1. Created by: Maryam Badakhshi, Shannon O’Keefe, Laura Poloni, Hasmita Singh

2. Overview 1) Background & Applications 2) Apparatus 3) Laser Safety

3. 1. Background & Applications

4. Optical Tweezers Public image by RockyRoccon 2007 Highly focused laser beam is used to physically hold and move microscopic dielectric objects Can manipulate objects with noncontact and direct trapping Advanced Physics Laboratory for the Optical Tweezers apparatus involves the determination of optical trap stiffness of silica beads through various methods

5. Manipulation of Nanodevices (Tong et. al., Nano Letters, 2010) Alignment and rotation of a silver nanowire (Nam et. al., IJPEM, 2009) Four spheres trapped and rotated by linearly scanning with laser light

6. (Gross et. al., Methods in Enzymology, 2010) Isolation and Visualization of DNA Trapping of two beads “Catching” a Single DNA Molecule Force-Extension analysis of the trapped DNA Staining with Fluorescent Dye Protein-coated DNA region Fluctuations in DNA molecule (Gross et. al., Methods in Enzymology, 2010)

7. 2. Apparatus

8. Main Components Very Dangerous! Safe!

9. Main Components

10. 3. Laser Safety

11. Optical Trap Laser Characteristics 980 nm  Infrared range 330mW maximum power Collimated beam Class 3B laser Optical Trapping Kit, Thorlabs. 2009.

12. Laser Classification Class 3B Laser Safety Interlocks Class 1 working environment Hazardous under direct and specular reflection, but not diffuse reflection Direct exposure to beam is an eye hazard Maximum power 500mW Considered incapable of causing injury

13. Hazards Diffuse reflections Invisible Most dangerous procedure, contact your TA/Instructor Eye injuries without laser safety glasses Stray Beams Beam Alignment Biological Effects

14. Cornea Focussing element Lens Fine focus Vitreous Humor Retina Image is projected from the cornea and lens Connection to brain through optic nerve Fovea Sharp vision Vitreous Humor Schematic of the eye by SurferSam Online.

15. Biological Effects Laser Light 400-1400nm Focussed beam on retina Amplification of light by human eye: 10,000 Extremely large irradiance Dependent on exposure time Retinal Hazard Region Thermal Effects Overheating Retina burns Scars / blind spots in the field of vision Invisible light: damage may only be detected post-injury Severe damage may require surgery or transplant Depending on location of the burn, could permanently lose: Central vision Peripheral vision Elements of Laser Safety, Gary E. Myers. 1998.

16. Laser Hazards Control Remove wristwatches or reflective jewellery Close and lock the room door Place “Laser Work in Progress” warning sign on door In case of an emergency, contact your TA/Instructor or UofT Campus Police 416-978-2222 Return the laser controller key when completed Turn off laser when changing samples Wear laser safety glasses AT ALL TIMES - Wavelength and Optical Density If someone unexpectedly enters, turn laser off Thorlabs. 2010. Laser Safety Industries. 2010.