Subject: How can we calculate the gain coefficient of a laser diode?

I want to calculate the threshold current density of quantum well laser diode. 
I have the formula for it. However, the formula contains a parameter "Beta" 
which is the differential gain coefficient. How can we calculate the Beta 
theoritically? I have the values of internal loss, mirror loss, Optical 
confinement factor, internal efficiency, transperancy current density, 
Wavelength, and dimenssions of active region & laser diope.  

Re: How can we calculate the gain coefficient of a laser diode?