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HW7 - 2 and σ se(3.39 μ m = 5 06 × 10-11 cm 2 1 2 Laser...

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ECE 455: Optical Electronics Homework 6 Due: Oct. 27, 2011 1 HeNe Laser Two laser transitions of the helium-neon laser share a common upper state. Answer the following questions about the threshold of each transition. Note that the optics have different characteristics at the two wavelengths. 30cm R(632.8 nm) = 0.999 R(3.39 μ m) = 0.999 R(632.8 nm) = 0.95 R(3.39 μ m) = 0.98 1cm α α (632.8 nm) = 0 (3.39 μ m) = 0.2 cm -1 40cm (a) What is the threshold gain for the 632.8 nm transition? (b) What is the threshold gain for the 3.39 μ m transition? (c) If the pump power is slowly increased from zero, which transition will begin lasing first? You may assume the population of the lower level of each transition is zero. Also, assume that σ se (632.8 nm) = 3 × 10 - 12 cm 2

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Unformatted text preview: 2 and σ se (3.39 μ m) = 5 . 06 × 10-11 cm 2 1 2 Laser Properties Verdeyen 8.21. Don’t do h or g. 2 3 Laser Properties Verdeyen 9.4 4 Mode-Locking The Nd:YAG has a gain bandwidth of 1 . 2 × 10 11 Hz (FWHM). A particular mode-locked Nd:YAG laser generates 50 nJ pulses. (a) Give an esimate of the shortest pulse that can be generated with an Nd:YAG gain medium. (b) Assuming the pulses are as short as possible, give an estimate of the peak power. (c) The end mirrors of the laser are 1.0 m apart and the laser is modelocked. How often does the laser emit a pulse? (d) What is the average power? (e) How many longitudinal modes are mode-locked together? Assume the full bandwith is 2.5 times the FWHM. 3...
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HW7 - 2 and σ se(3.39 μ m = 5 06 × 10-11 cm 2 1 2 Laser...

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