VCSEL Fabrication Technology For12-channel Parallel Optical Transmitter Module

With the development of economy and the improvement of life quality, higher requirement is put forward for communication rate. As the high-capacity data center in which the core of communication is located, the internal data transmission requires the signal transmission system with higher rate, more channels and without a long distance (no more than300miles generally). Traditional electronic interconnection has many bottlenecks which cannot be broken through on transmission, like bandwidth is limited; the data rate is difficult to reach a higher level; electro-magnetic compatibility problems, etc. As the general optical transmission can’t meet the requirements due to the limitation of cost, data rate and volume, it is the urgent need to develop the technology of VSR optical transmission. The plan of using12-channel parallel optical transmitter module becomes the typical representative of the technology in VSR optical transmission.12-channel parallel optical transmitter module is realized with VCSEL arrays, laser driver and control circuit part. VCSEL array is the core in optical transmitter module, whose main function is to transfer the high-frequency electrical signals into optical signals. Since VCSEL used in module works in high-frequency condition, the technological level in the preparation is much higher than in the low frequency case.The thesis introduces the design and development of VCSELs in12-channel parallel optical transmitter module and12-channel parallel optical transmitter elements.The development of12-channel VCSEL arrays is fabricated starting with the850nm GaAs-based epitaxial wafers grown by MBE mothod. adopting such technological processes as photolithography, wet etching, wet oxidation, magnetron sputtering and encapsulation, etc. The main focus in the thesis goes to the optimization of wet etching process and the completion of etching mesa with qualified depth-width ratio and low surface roughness with two-step etching process. The final etching result shows that the surface roughness reaches the nanometer scale. In addition, the preparation of GaAs micro-lens is achieved with single-step wet etching, in which, micro-lens can be integrated directly into bottom-out-of-light VCSEL. Taking micro-lens as output coupling lens to compose a composite cavity structure can effectively improve the optical quality of VCSEL.The preparation of12-channel parallel optical transmitter module is completed at 2.5Gbps data rate for single channel. The optical transmitter module adopts850nm vertical cavity surface emitting lasers developed by our laboratory as the light transmission source. The optical interface takes the form of standard MTP/MPO Fiber ribbon. Differential signal connection was performed with SMA-KHD9socket. The back-to-back eye diagram test and Bit-error-rate (BER) measurements show that module is capable of reliably transmitting data at over2.5Gbps.