Cavity ring-down lossmeter using a pulsed light emitting diode source and photon counting

A new mode of cavity ring-down measurements in which an incoherent, broadband light emitting diode (LED) is used as the spectroscopic source is described. Light from a pulsed LED (570 nm, 12 nm FWHM) was coupled into a 32 cm linear optical resonator and a ring-down waveform obtained on a gated photon counter. Cavity time constants observed were on the order of 3–4 µs, yielding effective optical path-lengths in excess of 1 km. In an effort to demonstrate the function of the instrument we have measured absorption and Rayleigh scattering by gases introduced into the measurement cell. Measurements of Rayleigh scatter by CO2 and 1,1,1,2 tetrafluoroethane (R-134a) were used to calibrate the instrument. The Rayleigh extinction coefficients determined through the LED–CRD method were found to agree with literature values to within 12% on average. In an additional set of experiments, a laboratory-generated vapour containing either iodine or ozone was introduced into the measurement cell in an effort to demonstrate the technique's ability to monitor absorbing gases. The ring-down time constants (τ) observed were found to decrease by 15–75% when the absorbing gases were added to the measurement cell. The observed decrease in cavity time constant was proportional to the quantity of absorbing gas within the measurement cell. Minimum detectable extinction coefficients (2s) of ≈2.5 × 10−7 cm−1 were achieved. The LED–CRD approach may lead to development of inexpensive gas sensors or monitoring systems for atmospheric extinction/visibility.

[1]  S. Milošević,et al.  Nonlinear effects in pulsed cavity ringdown spectroscopy of lithium vapour , 2000 .

[2]  G. T. Fraser,et al.  Doppler-free nonlinear absorption in ethylene by use of continuous-wave cavity ringdown spectroscopy. , 2000, Applied Optics.

[3]  David J. S. Birch,et al.  MHz LED source for nanosecond fluorescence sensing , 2002 .

[4]  Louis J. Gillespie,et al.  The Normal Vapor Pressure of Crystalline Iodine1 , 1936 .

[5]  M. Linne,et al.  Fixed-frequency cavity ringdown diagnostic for atmospheric particulate matter. , 1998, Optics letters.

[6]  Shardanand,et al.  Absolute Rayleigh scattering cross sections of gases and freons of stratospheric interest in the visible and ultraviolet regions , 1977 .

[7]  J. Wojtowicz,et al.  The Kinetics of the Homogeneous Gas Phase Thermal Decomposition of Ozone1 , 1960 .

[8]  G. P. Baxter,et al.  THE VAPOR PRESSURE OF IODINE. , 1907 .

[9]  S. Herndon,et al.  Detection of nitrogen dioxide by cavity attenuated phase shift spectroscopy. , 2005, Analytical chemistry.

[10]  Frank X. Mueller,et al.  Decomposition rates of ozone in living areas , 1973 .

[11]  James B. Burkholder,et al.  Temperature dependence of the ozone absorption spectrum over the wavelength range 410 to 760 nm , 1994 .

[12]  Richard N Zare,et al.  Cavity ring-down spectroscopy as a detector for liquid chromatography. , 2003, Analytical chemistry.

[13]  D. Romanini,et al.  CW cavity ring down spectroscopy , 1997 .

[14]  W. Simpson,et al.  Frequency-matched cavity ring-down spectroscopy , 1998 .

[15]  F P Milanovich,et al.  High sensitivity atmospheric transmission measurements using a cavity ringdown technique. , 1988, Applied optics.

[16]  Ming-Chang Lin,et al.  Kinetics of phenyl radical reactions studied by the cavity-ring-down method , 1993 .

[17]  D. Shallcross,et al.  410-nm diode laser cavity ring-down spectroscopy for trace detection of NO2 , 2003 .

[18]  Richard N. Zare,et al.  Cavity ring-down spectroscopy for quantitative absorption measurements , 1995 .

[19]  Hiroaki Misawa,et al.  Light emitting diode-based nanosecond ultraviolet light source for fluorescence lifetime measurements , 1995 .

[20]  Richard N Zare,et al.  Direct monitoring of absorption in solution by cavity ring-down spectroscopy. , 2002, Analytical chemistry.

[21]  D. Romanini,et al.  Non-linear effects by continuous wave cavity ringdown spectroscopy in jet-cooled NO2 , 1999 .

[22]  J. Winefordner,et al.  Monitoring atmospheric particulate matter through cavity ring-down spectroscopy. , 2002, Analytical chemistry.

[23]  W. Ubachs,et al.  Experimental verification of Rayleigh scattering cross sections. , 2000, Optics letters.

[24]  Richard N Zare,et al.  Stable isotope ratios using cavity ring-down spectroscopy: determination of 13C/12C for carbon dioxide in human breath. , 2002, Analytical chemistry.

[25]  Rayleigh scattering coefficients for dry air, carbon dioxide, and freon-12. , 1974, Applied optics.

[26]  F Ariese,et al.  Miniaturized cavity ring-down detection in a liquid flow cell. , 2005, Analytical chemistry.

[27]  Yabai He,et al.  Ringdown and cavity-enhanced absorption spectroscopy using a continuous-wave tunable diode laser and a rapidly swept optical cavity , 2000 .