Optical Fiber Communications 4th Edition by Gerd Keiser

Exercise 2

Approximate expressions for the transverse and lateral optical-field confinement factors T and L , respectively, in a Fabry-Perot lasing cavity are
And
Where
Here w and d are the width and thickness, respectively, of the active layer, and n 1 and n 2 are the refractive indices inside and outside the cavity, respectively.
( a ) Consider a 1300-nm InGaAsP laser diode in which the active region is 0.1 µ m thick, 1.0 mm wide, and 250 µ m long with refractive indices n 1 = 3.55 and n 2 = 3.20. What are the transverse and lateral optical- field confinement factors
( b ) Given that the total confinement factor is = T L , what is the gain threshold if the effective absorption coefficient is = 30 cm 1 and the facet reflectivities are R 1 = R 2 = 0.31