New Age Fibre Crystals

Transcription

1 1 New Age Fibre Crystals Philip Russell Max-Planck Research Group University of Erlangen Alfried Krupp von Bohlen und Halbach - Stiftung

2 Index 2 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

3 3 photonic crystal fibres

4 The 1991 idea 4 to trap light inside an hollow tube using the photonic band gap effect diameter of a human hair

5 5 Notes from 1991 CLEO/QELS, 13th May 1991

6 Making it: stacking 6 1 mm capillary (pure silica) birefringent core low index defect rare-earth doped high index defect

7 ~1 mm and drawing 7 ~1800 C overall collapse ratios as large as ~10,000 solid silica outer cladding incorporated continuous holes as small as 25 nm demonstrated draw photonic crystal fibre ~0.03 mm

8 The World s Longest Holes Guinness Book of Records Interplanetary Channel Tunnel Jupiter An Interplanetary Channel Tunnel would have the same aspect ratio as a hole 25 nm in diameter and 1 km long Earth

9 BlazePhotonics Bath Bath BlazePhotonics 9 Bath 10 μm photonic crystal fibres Erlangen Erlangen Erlangen

10 New Age Crystals 10 The Economist 21 Nov 1998

11 Iridescence in Nature 11 sea-mouse cross-section of hair ~1 μm

12 Topics 12 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

13 Wavevectors 13 β kn 1 k = 2 / π λ t1 t1 axial wavevector β is conserved across every region of structure transverse effective wavelength in material 1

14 PCF playing field 14 Birks et al, Electron.Lett. 31 ( ) 1995 normalised frequency ωλ/c vacuum full photonic band gaps PCF cladding silica normalised wavevector along fibre βλ propagating evanescent propagating evanescent propagating evanescent 45% air filling fraction silica:air index contrast 1.46:1 β

15 Single-mode fibre strait-jacket 15 normalised frequency ωλ/c Anthony Hopkins (Hannibal Lecter) vacuum silica normalised wavevector along fibre βλ propagating evanescent Ge-doped silica guided modes silica Ge-silica

16 PCF playing field 16 Birks et al, Electron.Lett. 31 ( ) normalised frequency ωλ/c vacuum full photonic band gaps PCF cladding silica normalised wavevector along fibre βλ propagating evanescent 45% air filling fraction silica:air index contrast 1.46:1 β

17 Topics 17 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

18 Solid core PCF (1995) 18 ~100 μm

19 Total internal reflection gives 19 unconditional evanescence glass tunnelling air glass anti-resonant

20 Endlessly single-mode PCF 20 Knight et al, OFC 1996 PD paper the first photonic crystal fibre... far-field pattern when carrying green & red light

21 Higher order modes are filtered away 21 evanescence anti-resonant unit cell resonant unit cell fundamental mode cannot squeeze between air-holes higher-order modes can escape into cladding

22 Building bars without TIR 22 material A material B material A resonant (light passes through) ka z t 01 transverse wavevector radius first zero of Bessel J 0

23 Unit cells & evanescence 23 A Bloch wave transfer matrix [M]: λλ =1 real eigenvalues: evanescence complex eigenvalues: propagation B [M] = transfer matrix unit cell boundary

24 Building a prison for light 24 bars of the prison cell the prison cell

25 Keeping light behind bars 25 anti-resonant windows anti-resonant bars

26 The hollow one 26 traps light by creating a complete 2D photonic band gap in the cladding ~100 μm

27 Topics 27 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

28 State-of-the-art HC PCF μm Mangan et al, OFC 2004, paper PDP μm 20.5 μm 1.7 db/km at 1550 nm

29 Hollow core 1 db/km 29 cladding core 2.8 million bounces per km (20 μm core, 1550 nm) 0.35 μdb/bounce (reflectivity )

30 Typical attenuation spectrum 30 Roberts et al, Opt. Exp. 13 ( ) Attenuation [db/km] ~1.7 db/km Wavelength [nm]

31 Loss induced by mode crossings nm 1530 nm 1400 nm Roberts et al, Opt. Exp. 13 ( ) 2005 effective mode index light line surface modes fundamental mode light-in-glass fraction normalised propagation constant [ βλ ]

32 Mode profiles at anti-crossing 32 Humbert et al, Opt. Exp. 12, 1477 (2004) fraction of light in glass changes dramatically with wavelength of the light

33 Eliminate surface states 33 Bath/Southampton, OpEx Jan 2008 Erlangen result db/m 0.02 db/m wavelength

34 Topics 34 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

35 Depth of focus & spot size 35 intensity 1/ a 2 interaction length a 2 / λ spot size Rayleigh length Lord Rayleigh

36 Depth of focus & spot size 36 intensity 1/ a 2 interaction length a 2 / λ spot size Rayleigh length Lord Rayleigh

37 Hollow capillaries leak 37 intensity 1/ a 3 2 absorption length a / λ 2 hollow capillary diameter strong leakage reducing diameter from 200 μm to 10 μm increases leakage 8000

38 Hollow core PCF: ~infinite Rayleigh length 38 intensity 1/ a absorption length 2 1/ α holey cladding infinite depth of focus holey cladding for gas-laser interactions the best low loss PCF is seven orders of magnitude better than a focused beam

39 intensity L eff vs beam radius 39 intensity effective length 10 μm bore >1,000, >10, Benabid et al, Science 298 (399) nm 1.7 db/km PCF area dominated 300 db/km PCF area dominated loss dominated Rayleigh bore radius (μm)

40 Hollow core PCF for rotational SRS THz Benabid et al, PRL 93 (123903) 2004 rotational very high attenuation for vibrational Stokes Stokes anti-stokes pump 125 THz

41 SRS conversion m Benabid et al, PRL 93 (123903) 2004 transmission coupled energy (nj) 2.9 m single-pass threshold at energy 1,000,000 times lower (35 m) near-perfect quantum efficiency achieved (2.9 m) multi-pass: Meng et al., Opt. Lett. 27 (1226) coupled energy (nj) hydrogen pressure 7 bar loss at second Stokes is 0.6 db/m

42 Topics 42 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

43 Dispersion Dispersion of 800 of pure nm core silicapcf 43 Knight et al, Phot Tech Lett, 12 ( ) nm GVD (ps/nm.km) PCF (measured) bulk silica anomalous normal zero at ~1300 nm zero dispersion can be designed wavelength (μm) to lie anywhere in this range zero chromatic dispersion (560 nm)

44 44 Recipe for Very Bright White Light: take solid-core PCF with zero chromatic dispersion wavelength close to a pulsed laser wavelength [zero chromatic dispersion keeps the energy packet together and enhances nonlinear effects]

45 Ti:sapphire laser pump (200 fs) 45 Ranka et al, Opt. Lett. 25 (25-27) 2000 visible spectrum diffraction grating higher grating orders PCF IR in (76 MHz 200 fsec, 2 nj) some 10,000 brighter than the sun, yielding more than 100 GW m 2 sterad 1

46 Applications 46 optical coherence tomography optical spectroscopy frequency metrology Nobel Prize 2005 fs frequency comb John Hall Roy Glauber Ted Hänsch

47 Hand-held SC source with microchip laser 47 Wadsworth et al, Opt Exp 12 ( ) mw average at 7.25 khz (0.6 ns, 1064 nm) = pulse energy 4.1 μj & peak power 6.9 kw m PCF with ZDW at 1039 nm wavelength (μm) flat to within factor of 2 6 μm pump power (mw) anomalous dispersion

48 Supercontinuum source (Fianium Ltd) 48 Fibre laser & amplifier (1020 nm, 5 ps, W launched) Repetition rate - 50 MHz, total SC power 6.5 W 4.5 mw/nm nm

49 Broad-band light sources spectral density (dbm/nm) PCF SC source (ps fiber laser) PCF SC source (ns microchip laser) SLEDs (4 wavelengths) incandescent lamp fiber ASE source 1 mw/nm 1 µw/nm nw/nm wavelength (nm)

50 Topics 50 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

51 Phonon dispersion 51 light a ω opt optical frequency SBS acoustic 0 wavevector π/a

52 Phonon dispersion 52 light a ω opt frequency optical SRS SBS acoustic 0 wavevector π/a

53 Acoustic modes in silica strand 53 flat bands Gustavo Wiederhecker frequency axial wavevector

54 frequency Forward Raman-like scattering optical dispersion 54 Dainese et al., Opt. Exp. 14, 4141, 2006 ω AS2 ω AS1 ω P ω S1 ω S2 acoustic dispersion frequency shift independent of laser frequency ω AC wavevector

55 Diagnostic techniques 55 Polarimetric launch equal amounts of light into both polarisation states of birefringent fibre use analyser at output to monitor relative pathlength changes useful for observing modes that cause elliptical core distortion pulsed light source Sagnac place PCF sample asymmetrically in long Sagnac loop mirror launch 100 ps pump pulses observe transmitted signal pulse generator

56 Photoacoustic measurements ps pulses launched with CW probe at a different wavelength Dainese et al., Opt. Exp. 14, 4141, 2006

57 Coherent control of phonon resonances cancellation laser pulses 57 Wiederhecker, PRL 100, (2008) acoustic oscillation time reinforcement 1 μm

58 Growth with number of pulses 58 PRL 100, (2008) two different PCFs theory (including acoustic lifetime) experiment + theory (including acoustic lifetime & EDFA saturation)

59 Coherent control of waveform pulses amplitude 0 1 pulse response is more single-frequency with 27 pulses favours a single resonant mode time (ns)

60 Topics 60 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

61 Gold wire in birefringent PCF 61 Lee et al., APL 93, (2008) 900 nm wire 600 nm wire

62 Spiralling plasmon mode Schmidt et al., Opt. Exp (2008) mode order 62 n m ε ε ( m 1) =, m 1 ε D M D + εm ka 0 2 dielectric metal metal wire radius a

63 Experimental set-up Lee et al., APL 93, (2008) 63

64 Transmission spectra 64 Lee et al., APL 93, (2008) 6 mm 25 mm

65 Ge nanowires 65 Tyagi et al., Opt Exp, (2008) 600 nm wires 1700 nm wire conductivity 49 Ω.m (crystalline Ge 47 Ω.m)

66 Micro-Raman signal 66 Tyagi et al., Opt Exp, (2008) μ-raman spectrometer crystalline Ge: 300 cm -1 linewidth 2.4 cm -1

67 Topics 67 Introducing PCF Out of the strait-jacket Bars, windows & cages Cutting the losses Gas-laser interactions Brighter than 10,000 suns Nanophononics Nanowires Impact & prospects Alfried Krupp von Bohlen und Halbach - Stiftung

68 Impact & prospects 68 transforming fibre optics intra-fibre devices biomedical/chemical sensors cold atom guiding laser guidance of particles/cells single mode fibre gas cells dispersion control nanophononic devices new regimes for nonlinear optics broad-band white light frequency comb measurement non-silica glass & polymer fibres metal & semiconductor nanowires fibre lasers & amplifiers high power & energy transmission