High energy optical parametric sources for multi-wavelength DIAL: a generic approach Jessica Barrientos Barria, Jean-Baptiste Dherbecourt, Myriam Raybaut, Antoine Godard, Jean-Michel Melkonian, Michel Lefebvre myriam.raybaut@onera.fr ONERA the French Aerospace Lab, Palaiseau, France
OUTLINE Context NESCOPO / OPA configuration : Principle of mode selection in NESCOPO Continuous fine tuning Multi- operation DIAL applications Conclusions and perspectives 2
Spaceborne lidar - Global monitoring of green house gases Main species of interest Species (µm) CO 2 1.57 / 2.05 CH 4 1.64 / 2.29 H 2 0 0.935 / 0.942 / 2.06 N 2 O 3.93 O 2 0.764 Usual optical sources 1 seeder / emitted wavelength Complicated frequency stabilization scheme for multi-wavelength operation ON OFF 2 3 2 1 3 1 2 2 3 2 OFF OFF 1 OFF 2 2- IDIAL for probing the lower troposphere multi- DIAL Gas 1 Gas 2 multi-species DIAL 3
Short range LIDAR applications 4 Need: Wavelength (µm) 6-14 µm: Defence & Security applications 3-5 µm : Air quality problematic Broadly tunable laser sources able to provide multiple wavelengths at preselected values => For multi-species detection, identification, quantification
Parametric conversion - background Our approach: Optical frequency synthesizer based on a specific doubly resonant OPO, pumped by a 1 µm single frequency laser Parametric conversion Pump laser ( p ) Signal ( s ) Depleted pump Idler ( i ) Energy conservation p s i Parametric oscillators (OPOs), amplifiers (OPAs) 5
Parametric conversion - background Singly resonant OPO : nanosecond regime PGB Pump 1.06 µm Signal 1.5 µm Idler 4 µm i M1 M3 s Multimode output p /2 Single frequency emission 2 main approaches : PGB - Injection seeding (ex : Merlin architecture) - Nested cavity approach (Onera patented) i Additionnal seed laser OPO cavity locking on the seed wavelength 1 additional seeder / emitted wavelength Multi-species operation (wavelength coverage) limited to the availablility of seeders 6
Spectral filtering using a NesCOPO Nested Cavity doubly resonant OPO (NesCOPO)* ω p M1 ω i M3 M2 ω s * Onera patented L/L too low clusters Well designed dissociation L Single Frequency L/L too large clusters 7
Spectral filtering using a NesCOPO Nested Cavity doubly resonant OPO (NesCOPO)* ω p M1 ω i M3 M2 ω s * Onera patented Single Frequency Doubly resonant arrangement low oscillation threshold Periodically poled NL materials (PPLN, PPKTP) large spectral coverage with a single device (ex : 1.5-1.6µm / 3 3.7 µm) => multi-species detection possible Vernier effect one single pair of signal and idler modes is selected within the PGB Single frequency over several 100nm without a seeding source No seeder needed => multi-wavelength possible => simple architecture 8
NESCOPO layout Mechanical assembly µ-nescopo under development 9
NESCOPO Continuous frequency tuning M1 M2 ω i M3 Parametric gain bandwidth ω p PZT i ω s PZT s+i ω i L i s L L 1 i i s L M3 ω s 10
Vernier frequency sampling tuning method T (%) M1 M2 λon1 λon4 λon3 λon2 λoff M3 λ Vernier frequency sampling ω s ω i ω i 11
Long range DIAL Instruments in development at Onera/DMPH Multi-species instrument for IP DIAL in the 2µm range for green-house gases 2µm / 2.2µm transmitter CO 2 (2.05µm), H 2 O (2.06µm), CH 4 (2.29 µm) >15 mj @ 2.05µm ESA TRP 19813, "Pulsed Laser Source in NIR for Lidar Applications" 2006-2009 CNES R&T programme 115606/00, Source paramétrique multi-longueurs d onde pour Lidar DIAL 2011-2012 Multi-species instrument for DIAL in the 1.5µm / 3 3.7µm range Green-house gases + TIC 1.5-1.6µm / 3-3.7 µm transmitter CO 2 (1.57µm), CH 4 (1.64 µm, 3.3 µm) TICs > 10 mj Onera SEPIA project (Surveillance des Emissions des Polluants Industriels dans l Atmosphère) Compact µlaser pumped device for local / short range sensing (technology transfert towards a PME) 12
Long range DIAL CO 2 Transmitter Specifications (CO2 lidar) 2 µm master-oscillator power amplifier architecture : NesCOPO Type II PPLN Pump Signal 2.05 µm Idler 2.21µm OPA PPLN type 0 4 KTPs J. Caron, Y. Durand λ/2 500 µj 60 mj Lame de filtrage λ/2 1064 nm Delay line 3 species targetted : G. Ehret et al. Appl. Phys. B 90, 593 608 (2008) ~70 mj High frequency stability < 2 MHz rms Stabilization several (3) GHz away from the line center > 99.9 % purity (1 GHz filter) CO 2 2.05µm (signal) H 2 O 2.06µm (signal) CH 4 2.2 µm (idler) 13
Long range DIAL CO 2 Transmitter Type II p ppln DROPO s DROPO i i 4 stages KTP Type 0 ppln Pump amplifier preamplifier (1mJ) 10ns delayed OPA pump Rayon à 1/e² (µm) 400 350 300 250 200 150 100 50 points expérimentaux M 2 horizontal : 1.03 M 2 vertical : 1.05 M 2 < 1.1 0 0 10 20 30 40 50 60 position du couteau (mm) 15 mj at 2.05 µm with a 60 mj pump level (30 Hz) Normalized pump power (a.u.) 1,0 0,8 0,6 0,4 0,2 Input pump pulse Depleted pump Depletion ratio 0,0 0 20 40 60 80 100 120 140 time (ns) KTP OPA stages : 50 % pump depletion 27 % conversion efficiency towards 2.05 µm 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 Optimisation still possible : > 75% total conversion efficiency recently demonstrated at 2µm using high aperture PPLN H. Ishizuki et al., Opt. Express. 20, (2012). Depletion ratio 14
Shot by shot free running frequency stability NESCOPO/OPA frequency fluctuations : measured at the output of the OPA stages, free running SHG Frequency (THz) 292,515720 292,515700 292,515680 292,515660 Standard dev. 30s : < 3MHz @ 2050 nm 146,25786 146,25785 146,25784 146,25783 Signal Frequency (THz) Frequency measurement : Wavemeter Future developments : Use of a gas cell &/or beat mode frequency with a laser diode to Implement active frequency locking 0 10 20 30 t (s) < 3MHz rms over 30s Signal frequency stability λs / λs = Ls / Ls (0.1 nm resolution PZT => 1 MHz) To be improved : better PZT & electronics, better opto-mechanical design locking (mid-term derive) Idler frequency stability = Pump ditter + signal frequency stability 15
Shot by shot frequency switching Line center ω p M1 M2 ω c M3 1 ω s 2- ON DIAL PZT c PZT s+c fixe λ ON 2 Parametric gain bandwidth ω s 0 ω p /2 λ ON 1 ωi λ ON 2 ω p ω p /2 16
Shot by shot frequency shifting for multi-wavelength DIAL Control electronics : - PZT control voltage (idler cavity length) - Temporal Synchronization with the pump pulse tension de consigne aux PZT (V) 0,10 0,05 0,00-0,05-33 0 33 Time (ms) Temps (ms) Shot by shot several GHz frequency switching demonstrated (up to 5 wavelengthes with a free running transmitter) Frequency locking of λ1 to be implemented Sequences of well defined λ to be generated (ex : +/- 3 GHz on each side of the line center) 4 2 0 tension de synchronisation (V) fréquence de l'onde signal (THz) 146,100 146,097 146,094 Fréquence de l'onde signal (THz) 146,101 146,100 146,099 146,098 146,097 146,096 33 ms 99000 99100 99200 99300 4 GHz 4 GHz shot by shot switching Time Temps (ms) (ms) 146,095 104 106 108 110 112 114 Time (ms) Temps (s) 2.05 µm frequency stability < 4 MHz for both λ1 and λ2 17
Conclusion & perspectives Main conclusions ØThe NESCOPO is a well suited for multi- / multi species DIAL ØShort range applications can be adressed using a very compact design (µlaser pumped) ØThe NESCOPO /OPA is a generic transmitter for DIAL (can be implemented for various gas species) Perspectives : ØTransmitters development : Ø Rugged 2µm / 2.2 µm transmitter for CO2, H2O, CH4 Ø 1.5-1.6 µm / 3-3.7 µm transmitter for CO2, CH4, Toxic industrial chemicals Ø Extension to the 8-12 µm band ØLidar measurements Ackowledgements ØThis work has been partially supported through contract 19813, "Pulsed Laser Source in NIR for Lidar Applications", within the Technology Research Programme of the European Space Agency (ESA), Ø This work has been partially supported by CNES through contract 115606/00, Source paramétrique multi-longueurs d onde pour Lidar DIAL, of the Research and Technology programme. ØThis work has been partially supported by grants from Région Ile de France. 18 ü Hardy B. et al, Appl. Phys B, 107, 643-647 (2012) ü Hardy B. et al, Opt. Lett., 36, 678 (2011) ü Berrou A. et al, Appl. Phys. B, 98, 217 ü Raybaut M. et al, Opt. Lett. 34, 2069 (2009)