Optical Fiber Communications 4th Edition by Gerd Keiser

Exercise 24

A GaAlAs laser diode has a 500- µ m cavity length, which has an effective absorption coefficient of 10 cm -1. For uncoated facets the reflectivities are 0.32 at each end. What is the optical gain at the lasing threshold
( b ) If one end of the laser is coated with a dielectric reflector so that its reflectivity is now 90 percent, what is the optical gain at the lasing threshold
( c ) If the internal quantum efficiency is 0.65, what is the external quantum efficiency in cases ( a ) and ( b )