Tunable diode lasers

A tunable diode laser operating at 4.3 pm is used to probe the P and/or R branch bands of tire following transitions. 

For the visible and near-ultraviolet portions of the spectmm, tunable dye lasers have commonly been used as the light source, although they are being replaced in many appHcation by tunable soHd-state lasers, eg, titanium-doped sapphire. Optical parametric oscillators are also developing as useful spectroscopic sources. In the infrared, tunable laser semiconductor diodes have been employed. The tunable diode lasers which contain lead salts have been employed for remote monitoring of poUutant species. Needs for infrared spectroscopy provide an impetus for continued development of tunable infrared lasers (see Infrared technology and RAMAN spectroscopy). 

R. Gdsar, H. Preier, G. Schmidtke, and G. ResteUi, eds.. Monitoring of Gaseous Pollutants by Tunable Diode Lasers, D. Reidel Publishing Co., Dordrecht, Germany, 1987. 

Krska R., Kellner R., Schiessl U., Tacke M. and Katzir, Fiber optic sensor for chlorinated hydrocarbons in water based on infrared fibers and tunable diode lasers, Appl. Phys. Lett., 1993 63 (14), 1868-1871 A. 

Hill, J. C. Majkowski, R. F. "Time-Resolved Measurement of Vehicle Sulfate and Methane Emissions with Tunable Diode Lasers" SAE Paper No. 800510, 1980. 

Tumorigenic responses, 25 222-223 Tumor necrosis factor (TNF) role in hemostatic system, 4 89 Tumors, hydrazine-related, 23 590—591 Tunable diode lasers (TDLs), 23 143 Tunable diode laser systems, 23 138 Tunable optical properties, windows with, 23 25... 

With respect to the considerations above, research is split into three parts. The first is connected to the kinetic description of the release of ammonia from the biomass as function of temperature. This research employs infrared spectroscopy using a tunable diode laser. Here very small biomass particles are used that are heated up very rapidly in a small reactor, which ensures that transport effects are virtually excluded from the kinetic release effects. Since ammonia is released in very small quantities it is quite hard to detect. Therefore, we first measure CO release, which is easier. In the second part we investigate the propagation of a conversion front in biomass layers. Here we perform experiments and try to establish a modeling approach for the propagation by analytical and numerical approaches. In the third part the gas-phase conversion processes are described in terms of... 

Tunable Diode Laser Measurements of Biomass Kinetics... 

Tunable Diode Laser Grid Reactor Experiments... 

A tunable diode laser system and optics (Laser Photonics, L5736) was used to monitor the species release rates during an experiment. It consists of a liquid-nitrogen cooled diode emitter. For CO absorption measurements the laser emits a beam tuned to a wavenumber of 2082 cm4. This line is chosen as it exhibits strong absorption and is not subject to interference from other species likely to be present in the pyrolysate. 

An example of a fuel layer model is discussed in the next section. In a first approximation no detailed description of the release of volatiles need to be included. Later, the results of the tunable diode laser experiments can be implemented in such a fuel layer model. 

The present research has treated important parts of the modeling of combustion and NOx formation in a biomass grate furnace. All parts resulted in useful approaches. For all these approaches successful first steps were taken. Currently, more research is underway to obtain improved results NH3 production is measured in the grid reactor with the tunable diode laser, detailed kinetics will be attached to the front propagation model, including the measured NH3 release functionalities, and for the turbulent combustion model heat losses are taken into account. In addition, the fuel layer model has to be coupled to the turbulent combustion model in the furnace. 

Long-path infrared absorption, using a tunable diode laser, which is claimed to have a sensitivity of 5 ppb for carbon monoxide over a 610-m path length. ... 

Ku, R. T., E. D. Hinkley, and J. O. Sample. Long-path monitoring of atmospheric carbon monoxide with a tunable diode laser system. Appl. Optics 14 854-861, 1975. 

Gieseler et al. utilized tunable diode laser absorption spectroscopy to detect water vapor concentrations, gas velocities and mass flow during freeze-drying of pure water at different pressure and shelf temperature settings and of a 5%w/w mannitol solution. The analyzer was interfaced to the spool that connected the dryer chamber to the condenser. The reported method was advantageous in that primary and secondary drying end-point control based upon mass flow rate was independent of freeze-dryer size and configuration. ... 

H. Gieseler, W.J. Kessler, M. Finson, et al.. Evaluation of tunable diode laser absorption spectroscopy for in-process water vapor mass flux measurements during freeze drying, J. Pharm. Sci., 96(7), 1776-1793 (2007). 

SECS SEMI equipment communications TDL tunable diode laser... 

Figure 24.2 Schematic diagram of the setup used to measure and control H2O concentration and gas temperature in the combustion region (in situ) of a forced 5-kilowatt combustor at Stanford University 1 — steel duct 2 — quartz duct 3 — A1 duct 4 — multiplexed beam 5 — tunable diode lasers 6 — data acquisition and control computer 7 — control signals 8 — primary air driver Aair sin(27r/of) 9 — fuel drivers Afuei sin(27r/of-f dfuei) 10 — demultiplexing box 11 — Si detector (ND filter) and 12 — laser beam...

Tunable diode-laser sensors offer considerable promise for combustion research and development and also for process sensing and control applications. These devices are rugged and relatively easy to operate and they have been demonstrated to yield simple and quantitative measurements of species, temperature, and velocity, where line-of-sight measurements are useful or preferred. These techniques will grow in use as costs of laser sources and fiber-optic components decrease and access to more wavelength regions improves. 

Welle, S.D., D.S. Baer, and R. K. Hanson. 1997. Tunable diode-laser absorption measurements of temperature, velocity, and H2O in hypervelocity flows. 33rd Joint Propulsion Conference Proceedings. NY AIAA. AIAA Paper No. 97-3267. 

Other infrared absorption techniques are also used in ambient air measurements, including tunable diode laser spectroscopy (TDLS), nondispersive infrared (NDIR) spectroscopy, and matrix isolation spectroscopy. These are discussed in more detail later. 

FIGURE 11.31 Comparison of gaseous HN03 measurements made simultaneously in Claremont, California, on two different days using FT-IR shown as with error bars and by a filter pack (FP), a difference denuder (DD), an annular denuder (AD), and tunable diode laser spectroscopy (TDLS) (adapted from Hering et al., 1988). 

Brassington, D. J., Tunable Diode Laser Absorption Spectroscopy for the Measurement of Atmospheric Species, in Spectroscopy in Environmental Science (R. J. H. Clark and R. E. Hester, Eds.), pp. 85-148, Wiley, New York, 1995. 

Fox, D. L L. Stockburger, W. Weathers, C. W. Spicer, G. I. Mackay, H. I. Schiff, D. J. Eatough, F. Mortensen, L. D. Hansen, P. B. Shepson, T. E. Kleindienst, and E. O. Edney, Intercomparison of Nitric Acid Diffusion Denuder Methods with Tunable Diode Laser Absorption Spectroscopy, Atmos. Environ., 22, 575-585 (1988). 

Fried, A., S. Sewell, B. Henry, B. P. Wert, T. Gilpin, and J. R. Drummond, Tunable Diode Laser Absorption Spectrometer for Ground-Based Measurements of Formaldehyde, J. Geophys. Res., 102, 6253-6266 (1997). 

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