Lab 4 Laser - Institutt for elektronikk og telekommunikasjon - NTNU

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1.1 Laser safety 6 8. Close your eyes if you bend down to pick something up from the floor. (see rule 7) 9. Do not wear a watch or jewelry with shiny flat surfaces. 10. Resist the impulse to look toward a flash or glare of light, it may be a laser beam illuminating your face. 11. Turn room lights ON when possible. The eye’s pupils open wide in a dark room and present a larger target for a stray laser beam. 12. Wear safety laser goggles when appropriate. 13. Follow laser operating instructions carefully. 14. Use common sense and be alert at all times.
1.2 Laser fundamentals 7 1.2 Laser fundamentals 1.2.1 Light amplification Atoms and molecules interact with light in three different processes: Absorption, spontaneous emission and stimulated emission. - Absorption: An atom or molecule can capture, ”absorb”, a photon of light and be excited, converted to a higher energy level. The photon must have a specific frequency n to provide the proper amount of energy E = hν to excite the atom or molecule. This process called ”stimulated absorption” is the atom’s response to electromagnetic stimulation by the incoming photon. Stimulated absorption is responsible for the colors of dyes, which absorb light of specific frequencies, while a black or gray object absorbs all frequencies equally.. - Spontaneous emission:An excited atom or molecule with excess stored energy E can release that energy spontaneously, by emission of a photon with frequency ν = E/h Spontaneous emission is responsible for the light emission by fires, fireflies, fluorescent paint, sunlight, LEDs, hot pokers, and most types of lamps. - Stimulated emission: An excited atom or molecule can be stimulated to release excess energy E in response to an incident photon of the exactly the right frequency (ν = E/h) and simultaneously release, or emit, two photons with the same frequency, using the energy of the incident photon plus the stored energy of the excited atom. Stimulated emission is the process that provides optical amplification in most lasers, since one photon in produces two photons out, an amplification factor of exactly two per event. Real atomic and molecular systems absorb or emit light at many discrete frequencies, each with a range, or bandwidth D ν centered around the main frequency ν = E/h. Optical amplification occurs when the rate of stimulated emission exceeds the rate of (stimulated) absorption, producing gain G where G = light out light in . (1.1) Amplification (G > 1) occurs in an atomic or molecular system with a population inversion, which means that the number of excited atoms (or molecules) exceeds the number of unexcited atoms or molecules. This means that there will be more stimulated emission than stimulated absorption.
Page 1 and 2: From pink light to red LASER Lab ex
Page 3 and 4: Chapter 1 Lab exercise: From pink l
Page 5: 1.1 Laser safety 5 Class Power Haza
Page 9 and 10: 1.2 Laser fundamentals 9 quencies o
Page 11 and 12: 1.3 Lab exercises 11 1.3.5 Polariza
Page 13: Bibliography [Duc04] Stephen Duchar

Lab 4 Laser - Institutt for elektronikk og telekommunikasjon - NTNU

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