Study of all optical switch using quantum dots structure

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In the study of quantum dots (QDs), QDs growth condition which includes previous conditions were investigated at first. To make uniform QDs, we use the phenomenon called Self Size Limiting (SSL), which is effective to arrange QDs size due to appearance of facet on the QDs. To enhance the effect of SSL, we grew QDs at low growth rate and low V/III ratio then we improve uniformity of the QDs on which (631) facet appeared. Next, growth condition for flat surface InP capping layer were investigated Reduction of growth rate and increase of V/III ratio were effective for surface flatness of InP capping layer. We improve surface flatness with the RMS value of 0.4nm. After then, optical property of the uniform QDs were investigated by PL spectra compared with conventional QDs. As the results, great improvement of FWHM as 40meV due to SSL was observed However, red shift of peak wavelength due to increase volume of the QDs was observed. We attempted to fabricate 2, 3, 5 stacking structure with InP spacing layer to investigate the dependence of stacking number and GaInAs under layer to QDs. At first, by inserting GaInAs under layer, In migration from under layer were prevented resulted in suppression of increase of QDs size. When we increase stacking number, QDs became large and low density with blue shift according to PL spectra It would be attributed to strain effect. In the study of all optical switch, we measured the nonlinear absorption and refractive index change in the waveguide grown by selective MOVPE growth. In the measurement of absorption loss by using the Fabry-Perot method, the absorption coefficient was more than 90cm^<-1> in the active region and less than 40cm^<-1> in the passive region. In the measurement of nonlinear refractive index change, we measured 0.025% refractive index change by using Mach-Zehnder interferometer And we have successfully obtained the all optical switching characteristics in the Mach-Zehnder type optical switch.