Tunable Cr:F Femtosecond Lasers

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Tunable CrF Femtosecond Lasers
Research and Industrial Applications

• Charlie Barnes Andy Carson
• Del Mar Ventures

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Femtosecond Products Offered ByDel Mar Ventures

• Pulse Pickers
• Femtosecond Autocorrelators
• Femtosecond Fluorescence Systems
• Wavelength Converters
• TiSapphire Lasers
• TiSapphire Multipass Amplification Systems
• CrForsterite Lasers and TW Systems

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Introduction to CrF Lasers

• Center wavelength of 1250 nm
• Tunable from 11001400nm
• Broadband absorption
• Directly pumped by Ytterbium Fiber Laser
• Sensitive to thermal effects

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Continuous Beam vs. Ultrashort Pulses
Continuous Beam (Ideal Case)
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Ultrashort Pulses (Ideal Case)
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Short Pulses vs. Long Pulses
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Mode-locking Multimode Lasers
RANDOM phase for all the laser modes
Irradiance vs. Time
Time
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Mode-locking Multimode Lasers
LOCKED phases for all the laser modes
In phase
Irradiance vs. Time
Out of phase
Out of phase
Time
Time
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Mode-locked pulses
Ultrafast lasers have thousands of modes!
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How do we mode-lock the laser?Kerr-Lensing
Kerr medium (n n0 n2I)
Low-intensity beam
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Making a mode-locked laser
Barrier
CW
Power
High loss
Time
c/2l
Pulsed
Power
Time
Low loss
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Elements of CrF ultrafast laser
Output Coupler
High Reflector
Lens
Curved Mirrors
Ybfiber Pump Laser
CrF Laser Crystal
Dispersion Compensating Prisms
High Reflector
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Pump Laser

• Ybfiber pump laser
• Extremely compact size
• No mode-beating
• Noise level lt 0.1
• Longer lifetime
• Costs 50 less than comparable NdYAG

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Chirped Pulse Amplification
Oscillator
Stretcher
Amplifier
Compressor
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TerraWatt System
Pump Laser PYL-10 1060 nm, 10 W
Pump Laser 1060 nm 30 ns, 30 mJ, 10 Hz
1250 nm 40- 80 fs 100 ?Hz 2 nJ
Oscillator
Regenerative Amplifier
Stretcher
Pump Laser 1060 nm 30 ns, 0.7 J, 10 Hz
Pump Laser 1060 nm 30 ns, 1 J, 10 Hz
1250 nm 200 ps 10 Hz 0.5 mJ
1250 nm 200 ps 10 Hz 50 mJ
Multipass Amplifiers
1250 nm 60 80 fs, 10 Hz, 120 mJ 1 2 TW
Compressor
1250 nm 200 ps, 10 Hz, 200 mJ
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Research and Industrial Applications

• High Resolution Imaging
• Photochemistry And Photobiology
• Material Processing
• Medical Applications
• High Energy Physics

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Advantages Femtosecond Lasers

• Short pulse duration
• Broadband
• Very high resolutions
• Less dispersion

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Emission Spectra CrForsterite
TiSapphire
CrForsterite
CrYAG
800 nm
1500 nm
1250 nm
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Advantages Cr4Fosterite
TiSapphire
CrForsterite
CrYAG
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Cr4Fosterite High speed communications
Attenuation
Dispersion
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Imaging with Ultrashort Laser Pulses

• Non Linear Effects
• in vivo
• Significantly improve the depth resolution

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Multi-Photon Microscopy
Third harmonic generation
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Third Harmonic Imaging
High intensities create non-linear optical effects
THL both sides of focus
THL destructively interferes
Index change breaks symmetry
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Third Harmonic Imaging
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THG
Optical fiber in index-matching fluid
Neurons
15 µm
D. Yelin and Y. Silberberg
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Optical Coherence Tomography

• Micron-scale cross-sectional
• in vivo imaging
• Real time

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Low Coherence Interferometry
Michelson Interferometer
Reference
Detector
Low-Coherence Source
High-coherence Source
Coherence Length
Detector
Detector
Mirror Displacement
Mirror Displacement
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OCT Images
Live Tadpole
Blood Vessel
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Femtosecond Spectroscopy

• Most chemical reactions occur in 10-15 sec
• Femtosecond spectroscopy monitoring reactions in
  real time
• Short pulse duration allows the detection
  short-lived transient chemical reactions

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Pump and Probe

• Medium is excited with femtosecond pulse
• Delayed probe pulse by increasing path length
  (microns)
• Short pulse duration allows short-lived
  reactions to be studied
• Very high resolutions

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Material Processing

• High peak power, TW with amplified systems
• Mulitphoton absorption
• Low thermal and mechanical side effects
• Ablation
• Induced structural changes

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Material Ablation

• Photons generate electrons

2) Electron avalanche
3) Plasma expansion
4) Electron-phonon coupling
5) Material is ejected
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Material Processing

• Variety of materials including dielectrics,
  semiconductors, metals, plastics
• Multiphoton absorption allows for processing of
  materials that are not very photosensitive.

(Herbert Welling, Laser Zentrum Hannover)
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What can we make?

• Micro gratings and periodic nanostructures
• Machined parts for industrial and medical
  applications
• Subsurface wave guides and all optical components

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Medical

• Laser Surgery
• Medical biopsy
• Hard tissue processing

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Corneal flap removal in LASIK
(Gerard Morou, University of Michigan)
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Applications in dentistry

• Alternative to mechanical drills and CW lasers
• Reduced thermal stress
• And micro cracks in enamel

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Femtosecond X-Ray Pulses

• Femtosecond X-ray pulses probe core electronic
  levels
• Indication of the structural changes
• Femtosecond X-rays can be generated through
  scattering visible laser beams by high energy
  electrons.

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Conclusion

• Many industrial and research applications
• High Resolution Imaging
• Photochemistry And Photobiology
• Material Processing
• Medical Applications
• High Energy Physics
• Del Mar Ventures offers a wide variety of
  femtosecond products

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Thank you for coming

• Charlie Barnes and Andy Carson
• Del Mar Ventures