Experimental Study On 1/f Noise Of Tunable Semiconductor Lasers

The wavelength-tunable semiconductor lasers play an important role in communications,sensing and detecting applications.1/f noise can be caused by internal defects,traps and structural incompleteness of tunable semiconductor lasers,presented as 1/f electrical noise and 1/f optical noise.The existence of 1/f noise has caused some practical problems on the application of tunable semiconductor lasers,such as linewidth broadening and low signal-to-noise.The thesis focuses on the 1/f noise characterization and the 1/f noise sources of tunable semiconductor lasers,specific research contents are as follows:(1)A measurement system is set-up for characterizing 1/f electrical noise of tunable semiconductor lasers.A DFB laser and two different types of DBR lasers are under tested with this system.Results show that there is a significant 1/f electrical noise in the active sections,for all of the three lasers.It is found that the active region of the DFB laser has a large series resistance,while the active region of the DBR laser has a large leakage current.Also,results show taht the passive sections of DS-DBR laser and SG-DBR laser have a significant 1/f electrical noise,which increases with the growth of the bias current and then tends to saturate.(2)The 1/f optical phase noise of a DS-DBR laser is studied experimentally.Measured results indicate that the 1/f optical phase noise level in the low frequency band of the laser increases significantly,when the passive sections of the DS-DBR laser is biased.(3)Aging experiments for the DS-DBR laser are carried out.In the early stage of aging,there is an annealing effect in the active section of the device.Also,significant degradation is found in the grating sections of the laser during aging,which results in an increase in the total 1/f electrical noise.Reliability assessment by using 1/f electrical noise characterization is further discussed.