Lab 4 Laser - Institutt for elektronikk og telekommunikasjon - NTNU

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1.3 Lab exercises 10 1.3 Lab exercises 1.3.1 Equipment Welding glasses for eye protection HeNe one-brewster discharge tube High Voltage(1900 V) power supply Alden cable with ballast resistor Output coupler-mirror (OC)99%@632.8nm Power meter Polarizer Quarter wave plate Chopper Photo diode with amplifier Oscilloscope 1.3.2 HeNe-tube The HeNe-tube is mounted in a stand with the electrical wires attached. Do NOT touch any of this. The tube is very fragile and easy to break! Plug the 220V power supply unit into the wall socket and wait for the tube to ignite. Describe the color of the light that is emitted. And measure the output power from the tube with the power meter. 1.3.3 HeNe-laser alignment Put the mirror onto the rail and put it 1 cm from the brewster-window. Observe the change of light color that is transmitted through the mirror. Why does the light have this color? Measure the power emitted. Now try to align the mirror so that the light gets reflected off the mirror and back through the brewster mirror so that lasing is obtained. Measure the power emitted from the laser at once when lasing is obtained. It is quite easy to see, because a flash of red light will occur when lasing starts. What is the µm readings when lasing starts? What is the effect when lasing starts? What is the maximum power that you can get out of this tube? What is the corresponding µm readings? Try to slide the mirror away from the tube. Measure and see how far you can slide while maintaining lasing. Plot the power of emitted radiation vs. length of the tube. Be careful and don’t touch the anode of the tube (High voltage)!! 1.3.4 Transversal modes Look at the mode picture projected at the wall (use a sheet of paper to get a better mode picture). Which TEM mode is this? Use a lens to inflate the mode picture if it is difficult to see. What happens when the mirror is or tilted back and forth? Why?
1.3 Lab exercises 11 1.3.5 Polarization Use the polarizers and the quarter wave plate to construct an analyzer. Determine the state of polarization by using an oscilloscope, the photodiode with amplifier and a chopper. What is the state of polarization? Measure also the state of polarization on the light that is reflected from the brewster window. What is the use of brewster windows? Why is the polarization state as it is?
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 and 6: 1.1 Laser safety 5 Class Power Haza
Page 7 and 8: 1.2 Laser fundamentals 7 1.2 Laser
Page 9: 1.2 Laser fundamentals 9 quencies o
Page 13: Bibliography [Duc04] Stephen Duchar

Lab 4 Laser - Institutt for elektronikk og telekommunikasjon - NTNU

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