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Our Plans

Our Plans. Invisibility: Is this possible? Yes!!! How it works & when we can buy our invisibility clothes? Energy from light: Solar cells & solar cell paints; Lasers: What they are & how they work; Laser tweezers: moving things with light without touching;

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Our Plans

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  1. Our Plans • Invisibility: • Is this possible? Yes!!! • How it works & when we can buy our invisibility clothes? • Energy from light: • Solar cells & solar cell paints; • Lasers: • What they are & how they work; • Laser tweezers: moving things with light without touching; • Laser applications: science, technology, & everyday life; • Today : Review of Science & technology of Light • Class #23

  2. Is this possible??? http://www.youtube.com/watch?v=JKPVQal851U

  3. Invisibility cloaks made of metamaterials http://www.youtube.com/watch?v=Ja_fuZyHDuk http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/3353461/Harry-Potter-invisibility-cloak-a-step-closer-to-reality.html

  4. How the cloaks of invisibility work: Recall that we did not see the glass rod immersed in vegetable oil because there was no light coming from the glass-oil interface First cloak of invisibility demonstrated to work at a particular wavelength of light No rays reflected from the cloak-surrounded object - it can not be seen & is invisible

  5. Negative refraction air n>0 Unusual bending of rays of light n<0

  6. Where would we see the fish if water had negative refraction index Note that the Snell’s law of refraction still works at such interfaces

  7. Structured metamaterials that can achieve negative refraction Model Image of a nano-fabricated material The size of these features has to be much smaller than the wavelength of light

  8. Transforming solar energy to electricity Solar Cells

  9. solar cells for energy by converting sunlight directly into electricity. The sun radiates ~1000W per square meter (see the map), so a 10 x 10 cm solar cell is exposed to nearly 10 watts of radiated power. Depending on the quality of the cell, it can produce an electrical output of 1 - 1.5 watts.

  10. Light shining from this side:

  11. Principal scheme of a solar cell Sunlight striking the photovoltaic cell is absorbed by the cell. The energy of the absorbed light generates particles with positive or negative charge Therefore, when an external load, such as an electric bulb or an electric motor, is connected between the front and back electrodes, electricity flows in the cell.

  12. Laser vs. other light sources • Rays: Waves: Laser Laser Flashlight Flashlight Light bulb Light bulb

  13. Principal components & how lasers work 1. Gain medium2. Laser pumping energy3. Mirror (100% reflection) 4. Output coupler mirror (98-99% reflection);5. Laser beam

  14. Light at Work • The term “LASER" is an acronym for Light Amplification by Stimulated Emission of Radiation. • Laser light is emitted in a narrow, low-divergence beam • Lasers are emitting light with a narrow monochromatic wavelength spectrum. • Laser in a research lab:

  15. Compare different light sources: Intensity-distribution curve of light from a incandescent lamp Intensity-distribution curve of light from a White fluorescent tube Laser

  16. Some of numerous applications • 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;

  17. 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.

  18. 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)

  19. A highly simplified view onHow “Optical Trapping” Works In the lateral plane: Along beam axis: Laser beam • Refraction changes light (photons) propagation direction; • In return, the particle experiences an opposite force; • Need refractive index of object > than that of medium;

  20. Phase-only SLM Focal Plane Focal plane Objective Objective Objective lens Prism Multiple traps: beam steering and shaping using spatial light modulators Equivalent ways of steering Image

  21. Manipulation of multiple micron-sized objects Manipulating bacteria Bacteria Pseudomonas aeruginosa: 9x9 array Manipulation by CW Nd: YAG (λ=1064nm), visualized by HeNe laser (λ=632.8nm)

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