Monolithically Integrated Wavelength Switchable Semiconductor Laser And High Speed Q-Modulation Technique

In the era of information technology and intelligent information age, which is characterized by the demand of enormous amount of information, very fast information transmission,and processing. the optical networks need to have a higher transfer rate, better dynamic flexibility and lower cost. The monolithically integrated wavelength switchable laser and high-speed modulator are key components for meeting these demand and will have a very important significance and broad prospects for optical communications in the future. This thesis is mainly devoted to the study of the design and fabrication of new monolithically integrated wavelength switchable laser, and the high-speed Q-modulation technique.First, a new monolithically integrated half-wave V-coupled cavity semiconductor laser is proposed. The device comprises two coupled cavities with different optical path lengths, which form V-shaped branches with a reflective 2x2 half-wave optical coupler at the closed end. The reflective 2x2 coupler is designed to have aπ-phase difference between cross coupling and self-coupling so as to produce synchronous power transfer functions. High single-mode selectivity is achieved by optimizing the coupling coefficient. The switchable wavelength range is greatly increased by using Vernier effect. The static and dynamic characteristics of the digital wavelength switching in the novel V-coupled-cavity semiconductor laser are investigated based on the multimode rate equations (MMRE), including the switching transients and switching delay.The fabrication processes for monolithically integrated optical devices based on InGaAsP/InP wafer are reviewed and studied, such as the lithography, inductivity-coupled plasma etching, planarization, metal deposition, deep trench etching, quantum well intermixing technique and so on. The experimental results are presented, which demonstrate for the first time the digital wavelength switching functionality of the V-coupled cavity laser employing the Vernier effect.For high speed Q-modulation techniques, the small-signal frequency response and the carrier density perturbation as the increasing modulation frequency are studied, comparison with direct modulation are also presented. The difference of large signal modulation between Q-modulation and direct modulation for different bit rate are investigated, the influence of pump current, Q factor of the laser, optical confine factor, gain suppression coefficient on Q-modulation are all discussed. Besides that, comparison for the Q-modulation results with different signal pattern is also discussed. It shows that the Q-modulation can provide a much higher bandwith, a lower wavelength chirp and higher energy efficiency. Finally, the implementation structures of Q-modulation laser are proposed. First, the Q-modulation structure of a uniform grating DFB laser with a rear reflector as the Q-modulator is analyzed, including the static and dynamic characteristics. The Q-modulation results are also investigated with a time domain traveling wave model, which confirms the results from the simple rate equations. The Q-modulation based on a phase-shifted DFB laser by changing the cavity loss is also analyzed. At last, a novel monolithically integrated channel-selectable wavelength converter is proposed based on cross-absorption modulation (XAM) and Q-modulation mechanism in a V-coupled-cavity semiconductor laser. Analysis shows that the wavelength converter has the advantages of high-speed, high power efficiency, high extinction ratio, large wavelength span and simple implementation.