Carrier dependence of the spontaneous emission factor in DBR lasers

We present the carrier dependence of the spontaneous emission factor, β, in distributed Bragg reflector (DBR) lasers using a specific example for InGaAs/InP multiple quantum wells (MQWs). Our approach is to isolate the spectral carrier dependent behaviour from cavity effects and examine the impact on the sub-threshold β value by considering three resonant modes at different positions in the spontaneous emission spectrum. The results indicate that conventional curve-fitting methods of determining β (assumed constant) from experimental data may incur significant errors since β may vary by up to a factor of 2.