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e894a2j

# e894a2j - 5(a What is the average number of round trips for...

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ENSC 460/894 Assignment 2: (Feb. 21 due Feb. 29 2008) 1 For a HeNe laser calculate the ratio of the spontaneous radiation coefficient to the stimulated coefficient (HeNe wavelength is 632.8 nm). (5 marks) 2 Assume a single layer antireflection coating is to be deposited on long IR ZnSe lens (n=2.4) for a wavelength of a CO 2 laser (10.4 microns). (a) What is the minimum thickness for this coating (3 marks) (b) What is the next smallest thickness that will give an AR coating. (2 marks) 3 Given an Argon Ion laser running its main green line, with a beam radius of 1 mm design a beam expander to expand the beam radius to 5 mm using a main lens of f = 30 cm. Do both Galilean and Keplerian expander and draw the design. State what f input lens is required and the length of the system (5 marks each) 4 Calculate the Q value for a CO 2 laser (wavelength 10.6 microns) with a 2 m cavity and mirror reflectances of 100% for the rear and 40% for the output window. (5 marks)
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Unformatted text preview: 5(a) What is the average number of round trips for a photon in a laser with mirror reflectances of 100% for the back mirror and 40% for the front mirror? (2 marks) (b) If the optical cavity length is 1.5 m, with is the cavity lifetime? (2 marks) 6. US Homeland security is worried that pilots may be blinded by people point laser points at distant airplanes. The most powerful laser pointer on the market is the BigHa pointer which has a 5 mW beam at 533 nm with w=1 mm. (a)What is the Rayleigh Range of the pointer? (b) What is distance where the beam average power density has reduced to 0.5mW/mm 2 . (c) If an airplane is 1 km from the pointer, what is the spotsize at the plane, its average power density and peak power density? 7 Calculate the approximate peak wavelengths from expected from the following materials given their bandgaps: GaAs (1.44 eV), GaP (2.26 eV) CdTe (1.50 eV), InP (1.35 ev), SiC (3.00 eV)...
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