Transcript Applications of Light in Science & Technology, Part 1

1. Lasers:
• What they are & how they work;
• Laser tweezers: moving things with
light without touching;
• Laser applications: science,
technology, & everyday life;
2. Invisibility:
• Is this possible?
Yes!!!
• How it works & when we can buy
our invisibility clothes?
3. Energy from light:
• Solar cells & solar cell paints;
4. Holography & Diffraction
Gratings
Movie on Optical Science &
Technology
Rays:
Waves:
Laser
Laser
Flashlight
Light
bulb
Flashlight
Light
bulb
Principal components & how lasers work
1. Gain medium
2. Laser pumping energy
3. Mirror (100% reflection)
4. Output coupler mirror (98-99%
reflection);
5. Laser beam
• The term “LASER" is an acronym for
Light Amplification by Stimulated
Emission of Radiation.
• Laser light is spatially coherent: either
emitted in a narrow, low-divergence
beam, or can be converted into one with
the help of lenses.
• Lasers are emitting light with a narrow
monochromatic wavelength spectrum.
Laser in a research lab:
Compare different light sources:
Intensity-distribution curve of light
from a incandescent lamp
Intensity-distribution curve of light from a
White fluorescent tube
Laser
Some of numerous applications
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In CD, Blue-Ray, DVD, andHD-DVD players,
Bar code readers;
Laser pointers & laser tweezers;
welding metal and other materials;
"marking"—producing visible patterns such as letters;
Military applications: range-finding, target designation, and
illumination, weapons;
• Medicine: laser surgery (i,.e., correction of cornea in the eye),
diagnostics, and therapeutic applications;
• Holography;
• Laser microscopy;
Moving Matter with Light without touching ???
Johannes Kepler
To explain why tails of comets always point away from the
Sun, Kepler suggested that the Sun was exerting a sort of
radiant pressure. This led him in 1609 to propose sailing from
the Earth to the Moon on light itself. This was and still is the
stuff of science fiction.
Moving and shaping matter with light
400 years later Kepler's ideas about
moving matter with light are a reality
(manipulated with invisible infrared light)
Moving and shaping matter with light
400 years later Kepler's ideas about
moving matter with light are a reality
(manipulated with invisible infrared light)
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A highly simplified view on
In the lateral plane:
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How “Optical Trapping” Works
Laser beam
Along beam axis:
Refraction changes light (photons) propagation direction;
In return, the particle experiences an opposite force;
Need refractive index of object > than that of medium;
Optical forces for micron-sized objects:
Power
F~
 pN for mW of laser powe r  Fgravity ~ 10 3 pN
c
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Multiple traps: beam steering and
shaping using spatial light modulators
Equivalent ways of steering
Phase-only SLM
Focal plane
Focal Plane
Objective
Objective
Prism
Objective
lens
Image
(1) Galvano mirrors can be scanned at
(1  10) kHz
(2) Acousto-Optic Deflectors
can be scanned at
(0.1  10) MHz
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Dynamically-reconfigurable focused laser beams
Intensity
Objective
Beam steering
Infrared CW Nd: YAG λ=1064nm co-localized with a HeNe Laser, λ=632.8nm
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Manipulation of multiple micron-sized objects
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Manipulation by CW Nd: YAG (λ=1064nm), visualized by HeNe laser (λ=632.8nm)
Manipulating micron-sized bacteria
6x6 array
Bacteria Pseudomonas aeruginosa:
9x9 array
Laser power ~ 10mW per trap
 Burns, cancer patients, cystic fibrosis patients
 Planktonic cells send quorum sensing molecules/signals to
determine if there are enough bacteria to start a biofilm
 Resistant to antibiotics
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Particle manipulation with multiple traps
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Shaping matter by infrared laser beams
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Thank you !!!
 Optically-manipulated micro-string ( using an infrared laser beam);