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Terahertz Spectroscopy and Applications Frank C. De Lucia Department of Physics

Terahertz Spectroscopy and Applications Frank C. De Lucia Department of Physics Ohio State University IEEE International Frequency Control Symposium June 5 - 7, 2006 Miami, Florida. PEOPLE Doug Petkie - Professor WSU Eric Herbst - Professor OSU Brenda Winnewisser - Adj. Professor OSU

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Terahertz Spectroscopy and Applications Frank C. De Lucia Department of Physics

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  1. Terahertz Spectroscopy and Applications Frank C. De Lucia Department of Physics Ohio State University IEEE International Frequency Control Symposium June 5 - 7, 2006 Miami, Florida

  2. PEOPLE Doug Petkie - Professor WSU Eric Herbst - Professor OSU Brenda Winnewisser - Adj. Professor OSU Manfred Winnewisser - Adj. Professor OSU Paul Helminger - Professor USA Atsuko Maeda - Research Associate Ivan Medvedev - Research Associate Andrei Meshkov - Graduate Student TJ Ronningen - Graduate Student Laszlo Sarkozy - Graduate Student David Graff - Graduate Student Cory Casto - Graduate Student Kerra Fletcher - Graduate Student Bryan Hern - Undergraduate Student Drew Steigerwald - Undergraduate Student John Hoftiezer - Electrical Engineer

  3. The Lay of the Land What is the basic physics of the SMM/THz? How does this impact technology and frequency control? What physics does it lead us to naturally - What are the important applications? Where is the excitement?

  4. What is the Physics of the SMM/THz? The Energetics: hn ≤ kT The Classical Size Scale ≤ 1 mm Noise Interactions: Gases, Liquids, and Solids Atmospheric Absorption Classical Scattering and Penetration

  5. Technology and Frequency Control

  6. What are the Field Applications? Atmospheric Chemistry Astrophysics Orion. IRAM 30-m telescope line survey

  7. Where is the New Excitement? New Physical Regimes Analytical Applications Medical Active and Passive Imaging

  8. The Physics - The Energetics Atoms and Molecules E (electronic) ~ 50000 cm-1 E (vibrational) ~ 1000 cm-1 E (rotational) ~ 10 cm-1 E (fine structure) ~ 0.01 cm-1 Radiation UV/Vis > 3000 cm-1 IR 300 - 3000 cm-1 FIR 30 - 300 cm-1 THz 3 - 300 cm-1 MW 1 - 10 cm-1 RF < 1 cm-1 Temperature kT (300 K) = 200 cm-1 kT (1.5 K) = 1 cm-1 kT (0.001 K) = 0.0007 cm-1 Fields qE (electron) >> 100000 cm-1 mE (1 D) ~ 1 cm-1 mB (electronic) ~ 1 cm-1 mB (nuclear) ~ 0.001 cm-1 The THz has defined itself broadly and spans kT

  9. [From Tom Crowe UVA/VDI] The ‘Gap’ in the Electromagnetic Spectrum Tubes, a little more - Photomixers, a little less hn/kT Size Cooling

  10. Thermal Noise and Power in the THz Blackbody Brightness [W/cm2-Hz] Blackbody Noise/mode Thermal Noise below cutofffrequencynmax in integration bandwidth B Thermal noise in bandwidth b with integration bandwidth B From E. Brown Number of modes/cm2 ~ 1/l2(cm)

  11. The THz is VERY Quiet even for CW Systems in Harsh Environments Experiment: SiO vapor at ~1700 K All noise from 1.6 K detector system 1 mW/MHz -> 1014 K 1mW/100 Hz -> 1018 K “Noise, detectors, and submillimeter-terahertz system performance in nonambient environments” Frank C. De Lucia J. Opt. Soc. B, 1275 (2004)

  12. What is the Physics of Interactions? Separate into Three Classes by Linewidth Low pressure gases: Q ~ 106 Atmospheric pressure gases: Q ~ 102 Solids and Liquids: Q ~ 1 - 100 (are there useful signatures?) (are these classical or QM?)

  13. Spectra as a Function of Molecular Size Population of levels Jmax 18 Jmax 30 Jmax 55 Jmax 96 Jmax 305

  14. Atmospheric Propagation

  15. Collisional Cooling: An Approach to Gas Phase Studies at Low Temperature Atom Envy - Molecule Envy

  16. Quantum Collisions 300 K 1 K _____________________ hnr ~ kT ~ Vwell Correspondence Principle The predictions of the quantum theory for the behavior of any physical system must correspond to the prediction of classical physics in the limit in which the quantum numbers specifying the state of the system become very large.

  17. Typical Spectra - HCN

  18. Sources and Metrology for the THzSynthesized Frequency Multiplication

  19. Jumping the THz via Frequency Synthesis Spectroscopy via Photomixing “Speed of Light from Direct Frequency and Wavelength Measurements of the Methane-Stabilized Laser,” K. M. Evenson, J. S. Wells, F. R. Petersen, B. L. Danielson, G. W. Lay, R. L. Barger, and J. L. Hall, Phys. Rev. Lett. 29, 1346-1349 (1972). Frequency Reference Spectroscopic Measurement

  20. The Multiplied FASSST Spectrometer VCO Frequency Reference 10.5 GHz Frequency Standard Mixer X8 Multiplier W-band Harmonic 10 MHz Comb Generator Amplifier Mixer W-band Amplifier 75-110 GHz Amplifier Low Pass Filter 10kHz – 1MHz x24 X3 Multiplier W-band Computer DAQ Gas Cell Detector 105 resolution elements/sec

  21. The Fundamental FASSST Spectrometer

  22. Frequency Control and Reference in the THz “A Tunable Cavity-Locked Diode Laser Source for Terahertz Photomixing,” S. Matsuura, P. Chen, G. A. Blake, J. C. Pearson, and H. M. Pickett, IEEE Trans. Microwave Theory and Tech. 48, 380 (2000). “Frequency and phase-lock control of a 3 THz quantum cascade laser.” A. L. Betz, R. T. Boreiko, B. S. Williams, S. Kumar, Q. Hu, J. L. Reno. Opt Lett. 30, 1837-9 (2005).

  23. I(f) f Frequency Synthesis via Femtosecond Demodulation “Spectral Purity and Sources of Noise in Femtosecond-Demodulation Terahertz Sources Drive by Ti:Sapphire Mode-Locked Lasers” J. R. Demers, T. M. Goyette, Kyle B. Ferrio, H. O. Everitt, B. D. Guenther, and F. C. De Lucia IEEE J. Quant. Electron. 37, (2004). “Microwave generation from picosecond demodulation sources” F. C. De Lucia, B. D. Guenther, and T. Anderson Appl. Phys. Lett. 47, 894 (1985)

  24. THz Synthesis from the Optical Comb As with Evenson, THz mixer bandwidth and efficiency highly desirable “Optical frequency synthesis based on mode-locked lasers” S. T. Cundiff, J. Ye, and J. L. Hall Rev. Sci. Instrum. 72, 3749 (2001)

  25. Atmospheric Remote Sensing JPL - Microwave Limb Sounder Ozone Destruction Cycle

  26. Microwave Limb Sounder

  27. Image courtesy of NRAO/AUI and Computer graphics by ESO

  28. “Generation and Distribution of the mm-wave Reference Signal for ALMA” M. Musha, Y. Sato, K. Nakagawa, K. Ueda, A. Ueda, and M. Ishiguro NMIJ-BIPM Workshop, Tsukuba 2004

  29. Orion. IRAM 30-m telescope line survey

  30. ‘New’ Applications - Holy Grails How do we Move Beyond “Whispered Excitement about the THz” Graham Jordan Opening Plenary Presentation SPIE Symposium: Optics/Photonics in Security and Defense Bruges, Belgium, 26 September, 2005 to A Field with many ‘Public’ Applications?

  31. Penetration Resolution Spectroscopic Identification The New York Times - July 11, 2005 High-Tech Antiterror Tools: A Costly, Long-Range Goal Millimeter wave machines . . .use trace amounts of heat released by objects . . .to create images that can identify hidden bombs . . . from about 30 feet away. Terahertz radiation devices can create images of concealed objects as well as identify the elemental components of a hidden item. The terahertz devices may be more promising since they could sound an alarm if someone entering a subway or train station had traces of elements used in bombs on them.

  32. Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method To be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) X Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity X Classical imaging X Point gas detection absolute specificity X Astrophysics (>$2x109) X Atmospheric (>$n x 108) X Remote gas detection modest specificity X specificity in mixtures at 1km X See through walls ~100 GHz >1 THz Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives/other solids close, sm obstruct, mixtures X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials

  33. Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method To be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) X Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity X Classical imaging X Point gas detection absolute specificity X Astrophysics (>$2x109) X Atmospheric (>$n x 108) X Remote gas detection modest specificity X See through walls ~100 GHz >1 THz Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives/other solids close, sm obstruct, mixtures X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials Legacy Applications Cost? Size? Speed? Breadth of Application?

  34. Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method To be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity Classical imaging X Remote gas detection X modest specificity Astrophysics (>$2x109) X Atmospheric (>$n x 108) X See through walls ~100 GHz >1 THz Point gas detection absolute specificity X Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives/other solids close, sm obstruct, mixtures X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials

  35. “it could be used to scan for diseases, such as cancer, the cells of which have a vibrant terahertz signature.” “New-wave body imaging - medical imaging using Terahertz radiation” e20 attenuation in 1 mm Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method to be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) X Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity X Classical imaging X Remote gas detection modest specificity X Point gas detection absolute specificity X Astrophysics (>$2x109) X Atmospheric (>$n x 108) X See through walls ~100 GHz >1 THz Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives/other solids close, sm obstruct, mixtures X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials

  36. “A camera that can see through clothes, skin and even walls without X-rays has been developed in what is being called one of the first great technological breakthroughs of the 21st century” Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method To be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity X Astrophysics (>$2x109) X Atmospheric (>$n x 108) X Classical imaging T&S Remote gas detection modest specificity T&S See through walls ~100 GHz >1 THz Point gas detection absolute specificity X Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials

  37. “Since cancerous tissue tends to have a higher water content than healthy tissue, terahertz radiation could be used to differentiate between the two.” A Good Challenge Impact Order demonstrated demonstrated clear path Phenomena VLP ($spent or $potential) best method To be demo Cancer/deep(spectra) X Cancer/surface(spectra) X T-Ray (deep medical) Mutation(spectra) X Broadband communications ~100 GHz >1 THz Explosives remote with specificity X Astrophysics (>$2x109) X Atmospheric (>$n x 108) X Classical imaging T&S Remote gas detection modest specificity T&S See through walls ~100 GHz >1 THz Point gas detection absolute specificity X Buried land mines > 6” ~100 GHz > 1THz < 6” >1 THz Cancer/surface (water) X Incapacitate and kill X Explosives/other solids close, sm obstruct, mixtures X Explosives close, sort, sm obstruct some materials Pharmaceuticals, bio close, sort, sm obstruct some materials ?

  38. Signatures: Explosives Spectra Clearly spurious results in both gas and solids have been reported

  39. How do you look at THz images?

  40. What is so favorable about the SMM/THz? What are the Opportunities? The SMM/THz combines penetrability with -a reasonable diffraction limit -a spectroscopic capability -low pressure gases have strong, redundant, unique signatures -solids can have low lying vibrational modes, especially at high THz frequencies Rotational transition strengths peak in the SMM/THz The SMM/THz is very quiet: 1 mW/MHz => 1014 K The commercial wireless market will provide us with a cheap technology It should be possible to engineer small (because of the short wavelength), high spectral purity (because we can derive via multiplication from rf reference) and low power (because the background is quiet/the quanta is small) devices and systems

  41. What is so Challenging about the SMM/THz? Efficient generation of significant tunable, spectrally pure power levels Practical broadband frequency control and measurement The need to develop systems without knowledge of the phenomenology Impact of the atmosphere

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