| Wavelength division multiplexing passive optical network (WDM-PON) system has become the most promising solution for the next optical access network due to its high capacity and performance. Low cost, high performance optical devices are the key to the success of WDM-PON system in the future. Comparing to the traditional discrete devices, the cost of the monolithic integrated light sources is lower and the performance is higher, which make them the inevitable direction of development for WDM-PON systems. This dissertation is concerned primarily with the theory and experimental study of the low cost, high performance sources in WDM-PON systems. Specifically, the main work contains the followings:Calculate the band structure and gain spectrum of the quantum well theoretically. The effects of the strain and well width to the band structure and gain spectrum are discussed in detail. The quantum well structure design principles and requirements for different applications are also discussed.Based on the time domain transfer matrix model and gain model, a simulation platform for semiconductor laser is developed to simulate and discuss the spatial hole burning (SHB) effect of the distributed feedback (DFB) laser. The effects of the grating structure including lump phase shift, distributed phase shift, multi-phase-shift, distributed coupling coefficient to the SHB phenomenon have been analyzed detailly. The effect of the normalization coupling coefficient to the modulation performance has also been discussed.Develop a new time domain dynamic model. The model integrates both time domain method and frequency domain method for laser and passive waveguide respectively. Then digital filter is used to get the two parts together organically. The un-flat gain spectrum is also considered using digital filter. Using this model, double microring resonator coupled semiconductor laser is simulated and analyzed with static and dynamic performance. The effects of the coupling coefficient and loss of the microring to the P-Ⅰ, small signal modulation, large signal modulation and wavelength switch are discussed in details.Design and optimize the InP based four channels, eight channels multimode interference (MMI) and array waveguide gratings (AWG). The effect of the fabrication error in MMI to its loss and bandwidth has been discussed. The analytical performance estimation method has been introduced to study the effect of the array waveguide gap and its taper width to the loss uniformity and max loss in center channel. Based on the results above, an InP based AWG is designed, and simulated by BPM method, whose indices meets all requirements.Fabricate the buried gratings using nanoimprint. A multi-layer mask method is developed to solve the problem that after gratings fabrication using nanoimprint resist directly, the buried quality of the metal-organic chemical vapor deposition (MOCVD) process is poor. Using the method, the threshold current of the laser has been reduced greatly.Study the butt-joint process. The effect of the etching methods of the dielectric and InP has been discussed. After improving the wet etching process and optimizing the dry etching process, a high quality butt-joint process has been applied. Based on the research before, a new fabrication flow has been proposed to solve the problem that after the butt joint process the surface of the active region is lower than passive region, and the nanoimprint process is hard to apply.A new plasma induced quantum well intermix (QWI) based on gray mask has been proposed. Multi-band-gap and continuous gradient band gap have been achieved using this method. The effect of the duty cycle and stripe width to the band-gap variation has been discussed.Improved self-alignment photolithography has been proposed to integrate the different waveguide structure. Using the silica growth on the resist and lift-off process, different waveguide structures have been integrated together.Based on the theory and technology research before, discrete chip including16channel DFB laser array for dense wavelength division multiplexing (DWDM) application with1550nm band,4channel DFB laser array for coarse wavelength division multiplexer (CWDM) application with1310nm band,4channel MMI and16channel AWG have been fabricated. The thermal corsstalk of the laser array when thermal tuning is studied. Using X-ray diffraction (XRD) and photoluminescence (PL) text, the effect of nanoimprint process to the epitaxial wafer and the lifetime of the DFB laser is investigated. Based on the theory and technology research before, monolithic integrated4channel DFB array with MMI coupler has been fabricated successfully. The average threshold current is less than10mA, and the side mode suppression ratio (SMRS) is larger than50dB. The monolithic integrated16channel DFB array with AWG coupler has also been fabricated using the same method, with the SMRS larger than40dB. The channel space is1.6nm with root mean square error less than0.1nm. |
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