Derive an expression for the threshold current density Jth of an injection laser which has one end face coated with a layer that is totally reflecting (R = 1). Assume that the relationship between the...

Derive an expression for the threshold current density Jth of an injection laser

which has one end face coated with a layer that is totally reflecting (R = 1).

Assume that the relationship between the input current density J[A/cm2] and

the gain coefficient g[cm−1] is given by J = Kg, where K is a constant. Also

assume that R0 is the reflectivity of the partially transmitting endface, and

that L, α, D, and d are as previously defined.