Digitally Wavelength Switchable Semiconductor Laser Based On V-coupled Cavity

WDM (wavelength-division multiplexing) is an important technical innovation in the fiber communication industry, and is the enabling force for further development of the optical networks. Semiconductor laser is one of the most important devices in the fiber communication system.Wavelength switchable semiconductor laser has the capability of dynamic wavelength switching upon particular demand, thus plays a crucial role in the next-generation broadband fiber communication systems and advanced optical networks. It can be used as backup light source in dense WDM (DWDM) systems, and also in optical burst switching, optical packet switching and reconfigurable optical add-drop multiplexer (ROADM). In this dissertation, we studied the digitally wavelength switchable laser based on V-coupled cavity, with laser structure optimization, fabrication research and device performance test.In the beginning of this dissertation, the basic structure and operating principle of the V-coupled cavity laser is introduced. With optimal design of the coupling phase and coupling coefficient of the half-wave coupler and the cavity length difference between the two cavities of the laser, we can obtain large range of wavelength switching by Vernier effect while maintaining very high side-mode suppression ratio (SMSR) in each channel. The influence of the coupling phase variation of the half-wave coupler on the laser performance and influence of potential dimension errors introduced by fabrication on the threshold gain difference of the laser are also analyzed.Then the detailed fabrication procedure of the V-couple cavity laser with InGaAsP/InP MQW is presented. Key steps such as pattern lithography, mask layer etching, waveguide and reflective mirror etching, planarization, metal contact sputtering and wafer thinning&polishing are analyzed and optimized. With every step in the whole procedure optimized, we successfully demonstrated two types of the V-coupled cavity laser with cleaved-facet and deep-etched facet, respectively.We characterized the fabricated devices for their performance under static bias and wavelength switching characteristics. With much mature structure design and more advanced fabrication process, the V-coupled cavity laser with deep-etched facet shows superior performance over the cleaved-facet ones. Under thermal effect tuning scheme, via single-electrode tuning method, we can obtain16consecutive switching channels with100GHz spacing and highest SMSR of40dB with10%cavity length difference and26consecutive switching channels with100GHz spacing and highest SMSR of37dB with5%cavity length difference. We also tested the devices under carrier injection effect, highest SMSR of32dB with9continuous switching channels is obtained in this case. The performances between these two schemes are compared and analyzed. In the end, the linewidth parameter of the V-coupled cavity laser is tested and obtained, and we show the first experimental result of the bandgap engineering with quantum well interxing on the V-coupled cavity laser.Finally we discussed the future research plans for the V-coupled cavity lasers.