Laser pumping: further increasing injection above threshold?

[Xiu Liu]

Above the threshold, the stimulation emission becomes dominant for lasing. If increasing the pumping, what will be the change of spontaneous emission and its contribution to the output power and FWHM of the signal, based on the threshold carrier density clamping and the threshold gain clamping, leading to the non-linear effect?

My question arises from the handout of Semiconductor Optoelectronics (Farhan Rana, Cornell University ) at section 11.5 and I am quite curious about the situation if further increasing the injection.

https://courses.cit.cornell.edu/ece533/Lectures/handout11.pdf

Many thanks

 

[Aaron Barnard]

Above the threshold, the contribution of spontaneous emission to the total output power and the FWHM of the signal will decrease as the pumping is increased. The reason for this is that as the number of carriers in the active region increases, the gain of the device will increase, which will result in stimulated emission becoming more dominant than spontaneous emission. As a result, the contribution of spontaneous emission to the total output power and FWHM of the signal will decrease. Additionally, the non-linear effect of threshold carrier density clamping and threshold gain clamping will cause the output power and FWHM of the signal to saturate at higher pump powers.