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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. - PowerPoint PPT Presentation
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New high-power ultrafast laser and potential applications in
biology and medicine
Jeremy AllamOptoelectronic Devices and Materials Research Group
Tel +44 (0)1483 876799Fax +44 (0)1483 876781
University of Surrey
School of Physics and Chemistry
Guildford, SurreyGU2 7XH, UK
ultrashort pulses (5fs)
broadband gain(700-1000nm)
high power(TW)
THz pulsegeneration
• pulse shaping• coherent control
parametric conversion
Why femtosecond lasers?
• timing physical processes
• time-of-flight resolution
generate: • UV• X-rays,• relativistic
electrons
1
2
3
(Titanium-sapphire properties)
CW DPSS pump
1-100 kHz rep. rate
TiS osc.
TiS CPA RGA
kHz DPSS pump
SP-OPO
HG
FM
OPA
WLG
HG
HG
700-1000nm350-500nm
550-800nm1.1-1.6µm
80MHz rep. rate
750-840nm1.1-3.0µm
3-10µm300nm-1.2µm
}}
Principles:
System:
AMPLIFICATION: regenerative chirped-pulse amplification
-> mJ pulses
LASER: self-phase modulation
in Ti Sapphire oscillator ->
<100fs pulses
CONTINUUM GENERATION: nonlinear processes
-> white light continuum
PARAMETRIC CONVERSION: white-light seeded
parametric amplification ->
broadband µJ pulses
Femtosecond high-power broadband source
Broadband sources for spectroscopyUV visible NIR MIR FIR MMW RF
THz
FEL Ultrafast electronics
OPA
Ti-S laser
Ti-S SHG
Ti-S THG
DFMSFMHG-OPA
Ultrafast revolution
electro-optic
samplingfree-space
THz
coherent control
NL pulse propagation
microwave photonics
ultrafast opto-electronics
biological / environ-mental
sensing
photo-chemistry
medical applications
material processing
non-linear optics
non-stochastic breakdown
optical spectro-scopy
high-energy physics
solid-state femtosecond
lasersintense (>1TW)
tunable (UV-MIR)
coherent
ultrashort (<10fs)
relativistic electron motion
high-harmonic
generation (UV, X-ray)
controllable ablation
THz device physics
Why femtosecond lasers in biology and medicine?
Conventional laser applications
imaging
Benefits by using femtosecond lasers
• wide spectral range• coherent control
ablation • more controllable• less damage
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
Ablation with femtosecond lasersConventional lasers(high average power)
Femtosecond lasers(high peak, low av. power)
• dominated by thermal processes (burning, coagulation), andacoustic 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
Femtosecond vs. picosecond laser ablation
deterministic -> predictable ablation
stochastic -> uncontrolled ablation
Femtosecond interstroma
Femtosecond LASIK
Femtosecond laser surgery of cornea - 1
Femtosecond laser surgery of cornea - 2
Lenticle removal using Femtosecond LASIK
Imaging using femtosecond light pulsesNonlinear imaging for 3D sectioning(e.g. TPA fluorescence)
scattering medium
ballistic photons‘snake’ photons
diffusive photons
time
early
ph
oton
s
Time-resolved imaging for scattering media
femtosecond pulse
detection
region of TPA
amplitude & phase LCD mask
in out
Coherent control of chemical pathwaysSpectral-domain pulse shaping:
ener
gy
distance
Coherently-controlled multi-photon ionisation: