Study On Semiconductor Optical Amplifier And FP Laser Diode With Small Divergence Angles Based On Waveguide Coupling

Semiconductor lasers and semiconductor optical amplifiers have been widely applicated in optical communication and optical interconnects.Limited by the asymmetric and small active regions,the far-field spots are asymmetric and the divergence angles are large,which both result in increased power consumption and packaging costs due to the low coupling efficiency.In this dissertation,a semiconductor optical amplifier(SOA)and a Fabry-Pérot(F-P)laser with small divergence angles are proposed,and the optimization design and experimental investigation are carried out respectively.The major contents of this dissertation include the following aspects:(1)The implementation scheme of the SOAs and the semiconductor lasers both with small divergence angles are introduced respectively.And then,the existing problems such as reliability hazards of the former,high threashold currents and difficulty to integrate of the latter and the common shortcoming of high manufacturing costs are pointed out.(2)Firstly,the slab-coupled waveguide(SCW)principle and the coupled-mode theory are introduced respectively.Then,the mode solver for device cross-sectional structure design and the broadband travelling wave model for device performance simulation are studied.Finally,the calculation programs of these two models,which provide effective simulation tools for the device design,are written and verified.(3)A semiconductor optical amplifier based on the slab-coupled waveguide(SCWSOA)with small divergence angles is designed.It can avoid the active region to be exposed to the air by using the traditional etching procedure.Simulation results show that the horizontal and vertical divergence angles of the SCW-SOA can be reduced to less than 20°with the small signal gain of 25.9 dB and the saturated input power of 6.6 dBm.Then,the SCW-SOA chips are fabricated by using the conventional manufacturing technique,and the experimental results show that the SCW-SOA only supports single transverse mode operation,and the measured far-field divergence angles are 12.7° × 26.5°(horizontal ×vertical),while the vertical divergence angle is reduced by more than half compared to the conventional SOA.(4)A twin-waveguide F-P laser with small divergence angles is designed,and its cross-sectional structure and the length of the tapered ridge section are optimized in detail.Affected by the tapered ridge and the underneath passive waveguide,its divergence angles are reduced with the substantially increased area of the lasing mode.Simulation results show that its vertical divergence anlge can be reduced from 28.5° to 14.3° with no significant deterioration of the static and dynamic characteristic compared to a straight-ridged twinwaveguide F-P laser.In addition,the extended design of the cross-sectional structure has been executed,which results in a lasing mode with more evenly distributed optical filed and larger spot area.The results indicate its potential to manufacture high-power semiconductor lasers to free them from the end-facet optical damage.