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answerhappygod
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(a) A laser emits light with a wavelength of 694 nm. If the laser cavity is 5 cm long and the cavity mirrors exhibit reflectivities of 1.0 and 0.96, what is the threshold small signal gain needed for laser operation? You should assume: (i) the spontaneous lifetime of the upper laser level is 3 ms (ii) the line width of the transition is 150 GHz, and (iii) the refractive index of the lasing material is 1.78 (b) What is the minimum population inversion required to achieve this level of gain? (c) What is the decay time for radiation inside the laser cavity? (d) Derive an expression for the Q factor of the cavity described above (i.e. in terms of the refractive index of the laser medium and the wavelength of the laser transition), and determine its value. [4] [8] [2] [6]
(a) A laser emits light with a wavelength of 694 nm. If the laser cavity is 5 cm long and the cavity mirrors exhibit reflectivities of 1.0 and 0.96, what is the threshold small signal gain needed for laser operation? You should assume: (i) the spontaneous lifetime of the upper laser level is 3 ms (ii) the line width of the transition is 150 GHz, and (iii) the refractive index of the lasing material is 1.78 (b) What is the minimum population inversion required to achieve this level of gain? (c) What is the decay time for radiation inside the laser cavity? (d) Derive an expression for the Q factor of the cavity described above (i.e. in terms of the refractive index of the laser medium and the wavelength of the laser transition), and determine its value. [4] [8] [2] [6]
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