ testing procedures that meet industrial conditions, i.e. very high pulse numbers and repetition rates. Measurements include determination of single and multiple pulse damage thresholds, absorption loss and degradation of optical properties under long-term irradiation. Absorption of excimer laser pulses is investigated by a calorimetric technique which provides greatly enhanced sensitivity compared to transmissive measurements. Thus, it allows determining both single and two photon absorption coefficients at intensities of standard excimer lasers. Results of absorption measurements at 248nm are presented for baremore » substrates (CaF{sub 2}, BaF{sub 2}, z-cut quartz and fused silica). UV calorimetry is also employed to investigate laser induced aging phenomena, e.g. color center formation in fused silica. A separation of transient and cumulative effects as a function of intensity is achieved, giving insight into various loss mechanisms.« less

Airborne Laser Infrared Absorption Spectrometer (ALIAS-II) for in situ Atmospheric Measurements of N(sub 2)0, CH(sub 4), CO, HCl, and NO(sub 2) from Balloon or RPA Platforms

NASA Technical Reports Server (NTRS)

Scott, D.; Herman, R.; Webster, C.; May, R.; Flesch, G.; Moyer, E.

1998-01-01

The Airborne Laser Infrared Absorption Spectrometer II (ALIAS-II) is a lightweight, high-resolution (0.0003 cm-1), scanning, mid-infrared absorption spectrometer based on cooled (80 K) lead-salt tunable diode laser sources.

A differential absorption lidar instrument for the measurment of carbon dioxide and methane in the lower troposphere (Conference Presentation)

NASA Astrophysics Data System (ADS)

Budinov, Daniel; Clements, Robert; Rae, Cameron F.; Moncrieff, John B.; Jack, James W.

2016-12-01

Developments in the remote detection of trace gases in the atmosphere using Differential Absorption Lidar have been driven largely by improvements in two key technologies: lasers and detectors. We have designed and built a narrow linewidth pulsed laser source with a well-controlled output wavelength and sufficient pulse energy to measure the concentration profile of CO2 and CH4 to a range in excess of 4km. We describe here the initial measurements of concentration profiles recorded with this instrument. The system is built around a custom-designed Newtonian telescope with a 40cm diameter primary mirror. Laser sources and detectors attach directly to the side of the telescope allowing for flexible customization with a range of additional equipment. The instrument features an all-solid-state laser source based on an optical parametric oscillator (OPO) pumped by an YLF based diode-laser pumped solid-state laser and seeded by a tuned DFB seed. This provides a range of available wavelengths suitable for DIAL within the 1.5-1.6 μm spectral region. The output of the OPO is beam expanded and transmitted coaxially from the receiver telescope. A gas cell within the laser source controls the seed wavelength and allows the wavelength to be tuned to match a specific absorption feature of the selected gas species. The source can be rapidly tuned between the on-line and off-line wavelengths to make a DIAL measurement of either CO2 or CH4 The receiver is based on an InGaAs avalanche photodetector. Whilst photodiode detectors are a low-cost solution their limited sensitivity restricts the maximum range over which a signal can be detected. The receiver signal is digitised for subsequent processing to produce a sightline concentration profile. The instrument is mounted on a robust gimballed mount providing full directional movement within the upper hemisphere. Both static pointing and angular scan modes are available. Accurate angular position is available giving the sightline vector and supporting the interpretation of the concentration profile. Initial measurements have been made in the planetary boundary layer above the City of Edinburgh and these will be presented and discussed. Earlier measurements demonstrated that the signal from atmospheric scatter could be detected at ranges in excess of 6km. The later measurements have shown scatter signals at greater ranges, but with increasing noise at the longer ranges. This is expected as the signal decreases with the inverse of the range whereas the noise remains effectively constant. Range resolved concentration profiles for sightline vectors lying within an angular sector have been used to create a 3D map of concentration for that volume. This will be presented and discussed.

Laser photoacoustic sensor for air toxicity measurements

NASA Astrophysics Data System (ADS)

Prasad, Coorg R.; Lei, Jie; Shi, Wenhui; Li, Guangkun; Dunayevskiy, Ilya; Patel, C. Kumar N.

2012-06-01

US EPA's Clean Air Act lists 187 hazardous air pollutants (HAP) or airborne toxics that are considered especially harmful to health, and hence the measurement of their concentration is of great importance. Numerous sensor systems have been reported for measuring these toxic gases and vapors. However, most of these sensors are specific to a single gas or able to measure only a few of them. Thus a sensor capable of measuring many of the toxic gases simultaneously is desirable. Laser photoacoustic spectroscopy (LPAS) sensors have the potential for true broadband measurement when used in conjunction with one or more widely tunable laser sources. An LPAS gas analyzer equipped with a continuous wave, room temperature IR Quantum Cascade Laser tunable over the wavelength range of 9.4 μm to 9.7 μm was used for continuous real-time measurements of multiple gases/chemical components. An external cavity grating tuner was used to generate several (75) narrow line output wavelengths to conduct photoacoustic absorption measurements of gas mixtures. We have measured various HAPs such as Benzene, Formaldehyde, and Acetaldehyde in the presence of atmospheric interferents water vapor, and carbon dioxide. Using the preliminary spectral pattern recognition algorithm, we have shown our ability to measure all these chemical compounds simultaneously in under 3 minutes. Sensitivity levels of a few part-per-billion (ppb) were achieved with several of the measured compounds with the preliminary laboratory system.

[Trace detection of ammonia at 1.531 microm].

PubMed

Jia, Hui; Guo, Xiao-Yong; Cai, Ting-Dong; Zhao, Wei-Xiong; Wang, Lei; Tan, Tu; Zhang, Wei-Jun; Gao, Xiao-Ming

2009-12-01

A compact instrument based on the off-axis integrated-cavity output spectroscopy (ICOS) technology was developed for sensitive measurements of gas mixing ratios (ammonia in air) at room temperature by using fiber-coupled distributed feedback (DFB) diode laser operating at 1.531 microm. The absorption line of ammonia at 6 528.764 cm(-1) was chosen for trace detection. The mirrors' effective reflectivity R2 of 0.996 9 was first calibrated by carbon dioxide under this condition, and the cavity 35.8 cm in length as an absorption cell could yield an optical path of presumably 115.46 m. As a result, a minimum detectable concentration of approximately 2.66 ppmv (S/N-3) at the total pressure of 100 torr was obtained. Then the lock-in amplifier was added in the system to acquire the second harmonic signal by combination of wavelength modulation technology, which could better suppress background noise and improve the signal-to-noise ratio, and a detection limit of 0.293 ppmv (S/N-3) was achieved eventually. This work demonstrated the potential of the system for a range of atmospheric species sensing in the future.

Wavelength and energy dependent absorption of unconventional fuel mixtures

NASA Astrophysics Data System (ADS)

Khan, N.; Saleem, Z.; Mirza, A. A.

2005-11-01

Economic considerations of laser induced ignition over the normal electrical ignition of direct injected Compressed Natural Gas (CNG) engines has motivated automobile industry to go for extensive research on basic characteristics of leaner unconventional fuel mixtures to evaluate practical possibility of switching over to the emerging technologies. This paper briefly reviews the ongoing research activities on minimum ignition energy and power requirements of natural gas fuels and reports results of present laser air/CNG mixture absorption coefficient study. This study was arranged to determine the thermo-optical characteristics of high air/fuel ratio mixtures using laser techniques. We measured the absorption coefficient using four lasers of multiple wavelengths over a wide range of temperatures and pressures. The absorption coefficient of mixture was found to vary significantly over change of mixture temperature and probe laser wavelengths. The absorption coefficients of air/CNG mixtures were measured using 20 watts CW/pulsed CO2 laser at 10.6μm, Pulsed Nd:Yag laser at 1.06μm, 532 nm (2nd harmonic) and 4 mW CW HeNe laser at 645 nm and 580 nm for temperatures varying from 290 to 1000K using optical transmission loss technique.

Sound absorption of metallic sound absorbers fabricated via the selective laser melting process

NASA Astrophysics Data System (ADS)

Cheng, Li-Wei; Cheng, Chung-Wei; Chung, Kuo-Chun; Kam, Tai-Yan

2017-01-01

The sound absorption capability of metallic sound absorbers fabricated using the additive manufacturing (selective laser melting) method is investigated via both the experimental and theoretical approaches. The metallic sound absorption structures composed of periodic cubic cells were made of laser-melted Ti6Al4 V powder. The acoustic impedance equations with different frequency-independent and frequency-dependent end corrections factors are employed to calculate the theoretical sound absorption coefficients of the metallic sound absorption structures. The calculated sound absorption coefficients are in close agreement with the experimental results for the frequencies ranging from 2 to 13 kHz.

Annealing pressure induced ions transfer in Cobalt-Ferrite thin films on amorphous SiO2/Si substrates

NASA Astrophysics Data System (ADS)

Huang, Shun-Yu; Chong, Cheong-Wei; Chen, Pin-Hui; Li, Hong-Lin; Li, Min-Kai; Huang, J. C. Andrew

2017-11-01

In this work, Cobalt-Ferrite (CFO) films were grown on silicon substrates with 300 nm amorphous silicon dioxide by Pulsed Laser Deposition (PLD) with different annealing conditions. The results of structural analysis prove that the CFO films have high crystalline quality with (1 1 1) preferred orientation. The Raman spectra and X-ray absorption spectra (XAS) indicate that the Co ions can transfer from tetrahedral sites to octahedral sites with increasing the annealing pressure. The site exchange of Co and Fe ions leads to the change of saturation magnetization in the CFO films. Our experiments provide not only a way to control the magnetism of CFO films, but also a suitable magnetic layer to develop silicon and semiconductor based spintronic devices.

Radiant energy absorption studies for laser propulsion. [gas dynamics

NASA Technical Reports Server (NTRS)

Caledonia, G. E.; Wu, P. K. S.; Pirri, A. N.

1975-01-01

A study of the energy absorption mechanisms and fluid dynamic considerations for efficient conversion of high power laser radiation into a high velocity flow is presented. The objectives of the study are: (1) to determine the most effective absorption mechanisms for converting laser radiation into translational energy, and (2) to examine the requirements for transfer of the absorbed energy into a steady flow which is stable to disturbances in the absorption zone. A review of inverse Bremsstrahlung, molecular and particulate absorption mechanisms is considered and the steady flow and stability considerations for conversion of the laser power to a high velocity flow in a nozzle configuration is calculated. A quasi-one-dimensional flow through a nozzle was formulated under the assumptions of perfect gas.

Laser surgery: using the carbon dioxide laser.

PubMed Central

Wright, V. C.

1982-01-01

In 1917 Einstein theorized tha through an atomic process a unique kind of electromagnetic radiation could be produced by stimulated emission. When such radiation is in the optical or infrared spectrum it is termed laser (light amplification by stimulated emission of radiation) light. A laser, a high-intensity light source, emits a nearly parallel electromagnetic beam of energy at a given wavelength that can be captured by a lens and concentrated in the focal spot. The wavelength determines how the laser will be used. The carbon dioxide laser is now successfully employed for some surgical procedures in gynecology, otorhinolaryngology, neurosurgery, and plastic and general surgery. The CO2 laser beam is directed through the viewing system of an operating microscope or through a hand-held laser component. Its basic action in tissue is thermal vaporization; it causes minimal damage to adjacent tissues. Surgeons require special training in the basic methods and techniques of laser surgery, as well as in the safety standards that must be observed. Images FIG. 5 PMID:7074503

Investigations of ion-irradiated uranium dioxide nuclear fuel with laser-assisted atom probe tomography

NASA Astrophysics Data System (ADS)

Valderrama, Billy

Performance in commercial light water reactors is dictated by the ability of its fuel material, uranium dioxide (UO2), to transport heat generated during the fission process. It is widely known that the service lifetime is limited by irradiation-induced microstructural changes that degrade the thermal performance of UO2. Studying the role of complex, often interacting mechanisms that occur during the early stages of microstructural evolution presents a challenge. Phenomena of particular interest are the segregation of fission products to form bubbles and their resultant effect on grain boundary (GB) mobility, and the effect of irradiation on fuel stoichiometry. Each mechanism has a profound consequence on fuel thermal conductivity. Several advanced analytical techniques, such as transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, etc. have been used to study these mechanisms. However, they each have limitations and cannot individually provide the necessary information for deeper understanding. One technique that has been under utilized is atom probe tomography (APT), which has a unique ability to spatially resolve small-scale chemical variations. APT uses the principle of field ionization to evaporate surface ions for chemical analysis. For low electrical conductivity systems, a pulsed laser is used to thermally assist in the evaporation process. One factor complicating the analysis is that laser-material interactions are poorly understood for oxide materials and literature using this technique with UO2 is lacking. Therefore, an initial systematic study to identify the optimal conditions for the analysis of UO2 using laser-assisted APT was conducted. A comparative study on the evaporation behavior between CeO2 and UO2 was followed. CeO2 was chosen due to its technological relevancy and availability of comparative studies with laser-assisted APT. Dissimilar evaporation behavior between these materials was identified and attributed to differences in laser absorption, oxide stability, and thermal conductivity between the two materials. After the conditions were identified, APT was utilized to study the role of temperature and GB structure on the segregation of Kr. Results indicate that high angle GBs contain more Kr relative to low angle GBs. The methodology presented can be applied to investigate small-scale chemical changes in other oxide materials.

Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.

PubMed

Linford, G J

1973-06-01

A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air.

Laser Irradiated Foam Targets: Absorption and Radiative Properties

NASA Astrophysics Data System (ADS)

Salvadori, Martina; Luigi Andreoli, Pier; Cipriani, Mattia; Consoli, Fabrizio; Cristofari, Giuseppe; De Angelis, Riccardo; di Giorgio, Giorgio; Giulietti, Danilo; Ingenito, Francesco; Gus'kov, Sergey Yu.; Rupasov, Alexander A.

2018-01-01

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminum targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target.

Absorptivity modulation on wavy molten steel surfaces: The influence of laser wavelength and angle of incidence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, A. F. H.

The modulation of the angle-dependent Fresnel absorptivity across wavy molten steel surfaces during laser materials processing, like drilling, cutting, or welding, has been calculated. The absorptivity is strongly altered by the grazing angle of incidence of the laser beam on the processing front. Owing to its specific Brewster-peak characteristics, the 10.64 {mu}m wavelength CO{sub 2}-laser shows an opposite trend with respect to roughness and angle-of-incidence compared to lasers in the wavelength range of 532-1070 nm. Plateaus or rings of Brewster-peak absorptivity can lead to hot spots on a wavy surface, often in close proximity to cold spots caused by shadowmore » domains.« less

Diode Lasers and Practical Trace Analysis.

ERIC Educational Resources Information Center

Imasaka, Totaro; Nobuhiko, Ishibashi

1990-01-01

Applications of lasers to molecular absorption spectrometry, molecular fluorescence spectrometry, visible semiconductor fluorometry, atomic absorption spectrometry, and atomic fluorescence spectrometry are discussed. Details of the use of the frequency-doubled diode laser are provided. (CW)

Nonlinear absorption of short intense laser pulse in multispecies plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kargarian, A.; Hajisharifi, K.; Mehdian, H.

In the present paper, the detailed investigation concerning the effect of inclusion of heavy negative ions into the finite background plasma on the laser absorption has been carried out by employing particle-in-cell simulation method. For this purpose, in this configuration, the laser energy absorption relying on the nonlinear phenomena such as phase-mixing, wave-breaking, and scattering has been studied in the Raman-Brillouin regime. It is shown that the inclusion of heavy negative ions suppresses the scattering while increases the phase-mixing time. Moreover, it is illustrated that this inclusion can increase the laser absorption in finite plasma environment, after saturation. The obtainedmore » results are expected to be relevant to the experiments on the mass spectrometry with laser desorption techniques as well as on the laser-plasma interaction with application to particles acceleration.« less

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

Determination of sulfur trioxide in engine exhaust.

PubMed Central

Arnold, D R

1975-01-01

Sulfur trioxide in the exhaust gas of an internal combustion engine is removed and concentrated by absorption in a solution of 80% isopropyl alcohol, which quantitatively absorbs it and inhibits the oxidation of any sulfur dioxide which may be absorbed. The absorbed sulfur trioxide (sulfuric acid) is determined by an absorption titration by using barium chloride as the titrant and thorin as the indicator. The sulfur dioxide content of the exhaust is measured continuously by means of a DuPont Model 411 ultraviolet photoanalyzer. PMID:50930

Three Dimensional Reconstruction Algorithm for Imaging Pathophysiological Signals Within Breast Tissue Using Near Infrared Light

DTIC Science & Technology

2006-07-01

months.31 A heated mixture of water, gelatin (G2625, Sigma Inc.), India ink (for absorption), and titanium dioxide powder (for scatter) (TiO2, Sigma Inc...for absorption, and titanium dioxide powder for scat- ter TiO2, Sigma Inc. that are solidified by cooling to room temperature. Optically...2713-2727. 8. Bolin, F.P., Preuss, L. E., Taylor, R. C., Ference, R. J, Refractive index of some mammalian tissue using a fiber optic cladding method

Process for separating carbon dioxide from flue gas using sweep-based membrane separation and absorption steps

DOEpatents

Wijmans, Johannes G.; Baker, Richard W.; Merkel, Timothy C.

2012-08-21

A gas separation process for treating flue gases from combustion processes, and combustion processes including such gas separation. The invention involves routing a first portion of the flue gas stream to be treated to an absorption-based carbon dioxide capture step, while simultaneously flowing a second portion of the flue gas across the feed side of a membrane, flowing a sweep gas stream, usually air, across the permeate side, then passing the permeate/sweep gas to the combustor.

Collisionless absorption of intense laser radiation in nanoplasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaretsky, D F; Korneev, Philipp A; Popruzhenko, Sergei V

The rate of linear collisionless absorption of an electromagnetic radiation in a nanoplasma - classical electron gas localised in a heated ionised nanosystem (thin film or cluster) irradiated by an intense femtosecond laser pulse - is calculated. The absorption is caused by the inelastic electron scattering from the self-consistent potential of the system in the presence of a laser field. The effect proves to be appreciable because of a small size of the systems. General expressions are obtained for the absorption rate as a function of the parameters of the single-particle self-consistent potential and electron distribution function in the regimemore » linear in field. For the simplest cases, where the self-consistent field is created by an infinitely deep well or an infinite charged plane, closed analytic expressions are obtained for the absorption rate. Estimates presented in the paper demonstrate that, over a wide range of the parameters of laser pulses and nanostructures, the collisionless mechanism of heating electron subsystem can be dominant. The possibility of experimental observation of the collisionless absorption of intense laser radiation in nanoplasma is also discussed. (interaction of laser radiation with matter)« less

Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franta, Benjamin, E-mail: bafranta@gmail.com; Pastor, David; Gandhi, Hemi H.

2015-12-14

Hyperdoped black silicon fabricated with femtosecond laser irradiation has attracted interest for applications in infrared photodetectors and intermediate band photovoltaics due to its sub-bandgap optical absorptance and light-trapping surface. However, hyperdoped black silicon typically has an amorphous and polyphasic polycrystalline surface that can interfere with carrier transport, electrical rectification, and intermediate band formation. Past studies have used thermal annealing to obtain high crystallinity in hyperdoped black silicon, but thermal annealing causes a deactivation of the sub-bandgap optical absorptance. In this study, nanosecond laser annealing is used to obtain high crystallinity and remove pressure-induced phases in hyperdoped black silicon while maintainingmore » high sub-bandgap optical absorptance and a light-trapping surface morphology. Furthermore, it is shown that nanosecond laser annealing reactivates the sub-bandgap optical absorptance of hyperdoped black silicon after deactivation by thermal annealing. Thermal annealing and nanosecond laser annealing can be combined in sequence to fabricate hyperdoped black silicon that simultaneously shows high crystallinity, high above-bandgap and sub-bandgap absorptance, and a rectifying electrical homojunction. Such nanosecond laser annealing could potentially be applied to non-equilibrium material systems beyond hyperdoped black silicon.« less

Phase Aberrations And Beam Cleanup Techniques In Carbon-Dioxide Laser Fusion Systems

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.

1981-12-01

This paper describes the various carbon dioxide laser fusion systems at Los Alamos from the point of view of an optical designer. The types of phase aberrations present in these systems, as well as the beam cleanup techniques that can be used to improve the beam optical quality, are discussed. As this is a review article, some previously published results are also used where relevant.

Remote measurements of ozone, water vapor and liquid water content, and vertical profiles of temperature in the lower troposphere

NASA Technical Reports Server (NTRS)

Grant, W. B.; Gary, B. L.; Shumate, M. S.

1983-01-01

Several advanced atmospheric remote sensing systems developed at the Jet Propulsion Laboratory were demonstrated under various field conditions to determine how useful they would be for general use by the California Air Resources Board and local air quality districts. One of the instruments reported on is the Laser Absorption Spectrometer (LAS). It has a pair of carbon dioxide lasers with a transmitter and receiver and can be flown in an aircraft to measure the column abundance of such gases as ozone. From an aircraft, it can be used to rapidly survey a large region. The LAS is usually operated from an aircraft, although it can also be used at a fixed location on the ground. Some tests were performed with the LAS to measure ozone over a 2-km horizontal path. Another system reported on is the Microwave Atmospheric Remote Sensing System (MARS). It is tuned to microwave emissions from water vapor, liquid water, and oxygen molecules (for atmospheric temperature). It can measure water vapor and liquid water in the line-of-sight, and can measure the vertical temperature profile.

Remote sensing of air pollution over large European cities by lidar

NASA Astrophysics Data System (ADS)

Koelsch, Hans J.; Kolenda, Juergen; Rairoux, Patrick; Stein, Bernhard; Weidauer, Dirk; Wolf, Jean-Pierre; Woeste, Ludger H.; Fritzsche, Klaus

1993-09-01

Progresses in remote sensing of the atmosphere using the Udar (Light detection and ranging) technique closely follows progresses in Laser technology. We developed a mobile DIAL (differential absorption Lidar) system, based on high repetition rate Excimerpumped dye lasers, for performing 2D and 3D-mappings of concentration of NO, N02, S02, and 03. The high sensitivity of the system has been used for numerous environmental studies and measurement campaigns, providing for the first time a direct correlation between emission and immission. Attractive results have been obtained under urban conditions, because of the presence of strong concentration gradients, and fast fluctuations due to traffic. A comparative study between Lyon, Stuttgart, Geneva and Berlin will be presented. In particular, the Berlin-campaign demonstrates the possibility of detecting unknown emitters and monitoring exportation-importation processes of atmospheric pollution. A new stationary DIAL system has been recently constructed and implemented on the top of a building in the center of the city Leipzig. It will routinely perform concentration mappings of nitrogen oxides, sulfur dioxide and ozone, giving access to long term evolution of pollution distributions.

Rigrod laser-pumped-laser resonator model: II. Application to thin and optically-dilute laser media

NASA Astrophysics Data System (ADS)

Brown, D. C.

2014-08-01

In part I of this paper, and to set the foundation for this part II, we derived the resonator equations describing the normalized intensities, output power, gain, and extraction efficiency for a standard resonator incorporating two dielectric mirrors and a gain element. We then generalized the results to include an absorbing region representing a second laser crystal characterized by a small-signal transmission T0. Explicit expressions were found for the output power extracted into absorption by the second laser crystal and the extraction efficiency, and the limits to each were discussed. It was shown that efficient absorption by a thin or dilute second laser crystal can be realized in resonators in which the mirror reflectivities were high and in which the single-pass absorption was low, due to the finite photon lifetime and multi-passing of the absorbing laser element. In this paper, we apply the model derived in part I to thin or dilute laser materials, concentrating on a Yb, Er:glass intracavity pumped by a 946 nm Nd:YAG laser, a Yb, Er:glass laser-pumped intracavity by a 977 nm diode laser, and an Er:YAG laser-pumped intracavity to a 1530 nm diode laser. It is shown that efficient absorption can be obtained in all cases examined.

Monitoring the inhibition of erosion by a CO2 laser with OCT

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Tom, Henry; Fried, Daniel

2014-02-01

Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the nonablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Teeth surfaces were irradiated with a carbon dioxide laser at low sub-ablative fluence to create an acid-resistant reference layer without damaging the enamel. The laser treated areas were compared with the unprotected areas using OCT during exposure to a pH cycling model for up to 6 days. The laser treated areas markedly reduced the rate of erosion.

Laser vaporization in treatment of superficial endometriosis of the uterine cervix

NASA Astrophysics Data System (ADS)

Wozniak, Jakub; Wilczak, Maciej; Opala, Tomasz; Pisarska-Krawczyk, Magdalena; Cwojdzinski, Marek; Pisarski, Tadeusz

1996-03-01

The study shows the treatment of superficial endometriosis of the uterine cervix in 79 patients. After first vaporization 74 patients were cured successfully. In two cases the laser procedure should be repeated and in 3 women the operation should be performed for the third time. All patients are still under control in our department and there is no recurrence observed. Carbon- dioxide laser vaporization under colposcopic control is an efficient method of treatment of superficial endometriosis of the uterine cervix that requires no anaesthesia. The healing process after laser procedures is fast and without complications. The number of recurrences is low. Use of carbon-dioxide laser under colposcopic control because of precise destruction of lesions, fast healing and a low number of recurrences seems to be the method of choice.

Application of the UV laser printing technique to soft gelatin capsules containing titanium dioxide in the shells.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2012-03-01

The purpose of this study was to examine application of ultraviolet (UV) laser irradiation to printing soft gelatin capsules containing titanium dioxide (TiO(2)) in the shells and to study effect of UV laser power on the color strength of printing on the soft gelatin capsules. Size 6 Oval type soft gelatin capsules of which shells contained 0.685% TiO(2) and 0.005% ferric dioxide were used in this study. The capsules were irradiated pulsed UV laser at a wavelength 355 nm. The color strength of the printed capsules was determined by a spectrophotometer as total color difference (dE). The soft gelatin capsules which contained TiO(2) in the shells could be printed gray by the laser. Many black particles, which were associated with the printing, were formed at the colored parts of the shells. It was found that there were two inflection points in relationship between output laser energy of a pulse and dE. Below the lower point, the capsules were not printed. From the lower point to the upper point, the capsules were printed gray and total color difference of the printing increased linearly in proportion with the output laser energy. Beyond the upper point, total color difference showed saturation because of micro-bubbles formation at the laser irradiated spot. Soft gelatin capsules containing TiO(2) in the shells could be performed stable printing using the UV laser printing technique. Color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Silicon Dioxide Planarization: Impacts on Optical Coatings for High Energy Laser

NASA Astrophysics Data System (ADS)

Day, Travis E.

The work of this thesis is devoted to examining the impact of silicon dioxide (silica or SiO2) planarization on the optical properties and laser damage resistance of thin-film coatings. SiO2 planarization is a process to smooth out fluence limiting nodular defects within multilayer coatings for high-energy laser applications. Mitigating these defects will improve the power handling abilities and improve the lifetime of laser coatings. Presented here is a combination of work with the aim of evaluating the optical and laser damage properties of SiO2 planarization within single layers, bilayers, and multilayers. As compared to control (non-planarized) samples, a 2-3x increase in the thin-film absorption, which decreases with post-process annealing, was discovered for SiO2 planarized samples. This suggests that planarization creates oxygen-related defects which can be annealed out and little impurity implantation. Investigations of laser damage resistance were carried out at lambda = 1030nm and pulse durations of tau = 220ps and 9ps. The laser damage of single and bilayer coatings is known to be dependent on the substrate-coating interface and this is further evidenced within this thesis. This is because the effects of planarization are masked by the extrinsic laser damage processes within the single and bilayers. Slight change (< 15%) in the laser induced damage threshold (LIDT) at 220ps and 9ps was observed for planarized single and bilayers. Depending on coating design, post-process annealing was shown to increase the LIDT by 10% to 75% at 220ps and 10% to 45% at 9ps. Although the fused silica substrate surface LIDT was shown to follow the √tau pulse scaling law for pulses above 10ps, the single and bilayer coatings do not follow this pulse scaling. The divergence from the √tau pulse scaling on the coatings suggests a variation in the laser damage initiation mechanisms between 220ps and 9ps. Multilayer high-reflecting (HR) mirrors with varying planarization design were also damage tested. A 6-7 J/cm2 LIDT, with 220ps, was observed for HR coatings with SiO2 planarization layers within high electric-field areas within the coating. However, SiO2 planarization at the substrate-coating interface, where the electric-field is minimal, and control (non-planarized) was shown to have a LIDT of 63 +/- 1.2 J/cm 2 and 21.5 +/- 0.5 J/cm2 for 220ps, respectively. At 9ps, the LIDT varied less than 90% difference between the various planarization designs. The substrate-coating planarization multilayer and control coating had an equal LIDT of 9.6 +/- .3 J/cm2 at 9ps.

Improvement in Suppression of Pulsed Nd:YAG Laser Light With Iodine Absorption Cells for Filtered Rayleigh Scattering Measurements

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E

1997-01-01

Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted laser light. This improvement allows the iodine cell to block significantly more of the stray laser light in filtered Rayleigh scattering experiments. Examples are given of filtered Rayleigh scattering measurements showing the effect of the etalon on measurements taken in a Mach 3 flow in the NASA Lewis 4 inch by 10 inch supersonic wind tunnel.

Polarizability calculations on water, hydrogen, oxygen, and carbon dioxide

NASA Technical Reports Server (NTRS)

Nir, S.; Adams, S.; Rein, R.

1973-01-01

A semiclassical model of damped oscillators is used as a basis for the calculation of the dispersion of the refractive index, polarizability, and dielectric permeability in water, hydrogen, and oxygen in liquid and gaseous states, and in gaseous carbon dioxide. The absorption coefficient and the imaginary part of the refractive index are also calculated at corresponding wavelengths. A good agreement is obtained between the observed and calculated values of refractive indices, and between those of absorption coefficients in the region of absorption bands. The calculated values of oscillator strengths and damping factors are also discussed. The value of the polarizability of liquid water was about 2.8 times that of previous calculations.

Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

DOEpatents

Cremers, D.A.; Keller, R.A.

1982-06-08

The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be rlated to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10/sup -5/ cm/sup -1/ has been demonstrated using this technique.

Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

DOEpatents

Cremers, D.A.; Keller, R.A.

1985-10-01

The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10[sup [minus]5] cm[sup [minus]1] has been demonstrated using this technique. 6 figs.

Enhancement of the static extinction ratio by using a dual-section distributed feedback laser integrated with an electro-absorption modulator

NASA Astrophysics Data System (ADS)

Cho, Chun-Hyung; Kim, Jongseong; Sung, Hyuk-Kee

2016-09-01

We report on the enhancement of the static extinction ratio by using a dual-section distributed feedback laser diode integrated with an electro-absorption modulator. A directly- modulated dual-section laser can provide improved modulation performance under a low bias level ( i.e., below the threshold level) compared with a standard directly-modulated laser. By combining the extinction ratio from a dual-section laser with that from an electro-absorption modulator section, a total extinction ratio of 49.6. dB are successfully achieved.

Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

DOEpatents

Cremers, David A.; Keller, Richard A.

1985-01-01

The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10.sup.-5 cm.sup.-1 has been demonstrated using this technique.

Efficient energy absorption of intense ps-laser pulse into nanowire target

NASA Astrophysics Data System (ADS)

Habara, H.; Honda, S.; Katayama, M.; Sakagami, H.; Nagai, K.; Tanaka, K. A.

2016-06-01

The interaction between ultra-intense laser light and vertically aligned carbon nanotubes is investigated to demonstrate efficient laser-energy absorption in the ps laser-pulse regime. Results indicate a clear enhancement of the energy conversion from laser to energetic electrons and a simultaneously small plasma expansion on the surface of the target. A two-dimensional plasma particle calculation exhibits a high absorption through laser propagation deep into the nanotube array, even for a dense array whose structure is much smaller than the laser wavelength. The propagation leads to the radial expansion of plasma perpendicular to the nanotubes rather than to the front side. These features may contribute to fast ignition in inertial confinement fusion and laser particle acceleration, both of which require high current and small surface plasma simultaneously.

Nonlinear absorption and optical limiting in gold-precipitated glasses induced by a femtosecond laser

NASA Astrophysics Data System (ADS)

Qu, Shiliang; Gao, Yachen; Jiang, Xiongwei; Zeng, Huidan; Song, Yinglin; Qiu, Jianrong; Zhu, Congshan; Hirao, K.

2003-09-01

Nonlinear absorptions of Au nanoparticles precipitated silicate glasses by irradiation of a focused femtosecond pulsed laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. Optical limiting (OL) effects in such glasses have been also measured. It is observed that the behaviors of transition from saturable absorption to reverse saturable absorption and the OL performances for different samples are significantly different, which depend drastically on the irradiation power density of the femtosecond laser used for the Au nanoparticles precipitation in the glass. Strong nonlinear absorptions in these samples are mainly attributed to the surface plasmon resonance (SPR) and free carrier absorptions of the precipitated Au nanoparticles.

Infectious papillomavirus in the vapor of warts treated with carbon dioxide laser or electrocoagulation: Detection and protection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawchuk, W.S.; Weber, P.J.; Lowy, D.R.

1989-07-01

Papillomavirus DNA has been reported recently in the vapor (smoke plume) derived from warts treated with carbon dioxide laser; this raises concerns for operator safety. We therefore have studied a group of human and bovine warts to define further the potential risk of wart therapy and to test whether a surgical mask could reduce exposure. Half of each wart was treated with carbon dioxide laser and the other half with electrocoagulation. The vapor produced by each form of therapy was collected with a dry filter vacuum apparatus and analyzed for the presence of papillomavirus. Vapor from human plantar warts wasmore » analyzed for the presence of human papillomavirus DNA, because there is no infectivity assay for human papillomavirus. Of plantar warts treated, five of eight laser-derived vapors and four of seven electrocoagulation-derived vapors were positive for human papillomavirus DNA. Greater amounts of papillomavirus DNA were usually recovered in the laser vapor than in the electrocoagulation vapor from the same wart. Bioassay readily detected infectious bovine papillomavirus in the vapor from bovine warts treated with either modality; more virus was present in laser-derived material. A surgical mask was found capable of removing virtually all laser- or electrocoagulation-derived virus, strongly suggesting that such masks can protect operators from potential inhalation exposure to papillomavirus.« less

Carbon Dioxide Absorbers: An Engaging Experiment for the General Chemistry Laboratory

ERIC Educational Resources Information Center

Ticich, Thomas M.

2011-01-01

A simple and direct method for measuring the absorption of carbon dioxide by two different substances is described. Lithium hydroxide has been used for decades to remove the gas from enclosed living spaces, such as spacecraft and submarines. The ratio of the mass of carbon dioxide absorbed to the mass of lithium hydroxide used obtained from this…

Thermal measurements of short-duration CO2 laser resurfacing

NASA Astrophysics Data System (ADS)

Harris, David M.; Fried, Daniel; Reinisch, Lou; Bell, Thomas; Lyver, Rex

1997-05-01

The thermal consequences of a 100 microsecond carbon-dioxide laser used for skin resurfacing were examined with infrared radiometry. Human skin was evaluated in a cosmetic surgery clinic and extirpated rodent skin was measured in a research laboratory. Thermal relaxation following single pulses of in vivo human and ex vivo animal skin were quantitatively similar in the 30 - 1000 msec range. The thermal emission from the area of the irradiated tissue increased monotonically with increasing incident laser fluence. Extremely high peak temperatures during the 100 microsecond pulse are attributed to plume incandescence. Ejecta thermal emission may also contribute to our measurements during the first several msecs. The data are combined into a thermal relaxation model. Given known coefficients, and adjusting tissue absorption to reflect a 50% water content, and thermal conductivity of 2.3 times that of water, the measured (both animal back and human forearm) and calculated values coincide. The high thermal conductance suggests preferential thermal conduction along the protein matrix. The clinical observation of a resurfacing procedure clearly shows thermal overlap and build-up is a result of sequential, adjacent pulses. A decrease of 4 - 6 degrees Celsius in surface temperature at the treatment site that appeared immediately post-Tx and gradually diminished over several days is possibly a sign of dermal convective and/or evaporative cooling.

Monolithic photonic integration technology platform and devices at wavelengths beyond 2μm for gas spectroscopy applications

NASA Astrophysics Data System (ADS)

Latkowski, S.; van Veldhoven, P. J.; Hänsel, A.; D'Agostino, D.; Rabbani-Haghighi, H.; Docter, B.; Bhattacharya, N.; Thijs, P. J. A.; Ambrosius, H. P. M. M.; Smit, M. K.; Williams, K. A.; Bente, E. A. J. M.

2017-02-01

In this paper a generic monolithic photonic integration technology platform and tunable laser devices for gas sensing applications at 2 μm will be presented. The basic set of long wavelength optical functions which is fundamental for a generic photonic integration approach is realized using planar, but-joint, active-passive integration on indium phosphide substrate with active components based on strained InGaAs quantum wells. Using this limited set of basic building blocks a novel geometry, widely tunable laser source was designed and fabricated within the first long wavelength multiproject wafer run. The fabricated laser operates around 2027 nm, covers a record tuning range of 31 nm and is successfully employed in absorption measurements of carbon dioxide. These results demonstrate a fully functional long wavelength photonic integrated circuit that operates at these wavelengths. Moreover, the process steps and material system used for the long wavelength technology are almost identical to the ones which are used in the technology process at 1.5μm which makes it straightforward and hassle-free to transfer to the photonic foundries with existing fabrication lines. The changes from the 1550 nm technology and the trade-offs made in the building block design and layer stack will be discussed.

Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing

PubMed Central

Zheng, Chuantao; Wang, Yiding

2017-01-01

A Pound-Drever-Hall (PDH)-based mode-locked cavity-enhanced sensor system was developed using a distributed feedback diode laser centered at 1.53 µm as the laser source. Laser temperature scanning, bias control of the piezoelectric ceramic transducer (PZT) and proportional-integral-derivative (PID) feedback control of diode laser current were used to repetitively lock the laser modes to the cavity modes. A gas absorption spectrum was obtained by using a series of absorption data from the discrete mode-locked points. The 15 cm-long Fabry-Perot cavity was sealed using an enclosure with an inlet and outlet for gas pumping and a PZT for cavity length tuning. The performance of the sensor system was evaluated by conducting water vapor measurements. A linear relationship was observed between the measured absorption signal amplitude and the H2O concentration. A minimum detectable absorption coefficient of 1.5 × 10–8 cm–1 was achieved with an averaging time of 700 s. This technique can also be used for the detection of other trace gas species by targeting the corresponding gas absorption line. PMID:29207470

Lasers '92; Proceedings of the International Conference on Lasers and Applications, 15th, Houston, TX, Dec. 7-10, 1992

NASA Technical Reports Server (NTRS)

Wang, Charles P. (Editor)

1993-01-01

Papers from the conference are presented, and the topics covered include the following: x-ray lasers, excimer lasers, chemical lasers, high power lasers, blue-green lasers, dye lasers, solid state lasers, semiconductor lasers, gas and discharge lasers, carbon dioxide lasers, ultrafast phenomena, nonlinear optics, quantum optics, dynamic gratings and wave mixing, laser radar, lasers in medicine, optical filters and laser communication, optical techniques and instruments, laser material interaction, and industrial and manufacturing applications.

Laser Atmospheric Absorption Studies.

DTIC Science & Technology

1977-05-01

A. Modification of Commercial C09 Laser 50 B. CW HF/DF Laser System * 53 C. Microcomputer Data Link 55 D . Fourier Transform...improved accuracy are used [5]. c. The absorption coefficient is listed for each absorbing species separately which some codes require. d . A super...series of water vapor absorption measurements was planned. The results of the first four lines studied are presented here in Figures 33a- d . Figure

Measurement of laser absorptivity for operating parameters characteristic of laser drilling regime

NASA Astrophysics Data System (ADS)

Schneider, M.; Berthe, L.; Fabbro, R.; Muller, M.

2008-08-01

Laser drilling in the percussion regime is commonly used in the aircraft industry to drill sub-millimetre holes in metallic targets. Characteristic laser intensities in the range of 10 MW cm-2 are typically employed for drilling metallic targets. With these intensities the temperature of the irradiated matter is above the vaporization temperature and the drilling process is led by hydrodynamic effects. Although the main physical processes involved are identified, this process is not correctly understood or completely controlled. A major characteristic coefficient of laser-matter interaction for this regime, which is the absorptivity of the laser on the irradiated surface, is still unknown, because of the perturbing effects due to laser beam geometrical trapping inside the drilled hole. So, by using time resolved experiments, this study deals with the direct measurement of the variation of the intrinsic absorption of aluminium, nickel and steel materials, as a function of the incident laser intensity up to 20 MW cm-2. We observe that for this incident intensity, the absorptivity can reach up to 80%. This very high and unexpected value is discussed by considering the microscopic behaviour of the heated matter near the vapour-liquid interface that undergoes possible Rayleigh-Taylor instability or volume absorption.

High Power Laser Processing Of Materials

NASA Astrophysics Data System (ADS)

Martyr, D. R.; Holt, T.

1987-09-01

The first practical demonstration of a laser device was in 1960 and in the following years, the high power carbon dioxide laser has matured as an industrial machine tool. Modern carbon dioxide gas lasers can be used for cutting, welding, heat treatment, drilling, scribing and marking. Since their invention over 25 years ago they are now becoming recognised as highly reliable devices capable of achieving huge savings in production costs in many situations. This paper introduces the basic laser processing techniques of cutting, welding and heat treatment as they apply to the most common engineering materials. Typical processing speeds achieved with a wide range of laser powers are reported. Accuracies achievable and fit-up tolerances required are presented. Methods of integrating lasers with machine tools are described and their suitability in a wide range of manufacturing industries is described by reference to recent installations. Examples from small batch manufacturing, high volume production using dedicated laser welding equipment, and high volume manufacturing using 'flexible' automated laser welding equipment are described Future applications of laser processing are suggested by reference to current process developments.

Stabilized Lasers and Precision Measurements.

ERIC Educational Resources Information Center

Hall, J. L.

1978-01-01

Traces the development of stabilized lasers from the Massachusetts Institute of Technology passive-stabilization experiments of the early 1960s up through the current epoch of highly stabilized helium-neon and carbon dioxide and continuous wave dye lasers. (Author/HM)

Carbon dioxide laser management cervical intraepithelial neoplasia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellina, J.H.; Wright, V.C.; Voros, J.I.

1981-12-01

In this report we describe the use of the carbon dioxide laser for the outpatient management of cervical intraepithelial neoplasia (CIN). A comparison of treatment effectiveness for different grades of CIN is also included. Two hundred fifty-six cases were evaluated by colposcopy, cytology, and histopathology, treated by at least 5 to 6 mm of laser vaporization, and followed up for an average of 10.7 months. Follow-up examinations included cytology, colposcopy, and directed biopsy if a suspicious lesion was discovered. During the follow-up, 18 cases of persistent CIN were identified (7.0%). Most of these were successfully managed with repeat laser treatment.more » Overall success of laser surgery for CIN, one or two applications, was 97.6%. Few complications were encountered. Laser surgery appears to offer acceptable treatment effectiveness, early identification of persistent disease, and easy retreatment when required. (Am. J. Obstet. Gynecol. 141:828, 1981.)« less

Carbon dioxide laser effects on caries-like lesions of dental enamel

NASA Astrophysics Data System (ADS)

Featherstone, John D. B.; Zhang, S. H.; Shariati, M.; McCormack, Sandra M.

1991-05-01

Previous studies by the authors have shown that carbon dioxide (CO2) laser light has marked effects on dental hard tissues and that these effects are wavelength-dependent. The aim of the present study was to determine whether treatment by CO2 laser of caries-like lesions in human enamel would inhibit subsequent lesion progression. Nine groups of 10 teeth each with preformed caries-like lesions were treated with/without CO2 laser (9.32 micrometers , 15 mJ or 25 mJ per pulse) by a pulsed laser (100-200 nsec) for either 200 or 400 pulses. Preformed lesions were then treated with acidulated phosphate fluoride for 5 minutes with control groups with no fluoride treatment. Teeth were subjected to a subsequent pH cycling challenge to determine the protection against lesion progression. Low energy laser treatment coupled with fluoride treatment entirely inhibited subsequent lesion progression in this model system.

Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Zarzana, K. J.; Rudich, Y.; Brown, S. S.

2016-01-01

Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1- reflectivity = 700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non-absolute detection methods. In addition to trace gases, this approach will be appropriate for measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.