Theoretical Investigation And Fabrication Of Quadr Upolar-Shaped Quantum Cascade Microcavity Lasers

Directional emission of light guided by quadrupolar-shaped quantum cascademicrocavity lasers solves the difficulty about the directional emission ofsymmetrical microcavity lasers. In this thesis, quadrupolar-shaped quantum cascademicrocavity lasrs and several related lasers are introduced in brief. Using the theoryof electromagnetic field and Maxwell equations in medium, this article detailedlyderives the optical field distribution of resonators with arbitrary cross section.Applied on the microcavity which is deformed ellipse with the configuration ofstadium, and the optical field distribution of different deformation factors issimulated with point-matching method and the software of mathematica. Theresults show that the stable distribution of optical field can be formed whenm=1 (ground mode), and ground mode gets the maximum atφ=45°,135°,225°,315°. It has the feature of "bow-tie" mode, and improves thedirectional emission of light. At the same time, it is found that the quadrupolar-shaped microcavity only possesses the "bow-tie" mode when0.1＜ε′＜0.2, while the stronger followed lights appears aroundφ=90°andφ=270°when the deformation factorε′= 0.2. Moreover, the followed lights getthe weaken value down to disappear when the deformation factor decreases. Butthe followed lights will appear again aroundφ=180°andφ=360°when thedeformation factor gets smaller valueε′= 0.06. So the distribution of optical fielddoes not reach the best effect when the deformation factor is bigger or smaller.Furthermore, it arrives at the best effect when the deformation factor is 0.1～0.15.However, there is no phenomenon of drawing out the light directionally in themicrocavity when m≥2, and high order modes do not form the stable "bow-tie"mode when the deformation factor gets any values. That is to say, the distributionof optical field of high order modes have no regular law, it is possible thatresonance can't be formed inside the lasers.In the experiment, the epitaxial slice of 650nm AlGaInP/GaInP multiplequantum wells is grown by MOCVD, and the quadrupolar-shaped microlaserswhose the maximum radius R=70μm and the deformation factors are respectively0.06,0.1,0.15 are fabricated by microposessing technology. Furthermore,continuous emission with multiple modes are achieved in the low temperature. Thetest shows the threshold current of lasers are respectively 120mA,80mA,40mA,when deformation factors areε′=0.06,ε′=0.1,ε′=0.15 in the condition ofcontinuous electrical injection at 80K. And the wavelength of multiple modesemission is between 600-650nm, peak wide is about 0.5nm, mode space is about 1nm, the light emission gets the maximum at 45°,135°,225°,315°, and themaximum of emission power can reach above several milliwatts.