Research On Polarization Characteristics Of Superluminescent Diodes

As one of the key light sources of sensing system,the luminescence characteristic of Superluminescent diode(SLD)is between lasers and light emitting diodes.Holding the characteristic of high output power,wide spectrum and weak temporal coherence,SLDs have been used in inertial navigation system,optical cable construction and maintenance equipments,medical instruments.In recent years,high accuracy sensing system has already been urgently-needed in Internet of things,Artificial intelligence and other technologies.As one of the important characteristics of SLDs which determine the accuracy of the sensing system,polarization has become a research focus.Therefore,carring out research on the control of polarization of SLDs will make great significance to expand SLDs'application scopes and scenarios in engineering field.Based on current semiconductor technology accumulation of our lab,we took the polarization characteristics of GaAs-based quantum dot SLDs and GaAs-based multiple quantum well SLDs as the research subject in this thesis.We optimized the fabrication process and studied the effects on polarization of waveguide's geometric parameters,light output direction,etching depth and current injection position.The main work and achievements are listed as follows:1.Optimized the key fabrication process of SLDs.(1)In photolithography development and ridge waveguide etching,glass and Teflon baskets were used to carry the wafer,which improved the steepness of the edge of the pattern produced by development and etching.(2)Constant temperature water bath was used in the photoresist peeling process after sputtering the Ti/Pt/Au electrode on the P side,which significantly reduces the difficulty of peeling process.(3)In the wafer thinning process,thin epitaxial wafers with specific thickness were used to protect wafers,effectively avoiding the risk of excessive wafer thinning.2.GaAs-based quantum dot SLDs were successfully fabricated based on shallow etched double groove J-shaped ridge waveguide structure.The SLD chip with ridge width of 10?m,length of 3mm,bending angle of 10°could operate at room temperature under continuous wave condition,it has an output power of 6mW and a full width at half maximum(FWHM)of 24.3 nm while the injected current is 350mA,and the corresponding power bandwidth product is 146nm·mW with the degree of polarization is 99%.3.We measured polarization by turned the light direction to straight waveguide and changed the injection position by microprobe.It is found that waveguide's geometric parameter,output light direction,etching depth,current injection position had an effect on polarization.The polarization between 4%and 99%on SLDs for its ridge width of 5?m,length of 2mm,bending angle of 10°.4.GaAs-based quantum well SLDs based on deeply etched double-groove J-shaped ridge waveguide were successfully fabricated.The SLD chip with a ridge width of 4?m,a length of 2mm,a bending angle of 8°could operate at room temperature under pulse condition(10%,500Hz),and it has an output power of 6.5mW while the injected current is 350mA.