Click to edit Master text styles
IRSENS II A Multi-Gas Sensor for Air Pollutants and Greenhouse Gases S.Nida1, M.J.Süess1, J.M.Wolf1, M.Beck1, J.Faist1 L. Emmenegger2, B. Tuzcon2, R. Brönnimann2, H. Looser3, T. Südmeyer4 ETH Zurich1 EMPA Dübendorf2 Fachhochschule Nordwestschweiz3 Université Neuchâtel4
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Motivation Click to
edit Master text styles
Gases Medical diagnosis
Environment
Sensing of small molecules (CO, CO2, NxOy, ...) Air quality control
Selective Sensitive
Portable Low power
Infrared Spectroscopy
Semiconductor System
Process control
Leak detection
Traffic security IrSens 2 – Selam Nida
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Click Goal to edit Master text styles
Current air pollution monitor (NABEL Station) in EMPA, Dubendorf
State of the Art method • Bulky • Expensive • High power consumption
Detect the 10 most important atmospheric gases with Infrared Laser Spectroscopy IrSens 2 – Selam Nida
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Click to edit Methods of Laser Master Spectroscopy text styles Molecular Bonds => mechanical oscillators Rotational Vibrational modes of molecules
Ro-vibrational energy level diagram
Allowed transitions at various resonant frequencies
Absorption at this resonant frequencies • Unique fingerprint
sensitive to mass (ω=√k/m)=> distinguish Isotopes IrSens 2 – Selam Nida
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Click toAbsorption Optical edit Master Spectroscopy text styles – MIR Region MIR Not enough energy to excite vibration of bonds
Fundamental mode
Overtones
Ionization
Energy
Fundamental absorption fingerprint of 10 most important pollutants IrSens 2 – Selam Nida
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Optical Click Spectroscopy to edit Master
text styles
L = 36 m, p = 100 hPa 1 ppm NO2 1.3% H2O
100 100 9595 9090 o iT )s (% n m ra )T (% io m s n ra
8585 8080
Laser tuning
1598 1598
1599 1599
1600 1600
1601 1601
1602 1602
-1
Wavenumber (cm ) -1) Wavenumber (cm
1. Tuning of the laser emission across the fingerprint region 2. Measure how much light is absorbed by the sample
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Click to Spectroscopy Optical edit Master text – Quantum styles Cascade Laser Barrier
well
Barrier
Inter-subband Lasers Multiple quantum wells
Quantum Cascade Laser
Broad Gain: transitions possible over a broad spectral range
Selectivity : Choose the wavelength
Selectivity and Tunability IrSens 2 – Selam Nida
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Click to editCell Interaction Master text styles Requirement: • Large optical path length- to increase the absorption signal • Minimize fringes –reduce the noise Parabolic multi-pass reflection cell • Confocal/parabolic =>12m/300ml • Robust absorption mask –highly reduced interference fringes –reduce the noise
Parabolic Multi-pass reflection cell M.Mangold, B.Tuzcon et al, Switzerland Patent 01884/12, 2012. IrSens 2 – Selam Nida
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Click to edit Master Achievements so fartext styles CO2 Spectroscopy 17O12C16O 18O12C16O 13C16O2 12C16O2
CO2 isotope analyzer Helicobacter pyroli Infection marker Quantify soil exchange Tracer for stratospheric air
Jouy et al, Analyst 2015 IrSens 2 – Selam Nida
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Click to edit Master Achievements so fartext styles Cocaine Spectroscopy
Jouy et al, Analyst 2015
Measurement of Cocaine in PCE
NO2 Spectroscopy the SPIE award for miniaturized Platforms at the Photonics Europe Innovation Village Dr. Markus Mangold Postdoctoral fellow c/o Dr. Lukas Emmenegger Laboratory for Air Pollution EMPA DĂźbendorf
A 36x40 cm spectroscopic platform IrSens 2 – Selam Nida
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Click to Goal Current edit Master -Multiple textGas styles sensing Simultaneous detection of the 10 most important gases
Detector
Laser Requirement: Distinct emission wavelength (Laser) for each gas Challenge: Power loss and beam combining complexity added
However, most of the components can be shared
Solution: One laser emitting at multiple wavelengths
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Multi-Wavelength Operation Click to edit Master text styles in QCLs Fabry Perot Cavity
Cladding
p To
Me
on lC ta
ct ta
r ing dd ato cla ul t
ns ac e Ci ont F : al InPMet ing d m lad tto c o B InP InP
Active region (AR)
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Multi-Wavelength Operation Click to edit Master text styles in QCLs Wavelength Selection- Distributed Feedback Lasers (DFBs) Cladding
DFB
Top
tal Me
ct n ta Co
ato InP clad r ding
AR
InP: Fe i
In
Active region (AR)
Pc lad d
nsu l
ing
Bo ttom
M
et a l Co nta ct
Periodic Modulation of the waveguide effective index
λ=2*Λg*neff H. Kogelnik and C. V. Shank, Journal of Applied Physics 43 (1972). A. Yariv and P. Yeh, Optical Waves in Crystals (John Wiley and Sons, 1984).
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Multi-wavelength Click to edit Master operation text styles of QCLs Distributed feedbacks (DFB)
T<175K
AR AR 2 1
First demonstration of multi-wavelength QCLs • Two stack active region • Two DFBs Intersubband=>delta like joint density of states Straub et. al, Electronics Letters, 2002
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Multi-wavelength DFB QCLs Click to edit Master text styles
Single mode and multi wavelength operation
DFB 1
DFB
2
Back
Front
InP cladding Active region InP:Fe insulator
electrical separation
Emission at two wavelengths, one at a time with electronic switch.
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Twin-DFB Click to editQCLs Masterdemonstration text styles Multiple gas (NO/NO2) detection from Automotive emission
Emissions in ambient air measured by a dual-QCL, comparison with chemo luminescence data (CLD). J. Jagerska et al. APL 105, 161109 (2014). J. Jagerska et al., Optics Express 23, 1512 (2014).
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Packing more Click to edit Master text styles Triple Wavelength Operation Triple stack active region Triple section DFB
DFB 1
DFB
2
DFB
3
electrical separation electrical separation
Problem: Reduced power from the back section Solution: Sampled Grating DFBs Proof of concept demonstrated (J Wolf, A Bismuto Unpublished)
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Sampled Grating (SG)text DFBstyles Click to edit Master
Z
Vernier selection S. Slivken et al., Appl. Phys. Lett. 100 (2012) T. Mansuripur et al., Optics Express. Vol 20, No 21 (2012) IrSens 2 â&#x20AC;&#x201C; Selam Nida
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Sampled Grating (SG)text DFBstyles Click to edit Master
Λ1
Z
Z1
Λ3
Λ2
Z Z2
Z1
Z2
T. Mansuripur et al., Optics Express. Vol 20, No 21 (2012) IrSens 2 – Selam Nida
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Click to edit Master text QCLs styles Triple-wavelength-SGDFB Back
Front
. .N.
...
xN
x
Λ2
Reflectivity
Λ1
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Click to edit Master text styles Plans conc. range [ppb]
waven umber
2-20
1046.4
1700
1275.5
SO2
0.1-10
1352
NO2
1-100
1600
NO CO ,N2O ,H2O
1-100
1900
1-10
2179
CO2
380
2281
Trace gas NH3,O3 CH4 ,N2O ,H2O
SGDFB DFB 1
DFB
2
Twin color DFB
Detecting 10 gases with 3 lasers IrSens 2 â&#x20AC;&#x201C; Selam Nida
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Click to edit Master text styles
T. Südmeyer
S. Nida M. Suess P. Jouy J. Faist
L. Emmenegger B. Tuzcon M Mangold J Jagerska R. Brönnimann
Thank you IrSens 2 – Selam Nida
H. Looser
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Click to edit Master text styles
Thank you
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Click to edit Master text styles Components
Electronics - Real-time fitting engine - Directly linked to HITRAN database
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Comparison Click to edit Master text styles 1. Ambient air sample passed through the sensor NO + O3=(excited)NO2
Photomultiplier at ~-4C
From an ozone lamp Fluoresces at visible and near IR – measure this
This step is reliable and precise NO data can be determined. Inexpensive and simple 3. Sample thought another path through heated MO* or Au metal catalyst • NO2 + catalyst -> NO • Measure total NO. • However interference from gas phase nitric acid, alkyl and multifunctional alkyl nitrates gives false positives upto 22% higher NO2 than other spectroscopic measurements 4. NO2=step 3-step 1
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Click Multi-gas to editSensing Master text –Thestyles QCL solution Intersubband lasers
Interband lasers
hν
hν
• Broad absorption (α) above hν
• Narrow absorption (α) at hν
QCL •
No cross absorption between two separate emission wavelengths • Multiple wavelength emission possible from a single waveguide IrSens 2 – Selam Nida
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Click to Laser Driver edit Master - Switching text styles
• Time multiplex pulser to sequentially turn on one laser, and hence getting the two spectra independently.
• Transmission signal aquired by a digitizer card and synchronized with the laser pulser. • Real time fitting of data with the HITRAN database automatically. • RS-232 communication with OpenSense Core Station.
J. Jagerska et al., Optics Express 23, 1512 IrSens 2 – Selam Nida
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Click to Laser Driver edit Master â&#x20AC;&#x201C;Quasi-CW text styles driving
Laser current from discharging capacitor Switches and trigger signal (TTL) controlled by a microcontroller.
Series resitors to chose the current flow across the laser. Several RC circuits to get the desired pulse shape
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Click to Laser Driver edit Master text styles State of the Art
Current Model
• Continuous wave (CW) laser driving • high power dissipation ~KW/cm2 • Bulky heat management systems
• Alternative driving scheme • Pulsed operation but long pulses – Quasi CW ~200μs • Intermittent scanning of the spectra
Quasi-CW driving
*
• Very simple RC circuit based driver • Charging a capacitor during the laser off period and turning on the laser by discharging the capacitor • No need for high quality and stable power supply
M. Fisher et al, Optics Express 22(6), 7014-7027, 2014 IrSens 2 – Selam Nida
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Application- measuring NOx with dual wavelength QCLs
Click to edit Master text styles Tuning with Current
Tuning with temperature
Laser process design and optimization to match the absorption lines with the emission frequencies of interest (here of NO2(a) and NO(b)) at a given temperature IrSens 2 â&#x20AC;&#x201C; Selam Nida
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Sensing Click to Schemes edit Master text styles Chemiluminecense – State of the art technique ●
NO2
Simple and inexpensive
Heated Molybdenum or Gold Catalyst
High likelihood of false positives
NO Excited species, fluoresces
Detect NO • Calibration required
Optical Sensing • Direct measurement • Very specific • Very sensitive
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