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 OpKcal Sciences, University of Arizona Collaborators Prof. Ewan Wright (co- PI) Prof. Miro Kolesik Graduate Students: David Carlson Tsung- Han Wu Gregory Jacob

2 XUV frequency comb development for precision spectroscopy and ultrafast science Outline Program mokvakon and goals Background: fs combs and intracavity HHG Time- resolved ionizakon dynamics with fsec s Technical achievements in the next generakon XUV comb Numerical simulakons of the fsec

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

4 Femtosecond frequency combs: the bigger picture EUV VUV UV visible IR Time domain and frequency domain applications

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

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 à Absolute phase detection à Attosecond pulse generation Increased flux à count rates Improved amplitude noise à Transient abs, HH interferometry Coherent synchronization à separate pump/probe sources

7 Femtosecond frequency combs: precision spectroscopy EUV VUV visible UV IR Atomic/molecular spectroscopy (e.g. He, He+ H2,H2+ O2, NH3, H2O ) - precision tests of fundamental constants (α, me/mp) and QED Molecular spectroscopy and dynamics, Direct measurement of Rydberg transikons (e.g. improve H2 dissociakon energy measurement) Nuclear Spectroscopy? Isomeric M1 transikon 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) MulK- pulse Ramsey spectroscopy from high harmonics (fs comb source) 51 nm (Helium 1S- 2P) *Kandula DZ et. al., PRL 105, (2010) Direct frequency comb spectroscopy in the XUV (JILA) 82nm (Ar) A. Cingoz et. al., Nature, 482, 68 (2011) 63nm (Ne) Thorium * 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 fs comb spectroscopy in the VUV to XUV Direct frequency comb spectroscopy gas cell FC P f = mf + f r o

10 fs 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 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

12 Dual-comb spectroscopy in the VUV to XUV Dual-comb spectroscopy in the VUV/XUV FC P FC LO Phase lock gas cell Goals: Develop robust dual-comb XUV source. 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 + 4hν P / η τ e.g. 10 μw 11 th harmonic (72 nm) SNR~ 1 s

13 Background: intracavity HHG

14 Intracavity HHG fs enhancement cavi/es (fsec s) Intracavity HHG Recent results High flux generation (77 µw 72nm) Direct comb spectroscopy 63nm (neon) Jones & Ye, Opt. Lep. 29, 2812 (2004) Jones & Ye, Opt. Lep. 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

15 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) fs amplificakon cavity: Paul et. al., Opt. Lep., 33, 2482 (2008) Chia et al, PRA A 87, (2013)

16 Intracavity HHG 50 MHz fs frequency comb (~ 110 nj per pulse) fs amplificakon cavity: Paul et. al., Opt. Lep., 33, 2482 (2008) Chia et al, PRA A 87, (2013) ~ μj per pulse HHG UVG fsec phosphor screen 15 th 13 th 11 th 9 th 7 th ~77 μw s at 72nm More details: J. Lee et. al, OpMcs Express 2011

17 Intracavity HHG Intracavity nonlinear phase shift: Δn plasma ρ e ρ critical Shift of linear resonance by FWHM: Φ max nonlinear π Finesse

18 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. LeJ. 36, 2991 (2011).

19 fsec nonlinear lineshape Experiment Numerical SimulaKon 0.5% input coupler 0.8% linear intracavity loss 600 fs 3 TOD - 5 fs 2 GDD 400 micron interackon region Key results from comparison: à residual stamc plasma background shius peak à dynamic ionizamon reduces peak enhancement

20 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) D.R. Carlson, J. Lee, J. Mongelli, E.M. Wright, and R.J. Jones, Opt. LeJ. 36, 2991 (2011). T.K. Allison et al, PRL 107, (2011).

21 Intracavity plasma diagnostics Measurement of the non- reciprocal phase shim seen by pump/probe pulse train due to ionizakon. probe pump AOM fsec à Enables extremely sensimve Mme resolved measurement of nonlinear phase shiu Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida 7

22 Intracavity plasma diagnostics Pump & probe lineshapes change in presence of gas (100 Torr Xe) Black: pump profile Blue: probe profile No gas 100 Torr backing pressure 200 Torr backing pressure Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida 7

23 Intracavity plasma diagnostics Probe resonant frequency vs. time delay servo locks at peak Probe sees only index change Δn due to plasma Probe resonance is shifted due to residual plasma At long probe delays, contribution from static plasma background Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida 7

24 Intracavity plasma diagnostics Probe resonant frequency vs. time delay servo locks at peak Probe sees only index change Δn due to plasma Probe resonance is shifted due to residual plasma At long probe delays, contribution from static plasma background Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida 7

25 Plasma Anisotropy Experiment: analyze 2 polarization states of probe beam versus delay probe AOM pump fsec

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

27 Preliminary experimental results Nonlinear Optical Anisotropy

28 Recent numerical simulations Preliminary results on the role of transverse spatial effects Full picture of intracavity plasma dynamics requires spatial and temporal modeling. Background ionization levels and spatial effects can be dramatically impacted by fsec parameters (e.g. cavity length, finesse, laser wavelength, etc ) Example: Plane-wave model versus spatial model Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

29 Recent numerical simulations Plane-wave model: predicts damped oscillations at high intensities. Simulations run for 3000 iterations with input intensity of Xenon gas, 800nm wavelength, 4m cavity length. Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

30 Recent numerical simulations Spatial model: predicts undamped oscillations at high intensities and corresponding oscillation of beam profile Simulations run for 3000 iterations with input intensity of Xenon gas, 800nm wavelength, 4m cavity length. Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

31 Recent numerical simulations Spatial model: predicts undamped oscillations at high intensities and corresponding oscillation of beam profile Simulations run for 3000 iterations with input intensity of Xenon gas, 800nm wavelength, 4m cavity length. Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

32 Development of next generation XUV comb. Power scaling the fs frequency comb: Ti:sapphire à Yb fiber system Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

33 Development of next generation XUV comb. Goals: Dual-comb Yb fiber-based system (design goal: >50W, 75MHz system) Vibration isolated vacuum chamber design CW reference lasers for precision locking to fsec resonance These technical goals are now all achieved! Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

34 High Power Fiber Frequency Comb 980nm Pump diode Ytterbium gain fiber WDM Pulse duration limited by residual third order dispersion. Power 10W with ~200fs pulse PZT/ mirror QWP Grating pairs QWP Isolator PBS Isolator Collimator QWP Collimator Collimator HI 1060 Nufern Yb-doped fiber 5m Amplitude(arb.) Time(fs) 980nm Pump diode WDM Coupler(50/50) Collimator Isolator Collimator Polarization controller HWP Isolator Power amplifier Compressor Yb-Er doped DC-PM fiber(7m) High power combiner Amplified output High power Pump diode (920nm) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

35 Nonlinear Amplification Ytterbium gain fiber 980nm Pump diode WDM HI 1060 Nonlinear TOD compensation e.g. L.Shah, et al, Opt.Express 13,4717 (2005). PZT/ mirror QWP Grating pairs QWP Isolator PBS Isolator Collimator QWP Collimator Collimator Pre-chirp pulse to optimize compressibility. H.-W. Chen et al, Optics Express 20, (2012) Pre-chirp grating pair Coupler(50/50) Collimator WDM Nufern Yb-doped fiber 5m Polarization controller 980nm Pump diode Laser output Polarization controller Isolator HWP Collimator Compressor Isolator Yb-Er doped DC-PM fiber(7m) High power combiner High power Pump diode (920nm) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

36 Nonlinear Amplification Ytterbium gain fiber 980nm Pump diode WDM 1 Autocorrelation trace with 5A Autocorrelation trace with 24A Preamp Autocorrelation trace pump with third order dispersion pump and pulse width 65fs 150mW 6W 25 W Collimator HI 1060 Amplitude (a.u.) Amplitude (a.u.) Amplitude (a.u.) QWP QWP Isolator QWP Collimator PZT/ mirror Grating pairs PBS Isolator Collimator Time(fs) Time(fs) Time(fs) Pre-chirp grating pair Coupler(50/50) Collimator WDM Nufern Yb-doped fiber 5m Polarization controller 980nm Pump diode Laser output Polarization controller Isolator HWP Collimator Compressor Isolator Yb-Er doped DC-PM fiber(7m) High power combiner High power Pump diode (920nm) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

37 Nonlinear Amplification Ytterbium gain fiber 980nm Pump diode PZT/ mirror QWP Grating pairs QWP Isolator PBS Isolator Collimator QWP Collimator Collimator WDM HI 1060 Amplifier output power(w) Intensity(arb.) W W, 55 fs Pump power(w) Time(fs) autocorrelation trace with 24A pump and 55fs pulse width Pre-chirp grating pair Coupler(50/50) Collimator WDM Nufern Yb-doped fiber 5m Polarization controller 980nm Pump diode Laser output Polarization controller Isolator HWP Collimator Compressor Isolator Yb-Er doped DC-PM fiber(7m) High power combiner High power Pump diode (920nm) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

38 High power Yb fiber frequency comb Current results with final stage amp: >50W, ~70fs pulse duration 2 x 104 PCF Spectrum Amplitude (a.u.) A autocorrelation trace 79fs Time Amplitude (a.u.) P o (W) DCF seed 3W 6.35W 9.9W 13.5W 17.2W 21W 24.9W 28.7W 32.7W Wavelength(nm) 69% Pump(W) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

39 Nonlinear Amplification-phase noise stabilization NPRO Nd:YAG laser (1064nm) Coupler(50/50) Coupler(50/50) Collimator grating Electrical Spectrum analyzer fiber comb Coupler(50/50) Power Amp. Collimator Collimator Coupler(50/50) grating Stabilized beatnote before vs after power amp 30 Beatnote after amp V.S different pump power Amplitude (dbm.) preamp without pump 1A pump 4A pump 12A pump Sapn:500KHz RBW:30Hz Amplified beatnote s/n also sensitive to pre-chirp High quality stabilized beatnotes can be maintained with nonlinear amplification scheme Frequency(MHz) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

40 Dual-comb Stabilization Scheme Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

41 Dual-comb Stabilization Scheme Dual-comb spectra in the IR Next step: VUV/XUV Amplitude(abr.) Individual comb beatnotes 1.6kHz separation Frequency(MHz) Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

42 Dual-comb Stabilization Scheme Current and future work Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

43 Conclusion Progress towards next generation XUV combs: -Yb-based >50 W dual frequency comb system achieved in IR - Novel cavity stabilization system implemented (more robust against plasma effects) Experimental and Numerical studies of intracavity time resolved ionization dynamics -Role of transverse spatial-effects (numerical) - new pump-probe diagnostic ability Dual comb spectroscopy in the VUV/XUV. - Observe individual comb modes in VUV/XUV for first time - Precision study comb coherence - Enable robust frequency comb spectroscopy (H 2 ) Long term outlook: -applications in both precision spectroscopy and attosecond science Precision Frequency Comb Spectroscopy FIO, October 8, 2013, Orlando, Florida

44 Nonlinear fsec: Numerical Simulations Numerical investigation of nonlinear pulse evolution in the presence of linear dispersion and instantaneous Kerr response. n 2 E n+1 (t) =F 1 { p R eff R input e i( (!)) F{ Kerr Effect Term z } { E n (t)e (i E 2 ) }} + i p 1 R in E in (t) (

45 Nonlinear fsec: Numerical Simulations Numerical investigation of nonlinear pulse evolution in the presence of linear dispersion and instantaneous Kerr response. n 2 E n+1 (t) =F 1 { p R eff R input e i( (!)) F{ Kerr Effect Term z } { E n (t)e (i E 2 ) }} + i p 1 R in E in (t) ( Nonlinear pulse compression and soliton-like steady-state solutions: Pulse Profile, 2nd Order 10fs 2, 3rd Order = 0fs 3, φ Scan Right to Left with Memory, Effective losses = Input Coupler = 1% Pulse Length In Femto Seconds Ø Peak intensity enhancements of 2-3 times compared to the linear case are possible Non Linear Coefficient α x 10 4