Near- and MID-IR Semiconductor Laser-Based Sensors for Industrial Process Monitoring

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1 VG Near- and MID-IR Semiconductor Laser-Based Sensors for Industrial Process Monitoring Mark G. Allen Physical Sciences Inc. May 2001 Physical Sciences Inc. 20 New England Business Center Andover, MA 01810

2 Sources and Target Gas Absorptions Direct current injection devices from µm; µm Frequency converted devices from µm (SHG); µm (DFG, OPO) InGaAs AIGaAs InGaAs GaSb InGaAIP GaN Type I QC VG SHG Si-Fiber Optic Window PPLN-based DFG, OPO Wavelength (µm) Absorption Strength (cm/molecule, Log Scale) NO, OH NO 2 O2 CO 2 H 2 O COOH NO CO NO CH 4 NO SO 2 Ro. Vibronic Vibration Overtones Fundamental Vibrational Modes E-3757a

3 Example of PSI Multi-Wavelength Near-IR TDL Sensor Configuration VG $ i(t) Time Waveform Generator #1 Temp Control #1 Current Control #1 Temp Control #2 Diode Laser #1 λ 1 Fixtured Collimator Mount Combustor or Facility Duct $ Fixtured Photodiode Mount Individual Dual PC Board Mount $ i(t) Time Waveform Generator #2 Current Control #2 Temp Control #3 Diode Laser #2 λ 2 λ 3 3x2 Coupler Ref erence λ 1 + λ 2 + λ 3 Signal λ 1 + λ 2 + λ 3 Measurement Path $ i(t) Time Waveform Generator #3 Current Control #3 Diode Laser #3 BRD D-6459z 19 in. Module Rack Mount Multiple lasers integrated into single instrument module Fiber/copper transmission of ~ 1000 s m to measurement location

4 Simultaneous Detection of CH 4, CO 2, and H 2 O Using Multi-plexed Diode Laser Sensor 0.5 Torr CH 4, 68.1 Torr CO 2, 14.1 Torr H 2 O 50 cm path, single-pass, room-temperature 1 VG Ab sorbance (a.u.) CH µm 2 ν 3 CO µm 3ν 1 +ν 3 H 2 O µm ν 1 + ν Laser 1 Laser 2 Laser Data Index 10 ms sweep (sum of three lasers), 200 sweep average, 2 second measurement time D-4910z

Grating-Coupler, Sampled Reflector Laser VG01-102-4 Gain 400 µm Coupler 500 µm Phase 150 µm Reflector SSG-DBR 900 µm hν p-inp n-inp

5 Grating-Coupler, Sampled Reflector Laser VG Gain 400 µm Coupler 500 µm Phase 150 µm Reflector SSG-DBR 900 µm hν p-inp n-inp InGaAsP 1.55 µm InGaAsP 1.14 µm InGaAsP 1.38 µm 0.15 µm 0.34 µm 0.05 µm 0.90 µm 0.20 µm D-5793z Current tuning is de-coupled from gain

Example GCSR Tuning Surface from ADC VG01-102-5 Provided by manufacturer Any point on this

6 Example GCSR Tuning Surface from ADC VG Provided by manufacturer Any point on this surface can be selected with ~1 µs or less This single laser can access CO, CO 2, OH, H 2 O, N 2 O,...

7 GCSR Scan of Laser Mix 4% CO, 9% CO 2, Balance He, N 2, H 2, atm Pressure Absorption Data HITRAN Simulation VG CO CO Laser Frequency (cm -1 ) D-6444z SSG reflector scan at fixed coupler, gain currents No phase current control (open circuit), resulting in mode-hops

8 Example TDL Sensor Dynamic Range: Atmospheric Trace NO 2 Monitor VG m Path Absorption nm 670 nm NO 2 Number Density (cm -3 ) C-9254az More than 10 4 linear dynamic range

9 Example Near-IR Diode Laser Species Sensors VG Demonstrated sensitivity in 1 m path at STP Species Wavelength (µm) Sensitivity (ppm-m) H 2 O 1.31, , 1 CO CO CH NO NO N 2 O HCN O HC" 1.2, NH Others added frequently

10 Comparison of Measured and Equilibrium CO Concentrations Methane air flame, atmospheric pressure VG CO Mole Fraction Equilibrium Concentration Measured Concentration (Normalized to φ =1.5) Equivalence Ratio D-6433z Acquired with GCSR laser

11 Diode Laser Sensors for Control of Oxygen-Enriched Furnaces VG Temperature Exhaust Gas Heat Flux Natural Gas TDL Sensor for CO, O 2 Oxygen Air Water Water D-5098z In partnership with AirLiquide for pulsed oxy-fuel furnace control

12 Chicago Research Center 0.9 O 2 Measurement Comparison VG O2 Number Density (x18 cm 3 ) Effect of gas recirculation Oxy Meas. Oxy TDL Oxy/Fuel Ratio RESEARCH AND DEVELOPMENT

13 Chicago Research Center O 2 Monitoring Demonstration Absorbance 440 kw Data Voigt Fit T flue =1363 K 5.2% Excess O 2 Relative Frequency (cm -1 ) O 2 Number Density 5.0E E E E E E E+18 VG Oscillating 80% of Natural Gas at 0.2 Hz Fuel-Lean Fuel-Rich Time (sec) 320 kw O 2 sensor response in pulsed fuel operation mode Noise contributions dominated by radiative emission fluctuations in furnace RESEARCH AND DEVELOPMENT

Chicago Research Center CO Monitoring Demonstration VG01-102-13 Absorption (au) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0-0.

(R14 transition, (3,0) band) CO Number Density (cm-3) 3.00E+16 2.50E+16 2.00E+16 1.50E+16 1.00E+16 5.00E+15 0.00E+00 0.

14 Chicago Research Center CO Monitoring Demonstration VG Absorption (au) Conditions: T=1244 K 10% CO by AAL G C Scan Time (au) BL Subtracted Voigt fit Isolated CO lineshape at 1244 K, 30 cm path (R14 transition, (3,0) band) CO Number Density (cm-3) 3.00E E E E E E E Hz Oscillating Frequency Fuel-rich Fuel-lean lean Time (sec) CO sensor response in pulsed fuel operation mode Noise levels reduced compared to O 2 data due to smaller detector aperture rms CO noise level ~ 160 ppm-m RESEARCH AND DEVELOPMENT

15 Two-Line Temperature Measurements Measure integrated absorbance from two transitions and define their ratio, R, as: R S S (T) (T) g g ( ω) ( ω) N dω N dω 1 2 VG = S S 1 2 T o exp hc(e1 E k 2 ) 1 T 1 T o where T o is an arbitrary reference temperature Sensitivity of the temperature measurement depends on the choice of absorption lines Accuracy of the temperature measurement depends on the accuracy of the measured ratio

16 Simultaneous Water Vapor Density and Thermometry H 2 -air flame, 70 cm pathlength, 3 second time constant VG H 2 O Temp 1.2x x10 18 Temperature (K) Equilibrium Thermocouple 1.0x x x x x Time (s) H 2 O Density (molecules/cc) D-8171az Temperature precision ±15 K, thermocouple disagreement < 50 K Density precision ±2 x cm -3 (<2%)

17 Optical Mass Flux Sensor Basics VG Basic physics: Detector θ V D-1495z Normalized Amplitude ω Laser Relative Wave number (cm -1 ) D-1496z u = c ω ωo cosθ N = ω ln(i/io ) dω o S" m = u ρ Technology: Velocity sensitivity to ~ 1 m/s at atm pressure ω v / ω a ~ 10-4

18 Continuous Gasdynamic Sensing in Supersonic Combustion In collaboration with Tohoku University, Sendai, Japan VG x x10 18 Temperature (K) Series1 Water Density (cm -3 ) 8.00x x x x10 17 Series3 Series Time (s) Time (s) Velocity (m/s) Series Time (s) 10 Hz sensor response in blowdown SCRAMJET model E-7683

NASA Dryden Full-Scale Engine Tests VG01-102-18 To A/D System From Laser Reference Beam #2 BRD #1 Signal Balanced Ratiometric Detectors (BRD) PSI-Fabricated Window Mounts BRD #2 Signal To A/D System

19 NASA Dryden Full-Scale Engine Tests VG To A/D System From Laser Reference Beam #2 BRD #1 Signal Balanced Ratiometric Detectors (BRD) PSI-Fabricated Window Mounts BRD #2 Signal To A/D System From Laser Reference Beam #1 Engine Hub Flow Direction P&W F100 Engine Signal Beam #1 5 1 =1.50m 0.92 m Bell Mouth Signal Beam #2 5 2 =1.31m From Laser NASA PIRC AR Coated Window Fiber-Coupled Launch Collimators From Laser Flexible Fiber Optic Cable D-0191z V-2272 P&W Engine Measurement Standards ρ = 0.9 to 1.0 kg/m3 Inlet pitot-static probes (ρ, u, m ) u = 0 to 170 m/s DEEC ( m ) m = 0 to 100 kg/s

20 Mass Flux Measurements NASA Dryden Full-Scale Engine Tests VG rms Uncertainty <±2% 180 Optical Mass Flux [lb/s] Pitot Static Mass Flux [lb/s] TDL sensor accuracy equivalent to or better than test facility standard D-0784z

Aeroengine Flight Mass Flux Sensor Ground testing on F-100 engine showed ± 2% uncertainty from idle to mil-spec power Laser Current (ma) 67.00 66.95 66.90 i PD 66.85 66.80 i laser 66.75 66.

21 Aeroengine Flight Mass Flux Sensor Ground testing on F-100 engine showed ± 2% uncertainty from idle to mil-spec power Laser Current (ma) i PD i laser Performance Level Test VG PD Current (ma) Vibration Level (db) db = Grm s 2 /Hz Flight sensor module on vibration test stand Sensor package (including optical interfaces) passed environmental tests and awaiting early 2001 flight vibration requirements for F-18 operability exceed Pegasus launch requirements Time (min) Example shake & bake test result E-2437z

PSI Airborne Diode Laser Sensors VG01-102-21 Ruggedized Hard

Hinged I/O Panel Cover Exterior Connector Panel V-1711 V-2195

22 PSI Airborne Diode Laser Sensors VG Ruggedized Hard Drive BRD Module Single Board Computer Data Acquisition Cards Hinged I/O Panel Cover Exterior Connector Panel V-1711 V-2195 (a) PSI/NASA O 2 Mass Flux Sensor (b) PSI/DOE UAV Hygrometer

23 Flight Mass Flux Sensor Engineering VG Supported by NASA Dryden Flight Research Center for Engine Control Applications F404-GE-400 Engines Laser Beam Trajectories Aft Sensor Mounts Engine Face Engine Inlet Individual Duct Cross Sections Correspond to Bulkhead Locations Flow FS379 Top View (not to scale) FS411 FS425 (throat) Aircraft Centerline 23.3 Optical Mass Flux Sensor Mounting Locations FS550.9 FS560 FS523 AFT Sensor Mount Locations Engine Face Proposed Sensor Mount Configuration (other locations shown as available Forward vo lume) Sensor Mounts (Landing Gear Bay) Side View Forward Sensor Mounts in Main Landing Gear Bay D-9510 Air Flow Duct In let D-9309z Schematic of F-18 installation 3-D view of optical interface layout Optical interface hardware installed and flying for ~ 8 months

Compact, Airborne Laser Multigas Sensor Program Goals Develop diode laser sensor for in-situ measurement of trace gas species from aircraft for atmospheric research on global climate change Develop

24 Compact, Airborne Laser Multigas Sensor Program Goals Develop diode laser sensor for in-situ measurement of trace gas species from aircraft for atmospheric research on global climate change Develop capability for multiple species measurement using several lasers and fiber-optic network Automate and size sensor for deployment on new generation of research aircraft: Unmanned Aerial Vehicles (UAVs) Altus UAV VG External air probe provides true in-situ sampling Probe remotely mounted from processor module Sensor Integration Instrumentation Rack 29.5 in. Payload Bay in. Fiber Optics and Electronic Cables External Air Probe SPM UAV payload parameters volume: 16 x 6 x 6 in. weight: 10 kg with probe power: 120 W Expandable to multiple lasers D-7770 Scale E-1100

25 Hand-Held TDL Gas Plume Sensor Collect topographic backscatter to check for gas absorption in illuminated region VG Internal or External Structure Gas Service Entry Presently under development for hazardous gas leak detection (HF, H 2 S, CH 4 ) in petro-chemical processing facilities 10 ppm-m sensitivity 5-20 m E-8716

26 Recent Advances in Room-Temperature Mid-IR Lasers MQW devices on GaSb substrates MIT Lincoln Lab, Univ. of Houston, Sarnoff, Univ. Montpellier multi-longitudinal mode, Fabry-Perot cavity quasi-cw peak power ~ 10 to 100 mw at room temperature VG Type II intersubband cascade on GaSb Univ. of Houston, AOI, Northwestern, NRL multi-longitudinal mode, Fabry-Perot cavity quasi-cw peak power ~ 100 mw, but only T 250K Type I intrasubband quantum cascade on InP Lucent Fabry-Perot and DFB, single-mode quasi-cw peak power ~ 10 s mw at T 350 K

27 Example Tuning, L-I, and V-I Characteristics of 5.4 µm DFB QC Device VG K Top Laser WL = 3.80e-4*T µm Bottom Laser WL = 3.99e-4*T µm 9 80 W avelength (nm) Voltage (V) K 275K 300K 275K 300K Peak Power (mw) Temperature (K) Temperature Tuning E-1487z Current (A) L-I, V-I Curves E-1488z Temperature measured at cryostat mount Data obtained at Lucent using liquid-n 2 mount

28 Lucent QC Laser Package VG Each chip contains six lasers, two of which are wired Top View Front View

29 Motivation VG Increasing regulatory pressure for pollutant and particulate omissions control on land and airborne gas turbine systems CO, NO levels < 5 ppm particulate levels ~ 10-4 g/m 3 In-situ monitoring of ~ 1 ppm levels of CO, NO difficult to accomplish with near-ir absorption MWIR emission/absorption offers possibilities for in-situ surveys of gaseous, particulate emissions FTIR: major species concentrations, temperature, some trace species QCL: high sensitivity measurement of CO, NO, SO 2

30 Example Detectivity Improvements Using Mid-IR Sensor Detection limits per meter absorption VG CO Potential Limit Demonstrated Limit Mid-IR Near-IR 2.3 µm 4.7 µm 300 K 3 ppm 20 ppb 0.1 ppb Flames 100 ppm 0.7 ppm 5 ppb NO Potential Limit Demonstrated Limit Mid-IR Near-IR 2.7 µm 5.2 µm* 300 K 30 ppm 600 ppb 30 ppb Flames 140 ppm 3 ppm 200 ppb *Sensitivity of 80 ppb demonstrated at 5.41 µm

31 Ambient CO Measurements Using QCL VG atm pressure, 21 m path, 300 K R (2) transition Absorbance Frequency [cm -1 ] Gated Integrator Absorbance [a.u.] Approximate Relative Frequency [cm -1 ] BRD F-0181 Measured level 200 ppb BRD-based detection limit ~ 5 ppb

32 Example NO Detection with QCL 32 mtorr NO in 50 cm cell VG Absorption Frequency (a.u.) Unresolved doublet 550 ppb-m detection limit E-5913

33 Example SO 2 Detection with QCL 0.5 Torr SO 2 in 50 cm cell VG Peak abs = 0.06 SNR = Absorption Frequency [au] 10 ppm-m detection limit extend to 100 ppb-m using sensitive detection techniques H 2 O vapor interferences will be important in combustion exhaust applications E-6084

34 Other QC-Laser Based In-Situ Sensors Under Development VG SO 2 and SO 3 measurements from combustion sources 7 to 9 µm region project 10 ppm-m detection limits at 600 K H 2 CO and CO measurements in ambient troposphere 5.6 and 4.6 µm project ~10 ppb sensitivity with 100 m Herriot Cell NO and CO measurements in combustion gases

Frequency-Converted Diode Laser Sources in the MID-IR VG01-102-34 Built around PPLN chip containing APE waveguides Two near-infrared diode lasers for input Difference-frequency

35 Frequency-Converted Diode Laser Sources in the MID-IR VG Built around PPLN chip containing APE waveguides Two near-infrared diode lasers for input Difference-frequency generation (DFG) to produce tunable mid-ir output radiation Tapered structures used to excite single mode of highly-multimoded waveguide Copyright 2000 by Laser Focus World/PennWell Corporation

36 Advantages of Guided-Wave DFG Source VG PPLN has high nonlinear coefficient Near-IR input lasers lead to room temperature operation, low cost, portability DFG process leads to broad wavelength coverage using tunability of near-ir lasers, engineering of PPLN Waveguides increase the conversion efficiency P 1 = η dev P 2 P 3 if η dev = 10%/W, two 100 mw lasers yield 1 mw

37 Waveguide DFG Power vs. Time VG E-03 Gemfire DFG (145 µw at 3.6 µm) 1.E-04 Power (W) 1.E-05 1.E-06 Lead-salt lasers (100 µw) 1.E-07 1.E Time (years) Data/designs provided by Gemfire Corporation

38 Methane Absorption Spectrum VG % Transmission CH 4 R(0) single sweep (5 ms) 30 cm path 0.5 Torr CH Wavenumber Data/designs provided by Gemfire Corporation

39 Spectrum of Water Vapor in Ambient Air 105 VG % Transmission open air at 23 o C 30% relative humidity 23 cm path x100 Frequency, cm Data/designs provided by Gemfire Corporation

40 CO 2 ISOTOPES AT 4.3 µm VG % Transmission R(25) 18 OCO R(12) 17 OCO R(37) Wavenumber Data/designs provided by Gemfire Corporation

41 The Next Level of Integration VG PUMP DIODE LASER FIBER PIGTAILS S-BEND 2-STEP EXCHANGE JUNCTION DIRECTIONAL COUPLER MIXING CHANNEL SIGNAL DIODE LASER Data/designs provided by Gemfire Corporation

42 Summary VG PSI has nearly a decade of experience in diode-laser-based gas sensors multi-million $ commercial spin-off company over 70 custom units delivered to research customers in the U.S., Europe, and Asia partnerships established with major industrial companies for eventual high volume applications Present research activities moving to advanced current-pumped mid-ir sources for DIAL and in-situ sensor applications partnerships established with Lucent and AOI/University of Houston licensed technology from Gemfire and growing capabilities in engineered non-linear optical materials for frequency-converted sources

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