Towards Nonlinear Endoscopes

Transcription

1 Towards Nonlinear Endoscopes Hervé Rigneault Institut Fresnel Marseille

2 Nonlinear optical contrast mechanisms: label free imaging ω S ω S ω P ω P TPEF SHG THG Raman CARS SRS ω P ω S = Ω R CARS SRS Molecular Imaging

3 Nonlinear microscope λ/2 Signal OPO1 L P delay Signal OPO2 D APD (CARS) E AOM Lock In Amplifier 1.5 MHz F APD (SRL) D (CARS) F Y X E PM (SFG) E PM (TPEF) PM E spectrometer

4 Two-Photon / Second harmonic image of tissues Immuno-stained cryo section of melanoma Collagen Cells (NADH) 1mm 100µm Image stitching: 70x70 images - size 100 µm x 100 µm Collagen structure modification in the tumor

5 Coherent Anti-Stokes Raman Scattering (CARS) Imaging 85µm 55µm 85µm 55µm 30µm 0µm 30µm 0µm Epi CARS Fwd CARS Ear mouse (2845cm -1 CH aliphatic) S. Brustlein, J. Biomed. Opt. 16, (2011)

6 Multimodal nonlinear imaging of living tissues 2705cm-1 - NR- CARS TPEF 2845cm-1 - R-CARS SHG Composite CARS (R-NR) SHG TPEF S. Brustlein, J. Biomed. Opt. 16, (2011)

7 Molecular penetration in human skin Distribution of active compound Anti-ageing concentration map up to to 50µm depth 80*80*27 (µm) See Poster FRISNO 13 C-D Coherent Raman microscopy X. Chen et al., J. Controlled Release 200, (2015)

8 Imaging myelin in mice spinal cord Mosaic 2013 Collaboration Franck Debarbieux INT/IBDML Marseille

9 Can we push nonlinear optics in the depth of tissues? - Using long wavelenghts (C Xu, Nat Phot 2013) 3photon-excitation with 1700nm up to 1.2mm in the brain - Using adaptive optics (Debarre Opt Lett 2009, Ji_Betzig Nat Meth 2009) - Using speckle imaging (not suitable for NLO) Penetration depth scales as [exp(-αz)]^n=exp(-nαz), with n the order of the NLO effect (n=2 TPEF, SHG; n=3 CRS THG) RFP tagged pyramidal neurones

10 Nonlinear Endoscopes? - Deliver ultrashort at the fiber end - Perform imaging

11 Deliver ultrashort pulses at the fiber end - Group velocity dispersion (GVD) - Material GVD - Waveguide dispersion - Autofluorescence - defects - unoxydized metal ions - color centers - Self Phase Modulation - Transient raise the local refractive index, phase shift and a corresponding spectral distortion and temporal chirp - Raman - Inelastic scattering produces wavelength generation and gain - Four wave mixing - Phase matched generation of new wavelengths - Soliton - Solutions of nonlinear propagation equation NLO Schrödinger equation (Anomalous dispersion regime)

12 Hollow core fibers

13 Hollow core (HC) Photonic crystal fiber (PCF) Suitable for ultra-fast beam delivery R. F. Cregan, et al., Science 285, (1999). G. Humbert, et al, Opt Express 12(8), (2004).

14 Kagome Lattice HC fiber Kagome fiber: Philip Russel group MPI Erlangen 150fs, 800nm, 150mW, 80MHz, F. Benabid, P. Russel Science 298, 399 (2002) 5ps, 730nm, 908nm, 100mW, 80MHz

15 CARS, SRS, TPEF, SHG endoscope like scheme with HC-PCF Signal OPO Pump: 966 nm P λ/2 M L delay Stokes: 1064 nm D λ/2 Y X 1m long fiber APD De-scanned detection using double-clad HC-PCF fiber for CARS nm pump/stokes delivery and signal collection spectrometer M S. Brustlein et al, Opt Exp 19, (2011)

16 TPEF in endoscope like scheme using Kagome fiber TTB molecular crystals Kagome (MPI Erlangen) Microscopy Endoscope Drosophila embryo Microscopy Endoscope

17 University of Lille Active endoscopes In collaboration with

18 Strategies for fs pulse delivery at the fiber end Goal: femtosecond pulse fiber delivery for nonlinear microscopy / endoscopy Challenge: Ti:Sapphire laser fs? Broadening Distortion (Dispersion / NL effects) Ti:Sapphire laser fs Precompensation system fs SHG, THG, TPEF, Raman Nice results, but: Precompensation: complex / works only within a narrow range of input parameters. No tunability Alternative idea: use intrinsic fiber nonlinear effects to generate a fs pulse at fiber end. Ti:Sapphire laser fs fs 18

19 Soliton generation in a PCF Nonlinear Schrödinger equation: Group velocity dispersion Nonlinear parameter Negative GVD Self-phase modulation Soliton Fourier-transform limited + = The linear and the nonlinear effects compensate: the shape of the soliton is preserved throughout the propagation

20 Soliton self frequency shift (SSFS)) Increasing input power Tunability achievable upon power change at the input of the fiber

21 High power soliton fiber design Soliton power: Parameters of the fiber Increase soliton power Optimize the fiber design! Solid-core photonic bandgap fiber (SC-PBG), designed and fabricated in IRCICA (Lille) by A. Kudlinski. Silica Germanium doped silica Air

22 MPM using soliton self frequency shift Ti:Sapph Laser, 1GHz rep rate

23 TPEF/SHG images using soliton Saint-Jalm et al., J. Biomed. Opt. 19, (2014) Imaging with solitons ( nm) Drosophila embryo TPEF 870 nm soliton 50 µs dwell time BaTiO 3 crystal SHG 850 nm soliton 70 µs dwell time 870 nm soliton 70 µs dwell time Mouse skin tissue TPEF (stratum corneum) SHG (collagen) 300 x 300 pixels, 10 accumulations each

24 TPEF tunability Rhodamine 6G in water (170 µm) Soliton: with GigaJet (1 GHz) Reference: with Chameleon (80 MHz) Spectroscopy and microscopy achieved through excitation by a soliton No need for precompensation: the fiber properties themselves ensure FT limited fs pulse at the output Tunability: up to 100 nm tuning range

25 Lensless endoscope

26 Lensless endoscope: an overview Diameter of the probe distal part: 300µm 100µm

27 The Fiber bundle

28 The Fiber bundle: Multi Core Fiber (MCF) Double Clad Bundle 169 Single Mode Fiber (SMF) Full 360 µm 169 SMF bundle SM diameter: 3.6 µm pitch = 11.8 µm Extemely low cross talk <-25 db SMFs: No mode dispersion problem Chromatic dispersion controlled Nonlinarities controlled Double silica cladding 260 µm NA 0.65 Lille

29 The concept: Active phase control in a fiber bundle A. Thompson, P. French, Opt Lett 36, 1707 (2011)

30 Phase delay control Laser Multi Core Fiber/probe Wavefront shaper

31 Phase calibration Before calibration After calibration After calibration, a distal focus appears. Satellite peaks due to periodicity of bundle. FoV =(λ/pitch)f Wavefront shaper Multi core fiber Sample

32 Distal point scanning by wavefront tilting Distal point scanning at video rate. Proximal end Distal end Wavefront shaper Multi core fiber Sample

33 Video rate imaging (distal detection) E. Andresen et al., Opt Lett 38, 619 (2012) 1951 USAF

34 Two-Photon lensless endoscope (proximal detection) Double Clad Bundle 169 SMF 1030nm, 180fs excitation Full 360 µm Proximal end Distal end 200 fs IR pulse Detector R6G crystal Fiber bundle Wavefront shaper E. Andresen et al., Opt Expr 21, (2013)

35 First images Fluo beads (TPEF) Z=0µm Z=10µm Z=20µm Cell imaging (Tubulin GFP)

36 Esben Andresen Siddarth Sivankutty Alberto Lombardini Serge Monneret Géraud Bouwmans

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