1. Broadband Mid-infrared Comb-Resolved Fourier Transform Spectroscopy Kevin F. Lee A. Mills, C. Mohr, Jie Jiang, Martin E. Fermann P. Masłowski

2. Spectroscopy absorption spectra of gases midinfrared strong fundamental vibrations

3. New system midinfrared comb & FTIR bright 30 mW coherent broadband parallel –fast comb resolution 200 kHz linewidth –optically referenced referenced to GPS

4. Comparison other methods single-frequency laser bright precise narrowband slow scan LED, glowbar broadband incoherent low resolution VIPA spectrometer comb-resolved narrowband ~10 nm midinfrared comb & FTIR bright 30 mW coherent broadband parallel –fast comb resolution 200 kHz linewidth –optically referenced referenced to GPS

5. Absorption Lines measure line parameters need resolution linewidths Doppler broadened to ~ 100 MHz want resolution ~ 10 MHz ~ 0.0003 cm -1 need speed multiple lines temperatures pressures 11 Torr 150 Torr

6. Frequency combs stable train of laser pulses stable frequency comb active coherent lock first tooth carrier envelope offset (CEO) optical tooth to a reference whole comb stable

7. Midinfrared comb OPO comb inherits repetition rate same optical reference scan comb lines by tuning reference wavelength access any frequency

8. Sample 100 m path length multipass cell uses coherence & power increases absorption parts-per-billion sensitivity minimum detectable absorption 10 -6 cm -1 Hz -1/2 low pressures and concentrations

9. Spectrometer Fourier transform spectrometer (FTIR) record intensity vs. path delay time domain data FT to get spectrum broadband for 10 MHz resolution 30 m optical path delay too long, use comb

10. Comb-resolved FTIR match FTIR to comb alternating pixels with and without comb lines spectrum with 200 kHz linewidth elements our FTIR 16 cm stage 8 pass 234 MHz 2'x2' breadboard

11. Absolute frequency comb frequencies from measured repetition rate GPS referenced FTIR self-calibrated 150 MHz mismatch with HITRAN 1 / f rep

12. Measure CO in Ar 50+ CO absorption lines scan comb by ~30 MHz steps 13 comb-resolved spectra 1 000 000+ comb teeth CO fundamental

13. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

14. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

15. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

16. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

17. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

18. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

19. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

20. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

21. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

22. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

23. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

24. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

25. Comb Scan of CO 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1

26. Comb Scan of CO 170 MHz 30 MHz spacing (chosen) 234 MHz FTIR resolution 11 Torr CO in Ar 2 ppm line P6 2119.7 cm -1 150 kHz linewidth

27. Lineshape analysis simple Voigt profile at high pressure see speed dependence at low pressure Voigt profile speed dependent Voigt profile Residuals 404 Torr27 Torr

28. Pressure dependence fit with 4 pressures compare to Wehr et al. 2006 shifting –17% match broadening –4% match 50 lines * 4 pressures 1 hour by comb 1 month by cw-CRDS CO fundamental P7

29. Summary OPO comb & FTIR broadband midIR comb-resolved