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CHIRPED-PULSE TERAHERTZ SPECTROSCOPY FOR BROADBAND TRACE GAS SENSING Eyal Gerecht, Kevin O....
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Transcript of CHIRPED-PULSE TERAHERTZ SPECTROSCOPY FOR BROADBAND TRACE GAS SENSING Eyal Gerecht, Kevin O....
CHIRPED-PULSE TERAHERTZ SPECTROSCOPY FOR BROADBAND
TRACE GAS SENSING
Eyal Gerecht, Kevin O. Douglass, David F. Plusquellic
National Institute of Standards and Technology Optical Technology Division, Gaithersburg, MD
Multi-Component Gas MonitorGHGs, VOCs, or breath analysis
Formaldehyde
CO
MethanolAcetone
Ethanol
CO2 (18O)
N2O
NO
0.805 0.875THzL.S. Rothman et al, “The HITRAN 2004 molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transf. 96, 139-204 (2005).
x48
White Cell
9 GHz Source
Mix AMCx48
YIG
YIG
AWG 12 GS/s
Chirped-Pulse THz Spectrometer
E. Gerecht, K.O. Douglass, D.F. Plusquellic, Optics Express, April 22, 2011, Vol. 19, Issue 9, pp. 8973-8984 (2011)Field group (MIT): 70-100 GHz,G.B. Park et al., 64th ISMS, 2009, RH07
LO
High Speed Data Transfer
360 MB/s 26.66 MS/sRecord and Transfer 80 MS in 3 s
At 40 GS/s:4000 records in 3 s80,000 averages in 60 sec.
Remote Data TransferWired x4 PCI Express
White Cell
M
3
M5
M1
M
2
M4
M
6
Power Transmission ~20%Currently aligned for 25 meter path length
V. B. Podobedov, D. F. Plusquellic, and G. T. Fraser, J. Quant. Spectrosc. Radiat. Transf. 91(3), 287–295 (2005).V. B. Podobedov, D. F. Plusquellic, K. E. Siegrist, G. T. Fraser, Q. Ma and R. H. Tipping, J. Quant. Spectrosc. Radiat. Transf. 109(3), 458-467 (2008).
0.5 m
Direct Absorption of a 5 Component Gas Mix
L.S. Rothman et al, “The HITRAN 2004 molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transf. 96, 139-204 (2005). H. M. Pickett, R. L. Poynter, E. A. Cohen, M. L. Delitsky, J. C. Pearson, and H. S. P. Muller, "Submillimeter, Millimeter, and Microwave Spectral Line Catalog," J. Quant. Spectrosc. Radiat. Transf. 60, 883-890 (1998).
Absorption - N2O at 853.3553 GHz
0 50 100 150 200 250 3000
0.5
1
1.5
2
2.5
f(x) = 0.00893065835605766 xR² = 0.99669476297959
Inte
nsity
Pressure (mTorr)
FID Detection of a 5 Component Gas Mix
0.54600 0.55666THz
FID
Sig
nal
(a.
u.)
0.55133 0.553990.54866
N2O170 ppb
OCS280 ppb
EtOH1600 ppb MeOH
100 ppb
Acetone8000 ppb
H2O2 ppbx5
00
100,000:1
x500
L.S. Rothman et al, “The HITRAN 2004 molecular spectroscopic database,” J. Quant. Spectrosc. Radiat. Transf. 96, 139-204 (2005). H. M. Pickett, R. L. Poynter, E. A. Cohen, M. L. Delitsky, J. C. Pearson, and H. S. P. Muller, "Submillimeter, Millimeter, and Microwave Spectral Line Catalog," J. Quant. Spectrosc. Radiat. Transf. 60, 883-890 (1998).
10.6 GHz in 500 nsec – 80K averages in 60 sec
FID Detection of MeOH 10 GHz Bandwidth
Field Magnitude
Intensity
*
**
*
In between limits
541060 552505ν / GHz
2.5 mTorr Pure
Signal Scaling?
779.760 869.760ν / GHz
Extending to Higher Bandwidths
Please See Justin Neil
RC06
90 GHz FID near 850 GHzMeOH -1.2 mTorr Pure
2ms acquisition time
ConclusionsDemonstrated Chirped pulse THz spectrometer
operating in 530 – 630 GHz and 780 – 870 GHz regions
Demonstrated phase stable operation
Demonstrated high sensitivity and rapid throughput for both absorption and FID emission measurements
We continue to make progress on the quantification of FID signals and sensitivities
Acknowledgements
Virginia L. Perkey – SURF student Eric M. Vess - SURF student Tektronix – equipment loan
NIST National Research Council ProgramPost Doctoral Research Opportunities
http://www.nist.gov/pml/div685/grp08/biophysics-group-research-opportunities.cfm