Propagation Properties Of Femtosecond Pulsed Beams In Dispersive

Major optics Graduate Zhen Zheng Supervisor Lu|¨ Baida professor With rapid development of the femtosecond pulsed laser techniques, ultrashort pulses covering the optical spectrum from the far infrared to the extreme ultraviolet and corresponding to several femtoseconds or tens of attoseconds, as short as few cycles, even single-cycle, can be produced in several laboratories around the world. For this reason, much attention is being paid to their propagation in vacuum, linear and nonlinear media, and optical systems. The present thesis is mainly concerned with the propagation properties of pulsed beams in dispersive media and the results are summarized as follows:1. Based on the Rayleigh-Sommerfeld diffraction integral, the far-field expression for ultrashort pulsed Gaussian beams with constant waist width in a dispersive medium is derived without involving the paraxial approximation.2. Chirps for ultrashort pulsed Gaussian beams with constant waist in a dispersive medium are analyzed and the normalized local time is newly defined.3. Redshifts and blueshifts for ultrashort pulsed Gaussian beams with constant waist are totally included in the spectrum expression.4. Under the condition that the propagation constant k>0,the paraxial expression for ultrashort pulsed Gaussian beams with constant diffraction length in a dispersive medium is derived eliminating the spatial singularity.5. Taking the Gaussian pulse as a typical example, the characteristics for ultrashort pulsed Gaussian beams with constant diffraction length between propagating in normal and abnormal dispersive media are summarized.6. The curvature radius of pulse fronts of ultrashort pulsed Gaussian beams with constant diffraction length are amended in dispersive media. And chirps resulting from dispersive media are also analyzed.