1. Mid-IR ethene detection using a quasi-phase matched LiNbO 3 waveguide 64th OSU International Symposium on Molecular Spectroscopy 23 rd June 2009

2. 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 hours  O3 ~ 9.7 days  NO3 ~ 5.2 months Why ethene? Urban Area ~ few ppbv Remote Area < 1 ppbv

3. C2H4C2H4 A.M.Parkes et al., Phys. Chem. Chem. Phys., 6 (2004) 5313-53178 HITRAN Database, 2008 Mid-IR vs Near-IR Mid-IRNear-IR DFG (2 to 5  m) QCLs (5 to 11  m)

4. C2H4C2H4 HITRAN Database, 2004 3081.002 cm -1 6150.300 cm -1  cm -1 (FWHM) 0.007170.01432  line / cm 2 molecule -1 cm -1 1.124 10 -20 5.08 10 -22 Gain ~ 46 Mid-IR vs Near-IR

5. ELECTRONICS LETTERS 17th August 2006 Vol. 42 No. 17 Applied Physics Letters 88, 061101, 2006 pp ss  i   p   s ii Frequency mixing and phase matching d eff = 17 pm/V ksks kpkp kiki

6. Bulk vs waveguide Applied Physics Letters 88, 061101, 2006 Waveguide structure improves conversion efficiency with respect to bulk

7. PZT Experimental set-up (OA-CEAS) 90 mW 28 mW ~ 200  W

8. 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.

9. Tunability of the laser source Wide tunability range of 35 cm -1 FWHM ~ 7 cm -1

10. Multi-pass absorption + WMS 1.29 Torr of C 2 H 4 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  )

11. OA-CEAS 1.8 Torr of C 2 H 4 in Ar (21.8 ppmv) Slow modulation = 0.8 Hz Chopper frequency = 2.6 kHz  = 0.01232 cm -1  = 0.00717 cm -1

12. OA-CEAS R = 99.901 ± 0.002 %  min (BW)= 1.6 x 10 -8 cm -1 Hz -1/2 (2  ) L = 1110 ± 20 m

13. 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 [C 2 H 4 ] min / molecule cm -3 (in air) Mixing ratio / ppbv (in air) Near-IR (@ 1.6  m) cw-CRDS 1.6  10 12 64 cw-CRDS + preconc. 4.7  10 10 1.9 Mid-IR (@ 3.2  m) MPA + WMS 5.4  10 11 21.8 OA-CEAS 2.2  10 11 8.9

14. 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

16. 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

17. Noise Analysis 330-370 kHz

18. Noise Analysis Applied Physics B 76, 473-477 (2003) 0.025 (200-500kHz)

19. cw-CRDS with Laser Detuning Technique Cavity Signal Laser Current