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Frequency Comb Vernier spectroscopy

Frequency Comb Vernier spectroscopy. C. Gohle , A . Renault , D.Z. Kandula, A . L . Wolf , W. Ubachs, K . S . E . Eikema Laser Centre, Vrije Universiteit Amsterdam, DeBoelelaan 1081, 1081 HV Amsterdam A. Ozawa, B. Bernhardt, B. Stein, A. Schliesser, Th. Udem, T.W. Hänsch

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Frequency Comb Vernier spectroscopy

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  1. Frequency Comb Vernier spectroscopy C. Gohle, A. Renault, D.Z. Kandula, A.L. Wolf, W. Ubachs, K.S.E. Eikema Laser Centre, Vrije Universiteit Amsterdam, DeBoelelaan 1081, 1081 HV Amsterdam A. Ozawa, B. Bernhardt, B. Stein, A. Schliesser, Th. Udem, T.W. Hänsch Max-Planck-Institut für Quantenoptik, Hans-Kopfermannstraße 1, 85748 Garching

  2. Outline • Introduction: • Frequency combs and Optical resonators • XUV comb generation • Optical vernier spectroscopy • Outlook

  3. Frequency combs and optical resonators

  4. +¥ S Am e-imwrt-iwct = m=-¥ Frequency Combs E(t)=A(t)eiwct 1n = n1r + 1CE , 1CE <1r, 7=2 1CE/1r

  5. Example: Hydrogen f(1S-2S) = 2 466 061 102 474 851(34) Hz

  6. Fabry perot resonators light source

  7. … provide stable references • Narrow Markers in Frequency space • If high finesse • High stability • ~10-15 @ 1 s • Hz linewidth @ 1 PHz • ~10-16m length stability

  8. … enhance nonlinear conversion • Pc=F/ • Output power grows with finesse2 or higher! • Example: • SHG 560nm->280nm • 900mW driving power • 20% conversion: 900mW->200mW

  9. … enhance sensitivity • Cavity absorbtion spectroscopy • Increased interaction length • Intrinsically narrow band • Cavity ring down • Intrinsically robust • Can be broad band

  10. Response function Can be matched to FC

  11. Cavity enhanced HHG • Obvious requirements • No dispersion • Electric field in the pulse envelope has to look the same for both pulses -> equidistant modespacing • frep = fFSR • Timedelay between pulses = cavity roundtrip time • fCEO matches • HHG inside the resonator

  12. XUV Output Circ. Power 40W, intensity in the focus 5 x 1013 W/cm2 Output: 10nW C. Gohle et al., Nature, 436, 234 (2005) R. J. Jones et al., PRL, 94, 193201 (2005)

  13. Coherence (of the 3rd harm.) C. Gohle et al., Nature, 436, 234 (2005) R. J. Jones et al., PRL, 94, 193201 (2005)

  14. … coherence! (probably)

  15. Possible Applications • Direct frequency comb spectroscopy in the XUV • It is cw, so no transients • Compact coherent XUV source for interferometry • High repetition rate high intensity source for coincidence measurements • BUT: power still low! • And many technical problems • Use an amplifier!

  16. Frequency Comb Vernier Spectroscopy

  17. 3,000,000 narrow band modes with 0.3 mW power Simultaneously tuneable and referencable 1 Direct comb spectroscopy, the good I(1) 300 THz band width and 100 MHz mode spacing. 1 300 THz Marian et al, PRL, 95, 023001 (2005)’ V.Gerginov et al. Optics Letters, 30, 1734 (2005)

  18. … and the bad • Large background • for absorbtion measurements • Causing stark shifts • Aliasing • Spectra difficult to interpret • Small power per mode • Small signal • Nonlinear (dopplerfree) spectroscopy difficult

  19. ... the remedy

  20. Data • Single scan (10ms) • Blue box: unique data • Red boxes: identified features • Gaussian PSF much larger than airy ! Brightness~Integral of airy

  21. arXiv:0706.1582v1 [physics.optics] Red:HITRAN data O2 magnetic dipole intercombinationline (760nm)

  22. Results* • Absorbtion: • Noisefloor • < 10-5/cm (100 Hz)1/2= • < 10-6/cm Hz1/2 (shotnoise: <10-8) • > 4 THz bandwidth • 1 GHz sampling (>4000 res. • Datapoints in 10 ms) • Quantitative agreement in • Amplitude and Frequency • to HITRAN** database • Phase: • - agrees with expectations (disp. features) • not optimized for good phase sensitivity • Still <0.1 mrad/Hz1/2 O2 A-Band * arXiv:0706.1582v1 [physics.optics] ** Rothman, L. S. et al., J. Quant. Spect. Rad. Trans., 96, 139-204 (2005)

  23. beautyful … reduced … may be possible … and the bad • Large background • for absorbtion measurements • Causing stark shifts • Aliasing • Spectra difficult to interpret • Small power per mode • Small signal • Nonlinear (dopplerfree) spectroscopy difficult

  24. Thanks (Hydrogen) Nikolai Kolachevski Janis Alnis Arthur Matveev Elisabeth Peters Maximilian Herrmann (Ion Traps) Sebastian Knünz Valentin Batteiga Akira Ozawa (fs-Cavities) Birgitta Bernhardt Jens Rauschenberger Theodor W. Hänsch Albert Schliesser Thomas Udem Funding:

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