XUV frequency comb development for precision spectroscopy and ultrafast science

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1 XUV frequency comb development for precision spectroscopy and ultrafast science R. Jason Jones (PI) College of Optical Sciences, University of Arizona Collaborators Graduate Students: Prof. Ewan Wright (co PI) Prof. Miro Kolesik John Mongelli David Carlson Tsung Han Wu AFOSR Program Review, Dec. 18, 2012

2 XUV frequency comb development for precision spectroscopy and ultrafast science Outline Program motivation and goals Intra cavity high harmonic generation Time resolved ionization dynamics in (with) fsec s Recent technical improvements Numerical simulations of the fsec

3 Femtosecond frequency combs EUV VUV UV visible IR f r f o Fourier Transform optical m f r f o Frequency Time

4 Femtosecond frequency combs: time domain implications EUV VUV UV visible IR fs

5 Femtosecond frequency combs: time domain implications EUV VUV UV visible IR Attosecond Science fs femtosecond pulse synchronization controlled, high electric field strengths Sub-cycle control of ionization dynamics Absolute phase detection Attosecond pulse generation

6 Femtosecond frequency combs: time domain implications EUV VUV UV visible IR Attosecond Science at MHz rep rates fs femtosecond pulse synchronization controlled, high electric field strengths Sub-cycle control of ionization dynamics Absolute phase detection Attosecond pulse generation Increased flux count rates Improved amplitude noise Transient abs, HH interferometry Coherent synchronization separate pump/probe sources

of Rydberg transitions (e.g. improve H 2 dissociation energy measurement) - Nuclear Spectroscopy?

7 Femtosecond frequency combs: precision spectroscopy EUV VUV UV visible IR Atomic/molecular spectroscopy (e.g. He, He + H 2,H 2+ O 2, NH 3, H 2 O ) precision tests of fundamental constants (α, m e /m p )and QED Molecular spectroscopy and dynamics, Direct measurement of Rydberg transitions (e.g. improve H 2 dissociation energy measurement) - Nuclear Spectroscopy? Isomeric M1 transition in Th 229 (~160 nm) A solid state nuclear frequency standard? Peik et al, Europhys Lett. 61, 181 (2003) Beck et al, PRL 98, (2007) Rellergert et al, PRL 104, (2010) Campbell, et al, PRL 106, (2011) Thorium Hudson group, UCLA

8 Femtosecond frequency combs: precision spectroscopy EUV VUV UV visible IR Examples of recent EUV/VUV spectroscopy results: Synchrotron (SOLEIL) Fourier Transform Spectrometer 40nm 250 nm *de Oliveria, N. et al. Nature Photonics 5, (2011) 2 pulse Ramsey spectroscopy from high harmonics 87 nm (Ar) Eramo, et al, PRL 106, (2011) Multi pulse Ramsey spectroscopy from high harmonics (fs comb source) 51 nm (Helium 1S 2P) *Kandula DZ et. al., PRL 105, (2010) Thorium Direct frequency comb spectroscopy in the XUV (JILA) 82nm (Ar) A. Cingoz et. al., Nature, 482, 68 (2011) 63nm (Ne) * e.g. studies of H 2, predissociated Rydberg states, super-excited states for planetary science and cosmology ** Improved 4 He ionization energy Hudson group, UCLA

9 Dual-comb spectroscopy in the VUV to XUV Direct frequency comb spectroscopy gas cell FC P f mf f r o

10 Dual-comb spectroscopy in the VUV to XUV Direct frequency comb spectroscopy gas cell FC P f mf f r o

11 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy S. Schiller, Opt. Lett. 27, 766 (2002). gas cell FC P Phase lock FC LO f mf f r o

12 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy S. Schiller, Opt. Lett. 27, 766 (2002). gas cell FC P Phase lock FC LO j f b j 3 f b f mfr fo f mf f LO LO LO r o

13 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy S. Schiller, Opt. Lett. 27, 766 (2002). gas cell FC P Phase lock FC LO j f b j 3 f b Example: HCN gas Coddington et. al., PRL 100, (2010) f mfr fo f mf f LO LO LO r o

14 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy in the VUV/XUV gas cell FC P Phase lock FC LO Enough power to detect beatnotes in VUV? SNR P / N NEP 2 4h P / e.g. 10 μw 11 th harmonic (72 nm) SNR~ 1 s

15 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy in the VUV/XUV FC P FC LO Phase lock gas cell Goals: Detection of individual comb components in the VUV & XUV Enable broader range of spectroscopic and time-resolved studies in the VUV & XUV Enough power to detect beatnotes in VUV? SNR P / N NEP 2 4h P / e.g. 10 μw 11 th harmonic (72 nm) SNR~ 1 s

16 High harmonic generation Robust approach: harmonics generated into soft x ray regime W/cm 2 EUV Gas jet thin foil P.B. Corkum, PRL 49, 2117 (1994) M. Lewenstein et. al., PRA 49, 2117 (1994)

17 High harmonic generation fs enhancement cavities (fsec s) Jones & Ye, Opt. Lett. 29, 2812 (2004) Jones & Ye, Opt. Lett. 27, 1848 (2002) W/cm 2

18 High harmonic generation fs enhancement cavities (fsec s) Intracavity HHG Jones & Ye, Opt. Lett. 29, 2812 (2004) Jones & Ye, Opt. Lett. 27, 1848 (2002) (JILA) R. J. Jones et. al., PRL 94, (2005) (MPQ) C. Gohle et. al., Nature 436, 234 (2005) W/cm 2

19 High harmonic generation fs enhancement cavities (fsec s) Intracavity HHG Recent results High flux generation (77 μw 72nm) Direct comb spectroscopy 63nm (neon) Jones & Ye, Opt. Lett. 29, 2812 (2004) Jones & Ye, Opt. Lett. 27, 1848 (2002) (JILA) R. J. Jones et. al., PRL 94, (2005) (MPQ) C. Gohle et. al., Nature 436, 234 (2005) (Arizona) J. Lee et. al., Opt. Express 19, (2011) (JILA) A. Cingoz et. al., Nature, 482, 68 (2011) W/cm 2

20 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) Paul et. al., Opt. Lett., 33, 2482 (2008)

21 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) ~ μjper pulse

22 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) ~ μjper pulse HHG

23 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) ~ μjper pulse HHG UVG fsec phosphor screen 15 th 13 th 11 th 9 th 7 th ~77 μw s More details: J. Lee et. al, Optics Express 2011

Incident power from laser Phase matching ionization UVG fsec 15 th

24 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) HHG ~ μjper pulse phosphor screen fsec design considerations Incident power from laser Phase matching ionization UVG fsec 15 th 13 th 11 th 9 th 7 th ~77 μw s More details: J. Lee et. al, Optics Express 2011

25 Intracavity HHG Macroscopic phase matching for efficient frequency conversion k qk f k q

26 Intracavity HHG Macroscopic phase matching for efficient frequency conversion k P 1 2q n PN atm r e q 2 1 q 2( q 1) b neutral atom dispersion (+) Free electron dispersion ( ) Gouy phase mismatch ( ) P: pressure η: ionization fraction b: confocal parameter q: harmonic order

27 Intracavity HHG Macroscopic phase matching for efficient frequency conversion k P 1 2q n PN atm r e q 2 1 q 2( q 1) b neutral atom dispersion (+) Free electron dispersion ( ) Gouy phase mismatch ( ) P: pressure η: ionization fraction b: confocal parameter q: harmonic order

28 Intracavity HHG Macroscopic phase matching for efficient frequency conversion k P 1 2q n PN atm r e q 2 1 q 2( q 1) b neutral atom dispersion (+) Free electron dispersion ( ) Gouy phase mismatch ( ) P: pressure η: ionization fraction b: confocal parameter q: harmonic order

29 Intracavity HHG Intracavity nonlinear phase shift: n plasma e critical Shift of linear resonance by FWHM: max nonlinear Finesse

30 100 micron gas jet HHG power vs. pressure EUV Power (W) Pressure (Torr) Intracavity IR Power (W) Decreased intracavity power with increasing backing pressure

31 Numerical simulation of intracavity pulse evolution Split-step solver for nonlinear Schrodinger equation Keldysh theory provides ionization rates pressure = 20 Torr Assumes Δ=0 then shifts to Δ=Δ p nonlinear phase limits intracavity enhancement D.R. Carlson, J. Lee, J. Mongelli, E.M. Wright, and R.J. Jones, Opt. Lett. 36, 2991 (2011).

32 fsec resonant lineshape 50 MHz fs frequency comb fsec D.R. Carlson, J. Lee, J. Mongelli, E.M. Wright, and R.J. Jones, Opt. Lett. 36, 2991 (2011).

33 fsec resonant lineshape 50 MHz fs frequency comb photodiode fsec D.R. Carlson, J. Lee, J. Mongelli, E.M. Wright, and R.J. Jones, Opt. Lett. 36, 2991 (2011).

34 fsec resonant lineshape 50 MHz fs frequency comb photodiode fsec D.R. Carlson, J. Lee, J. Mongelli, E.M. Wright, and R.J. Jones, Opt. Lett. 36, 2991 (2011).

35 fsec nonlinear lineshape Experiment Numerical Simulation 0.5% input coupler 0.8% linear intracavity loss 600 fs 3 TOD 5 fs 2 GDD 400 micron interaction region

36 fsec nonlinear lineshape Experiment Numerical Simulation p 0.5% input coupler 0.8% linear intracavity loss 600 fs 3 TOD 5 fs 2 GDD 400 micron interaction region peak nonlinear p 2 f rep

37 fsec nonlinear lineshape Experiment Numerical Simulation 0.5% input coupler 0.8% linear intracavity loss 600 fs 3 TOD 5 fs 2 GDD 400 micron interaction region Key results from comparison: residual static plasma background shifts peak dynamic ionization reduces peak enhancement

38 Cavity bistability Servo locking position See T.K. Allison et al, PRL 107, (2011)

39 Summary: limitations from ionization 1. Limits peak intracavity intensity 2. Bi-stability frustrates active stabilization of fsec 3. Phase-matching limitations (static background plasma levels)

40 Direct plasma decay measurement Measurement of the non reciprocal resonance between pump/probe pulse train due to ionization. probe pump fsec measure difference in pump/probe resonance versus delay Enables extremely sensitive time resolved measurement of nonlinear phase shift

43 Dynamic shift of probe resonance.

47 Gas jet on

49 Nonlinear Optical Anisotropy Plasma birefringence -time scales? -physical mechanisms? Numerical simulations: J. Andreasen, E. Wright, M. Kolesik Miro slides here Following pump ionization, anisotropic electron momentum distribution can persist for τ~1/ω p arxiv:

50 Nonlinear Optical Anisotropy Miro slides here

51 Nonlinear Optical Anisotropy Experiment: analyze 2 polarization states of probe beam versus delay probe AOM pump fsec

52 Nonlinear Optical Anisotropy Measured linear splitting of S and P states of fsec

53 Technical improvements for next generation XUV system Dual-comb Yb fiber based system (design goal: 50W, 75MHz system) Vibration isolated vacuum chamber design CW reference lasers for precision locking to linear fsec resonance

54 Dual-comb stabilization schematic

55 Dual-comb stabilization schematic

56 Nonlinear fsec: Numerical Simulations Numerical investigation of nonlinear pulse evolution in the presence of linear dispersion and instantaneous Kerr response. n 2

Nonlinear fsec: Numerical Simulations Numerical investigation of nonlinear pulse evolution in the presence of linear dispersion and instantaneous Kerr

57 Nonlinear fsec: Numerical Simulations Numerical investigation of nonlinear pulse evolution in the presence of linear dispersion and instantaneous Kerr response. n 2 Nonlinear pulse compression and soliton-like steady-state solutions: Peak intensity enhancements of 2-3 times compared to the linear case are possible.

58 Summary Experimental and numerical efforts to design next generation XUV frequency comb system Development of dual-comb spectroscopy in the VUV and XUV. Novel time-resolved measurement capability of intracavity optical nonlinearities w/ the fsec

1. Introduction. 2. New approaches

1. Introduction. 2. New approaches New Approaches To An Indium Ion Optical Frequency Standard Kazuhiro HAYASAKA National Institute of Information and Communications Technology(NICT) e-mail:hayasaka@nict.go.jp ECTI200 . Introduction Outline