An Er-doped optical fibre of length 1m has the spectroscopic parameters given in

Question

An Er-doped optical fibre of length 1m has the spectroscopic parameters given in Table below. The fibre is strongly pumped so that the Er ions are nearly fully inverted (all in the excited state) along the entire fibre. Determine the mirror reflectivity needed (assume they are the same at each end) for lasing to occur, and assume the loss coefficient of the laser system to be negligible. Will the Fresnel reflection (R =0.04) from the glass-air interface be enough to initiate lasing? Typical parameters for selected solid-state or liquid lasers

Explanation / Answer

a) Mirror reflectivity = Ro % * exp(-2(r/wm)k)

                                 =   100 % * exp(-2(0.6 * 0.1 * 5)3)

                                =   94.74 %

b)   Yes, Fresnel Reflection from glass air interface be enough to initiate lasing .

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