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New high-power ultrafast laser and potential applications in biology and medicine

New high-power ultrafast laser and potential applications in biology and medicine. University of Surrey School of Physics and Chemistry Guildford, Surrey GU2 7XH, UK. Jeremy Allam Optoelectronic Devices and Materials Research Group Tel +44 (0)1483 876799 Fax +44 (0)1483 876781.

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New high-power ultrafast laser and potential applications in biology and medicine

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  1. New high-power ultrafast laser and potential applications in biology and medicine University of Surrey School of Physics and Chemistry Guildford, Surrey GU2 7XH, UK Jeremy Allam Optoelectronic Devices and Materials Research Group Tel +44 (0)1483 876799 Fax +44 (0)1483 876781

  2. Why femtosecond lasers? (Titanium-sapphire properties) • timing physical processes • time-of-flight resolution ultrashort pulses (5fs) THz pulse generation 1 broadband gain (700-1000nm) • pulse shaping • coherent control 2 generate: • UV • X-rays, • relativistic electrons high power (TW) parametric conversion 3

  3. Femtosecond high-power broadband source Principles: System:

  4. Broadband sources for spectroscopy UV visible NIR MIR FIR MMW RF Ti-S THG Ti-S SHG Ti-S laser OPA SFM DFM HG-OPA THz Ultrafast electronics FEL

  5. Ultrafast revolution

  6. Why femtosecond lasers in biology and medicine? Conventional laser applications Benefits by using femtosecond lasers • more controllable • less damage ablation • wide spectral range • coherent control spectroscopy • nonlinear imaging (e.g. TPA, THG) ->3D optical sectioning -> contrast in transparent samples • time-of-flight resolution: early photons in diffusive media • THz imaging imaging

  7. Ablation with femtosecond lasers Conventional lasers (high average power) Femtosecond lasers (high peak, low av. power) • dominated by thermal processes (burning, coagulation), and acoustic damage • collateral damage (cut cauterised) • absorption within illuminated region • stochastic -> uncontrolled ablation • dominated by non-thermal processes (‘photodisruption’) • little collateral damage (cut bleeds) • strong NL effects only at focus (-> sub-surface surgery) • deterministic -> predictable ablation * due to dynamics of photoionisation (by light field or by multi-photon absorption) and subsequent avalanche ionisation

  8. Femtosecond vs. picosecond laser ablation deterministic -> predictable ablation stochastic -> uncontrolled ablation

  9. Femtosecond laser surgery of cornea - 1 Femtosecond LASIK Femtosecond interstroma

  10. Femtosecond laser surgery of cornea - 2 Lenticle removal using Femtosecond LASIK

  11. Imaging using femtosecond light pulses Nonlinear imaging for 3D sectioning (e.g. TPA fluorescence) femtosecond pulse detection region of TPA Time-resolved imaging for scattering media scattering medium diffusive photons early photons ‘snake’ photons time ballistic photons

  12. Coherent control of chemical pathways Spectral-domain pulse shaping: Coherently-controlled multi-photon ionisation:

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