Light at Work

1. Light at Work • Lasers: • What they are & how they work; • Laser tweezers: moving things with light without touching; • Laser applications: science, technology, & everyday life; • Invisibility: • Is this possible? Yes!!! • How it works & when we can buy our invisibility clothes? • Energy from light: • Solar cells & solar cell paints; • Holography & Diffraction Gratings • Movie on Optical Science & Technology

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

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

4. Light at Work • 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:

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

6. 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;

7. 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.

8. 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)

9. 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)

10. 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; • Optical forces for micron-sized objects:

11. Galvano mirrors can be scanned at Phase-only SLM Focal Plane Focal plane Objective Objective Objective lens Prism (2) Acousto-Optic Deflectors can be scanned at Multiple traps: beam steering and shaping using spatial light modulators Equivalent ways of steering Image

12. Dynamically-reconfigurable focused laser beams Intensity Objective Beam steering Infrared CW Nd: YAG λ=1064nmco-localized with a HeNe Laser, λ=632.8nm

13. Manipulation of multiple micron-sized objects Manipulation by CW Nd: YAG (λ=1064nm), visualized by HeNe laser (λ=632.8nm)

14. Manipulating micron-sized bacteria Bacteria Pseudomonas aeruginosa: 9x9 array 6x6 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

15. Particle manipulation with multiple traps

16. Shaping matter by infrared laser beams

18. Thank you !!! • Optically-manipulated micro-string ( using an infrared laser beam);