| Multi-wavelength DFB laser arrays have been considered as a very important sourcein the DWDM systems. It can be used as array sources with fixed wavelength at the TXmodules and as tunable source in the system backup by wavelength selection andfine-tuning to achieve widely range running of wavelength. Furthermore，it also can beused in the next-generation reconfigurable optical networks to provide dynamicwavelength, add/drop wavelength and automatic recovery wavelength configuration, whichextremely enhance the functionality and flexibility of optical network and has wideapplications.Traditionally, we use double-light beam interfering method and electron beamlithography to fabricate the DFB laser grating. But it has low precision and is difficult tofabricate the non-uniform grating by double-light beam interfering method. It will spendmuch time to fabricate the grating with large area and minisize using electron beamlithography. So it is difficult to meet the requirement of high-precision, high-yield andnon-uniform grating fabrication. Moreover, in conventional quantum wellintermixing(QWI) technology of DFB monolithic integration, it needs several epitaxialgrowth and lithography processes to get more than two different wavelengths whichincreases the complexity and potential instability for wafer. The paper researches thenanoimprint lithography method to fabricate the DFB laser grating, a new QWI technologyand wavelength locker for DFB laser arrays. The main contents and innovations are asfollows:1.The background and developed status of multi-wavelength DFB laser arrays, thebasic theory of semiconductor lasers, including the principles, basic structure, outputcharacteristics and the influence of DFB grating period to output frequency, have beenoverviewed. The condition of generation and amplification of DFB laser have been deriverfrom coupled-mode theory.2.The process of multi-wavelength DFB laser arrays is given, including Metal-Organic Chemical Vapor Deposition(MOCVD), lithography technique, etchingtechnique and the fabrication of DFB grating using nanoimprint lithography.3.The fabrication of DFB grating using nanoimprint lithography have been researched.The new method we used to transfer grating pattern is called soft mold imprinting, twocritical steps are included, which are fabricating the soft mold(a Hot Embossing process)and transferring grating pattern from soft mold to substrate(a UV-Imprint process).The process inherits the advantages of general nanoimprint lithography, such as low-cost,high-precision, high-yield and non-uniform grating fabrication, furthermore the soft moldcan self-adapt to the undulations on the wafer surface.It is useful for fabrication of highquality DFB gtatings. Meanwhile with the self-cleaning of the soft mold, useful life of thestamp was extended,which made a large cost-down further more.4.Based on the principle and the conventional technology of QWI, a new method isproposed and experimentally studied. The wafer is bombarded by Ar plasma generated byinductively coupled plasma(ICP) etcher to create defects which diffuse into the quantumwells.The diffusion will change the components of quantum wells and barriers whichmakes the offset of wavelength. The degree of offset can be controlled by depositing SiO2mask with different duty ratio upon the wafer. In the same wafer more than twowavelengths can be obtained and the maximum offset is75nm through one epitaxialgrowth and lithography processes. The experiment shows that this method is effective.5.According to the our DFB laser arrays, a practical wavelength locker using etalonhas been designed. The power-current-voltage and spectral of laser are obtained.6.The centre wavelength of the multi-wavelength DFB laser arrays is1550nm.It has13channels and the adjacent channel is100GHz. The side mode suppression ratio of everychannel is higher than40dB. The result meets the source standards of DWDM systems. |
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