mid-ir ethene detection using a quasi-phase matched linbo 3 waveguide 64th osu international...
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![Page 1: Mid-IR ethene detection using a quasi-phase matched LiNbO 3 waveguide 64th OSU International Symposium on Molecular Spectroscopy 23 rd June 2009](https://reader035.vdocument.in/reader035/viewer/2022062809/56649ee45503460f94bf2849/html5/thumbnails/1.jpg)
Mid-IR ethene detection using
a quasi-phase matched
LiNbO3 waveguide
Mid-IR ethene detection using
a quasi-phase matched
LiNbO3 waveguide
• 64th OSU International Symposium on Molecular Spectroscopy
• 23rd June 2009
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Biogenic sources
- Plant Hormone 'ripening hormone'
Anthropogenic sources
- Organic chemical industry (polyethylene products)
- Vehicle exhaust
(Ethene as indicator of UV-induced lipid peroxidation)
OH ~ 20 hoursO3 ~ 9.7 daysNO3 ~ 5.2 months
Why ethene?
Urban Area ~ few ppbv
Remote Area < 1 ppbv
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2900 3000 3100 3200 6148 6152
0.0
0.2
0.4
0.6
0.8
1.0
1.2
line
/ 10-2
0 cm2 m
olec
ule-1
cm
-1
Wavenumber /cm-1
C2H4
A.M.Parkes et al., Phys. Chem. Chem. Phys., 6 (2004) 5313-53178HITRAN Database, 2008
Mid-IR vs Near-IR
Mid-IR Near-IR
DFG (2 to 5m)
QCLs (5 to 11m)
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3080.9 3081.0 6150.2 6150.3 6150.4-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
/
10-1
8 cm
2 mo
lecu
le-1
wavenumber /cm-1
C2H4
HITRAN Database, 2004
3081.002 cm-1 6150.300 cm-1
cm-1 (FWHM) 0.00717 0.01432
line / cm2 molecule-1 cm-1 1.124 10-20 5.08 10-22
Gain ~ 46
Mid-IR vs Near-IR
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ELECTRONICS LETTERS 17th August 2006 Vol. 42 No. 17Applied Physics Letters 88, 061101, 2006
ps
ips
i
Frequency mixing and phase matchingPerfect phase matchingQuasi-phase matchingWithout phase-matching
deff= 17 pm/V
0i
i
s
s
p
p nnn
ks
kp
ki
1
2k
01
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Bulk vs waveguide
Applied Physics Letters 88, 061101, 2006
Waveguide structure improves conversion efficiency with respect to bulk
WGBulk
300
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PZT
Experimental set-up (OA-CEAS)
90 mW
28 mW
~ 200 W
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Characterization of the laser source
Conversion efficiency = 12.3 % W-1
Experimental phase matching curve in good agreement with the simulated one
Beam profile analysis gave a Gaussian beam waist of ~2 mm.
30 40 50 60 70 80
0.0
0.2
0.4
0.6
0.8
1.0
Nor
mal
ized
Con
vers
ion
Eff
icie
ncy
TCrystal
/ oC
2
sin 2 Lkc
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3220 3225 3230 3235 3240 3245 3250 3255 32600
2
4
6
8
10
12
14
pump
/nm
1062.0671062.3561062.7031063.1101063.3601063.6501064.0041064.150
Con
vers
ion
Effi
cien
cy %
/W
Idler
/nm
Tunability of the laser sourceWide tunability range of 35 cm-1
FWHM ~ 7 cm-1
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Multi-pass absorption + WMS
3080.94 3080.96 3080.98 3081.00 3081.02 3081.04
-0.2
0.0
0.2
0.4
0.6
WM
S S
igna
l a.u
.
Wavenumber /cm-1
Upper-state Local Quanta
Lower-state
Local Quanta
Molecule /cm-1
Term Symbol
Integrated cross section /cm2 cm-1
J' Ka' Kc' J'' Ka'' Kc''
C2H4 3081.0016 RP0(14) 1.09 · 10-20 13 1 13 14 0 14
C2H4 3081.0016 PR6(10) 1.64 · 10-22 11 5 6 10 6 5
C13CH4 3081.0016 PQ3(10) 1.76 · 10-22 10 2 8 10 3 7
1.29 Torr of C2H4 in Ar (500 ppmv)
Slow modulation = 1 Hz
Fast modulation = 20 kHz
c = 5 ms
Idler power = 193 W
L = 56 m
Modulation depth → b = 2
min (BW)= 1.63 x 10-8 cm-1 Hz-1/2 (2)
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3080.96 3080.98 3081.00 3081.02 3081.04 3081.06
0.00
0.04
0.08
0.12
0.16
c = 5 ms
c = 50 ms
3080.96 3081.00 3081.04
0.0
0.1
0.2
(I0-I
)/I
/cm-1
(Io-I
)/I
/cm-1
OA-CEAS
1.8 Torr of C2H4 in Ar (21.8 ppmv)
Slow modulation = 0.8 Hz
Chopper frequency = 2.6 kHz
= 0.01232 cm-1
= 0.00717 cm-1
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3080.97 3081.00 3081.03 3081.06 3081.09
0.0
0.1
0.2
0.3
0.4
0.5
0 1 2 3 40
2
4
6
area
/ 10
-3 c
m-1
[C2H
4] / 1012 molecule cm-3
(Io-I
)/I
/ cm-1
OA-CEAS
R = 99.901 ± 0.002 % min (BW)= 1.6 x 10-8 cm-1 Hz-1/2 (2)
L = 1110 ± 20 m
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Conclusions and future work
Mid-IR light has been characterized. The CONVERSION EFFICIENCY of the
waveguide, the BEAM PROFILE and the TUNABILITY of the system have been
tested.
Applications of the DFG spectrometer as a new laser sources @ 3.2 m for
ethene detection have been proved using MULTI-PASS ABSORPTION coupled
with WMS, and OA-CEAS.
A.M.Parkes et al., Phys. Chem. Chem. Phys., 6 (2004) 5313-53178
Technique[C2H4]min
/ molecule cm-3 (in air)Mixing ratio
/ ppbv (in air)
Near-IR(@ 1.6 m)
cw-CRDS 1.6 1012 64
cw-CRDS + preconc. 4.7 1010 1.9
Mid-IR(@ 3.2 m)
MPA + WMS 5.4 1011 21.8
OA-CEAS 2.2 1011 8.9
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Acknowledgements
Prof. Andrew Orr-Ewing
Dr. Mike Nix
Keith Rosser
Dr James Smith
Charles Murray
Bristol Laser Group
Prof. Gus Hancock
Dr Grant Ritchie
Dr Rob Peverall
Luca Ciaffoni
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10 15 20 25 30 35
Inte
nsit
y / a
rb. u
nits
Frequency / MHz
EDFA Pump 1 ( = 980 nm) Pump 2 ( = 1480 nm) Both Pumps
FWHM ~ 0.5 MHz
10 15 20 25 30 35
1583 nm DFB Diode LaserFWHM ~ 1.1 MHz
inte
nsity
/ ar
b. u
nits
Frequency /MHz50 100 150 200-85
-80
-75
-70
-65
-60
N
oise
(dB
VR
MS)
Frequency / kHz
Pseed
= 0 mW P
seed = 0.4 mW
Pseed
= 0.8 mW P
seed = 1.2 mW
Spectrum analysis of the EDFA output- Fabry-Perot spectrum analyzer → laser bandwidth ~ 500 kHz- 1480 nm pump more noisy than 980 nm- FFT spectrum analyzer → ASE at seeding powers < 1 mW
Characterization of the laser source
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Noise Analysis
330-370 kHz
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0 20 40 60 80 100
0
100
200
300
400
500
600
shot-noise
background
N = a0 + a
1 I + a
2 I2
a
0 = 147.1 ±7.6
a1 = 0.32 ±0
a2 = 0.0355 ±0.0016
No
ise
N (
pA
2 /Hz)
Detector Current I (A)
Noise Analysis
Applied Physics B 76, 473-477 (2003)
0.025 (200-500kHz)
N 2
B2eI
N 2eIB
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cw-CRDS with Laser Detuning Technique
Cavity
Signal
Laser
Cur
rent