2. A He-Ne laser utilises a resonant cavity of length 25 cm and an output mirror with 99% reflectivity. [7] [2] (a) Desc

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2 A He Ne Laser Utilises A Resonant Cavity Of Length 25 Cm And An Output Mirror With 99 Reflectivity 7 2 A Desc 1 (101.01 KiB) Viewed 73 times

2. A He-Ne laser utilises a resonant cavity of length 25 cm and an output mirror with 99% reflectivity. [7] [2] (a) Describe how a He-Ne laser operates. Your answer should refer to the fundamental processes required to initiate lasing action and should include a sketch of the electron energy levels of Helium and Neon and the specific transition responsible for the emission of red light at a wavelength of 632.8 nm. (b) What is the mode separation for the laser? (C) What is the wavelength and number of the mode nearest to the line centre? Clearly state any assumptions that you make. (d) Describe the various reasons why the spectral transition has a finite width (i.e. line profile function). (e) Assuming that Doppler broadening is the dominant factor, what is the full width at half maximum of the gain curve of the cavity? The atomic mass of He is 4.00 amu and the atomic mass of Ne is 20.18 amu. [3] [4]