Laser Pulse Compression Based On Integrated Silicon Waveguides

Silicon has been considered as a basic material for optoelectronic integration due to its high refractive index and excellent optical characteristics. In particular, silicon wire waveguides based on silicon-on-insulator (SOI) structure have exhibited adjustable dispersion and high nonlinearity etc., which makes it possible to generate and compress laser pulse based on silicon wire waveguides. This thesis focuses on laser pulse generation method through pulse compression and mode-locking in laser cavity based on two-photon absorption (TPA) and free-carrier absorption (FCA) in an intracavity silicon wire waveguide. Also, integrated laser pulse compression methods based on silicon waveguides are proposed. By optimizing the structure and dimension of the used silicon waveguide, adjusting the electrical parameters applied to the silicon waveguide or the amplifier, and optimizing the dispersion and nonlinearity of silicon waveguide, the effective laser pulse compression inside and outside cavity are both effectively realized.We introduce the research progress on the pulse compression and silicon-based lasers. The theoretical model of pulse compression and mode-locking in silicon waveguides is established. The factors that influence the output pulse are theoretically and experimentally investigated, including pumping current, modulation depth, and duty cycle of the modulation signal. The experimental results agree well with the theoretical analysis. It is shown that smaller duty cycle of the modulation signal, larger modulation depth, or larger pump power is beneficial for pulse compression.We also explore the integrated pulse compression method outside the laser cavity. A kind of typical pulse compression method is based on the chirp compensation by the dielectric dispersion in the compression media. Therefore, larger dispersion is beneficial to reduce compressor’s volume. An integrated pulse compression method is proposed based on a SOI waveguide and the waveguide length is optimized to be as long as50cm to achieve a compression factor of0.078. In order to shorten the length of the compression waveguide, a media with higher dispersion value should be used. By using a silicon line-defect photonic crystal waveguide, the integrated pulse compression method is proposed, where the required waveguide length is only as long as1.75mm to achieve a compression factor of0.096. By comparing the waveguide lengths of the two methods, one can find that increase the dispersion value is quite beneficial to decreasing the device volume.