(One) latest development(s)

Transcription

1 1 (One) latest development(s) in photonic crystal fibres Philip Russell MAX PLANCK INSTITUTE for the science of light & Department of Physics Friedrich-Alexander-Universität Erlangen-Nuremberg FAU Alfried Krupp von Bohlen und Halbach - Stiftung

2 Topics 2 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

3 Hollow core PCF (concept 1991, realised 1998) Cregan et al., Science 285, 1537 (1999) 4 hollow channels silica glass Light trapped by a full 2D photonic band gap What s it useful for? ~100 µm

4 A lens focuses over a short distance 5 spot size 2a depth of focus Lord Rayleigh

5 HC-PCF keeps light focused long-range 6 PCF cladding ~infinite depth of focus PCF cladding 1.55 μm intensity path-length enhancement factor: 1 db/km 10 μm

6 Ideal for nonlinear optics in gases 7 Light trapped in a single mode in empty space (zero diffraction, reproducible intensity profiles) Gases can be pumped into core Self-focusing effects practically eliminated Low transmission losses long path-lengths Chromatic dispersion controllable & uniform Small core area: high intensity for a given power

7 Topics 8 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

8 Introducing kagome-lattice PCF 9 core radius ~14 μm spectral broadening in noble gas-filled capillaries (e.g., Murnane & Kapteyn, JILA Krausz MPQ Munich Nisoli & di Silvestri, Milan) capillary vs kagome-pcf capillary loss at 800 nm kagome loss ~1 db/m FAU radius (μm)

9 Modal dispersion in Ar-filled kagome PCF azimuthal order radial order 10 Nold et al., Opt Lett 35, 2922 (2010) Ar pressure NB: Raman is scattering absent in atomic gases

10 note low values of dispersion Pumping up the dispersion argon 11 Joly et al, PRL 106, (2011) kagome PCF 29.6 μm diameter FAU

11 Topics 12 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

12 Effect of increasing pulse energy nm, 30 fs pump pulses Ar-filled PCF 20 cm

13 spectral power Experimental observation 14 Joly et al, PRL 106, (2011) UV generation point moves backwards UV is in the HE 11 mode up to 8% conversion efficiency pressure & energy tunable FAU wavelength (nm)

14 optimised Tunability of UV wavelength 15 KaFai Mak & John Travers (unpublished) vacuum UV UV C - germicidal UV B UV A UV wavelength (nm) FAU close to 10% conversion near-ir to deep-uv

15 Topics 16 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

16 frequency Resonant radiation from solitons 17 b = = bb + + b W+ b W+g b WP 2 / 2+ b W 3 / 6 sol W = 0 resonant radiation b = b 0 FAU wavevector

17 β β sol (m 1 ) Higher order dispersion phase-matching β linear = β soliton normal anomalous full dispersion 26 μm core 10 bar Ar 1.3 μj, 30 fs 800 nm no higher order dispersion FAU wavelength (nm)

18 β β sol (m 1 ) Tunable phase-matching from nm 19 1 bar bar normal anomalous 100 FAU wavelength (nm)

19 distance (cm) 25 Solutions of the GNLSE zero GVD Hölzer et al. CLEO 2010 Joly et al. PRL FAU N = 4 soliton Ar pressure: 6 bar core diameter 26 μm pump energy: 1 μj pulse duration: 50 fs frequency (PHz)

20 Ideal 7-th order soliton 21 N = 7 ideal soliton (no higher order dispersion) z / L sol t / τ μm core diameter 10 bar Ar 1.3 μj, 30 fs, 800 nm FAU

21 7-th order soliton fission 22 N = 7 full linear dispersion & freq. dependence of γ L fission = 2 Np L sol z / L sol t / τ μm core diameter 10 bar Ar 1.3 μj, 30 fs, 800 nm FAU

22 Topics 23 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

23 Ionization at temporal focus? 24 Free electron densities of ~10 17 cm 3 are achieved at peak intensities of ~10 14 W.cm 2 over length scales of several cm E. Yablonovitch: "Self-phase modulation of light in a laser-breakdown plasma," PRL 32, (1974)

24 intensity (TW/cm 2 ) Index change at maximum compression numerical modelling Δn > 0 Δn < Δn ( 10 5 ) FAU time (fs)

25 input energy (μj) 26 μm core diam. 34 cm fibre 1.7 bar Ar 65 fs, 800 nm 8 7 Experimental 26 Hoelzer et al, PRL107, (2011) wavelength (nm)

26 input energy (μj) Numerical modelling including ionization 26 μm core diam. 34 cm fibre 1.7 bar Ar 65 fs, 800 nm Hoelzer et al, PRL107, (2011) modelling using uni-directional full-field wave equation quasi-static tunnel-ionization model wavelength (nm)

27 input energy (μj) 26 μm core diam. 34 cm fibre 1.7 bar Ar 65 fs, 800 nm Numerical modelling without ionization Hoelzer et al, PRL107, (2011) wavelength (nm)

28 Topics 29 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary

29 Summary 30 Features ultrafast single-mode lasergas interactions with adjustable dispersion very simple set-up (short length of Ar-filled PCF) highly stable and does not suffer optical damage spatially coherent (can be focused to small spot) self-compression to a few cycles long nonlinear fibre optics in the ionization regime blue-shifting solitons ejected via ionization Applications UV resonant Raman spectroscopy excitation of self-fluorescence of biological materials chemistry on fs timescales high resolution laser directwrite & lithograpy seeding of free-electron lasers detailed studies of carrierenvelope effects high-harmonic generation from self-compressed oscillator pulses at high repetition rates

30 Index 31 Photonic crystal fibres Pressure-controlled dispersion Deep-UV generation in Ar Dispersive waves in the UV Ionization effects Summary FAU Joly: PRL 106, (2011) Hoelzer: PRL 107, (2011) Saleh: PRL 107, (2011) Chang: Opt Exp 19, (2011) Travers: JOSA B 28, A11-A26 (2011)