Comparison of Gain Measurement Techniques for Characterization of Quantum Dot Lasers

This paper presents a comparative analysis of three gain measurement methods which are H&P (Hakki & Paoli), SC (Segmented-Contact) and IA (Integrated-Amplifier) for the gain characterization of 1300nm (O-band) InAs/GaAs QD (Quantum Dot) laser devices. In this case, during continuous mode operation at a fixed heat-sink temperature of 17oC, the experimental conditions, measured spectral ranges and signal to noise ratio are compared and advantages are discussed. The devices used for the analysis are fabricated as multi-section, single mode structures. Before self-heating, each of the methods show identical results but SC proved to be better in terms of accuracy of internal loss measurement. The H&P method has been shown the only choice for high current density gain measurements at a fixed junction temperature under consideration. The method to remove self-heating effects via H&P is also discussed and via this method a high current density gain analysis upto 5.5kA/cm2(~ 8e-h pairs)is performed under 30oC fixed junction temperature condition. In comparison to other methods, the IA method has shown to be advantageous in terms of low current density measurements exhibiting the capability of accessing wider spectral ranges and performing the gain characterization where laser material operates in loss.