Photonic Crystal Fibre for Stimulated Raman Scattering and Spectral Phase Characterization

Abstract: Photonic Crystal Fibres (PCF) as novel waveguides, have found various applications. In this thesis, two of them are investigated, namely spectral phase characterization using a solid-core PCF and stimulated Raman scattering using a hollow-core PCF.

Spectral phase characterization is an important feature for appropriate interpretations and simulations in experiments where femtosecond pulses are used. Here, a reference pulse is used and analyzed through linear spectra interferometry, which offers a better sensitivity and reliability. Both, the reference pulse and the pulse to be measured, will propagate in a solid-core PCF: For the reference pulse a fibre with minimum dispersion effect is used. As a consequence of self-phase modulation, the pulse in the time domain will remain the same, while its spectrum wil broaden. This is the mean feature used, as a benefit of solid-core PCF. Afterwards both pulses are superposed and the interference spectral fringes will reveal the spectral phases.

 

The second application is regarding stimulated Raman scattering. Since discovered it become a broad topic for research. This inelastic scattering phenomenon has shown orders of magnitude enhancement when performed using a hollow-core PCF, as a consequence of long interaction lengths between low-density media such as gases and the laser light. In order to lower the threshold of the pump power required for its generation, additionally a seed laser is used. Here, this laser is modulated using an acousto-optic modulator. This configuration aims to observe the effect of the modulated seed on the generation of the Stokes pulses and the pump depletion.