Gerd A. Wagner and David F. Plusquellic, "Ground-based, integrated path differential absorption LIDAR measurement of CO2, CH4, and H2O near 1.6 μm," Appl. Opt. 55, 6292-6310 (2016)
A ground-based, integrated path, differential absorption light detection and ranging (IPDA LIDAR) system is described and characterized for a series of nighttime studies of , , and . The transmitter is based on an actively stabilized, continuous-wave, single-frequency external-cavity diode laser (ECDL) operating from 1.60 to 1.65 μm. The fixed frequency output of the ECDL is microwave sideband tuned using an electro-optical phase modulator driven by an arbitrary waveform generator and filtered using a confocal cavity to generate a sequence of 123 frequencies separated by 300 MHz. The scan sequence of single sideband frequencies of 600 ns duration covers a 37 GHz region at a spectral scan rate of 10 kHz (100 μs per scan). Simultaneously, an eye-safe backscatter LIDAR system at 1.064 μm is used to monitor the atmospheric boundary layer. IPDA LIDAR measurements of the and dry air mixing ratios are presented in comparison with those from a commercial cavity ring-down (CRD) instrument. Differences between the IPDA LIDAR and CRD concentrations in several cases appear to be well correlated with the atmospheric aerosol structure from the backscatter LIDAR measurements. IPDA LIDAR dry air mixing ratios of and are determined with fit uncertainties of 2.8 μmol/mol (ppm) for and 22 nmol/mol (ppb) for over 30 s measurement periods. For longer averaging times (up to 1200 s), improvements in these detection limits by up to 3-fold are estimated from Allan variance analyses. Two sources of systematic error are identified and methods to remove them are discussed, including speckle interference from wavelength decorrelation and the seed power dependence of amplified spontaneous emission. Accuracies in the dry air retrievals of and in a 30 s measurement period are estimated at 4 μmol/mol (1% of ambient levels) and 50 nmol/mol (3%), respectively.
Axel Amediek, Gerhard Ehret, Andreas Fix, Martin Wirth, Christian Büdenbender, Mathieu Quatrevalet, Christoph Kiemle, and Christoph Gerbig Appl. Opt. 56(18) 5182-5197 (2017)
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The wavelength regions covered are from 1.5 to 1.65 μm, near 2.05 and 3.3 μm. The transmitter properties specified include the average output power (), output pulse energy (), pulse repetition rate (), and wavelength region () (n.s. indicates not specified; N/A indicates not applicable). The symbol definitions include the following: PMT, photomultiplier tube; APD, avalanche photo diode.
Table 2.
Transmitter Requirements for Ground-based, Eye-safe IPDA LIDAR System for Continuous Nighttime Monitoring of , and for Ranges up to 5 kma
The symbol definitions include the following: PMT, photomultiplier tube; APD, avalanche photo diode; atm., atmosphere.
Table 3.
Specifications [44] of and IPDA LIDAR System Having a Coaxial Transceiver Arrangementa
Transmitter
ECDL tuning range
1585 to 1646 nm,
New focus velocity 6330H
C-, L-band amplifier
single pass, PM,
Thorlabs SF9C1082P (BOA1),
Thorlabs SF9C1080P (BOA2)
Arb. waveform generator
24 GS/s, 10 bits,
Tektronix AWG7122C
AOM
Brimrose
EOM
EOSpace (EOM1, EOM2)
Reference detector
New focus 1811 (DET-REF)
PDH detector
Thorl. PDA10CF (DET-PDH)
Fiber splitter
OZ optics (95:5%, FS1)
Timbercon (90:10%, FS2)
Filter cavity
confocal, length ,
finesse
Wavelengths single scan
123
Single scan tuning range
37.5 GHz
Scan repetition frequency
10 kHz
Output power
10 to 13 mW
Receiver
Telescope diameter, type
279.4 mm, Schmidt-Cassegrain,
Celestron EdgeHD 11
Detector type
Photomultiplier tube,
Hamamatsu H10330A-75 SEL
DAQ
AD conversion
16 bit, 2 Ch., 200 MS/s, DS,
GaGe CSE1622
The symbol definitions include the following: ECDL: External-Cavity Diode Laser, PM: Polarization Maintaining, DAQ: Data Acquisition, AD: Analog-to-Digital, DS: Data Streaming.
Table 4.
Best-fit Values to Eq. (7) of the Average Photon Counts, , and the Other Degrees of Freedom, , that Contribute to the Total Observed Variance, , for 10 Sets of Integrated Intensity Measurements made at 5 Different Frequencies Using a Stationary and Moving Transceivera
FIT
FIT
CALC.
CALC.
DATA
FREQ.
Stationary transceiver
(a)
160(1)
118.78(2)
0.742(5)
207
210
(b)
133(1)
113.61(4)
0.854(6)
210
219
(c)
75(1)
105.05(5)
1.40(2)
251
249
(d)
136(2)
110.42(4)
0.81(1)
199
204
(e)
71(1)
108.23(8)
1.52(2)
273
268
Moving transceiver
(a)
39.5(4)
97.16(7)
2.45(2)
336
334
(b)
36.3(4)
92.23(7)
2.54(3)
326
319
(c)
33.6(3)
88.45(7)
2.63(2)
321
318
(d)
37.7(2)
84.10(3)
2.23(1)
272
266
(e)
35.0(1)
85.87(3)
2.453(7)
296
288
The contributions to the calculated variance, , are also given based on Eq. (8).
Table 5.
Measured ASE Suppression Factors, , for Baseline Corrections of the and Dataa
Trace
Int. [a.u.]
Int. [a.u.]
(b)
0.37293
–
0.64072
–
(c)
0.31473
0.413
0.44425
0.533
(d)
0.30936
0.410
–
–
(e)
0.31100
0.420
0.45576
0.501
Averages
0.414(22)
0.517(50)
The traces [see Figs. 12(a) and 12(b)] are defined as follows: (b): background (AWG OFF), (c): high frequency, (d): center frequency, (e): low frequency. Traces are interpolated over the region defined by the bandwidth of laser and OSA resolution and converted to power scale prior to integration. Uncertainties given in parenthesis are determined from the scatter in 9 measurements for the wavelength region and in 2 measurements for the region.
Measurement errors are given in %, (ppm) for , and nmol/mol (ppb) for . Uncertainties are specified as Type A, , or except for temperature and pressure uncertainties taken from weather stations which are Type B, [57].
Table 7.
Specifications [44] of Aerosol Backscatter LIDAR System with Coaxial Transceiver Arrangementa
Transmitter
Nd:YAG Wavelength
1064.15 nm,
Bright solutions SOL40-1064
Pulse repetition frequency
10 kHz
Output pulse energy
4 μJ
Output fiber
Single-mode PCF,
NKT Photonics LMA-25
Collimated beam diameter
50.8 mm
Receiver
Telescope diameter, type
279.4 mm, Schmidt-Cassegrain,
Celestron C11-A XLT
Elevation
Field of view
Detector type
Photomultiplier Tube, 3% QE,
Hamamatsu H10330A-75
DAQ
AD conversion
1 bit, 1 Ch., PC,
FAST ComTec P7888
The symbol definitions include the following: PCF: Photonic Crystal Fiber, QE: Quantum Efficiency, DAQ: Data Acquisition, AD: Analog-to-Digital, PC: Photon Counting.
Tables (7)
Table 1.
Specifications of Deployed , DIAL and IPDA LIDAR Systems Using Direct Detection and Systems of Relevance for This Work Using Coherent Detectiona
The wavelength regions covered are from 1.5 to 1.65 μm, near 2.05 and 3.3 μm. The transmitter properties specified include the average output power (), output pulse energy (), pulse repetition rate (), and wavelength region () (n.s. indicates not specified; N/A indicates not applicable). The symbol definitions include the following: PMT, photomultiplier tube; APD, avalanche photo diode.
Table 2.
Transmitter Requirements for Ground-based, Eye-safe IPDA LIDAR System for Continuous Nighttime Monitoring of , and for Ranges up to 5 kma
The symbol definitions include the following: PMT, photomultiplier tube; APD, avalanche photo diode; atm., atmosphere.
Table 3.
Specifications [44] of and IPDA LIDAR System Having a Coaxial Transceiver Arrangementa
Transmitter
ECDL tuning range
1585 to 1646 nm,
New focus velocity 6330H
C-, L-band amplifier
single pass, PM,
Thorlabs SF9C1082P (BOA1),
Thorlabs SF9C1080P (BOA2)
Arb. waveform generator
24 GS/s, 10 bits,
Tektronix AWG7122C
AOM
Brimrose
EOM
EOSpace (EOM1, EOM2)
Reference detector
New focus 1811 (DET-REF)
PDH detector
Thorl. PDA10CF (DET-PDH)
Fiber splitter
OZ optics (95:5%, FS1)
Timbercon (90:10%, FS2)
Filter cavity
confocal, length ,
finesse
Wavelengths single scan
123
Single scan tuning range
37.5 GHz
Scan repetition frequency
10 kHz
Output power
10 to 13 mW
Receiver
Telescope diameter, type
279.4 mm, Schmidt-Cassegrain,
Celestron EdgeHD 11
Detector type
Photomultiplier tube,
Hamamatsu H10330A-75 SEL
DAQ
AD conversion
16 bit, 2 Ch., 200 MS/s, DS,
GaGe CSE1622
The symbol definitions include the following: ECDL: External-Cavity Diode Laser, PM: Polarization Maintaining, DAQ: Data Acquisition, AD: Analog-to-Digital, DS: Data Streaming.
Table 4.
Best-fit Values to Eq. (7) of the Average Photon Counts, , and the Other Degrees of Freedom, , that Contribute to the Total Observed Variance, , for 10 Sets of Integrated Intensity Measurements made at 5 Different Frequencies Using a Stationary and Moving Transceivera
FIT
FIT
CALC.
CALC.
DATA
FREQ.
Stationary transceiver
(a)
160(1)
118.78(2)
0.742(5)
207
210
(b)
133(1)
113.61(4)
0.854(6)
210
219
(c)
75(1)
105.05(5)
1.40(2)
251
249
(d)
136(2)
110.42(4)
0.81(1)
199
204
(e)
71(1)
108.23(8)
1.52(2)
273
268
Moving transceiver
(a)
39.5(4)
97.16(7)
2.45(2)
336
334
(b)
36.3(4)
92.23(7)
2.54(3)
326
319
(c)
33.6(3)
88.45(7)
2.63(2)
321
318
(d)
37.7(2)
84.10(3)
2.23(1)
272
266
(e)
35.0(1)
85.87(3)
2.453(7)
296
288
The contributions to the calculated variance, , are also given based on Eq. (8).
Table 5.
Measured ASE Suppression Factors, , for Baseline Corrections of the and Dataa
Trace
Int. [a.u.]
Int. [a.u.]
(b)
0.37293
–
0.64072
–
(c)
0.31473
0.413
0.44425
0.533
(d)
0.30936
0.410
–
–
(e)
0.31100
0.420
0.45576
0.501
Averages
0.414(22)
0.517(50)
The traces [see Figs. 12(a) and 12(b)] are defined as follows: (b): background (AWG OFF), (c): high frequency, (d): center frequency, (e): low frequency. Traces are interpolated over the region defined by the bandwidth of laser and OSA resolution and converted to power scale prior to integration. Uncertainties given in parenthesis are determined from the scatter in 9 measurements for the wavelength region and in 2 measurements for the region.
Measurement errors are given in %, (ppm) for , and nmol/mol (ppb) for . Uncertainties are specified as Type A, , or except for temperature and pressure uncertainties taken from weather stations which are Type B, [57].
Table 7.
Specifications [44] of Aerosol Backscatter LIDAR System with Coaxial Transceiver Arrangementa
Transmitter
Nd:YAG Wavelength
1064.15 nm,
Bright solutions SOL40-1064
Pulse repetition frequency
10 kHz
Output pulse energy
4 μJ
Output fiber
Single-mode PCF,
NKT Photonics LMA-25
Collimated beam diameter
50.8 mm
Receiver
Telescope diameter, type
279.4 mm, Schmidt-Cassegrain,
Celestron C11-A XLT
Elevation
Field of view
Detector type
Photomultiplier Tube, 3% QE,
Hamamatsu H10330A-75
DAQ
AD conversion
1 bit, 1 Ch., PC,
FAST ComTec P7888
The symbol definitions include the following: PCF: Photonic Crystal Fiber, QE: Quantum Efficiency, DAQ: Data Acquisition, AD: Analog-to-Digital, PC: Photon Counting.