Modeling for Generating Femtosecond Pulses in an Er-Doped Fiber Using Externally Controlled Spectral Broadening and Compression Mechanisms

Abstract

A model for generating femtosecond laser pulses from a low-power mode-locked laser of moderate temporal half-width was proposed. This was achieved by injecting the pulse into a single-mode inverted-populated Er-doped fiber where self-focusing and absorption were avoided. To initiate spectral broadening, the pulse was phase-modulated by subjecting a part of the fiber to an electric field of suitable intensity and frequency generated into a circular capacitor. To stimulate temporal compression, the phase-modulated pulse was introduced into a combination of two prism sets located symmetrically with respect to the x-axis. After passing the pulse through the first prism set, its spectral components were spatially separated in the y-axis. The spectral phases were manipulated by redirecting the spectral components through a slab cross-section that was subjected to a spatially modulated DC electric field. After passing the slab, the pulse is directed into the second prism set, where the spectral components were spatially overlapped and propagated outside the compressor with the same slope and dimension as before entering the compressor. Constructive super positioning of the phase-manipulated spectral components gave maximum intensity only at a specified location.