June 2009 Fiber Laser Burn-In Testing Challenge Review Questions and Problems 1. Which of the following is NOT a property of laser light? a. Coherence b. Low divergence c. Monochromatic d. Dispersive 2. The four basic elements of a laser are: a. Pump, gas, energy supply, mirrors b. Pump, laser rod, mirrors, aperture c. Pump, medium, cavity, output coupler d. Energy source, Q switch, resonator, output coupler 3. Which structure of the eye is most affected by VISIBLE light? a. Cornea b. Retina c. Lens d. Zonnules of zinn 4. Which class of laser is generally exempt from radiation hazard controls during operation? (This also applies to a laser system with this classification.) a. I b. II c. IIIa d. IIIb e. IV 5. Which class of lasers are hazardous to view under any condition (including diffuse reflection)? a. I b. II c. IIIa d. IIIb e. IV 6. Which class of laser is associated with skin and fire hazards? a. I b. II c. IIIa d. IIIb e. IV June 2009 7. Intrabeam viewing means a. Staring at the beam from the side b. Staring at diffuse reflection of the beam c. Opening the laser and staring at the side of the tube d. Looking directly into the beam 8. The MPE is a. The maximum permitted wavelength for a viewing situation b. The maximum level of laser exposure that will not have a hazardous effect c. The minimum distance from a laser where the laser presents a hazard d. The maximum radiation allowed from a laser 9. What are the units of irradiance? a. Joule/m b. Watt c. W/cm2 d. None of the above 10. The NHZ a. b. c. d. The space within which the MPE is exceeded during normal laser operation The distance where the laser’s divergence becomes twice the normal The space where it’s OK to stand and view the laser The distance from a laser at which the exposure falls below the MPE 11. Which of the following is not a consideration when purchasing laser safety eyewear? a. Wavelength b. Laser power c. Optical density d. Fashionable frames 12. Which of the following are administrative controls? a. Beam stop b. Interlock c. Warning sign at entrance d. Key switch e. employee training f. standard operating procedures 13. Which of the following are engineering controls? a. Beam stop b. Interlock c. Warning sign at entrance d. Key switch e. Employee training f. Standard operating procedures June 2009 14. A fiber laser is what type of laser? a. Atomic gas b. Solid state c. Liquid d. Molecular gas 15. What is an "LSO"? 16. List two "non beam" laser hazards. 17. What is an interlock and how does it work? 18. Find the photon energies of a) a 532 nm green photon and b) a 1060 nm infrared photon. 19. Why are IR lasers used for material processing rather than visible lasers? 20. Why is it important for a fiber laser used for cutting to have single mode output (TEMoo)? 21. What type of power meter would you use to measure a 10kW laser beam? Use the Internet to find out. June 2009 Fiber Laser Burn-In Testing Challenge Review Questions and Problems ANSWERS 1. d 2. c 3. b 4. a 5. e 6. e 7. d 8. b 9. c 10. a 11. d 12. c,e,f 13. a,b,d 14. b 15. Laser Safety Officer. An LSO is required at institutions with Class IIIb lasers and above. 16. Non beam hazards include: electrical hazards, laser generated air contaminants (LGAC), cryogenics, explosion, etc. More complete lists may be found on the Internet. 17. An interlock is a safety device that shuts off power when safe operating conditions are exceeded. For example, a household circuit breaker is a sort of interlock that shuts off a circuit when current rating is exceeded. Other interlocks my shut off power when a temperature rating is exceeded or fluid flow is interrupted. 18. E = hc/ so for a 532 nm, E = 2.33 eV and for 1060 nm, E = 1.17 eV 19. Although IR photons individually have lower energy than visible photons, IR lasers are able to create far more photons leading to a higher power beam. 20. The TEMoo (or Gaussian) mode can be focused to a smaller spot size than any other beam mode. 21. High power lasers require thermal detectors for power measurement (rather than quantum detectors.) See LIGHT- Introduction to Optics and Photonics Chapter 3.