Simulation, Fabrication, and Characterization of Semiconductor Lasers
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Semiconductor lasers are very important in today’s world, considering their applications in communication, medical, spectroscopy and also in our daily lives.This thesis discusses three different types of laser: broad area, ridge waveguide and mode locking laser. Broad area laser (BAL) is the simplest to fabricate among these three lasers which is utilized for characterization of the material, whereas the ridge waveguide laser confines light within the fabricated ridge. The mode lock laser is similar to ridge waveguide laser except that the contact metal is divided into two sections. One section acts as the gain medium and the other section works as the saturable absorber thus providing passive modelocking. The measured threshold current for BAL is around 140 mA whereas it is 26 mA and 36 mA for ridge waveguide and passively mode locked laser respectively for 1 mm cavity length. The threshold current density is also calculated 139.91 A/cm2 for infinite cavity length. Optical spectrum measurement showed wavelength around 892 nm to 898 nm for all the lasers. External differential quantum efficiency is measured for different cavity lengths from which internal quantum efficiency is found 85.5% and also internal loss 5.85 cm−1. Finally, the characteristic temperature for the diode laser is found 208.3 0C. It is also shown that the slope decreases and the threshold current increases for increasing reverse bias for the passively mode locked laser.