Novel sources for polarisation squeezing and polarisation entanglement using photonic crystal fibres

Photonic crystal fibres (PCF) can be tailored to introduce a high effective nonlinear Kerr effect and to create lower amounts of excess noise compared to standard fibres. By exploiting both polarisation axes of the polarisation maintaining PCF we can generate two independent polarisation squeezed beams that can be used to create polarisation entanglement. We generated a maximum squeezing of-3.9 Aring plusmn 0.3 dB and a corresponding anti-squeezing of 16.8 Aring plusmn 0.3 dB. Furthermore we investigate the generation of polarisation squeezing in photonic crystal fibres by using a single pass setup where both the slow and fast axis has to be utilized. Taking advantage of these features and using ultrashort pulses we create polarisation squeezed states with notably higher purity than obtained in standard fibres.