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Journal of Applied Physics
Volumn 104, Issue 9, 2008, Pages
Trace gas measurements using optically resonant cavities and quantum cascade lasers operating at room temperature
Author keywords

[No Author keywords available]
Indexed keywords

ABSORPTION; CHEMICAL SENSORS; CONCENTRATION (PROCESS); GAS ABSORPTION; LASERS; PULSED LASER APPLICATIONS; QUANTUM CASCADE LASERS; SPECTROMETERS; SPECTROMETRY;
EID: 56349096481     PISSN: 00218979     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.3008014     Document Type: Article
Times cited : (39)
References (85)
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    • Hemerik, M.M.1    Kroesen, G.M.W.2
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    • 56349093613 scopus 로고    scopus 로고
    • Ph.D. thesis, Eindhoven University of Technology.
    • M. Hemerik, Ph.D. thesis, Eindhoven University of Technology, 2001.
    • (2001)
    • Hemerik, M.1
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  • 62
    • 56349171013 scopus 로고    scopus 로고
    • The MDND was calculated with 50 ppb at atmospheric pressure. The NEA was estimated via the minimum round triloss for 16 ppb standard deviation (Fig. 7 in Ref.) and converted into kmin. Equation for 20 s averaging (without 2) yields the NEA.
    • The MDND was calculated with 50 ppb at atmospheric pressure. The NEA was estimated via the minimum round trip loss for 16 ppb standard deviation (Fig. 7 in Ref.) and converted into kmin. Equation for 20 s averaging (without 2) yields the NEA.
  • 63
    • 56349136148 scopus 로고    scopus 로고
    • Figure 8 in Ref. implies a minimum detectable absorption of 3× 10-3 for 1500 m in 4 s. The NEA follows from Eqs. and the MDND from 0.7 ppb at 100 Torr or 0.8 ppb at 70 Torr. Those minimum concentrations are given as rms noise from approximately ten different 4 s scans and are therefore smaller than a minimum absorption of 3× 10-3 would suggest.
    • Figure 8 in Ref. implies a minimum detectable absorption of 3× 10-3 for 1500 m in 4 s. The NEA follows from Eqs. and the MDND from 0.7 ppb at 100 Torr or 0.8 ppb at 70 Torr. Those minimum concentrations are given as rms noise from approximately ten different 4 s scans and are therefore smaller than a minimum absorption of 3× 10-3 would suggest.
  • 64
    • 56349123537 scopus 로고    scopus 로고
    • Figure 3 in Ref. implies an absorption of 0.0005 for 13 ppb NO (50 Torr) for a SNR=5, i.e., the minimum detectable absorption is ∼ 10-4. For N=100 scans the SNR was improved by N1/2 while for 10 000 averages an additional factor 2.5 is achieved, i.e. a factor 25 in total compared to a single scan. The NEA follows from Eqs. (without 2 because Leff =100 m was not calibrated).
    • Figure 3 in Ref. implies an absorption of 0.0005 for 13 ppb NO (50 Torr) for a SNR=5, i.e., the minimum detectable absorption is ∼ 10-4. For N=100 scans the SNR was improved by N1/2 while for 10 000 averages an additional factor 2.5 is achieved, i.e. a factor 25 in total compared to a single scan. The NEA follows from Eqs. (without 2 because Leff =100 m was not calibrated).
  • 65
    • 56349149270 scopus 로고    scopus 로고
    • The Allan variance minimum of 0.03 ppb after 30 s corresponds to 3× 10-6 absorbance noise and kmin =1.5× 10-10 cm-1, respectively (Ref.). Since the short term noise (1 s) is 0.06 ppb the corresponding values were also scaled by a factor 2, i.e. the NEA is ∼3× 10-10 cm-1 Hz-1/2. The MDND follows from 0.03 ppb at 20 Torr.
    • The Allan variance minimum of 0.03 ppb after 30 s corresponds to 3× 10-6 absorbance noise and kmin =1.5× 10-10 cm-1, respectively (Ref.). Since the short term noise (1 s) is 0.06 ppb the corresponding values were also scaled by a factor 2, i.e. the NEA is ∼3× 10-10 cm-1 Hz-1/2. The MDND follows from 0.03 ppb at 20 Torr.
  • 68
    • 56349112124 scopus 로고    scopus 로고
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    • Uherek, E.1    Sander, R.2
  • 69
    • 56349161348 scopus 로고    scopus 로고
    • Combining Eqs. without integration yields L eff -1 ln (I0 /I) =k=nSf (- 0), where f describes the line profile. In the case of low pressures (<5 mbar) f can be approximated by a Doppler profile and k or f can be analytically expressed at 0, i.e. L eff -1 ln [I0 (0) /I (0)] =k (0) =nS×2 (ln 2/π) 1/2 /Δ line, where Δ line is the FWHM and thus nS∼ln (I0 /I) at the maximum.
    • Combining Eqs. without integration yields L eff -1 ln (I0 /I) =k=nSf (- 0), where f describes the line profile. In the case of low pressures (<5 mbar) f can be approximated by a Doppler profile and k or f can be analytically expressed at 0, i.e. L eff -1 ln [I0 (0) /I (0)] =k (0) =nS×2 (ln 2/π) 1/2 /Δ line, where Δ line is the FWHM and thus nS∼ln (I0 /I) at the maximum.
  • 70
    • 56349116489 scopus 로고    scopus 로고
    • Leff was calculated from τ0 =3.5 μs. After 8 s the relative error of τ was 4.7× 10-3; Eqs. yield the NEA (without 2 because R was not calibrated). The MDND follows from the detection limit of 0.7 ppb at 60 Torr (Ref.).
    • Leff was calculated from τ0 =3.5 μs. After 8 s the relative error of τ was 4.7× 10-3; Eqs. yield the NEA (without 2 because R was not calibrated). The MDND follows from the detection limit of 0.7 ppb at 60 Torr (Ref.).
  • 71
    • 56349124001 scopus 로고    scopus 로고
    • After 600 scans at 600 Hz the standard deviation was 10-4. The NEA follows from Eqs. and the MDND from 0.25 ppb detection limit at STP (Ref.). Leff was estimated from τ0 =0.93 μs.
    • After 600 scans at 600 Hz the standard deviation was 10-4. The NEA follows from Eqs. and the MDND from 0.25 ppb detection limit at STP (Ref.). Leff was estimated from τ0 =0.93 μs.
  • 72
    • 56349146674 scopus 로고    scopus 로고
    • The MDND was calculated with 16 ppb at 30 Torr (Ref.). A minimum detectable absorption of 0.01 with Leff =670 m in 200 s yields the NEA with Eqs..
    • The MDND was calculated with 16 ppb at 30 Torr (Ref.). A minimum detectable absorption of 0.01 with Leff =670 m in 200 s yields the NEA with Eqs..
  • 73
    • 56349127124 scopus 로고    scopus 로고
    • Leff was calculated from Reff =99.4% and 50 cm base length. The MDND follows from 100 ppb at 50 Torr whereas the NEA was calculated with 0.15% standard deviation in absorption for 3.3 s averaging and Leff =83.3 m (Ref.).
    • Leff was calculated from Reff =99.4% and 50 cm base length. The MDND follows from 100 ppb at 50 Torr whereas the NEA was calculated with 0.15% standard deviation in absorption for 3.3 s averaging and Leff =83.3 m (Ref.).
  • 74
    • 56349103844 scopus 로고    scopus 로고
    • Figure 10 in Ref. implies a minimum detectable absorption of 3× 10-4 for 75 m in 15 s. The NEA follows from Eqs. and the MDND from 10 ppb at 100 Torr.
    • Figure 10 in Ref. implies a minimum detectable absorption of 3× 10-4 for 75 m in 15 s. The NEA follows from Eqs. and the MDND from 10 ppb at 100 Torr.
  • 75
    • 56349125418 scopus 로고    scopus 로고
    • Figure 4 in Ref. implies a minimum detectable absorption of 6× 10-3 for 700 m in 1 s. The NEA follows from Eqs. and the MDND from 3.2 ppb at 200 Torr.
    • Figure 4 in Ref. implies a minimum detectable absorption of 6× 10-3 for 700 m in 1 s. The NEA follows from Eqs. and the MDND from 3.2 ppb at 200 Torr.
  • 76
    • 56349091650 scopus 로고    scopus 로고
    • Figure 5 in Ref. implies a minimum detectable absorption of 6× 10-4 for 500 m in 4 s. The NEA follows from Eqs. and the MDND from 3.6 ppb at 100 Torr.
    • Figure 5 in Ref. implies a minimum detectable absorption of 6× 10-4 for 500 m in 4 s. The NEA follows from Eqs. and the MDND from 3.6 ppb at 100 Torr.
  • 77
    • 56349161846 scopus 로고    scopus 로고
    • With the given gain factor 6760 Reff is estimated to be 99.9852%. Consequently Leff is 5560 m for a base length of 82.3 cm. The MDND follows from the 3 ppb detection limit at 30 Torr (Ref.).
    • With the given gain factor 6760 Reff is estimated to be 99.9852%. Consequently Leff is 5560 m for a base length of 82.3 cm. The MDND follows from the 3 ppb detection limit at 30 Torr (Ref.).
  • 78
    • 56349131531 scopus 로고    scopus 로고
    • The MDND was calculated from the Allan variance minimum of 0.12 ppm at 14 Torr after 240 s corresponding to a peak absorbance precision of 6× 10-5. This value was scaled with ∼10 since it does not scale with the square root of averages (Ref.) to determine the short term deviation (1 s) yielding 1.1 ppm. The NEA follows from Eqs. for 56 m path length.
    • The MDND was calculated from the Allan variance minimum of 0.12 ppm at 14 Torr after 240 s corresponding to a peak absorbance precision of 6× 10-5. This value was scaled with ∼10 since it does not scale with the square root of averages (Ref.) to determine the short term deviation (1 s) yielding 1.1 ppm. The NEA follows from Eqs. for 56 m path length.
  • 79
    • 56349127575 scopus 로고    scopus 로고
    • The MDND was calculated for the smallest pressure given in Ref. (20 Torr) and 2.5 ppb CH4 and 1.0 ppb N2 O, respectively. The NEA follows from Eqs. (without 2) for 3.5× 10-5 minimum peak absorbance, 30 s averaging, and 100 m path length.
    • The MDND was calculated for the smallest pressure given in Ref. (20 Torr) and 2.5 ppb CH4 and 1.0 ppb N2 O, respectively. The NEA follows from Eqs. (without 2) for 3.5× 10-5 minimum peak absorbance, 30 s averaging, and 100 m path length.
  • 80
    • 56349169157 scopus 로고    scopus 로고
    • The NEA follows from Eqs. for 1.4× 10-4 absorbance precision at 1 s sampling rate. For N2 O this yields a MDND calculated from 3 ppb at 60 Torr. For CH4 the MDND was estimated from the Allan variance after 200 s: 0.7 ppb at 50 Torr (Ref.).
    • The NEA follows from Eqs. for 1.4× 10-4 absorbance precision at 1 s sampling rate. For N2 O this yields a MDND calculated from 3 ppb at 60 Torr. For CH4 the MDND was estimated from the Allan variance after 200 s: 0.7 ppb at 50 Torr (Ref.).
  • 81
    • 56349132948 scopus 로고    scopus 로고
    • Figure 5 in Ref. implies a minimum absorbance of 4× 10-5 for a 1 Hz sampling rate at 56 m path length which yields the (short term) NEA from Eqs. (without 2). The MDND follows from 35.5 Torr (Fig.) and the Allan variance minimum of 0.06 ppb.
    • Figure 5 in Ref. implies a minimum absorbance of 4× 10-5 for a 1 Hz sampling rate at 56 m path length which yields the (short term) NEA from Eqs. (without 2). The MDND follows from 35.5 Torr (Fig.) and the Allan variance minimum of 0.06 ppb.
  • 82
    • 56349094961 scopus 로고    scopus 로고
    • The MDND was calculated for 48 Torr and 1 s averaging time (Fig.) by means of the given NEAs, i.e., 0.12 and 0.26 ppb for the LN and TE cooled detectors, respectively (Ref.).
    • The MDND was calculated for 48 Torr and 1 s averaging time (Fig.) by means of the given NEAs, i.e., 0.12 and 0.26 ppb for the LN and TE cooled detectors, respectively (Ref.).
  • 83
    • 56349164017 scopus 로고    scopus 로고
    • The MDNDs follow from 34 and 14 ppb for CH4 and N2 O at atmospheric pressure, respectively. The NEA was estimated from the noise of 0.4 μV and the calibration factor of 715 V/W cm-1 scaled with the output power of 8 mW (Ref.).
    • The MDNDs follow from 34 and 14 ppb for CH4 and N2 O at atmospheric pressure, respectively. The NEA was estimated from the noise of 0.4 μV and the calibration factor of 715 V/W cm-1 scaled with the output power of 8 mW (Ref.).
  • 84
    • 56349152906 scopus 로고    scopus 로고
    • The MDND follows from 4 ppb at 50 Torr for a 3 s lock-in time constant. The normalized NEA was scaled with the output power of 19 mW (Ref.).
    • The MDND follows from 4 ppb at 50 Torr for a 3 s lock-in time constant. The normalized NEA was scaled with the output power of 19 mW (Ref.).
  • 85
    • 56349124926 scopus 로고    scopus 로고
    • The MDND was calculated with 0.1 ppb at 770 Torr after 100 s (Allan variance plot). The normalized NEA was scaled with the output power of 6.6 mW (Ref.).
    • The MDND was calculated with 0.1 ppb at 770 Torr after 100 s (Allan variance plot). The normalized NEA was scaled with the output power of 6.6 mW (Ref.).

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