Analytic Study Of Silicon-based GaN Wavelength-tunable DFB Laser

Wavelength tunable diode laser as an important light source which is playing an increasinglyimportant role in these areas such as wavelength division multiplexing(WDM),reconfigurableoptical add/drop multiplexing(ROADM), interferometry and spectroscopy and so on.This dissertation analyzed and studied the working mechanism of GaN wavelengthtunable distributed feedback (DFB) lasers based on microelectromechanical systems (MEMS)technology. Meanwhile, the mathematical model and simulation model was established. Byanalysis and simulation in visible light band of single longitudinal mode of laser output, Thestructure parameters of tunable DFB laser in which specific wavelength output was got. From thesimulation results, if the number of lattice in grating, grating width and the thickness of activelayer is constant, changing the grating period by mechanical adjustment, we can realizethe distributed feedback laser wavelength tunable combined with the MEMS technology, which canbe helpful to the design of tunable lasers.The main innovations of the dissertation are summarized as follows:First, a wavelength tunable DFB laser structures with the mechanical cantilever beam designsupport suspended photonic gratings based on microelectromechanical system (MEMS) is presented.we design grating for self-supporting structure suspension to realize the DFB laser wavelengthtunable. The grating is driven by electrostatic comb structure, both ends of which are connectedwith mechanical spring as a cantilever beam. Besides the common DFB laser has the characteristicsof simple structure and high reliability, the laser also has the advantages of line width, wide tuningrange and fast tuning speed.Second, a mathematical model is applied to design, analyze wavelength tunable DFB lasers:for the grating, that the GaN material itself has the characteristics of widely luminous range and thepreparation of grating, we analyzed the influence of the number of lattice in grating, the gratingperiod and grating depth for the grating mode selection, by using finite element software Comsoland Prague diffraction grating theory, and reverse validate the Prague formula; and then, afterdetermining the grating module of wavelength tunable DFB laser, the coupled wave theory and theequivalent dielectric slab waveguide theory are combined to analyze the output characteristic of thelaser integrated single two-dimensional steady model, and the characteristics of the laser line-width.The mathematical model plays a good role in the design of all kinds of wavelength tunable DFBlaser.Last, through the finite element simulation software Comsol, a2D steady state model of GaNDFB lasers was established. With the simulation of single longitudinal mode laser output in thevisible light band, we got the structure parameters and the output wavelength of DFB laser resonantlight conditions. Parametric scanning which focuses on the number of lattice in grating, grating thickness, grating width,grating period and active layer thickness. The simulation results canprovide data support to realize DFB laser wavelength tunable based on MEMS technology.