1. CALIFORNIA INSTITUTE OF TECHNOLOGY Doppler-Limited Spectroscopy with a Decade- Spanning THz Frequency Comb

2. Dan Holland, Caltech PhD Thesis, (2014)

3. Crocket, N. A.; et al. Astrophys. J. 2014, 787, 112. Astrochemistry: 10 -8 Precision Needed

4. Saykally, Richard J., and Geoffrey A. Blake. "Molecular interactions and hydrogen bond tunneling dynamics: Some new perspectives." Science 259.5101 (1993): 1570-1575. θ (degrees) -90 270 0 90 180 THz Spectroscopy of Molecular Clusters: 10 -8 Precision Needed RH08 Brandon Carroll

5. Spectroscopy in the THz Pulsed THz (Time Domain THz) Continuous Wave High Precision (<10 -10 ) Low Bandwidth (0.2 THz) Low Precision (10 -5 ) High Bandwidth (>10 THz) vadiodes.com/

6. Frequency Combs: Nobel Prize in Physics 2005 (J. Hall, T. Hansch) 1/ nobelprize.org

7. Finneran, Ian A., et al. "Decade-Spanning High-Precision Terahertz Frequency Comb." Physical Review Letters 114.16 (2015): 163902.

8. THz Emitter +V Photoconductive Material 800 nm (no CEPS) THz (CEPS) ~50 fs ~1 ps CEPS = Carrier Envelope Phase Stabilized

9. Finneran, Ian A., et al. "Decade-Spanning High-Precision Terahertz Frequency Comb." Physical Review Letters 114.16 (2015): 163902.

10. Time Domain THz Spectroscopy: Detection DETECTION PHOTODIODES WOLLASTON PRISM 800 nm pulse THz pulse time λ/4ZnTe

11. Finneran, Ian A., et al. "Decade-Spanning High-Precision Terahertz Frequency Comb." Physical Review Letters 114.16 (2015): 163902.

12. Start Lap 1 Lap 2 Asynchronous Optical Sampling 800 nm pulse THz pulse time

19. Limits of the Comb >21,000 pulses 107 seconds lab time with 200 Hz offset Equivalent to 40 km delay line at Mach 1.1! Finneran, Ian A., et al. "Decade-Spanning High-Precision Terahertz Frequency Comb." Physical Review Letters 114.16 (2015): 163902.

21. Comparison with other THz combs Bandwidth (THz)Precision # Teeth This work 2.3 Hsieh et al. 1.9 10 -6 10 -9 28,000 7,600 Rösch et al. 0.680 10 -10 Finneran, IA, et al. Physical Review Letters 2015. Hsieh, YD, et al. Scientific reports 2014. Rösch, M, et al. Nature Photonics 2015.

22. Doppler-Limited Water Vapor: RMS = 92 kHz Finneran, Ian A., et al. "Decade-Spanning High-Precision Terahertz Frequency Comb." Physical Review Letters 114.16 (2015): 163902. 3 21 − 3 12 2 12 − 1 01 3 03 − 2 12

23. Conclusions THz comb has sufficient precision for astrochemistry and cluster spectroscopy. Precision could be improved for applications in metrology!

24. Acknowledgments The Blake Group NSF Professor Jun Ye