Research of a hig-performance dynamic-single-mode laser

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The main purpose of this research is to realize high-performance dhnamicsingle-mode (DSM) lasers with distributed Bragg reflectors (DBR) by clarifying the dynamic propertis under a high-speed direct modulation both theoretically and experimentally. In order to achieve this purpose, we invented a new waveguide coupling structure called Bundle-Integrated-Guide (BIG), which enables us to attain very high coupling efficiency between the active and the passive waveguide regions in DBR laser and also high reproducibility in its fabrication process. Specific results obtained in this research are summatized as follow.We theoretially pointed out that superior lasing properties, such as a lower threshold current, a higher side-mode suppression ratio, and a wider temperature range for a fixed-single-mode operation, would be obrained by shortening the active region length of DBR-DSM lasers and we also proved that experimentally from the lasing properties of BIG-DBR-DSM lasers.We measured the spect … More ral behaviour of the BIG-DBR-DSM laser under a highspeed direct modulation, such as wavelength chitping and the side-mode-suppression ratio during the modulation period, and clarified these dyanmic properties in terms of 2-mode rate equations.Spectral linewidht of DBR laser and its dependence on the cavity structure was theoretically analized and the result was found to be in good agreement with experimental results obtained for BIG-DBR-DSM lasers. Quite a narrow linewidht of 6.5MHz was obtained at the bias level of 2.2 times the thershold.To improve the reproducibility of BIG-DBR lasers ans to obtain higher lasing performances, a new fabrication process using an island-type pattern etching ans selective regowth was proposed and much improvement was obtained such as high output power of 12.4mW and high side-mode suppression ratio larger than 38dB. Moreover, a novel distributed reflector (DR) laser was proposed to achieve lower threshold current and higher output power operation, and was realized with superior single-mode operation properties. Less