An Asynchronous Optical Sampling THzTDS Spectrometer and THz

An Asynchronous Optical Sampling THz-TDS Spectrometer and THz Frequency Comb Spectrometer Jacob Good, Dan Holland, Ian Finneran, Brandon Carroll, Marco Allodi, Geoff Blake California Institute of Technology

Gas-Phase Rotational Spectroscopy D 2 O 10 THz/100 k. Hz 10 -8 precision 10 ppb https: //www. astro. uni-koeln. de/cgi-bin/cdmsinfo? file=e 020502. cat

What does 10 -8 Precision Look Like? 108 nm to 1 nm 10 -8 precision 10 ppb publications. nigms. nih. gov/chemhealth/images/ch 4_size. jpg

Part I: Building the Spectrometer

Time Domain Spectroscopy coherent. com; Dan Holland, Caltech Ph. D Thesis, (2014)

Delay Line Scan Rate vs Scan Range 10 THz to 10 GHz 10 -3 precision 1 ppm 10 THz 10 GHz Dan Holland, Caltech Ph. D Thesis, (2014)

ASynchronous OPtical Sampling Master Slave coherent. com; Dan Holland, Caltech Ph. D Thesis, (2014)

ASOPS Sweep Rate vs Scan Range 80 THz 10 THz to 10 MHz 10 -6 precision 1 ppm 10 MHz Dan Holland, Caltech Ph. D Thesis, (2014)

ASOPS-THz-TDS System THz Electro-Optic Detection Personal Computer Master Ti: Sapph 180 MS/s Digitizer Wollaston λ/4 Prism 10 MHz Rb Standard Periscope Zn. Te Lens ITO Slow PZT Sample Cell 12. 5 cm Scan Triggering Frequency Counter 90% 50% PMT Clock PD Slave Ti: Sapph Slow PZT Balanced PDs Slave PD Periscope Fast PZT BBO THz Emitter Lens 50% Master PD PLL Electronics 50% 90% Nitrogen Purge Box

80 MHz ASOPS THz Pulse J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

80 MHz ASOPS Bandwidth J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

Part II: Gas-Phase Spectroscopy

Water 1 Torr − 80 MHz ASOPS J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

Pressure Broadened Line Shape -2. 67 MHz Observed - Calculated 114 MHz FWHM Lorentzian Line Shape 10 THz to 10 MHz 10 -6 precision

CH 3 CN 2 Torr − 80 MHz ASOPS ν = 2 B(J + 1) − 2 DJKK 2(J + 1) J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

CH 3 CN − Unresolved Structure ν = 2 B(J + 1) − 2 DJKK 2(J + 1)

5 MHz FCS THz Pulse Train J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

18 Pulse Frequency Comb I. A. Finneran, J. T. Good, et al. , Phys. Rev. Lett. 114, 163902, (2015)

5 MHz FCS Bandwidth J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

CH 3 CN 150 m. Torr − 5 MHz FCS J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

5 MHz FCS vs 80 MHz ASOPS 3 J = 46 K=6 2 5 4 1 0 J. T. Good, et al. , Rev. Sci. Instrum. , In Prep

Doppler Broadened Line Shape 0. 086 MHz Observed - Calculated 4. 7 MHz FWHM Gaussian Line Shape 10 THz to 100 k. Hz 10 -8 precision

Me. OH 140 m. Torr FCS

Me. OH 140 m. Torr FCS

Me. OH 140 m. Torr FCS

Me. OH 140 m. Torr Peak Fitting 8. 5 MHz FWHM Gaussian Line Shape

Me. OH 140 m. Torr Prediction (THz) Observed (THz) Log Intensity Error (MHz) 1. 588594756 1. 588595486 -2. 2727 0. 730 1. 588597991 Fixed -2. 6116 N/A 1. 588597992 Fixed -2. 6116 N/A 1. 588608982 1. 588608450 -2. 2406 -0. 532 1. 588621485 1. 588620710 -2. 3539 -0. 775 1. 588638007 1. 588637823 -2. 2148 -0. 184 1. 588668167 1. 588669835 -2. 4023 1. 668 1. 588679307 1. 588679276 -2. 1959 -0. 031 RMS 0. 54 MHz

Long Path Double Pass Cell THz Electro-Optic Detection Personal Computer Master Ti: Sapph 180 MS/s Digitizer Wollaston λ/4 Prism 10 MHz Rb Standard Periscope Zn. Te Lens ITO Slow PZT Scan Triggering Frequency Counter 90% 50% PMT Clock PD Slave Ti: Sapph Slow PZT Balanced PDs BBO Slave PD Periscope THz Emitter Fast PZT Lens 50% Master PD PLL Electronics 50% 90% Sample Cell 2 x 0. 94 m 188 cm / 12. 5 cm = 15 x enhancement Rooftop Reflector THz Polarizer

21, 470 Pulse Frequency Comb 10 THz to 10 k. Hz >10 -9 precision I. A. Finneran, J. T. Good, et al. , Phys. Rev. Lett. 114, 163902, (2015)

THz Bandwidth vs Pulse Width P. J. Hale, et al. , Opt. Express, 22, 26358 -26364, (2014)

Prism Compressor http: //www. swampoptics. com/images/tutorial_compressor_fig 2. gif

Acknowledgements • Blake Group • Prof. Jun Ye • NSF Funding

THF 5 Torr − 80 MHz ASOPS

THF − Pseudorotational Modes Q Q P R PR PR