New high-power ultrafast laser and potential applications in biology and medicine Jeremy Allam...
-
Upload
tamsin-oliver -
Category
Documents
-
view
219 -
download
1
Transcript of New high-power ultrafast laser and potential applications in biology and medicine Jeremy Allam...
New high-power ultrafast laser
and potential applications in
biology and medicine
Jeremy Allam
Optoelectronic 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
3-10µm
300nm-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 spectroscopy
UV visible NIR MIR FIR MMW RF
THz
FEL Ultrafast electronics
OPA
Ti-S laser
Ti-S SHG
Ti-S THG
DFMSFM
HG-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
lasers
intense (>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 pulses
Nonlinear imaging for 3D sectioning(e.g. TPA fluorescence)
scattering medium
ballistic photons‘snake’ photons
diffusive photons
time
ear
ly
pho
tons
Time-resolved imaging for scattering media
femtosecond pulse
detection
region of TPA
amplitude & phase LCD mask
in out
Coherent control of chemical pathways
Spectral-domain pulse shaping:
ener
gy
distance
Coherently-controlled multi-photon ionisation: