Nonlinear optical effects in optically trapped microparticles

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Nonlinear optical effects in optically trapped
microparticles

• A laser beam of 10 mW power is focused to 1
  mm-diameter beam

January 12. 2006
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Pe0( c (1) E c(2)E2c(3)E3 ) where c (1)
is the linear susceptibility c (2) , c (3) are
the second and third order nonlinear
susceptibilities
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http//phys.strath.ac.uk/
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http//phys.strath.ac.uk/
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http//phys.strath.ac.uk/
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Nonlinear optical effects in optically trapped
microparticlesExperiments.

• 1. S. Sato and H. Inaba (Research Institute of
  Electrical Communications, Tohoku University,
  Japan)
• Observation of second harmonic generation from
  optically trapped
• microscopic LiNbO3 particle using NdYAG Laser,
• Electronics Letters, 28, 286 (1992).

CW, 50 mW
LiNbO3 (1.5 mm)
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• 2. L. Malmqvist and H. M. Hertz (Department of
  Physics, University Lund, Sweden)
• Two-color trapped-particle optical microscopy,
• Optics Letters 19, 853 (1994).

Dyed photoresist
glass
CW, 50 mW
LiNbO3 particles made by grinding a crystal In a
mortar, then mixed with water, and after a few
days the top layer of the water-particle mixture
was used for trapping (50-100 nm)
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• 3. S. Sato and H. Inaba (Tohoku University,
  Japan)
• Second-harmonic and sum-frequency generation
  from optically trapped KTiOPO4 particles by use
  of NdYAG and TiAl2O3 lasers,
• Optics Letters 19, 927 (1994).

TiSapphire pulsed laser (722-893 nm) ( CW) 10 mW
average power
KTP particles (50-100 nm)
Nd-YAG CW laser (1064 nm) 100 mW average power
SHG and sum frequency
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• 4. L. Malmqvist and H. M. Hertz (Department of
  Physics, Lund Institute of Technology, Sweden)
• Second-harmonic generation in optically trapped
  nonlinear particles with pulsed lasers,
• Applied Optics 34, 3392 (1995).

100 mW FH - between 1 pW and 10 nW SH
Degradation of SHG
LiNbO3 and KTP particles (50-100 nm)
Nd-YAG pulsed laser 10-25 kHz repetition
rate Pulse width 320-950 ns 100 mW average power
Traps both KTP and LiNbO3
TiSapphire pulsed laser 76 MHz repetition
rate pulse width 100 fs 100 mW average power
ms (repetition rate)
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Traps only KTP
Pulse (1 ms)
time
0.01 s to escape from the trap
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• 5. E. V. Perevedentseva, A. V. Karmenyan, F.-J.
  Kao, and A. Chiou (Institute of Biophotonic
  Engineering, National Yang Ming Univeristy,
  Taipei, Taiwan)
• Second-harmonic generation of biotin and biotin
  ester microscrystals trapped in optical tweezers
  with a mode-locked T.-Sapphire Laser,
• Scanning 26, 78 (2004).

TiSapphire pulsed laser 76 MHz repetition
rate pulse width 150 fs average intensity was
between 0.3 108 W/cm2 and 3 108 W/cm2 740 -920
nm
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Biotin, also known as vitamin H or B7 and
C10H16N2O3S (Biotin Coenzyme R, Biopeiderm), is
a water-soluble B-complex vitamin which is
composed of an ureido ring fused with a
tetrahydrothiophene ring. A valeric acid
substituent is attached to one of the carbon
atoms of the tetrahydrothiophene ring. Biotin is
important in the catalysis of essential
metabolic reactions to synthesize fatty acids,
in gluconeogenesis, and to metabolize leucine.
It is commonly found in pyruvate dehydrogenase
as a carrier of HCO3-.
http//en.wikipedia.org/wiki/Biotin
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Resonance transition ?
Experimental results
Signal degradation and crystal size reduction
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A TiSapphire laser, 800 nm 100 fs, 80 MHz (12 ns
pulse space) or CW
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• How the nonlinear generation of optical waves
  with different frequencies changes the radiation
  force exerted to a nonlinear trapped
  microparticle?

• Two main mechanisms
• Optical waves with new frequencies produce also
• the radiation forces.
• 2. The nonlinear Kerr effect changes the
  refractive index
• of the trapped nonlinear particle, hence, the
• radiation forces (both the gradient force and
  the
• scattering force).

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• Calculations of the radiation forces exerted on a
  nonlinear trapped microparticle.

• R. Pobre and C. Saloma (National Institute of
  Physics,
• University of Philipines, Manila, The
  Philipines)
• Single Gaussian beam interaction with a Kerr
  microsphere
• characteristics of the radiation force,
• Applied Optics, 36, 3515 (1997).

Geometrical optics regime 2pR/lgt100 A Kerr
nonlinear effect nsns0I n2
Sinq/Sinqtns/n
q
Nonlinear refraction
qt
Linear refraction
z
R
Focal plane of a Gaussian beam
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n(I)n0 n2 I
Restorting force vs incident power
No trapping
Linear case
Stable trapping
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2. R. Pobre and C. Saloma (National Institute of
Physics, University of Philipines, Manila, The
Philipines) Nonlinear force on a nonlinear
microsphere by a tightly focused Gaussian beam,
Applied Optics, 41, 7694 (2002).
2pR/l lt100 wavelength and sphere radius are
comparable A Kerr nonlinear effect nsns0I n2
The Mie-problem scattering a plane wave on
a sphere of the arbitrary refractive index and
radius.
Outside of the sphere
Eincident and Escattered
Inside the sphere
Einternal
nsns0 Einternal Einternal n2
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Linear sphere
Nonlinear sphere
Displacement (microns)
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Size-dependence of nonlinear effects Colloids
are bridges between molecules and solids
molecule
solids
Optical trap?
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• To check second harmonic signals from cells that
  we are using
• (yeast, Jurkat ). 1064 nm trap.
• 2. Jordi Martorells polysterene spheres covered
  by molecules with high
• ksi(2). Size dependence
• 3. PFM with nonlinear optical detection (Jordis
  spheres). Sensitivity?

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