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

2. Overview 1) Introduction 2) Background & Applications 3) Apparatus 4) Laser Safety

3. 1. Introduction

4. Experiment Context --Presentation No presentation component available in the Advanced Physics Labs courses This presentation component is meant to be introduced to the students by the professor or TA of the course, in advance to the experiment

5. Experiment Context --Students Main purpose: Give general information about the experiment and apparatus Applications for the apparatus Students may use this presentation to choose their experiment Also to acquaint students with laboratory concepts, the equipment, and the safety procedure

6. Relevant Courses This experiment is based on knowledge of Energy Equipartition theory that may be related to back ground courses in both Engineering and Arts and Sciences : Phy293  Engineering PHY256H1  Arts and Science This lab may also be used in the following courses: PHY424/426/428/429 (A&S) and PHY327/427/428/429 (Engineering)

7. Experiment Learning Objectives Students will have the opportunity to : Work on interesting and challenging experiments Deepen their understanding of the underlying Physics Further develop laboratory, analysis and communication skills This presentation introduces the Optical Trapping apparatus and the many interesting applications of it

8. 2. Background & Applications

9. Manipulation of Nanowires (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

10. (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)

11. 3. Apparatus

12. Main Components Very Dangerous! Safe!

13. 4. Laser Safety

14. Optical Trap Laser Characteristics 980 nm  Infrared range 330mW maximum power Collimated beam Class 3B laser

15. 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

16. Hazards Diffuse reflections Invisible Most dangerous procedure, contact your TA/Instructor Eye injuries Stray Beams Beam Alignment Biological Effects

17. 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

18. 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 Invisible light: damage may only be detected post-injury Severe damage may require surgery or transplant Scars / blind spots in the field of vision Depending on location of the burn, could permanently lose: Central vision Peripheral vision

19. Laser Hazards Control Wear laser safety glasses AT ALL TIMES - Wavelength and Optical Density Remove wristwatches or reflective jewellery Close and lock the room door Place “Laser Work in Progress” warning sign on door If someone unexpectedly enters, turn laser off 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