Rapid temperature tuning of a 14-μm diode laser with application to high-pressure H_2O absorption spectroscopy

Abstract

Enhanced wavelength tuning of a distributed-feedback InGaAsP diode laser is demonstrated by use of rapid temperature cycling. The laser-active region is cycled from -10 to +50 degrees C (scanning the output from 1399 to 1403 nm) at kilohertz rates by pulsed heating with an auxiliary 532-nm laser. Such 4-nm scans represent a ten-fold increase in the wavelength-scanning range offered by standard current-tuning techniques and thus extend the capabilities of scan-wavelength sensors and systems. As an example application, we demonstrate absorption spectroscopy of H(2)O vapor at a pressure of 10 atm.

Wavelength-agile sensor applied for HCCI engine measurements

“…Many wavelength-agile sources have recently emerged, including vertical-cavity emitting lasers [1][2][3][4], thermally cycled diodes [5], chirped white pulses [6][7][8], variable Raman shifters [9], and scanning-grating systems [10]. The source presented in this paper is of the scanning-grating type.…”

“…All of these sources have been primarily developed because they enhance standard absorption spectroscopy techniques, providing sensors that are particularly well suited to combustion problems. The benefits of wavelength-agility in absorption spectroscopy have been previously outlined [5,6,[10][11][12]. In brief, wavelength-agile lasers allow broad segments of absorption spectra to be continuously monitored, thus providing continuous records of gas temperature and composition with fast time response.…”

Towards a standard for the dynamic measurement of pressure based on laser absorption spectroscopy

“…and Sanders for rapid wavelength tuning. [70, 71] This tuning method also has the potential for scanning over many transitions rapidly (< 1 ms). The resulting spectra could be analyzed with a multi-spectrum fit [72] where each transition is fit together in order to determine the pressure and temperature.…”

Laser Diagnostics for Reacting Flows

“…4 Images of a heated, turbulent jet using 308/266nm excitation of 3-pentanone. The jet core contains about 4.5% 3-pentanone while the co-flow contains 1.5%.…”

“…In reality, we assume the parameters of the size distribution and find the distribution parameters that best fit our transmission data. Then we can return to equation (4) to determine N, and consequently the liquid volume fraction occupied by the liquid particles. …”